Transmission dilemma

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ChrisRom

ChrisRom

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I have a 65 Dart GT convertible in decent shape. It is a slant 6 automatic with floor console.
The poor 6 is on its last legs with big time blow-by, low compression (90-100), and now the entire exhaust under the car got messed up when unloading it from a trailer.

I have a rebuilt 340 in my garage left over from a 73 Challenger, also I have a good 727 from the same car and a A833 OD with long tail, bell housing and shifter.
My dilemma is what direction to go - manual or automatic. (secret preference is the stick of course).
I am looking for a rear end - more than likely going to a 8 1/4 from a Cherokee, modified - it seems to be the most economical direction - either 3.55 or 3.07 based on the transmission.
Need a larger radiator, I have the a-body exhaust manifolds - will get a TTI DIY exhaust kit to go with it.
The front is 5x4.5 with disk brake conversion, the rear is 7 1/4 with small pattern but I have a spare 7 1/4 with large bolts, not yet installed.
I am doing all the work myself but since we are in a slump with this corona mess, the money is getting tighter(reduced weekly hours), so I am looking for the most economical option. Good thing is that I have more time to work on this project.
This is a cruiser not a racer, just having fun around town with it, and would like to get some hwy time too - not a screamer at 70mph.

What do you guys think is the most economical direction?

Thanks,

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Sounds like a good plan of attack. The automatic transmission will probably be the most economical way to go. Collecting all of the pieces for the 4 speed isn't difficult, just time consuming & making sure all of the parts play well together. Just my .02. Keep us posted on your project as you go.
 
Awesome car just as it is.

I'd sell the V8 & four speed & put the money towards the /6 rebuild.
 
Thanks, that's not a bad idea.... something to consider in these tough times.
I can rebuild the /6 myself, just need a machine shop to do the work and then buy a rebuild kit... don't know how much those cost.
Still need a /6 exhaust.
 
You might need to modify the transmission tunnel on that early A to get that 727 in there! A 904 will slide right in. 65'
 
turbo the slant 6 and KABOOM
 
Long tail A833 is for B, and E body, a handful of C bodys, and pickups. You need a short tail A body A833 to have the shifter come out in the right spot.
 
But you can convert the long tail to a short with just two parts, the mainshaft and the extension.
And I was able to fit a long-tail into my 68 Barracuda by hacking off the front shifter pad and just fabricating a new adapter to put the shifter where I wanted it.
If you are serious about your car just being a cruiser, then you could, in theory , use the overdrive A833 with it's 3.09 low gear. And you can run just about any rear gear you please. However; I strongly advise to chose a rear gear that will put that 1.67 second gear, at a roadspeed that your short-stroke 340 will actually pull from.
If your 340 has a 340 cam it will not get any better fuel economy at 1800 rpm than at 2200, perhaps not even 2400 will be the sweetspot. The 340 cam was never meant to be a cruiser-cam.
With that in mind, 3.55s will cruise at 70=2440 with 25" tires. So you got that covered.
And 3.09x355=10.97 a fabulous starter gear.
But the cruncher is at 30 mph, which is 2400rpm in second, 4430 in first. If you really are just cruising, then 2400 @30 mph with a 340 cam is not really rapid transit.
And if the car is loaded up with 3 passengers, she might be a lil sluggish.
But it gets worse;
when just cruising around, I like to shift early, at no more than 2800; the pipes are singing sweetly, and my cam has just begun to pull. But with the A833od; shifting into second from 2800 in first, gets you 1500 rpm, and I'll bet your 340 cammed 340, is gonna struggle with that.
So like I say; in theory, you can use that box, but finally pulled mine out, and mothballed it.
What you need, IMO, is an A999 with a hi stall, loc-up, and 2.94s. With 25s this gets you 70=2770 in loc-up. and a starter gear of 2.94x2.74=8.58 which is crap until you put the hi-stall on it, say a 2800, then it will be just fine.
and rpm at 30 mph? Well that would be 1830 in second 3250 in first, which is plenty of rpm for a cruiser and a 2800TC.
But I sure wouldn't run a 340 cam in that thing.
Because that cam does not power peak until maybe 5000 or so rpm....... which, with 2.94s doesn't come until 44 mph in 2.74 first gear. At Part Throttle and below about 2200rpm, that cam is a miserable gas-hog of a cam; and guess what; above^ we saw that 30mph in second gear was 1830rpm. So then, I would want a cam that is more efficient at 1830 rpm. And not care about power at 5000/44mph..
If you want your cake and eat it too, you will need an overdrive AND more than 3 other gears. So that points to a 5-speed manual, or
an overdrive auto with a hi-stall and a loc-up. And for a cruiser, I would NOT use a Mopar 340 cam. If you went down 1 to 1.5 cam sizes,and switched to a faster rate of lift and tightened up the LSa to 110/112, then you might be able to use that Mopar A833od box, with 3.91s. But that smaller cam with it's much earlier Ica might drive your iron-headed 340 into detonation; so it's kindof a balancing act.
Or, on a budget, just slow down on the hiway; 9.5% is about the equivalent of one rear gear from 3.91s on down; skipping 3.73s which is a half gear or about 5%.
In any case; just trying to help.
Happy HotRodding
 
AJ/FormS said:
But you can convert the long tail to a short with just two parts, the mainshaft and the extension.
And I was able to fit a long-tail into my 68 Barracuda by hacking off the front shifter pad and just fabricating a new adapter to put the shifter where I wanted it.
If you are serious about your car just being a cruiser, then you could, in theory , use the overdrive A833 with it's 3.09 low gear. And you can run just about any rear gear you please. However; I strongly advise to chose a rear gear that will put that 1.67 second gear, at a roadspeed that your short-stroke 340 will actually pull from.
If your 340 has a 340 cam it will not get any better fuel economy at 1800 rpm than at 2200, perhaps not even 2400 will be the sweetspot. The 340 cam was never meant to be a cruiser-cam.
With that in mind, 3.55s will cruise at 70=2440 with 25" tires. So you got that covered.
And 3.09x355=10.97 a fabulous starter gear.
But the cruncher is at 30 mph, which is 2400rpm in second, 4430 in first. If you really are just cruising, then 2400 @30 mph with a 340 cam is not really rapid transit.
And if the car is loaded up with 3 passengers, she might be a lil sluggish.
But it gets worse;
when just cruising around, I like to shift early, at no more than 2800; the pipes are singing sweetly, and my cam has just begun to pull. But with the A833od; shifting into second from 2800 in first, gets you 1500 rpm, and I'll bet your 340 cammed 340, is gonna struggle with that.
So like I say; in theory, you can use that box, but finally pulled mine out, and mothballed it.
What you need, IMO, is an A999 with a hi stall, loc-up, and 2.94s. With 25s this gets you 70=2770 in loc-up. and a starter gear of 2.94x2.74=8.58 which is crap until you put the hi-stall on it, say a 2800, then it will be just fine.
and rpm at 30 mph? Well that would be 1830 in second 3250 in first, which is plenty of rpm for a cruiser and a 2800TC.
But I sure wouldn't run a 340 cam in that thing.
Because that cam does not power peak until maybe 5000 or so rpm....... which, with 2.94s doesn't come until 44 mph in 2.74 first gear. At Part Throttle and below about 2200rpm, that cam is a miserable gas-hog of a cam; and guess what; above^ we saw that 30mph in second gear was 1830rpm. So then, I would want a cam that is more efficient at 1830 rpm. And not care about power at 5000/44mph..
If you want your cake and eat it too, you will need an overdrive AND more than 3 other gears. So that points to a 5-speed manual, or
an overdrive auto with a hi-stall and a loc-up. And for a cruiser, I would NOT use a Mopar 340 cam. If you went down 1 to 1.5 cam sizes,and switched to a faster rate of lift and tightened up the LSa to 110/112, then you might be able to use that Mopar A833od box, with 3.91s. But that smaller cam with it's much earlier Ica might drive your iron-headed 340 into detonation; so it's kindof a balancing act.
Or, on a budget, just slow down on the hiway; 9.5% is about the equivalent of one rear gear from 3.91s on down; skipping 3.73s which is a half gear or about 5%.
In any case; just trying to help.
Happy HotRodding
Click to expand...

Thank you for your insight. I learned a lot.
My 340 is a low compression 1973 model left over from my Challenger project. It has the 1.88 intake valves, j heads, and factory cam. It has been rebuilt by the prev. owner to factory specs.
I would be interested to see a picture of your car interior with the shifter location at the rear of the long case A833, between the seats.
Right now because of the "wife imposed financial austerity", I will have to use what I have - the 340 and 727. Don't know if I can find somebody to trade the 727 for a A999 with lockup TC.... it would be nice if I do. I see them in the junkyards at $250 a pop. But may need refreshing - another $100 for a rebuild kit.
Still looking for a 8-1/4 rear end. I see Cherokee units with 3.07 ratio for around $150 at the same yard. plus another $100 to relocate the perches and shock mounts.
Will also need a $300 shifter assembly (Pro-matic2)
And exhaust.
It doesn't look that bad.
 
For anybody that did a 727 transplant - how much hammering needs to be done to the hump to be able to fit a 727 in there? I read a statement - use a big hammer.... is that a width or height issue on fitting these transmissions in?
 
Chris, that is referred to as "sledge hammer surgery". LMAO
 
Demonracer said:
Chris, that is referred to as "sledge hammer surgery". LMAO
Click to expand...

Best investment I ever made was a 4 post lift.... plenty of room underneath to swing a sledge hammer if I have too. That would be the cheapest part of the project.
 
If you are going to run the 340, build a stout 904 & go for it. I'm running a RMVB trans brake 904 in my bracket car with no problems.
 
Chris; I think you might be in a bit of a pickle
The Wallace Calculator says; if your
Static compression ratio really is 8:1, and
Ica of 64*(268/276/114 cam); and 640 ft elevation
Effective stroke is 2.57 inches.
Your dynamic compression ratio is ............ 6.43:1 .
Your dynamic cranking pressure is ............ 119 PSI.
V/P (Volume to Pressure Index) is ............... 94VP
read about VP here; V/P Index Calculation
At VP of 94 your 340 is gonna come off idle, feeling just about like a 273.(see below)

With 3.07 gears it will be even worse, and the unknown stall speed is probably gonna hurt real bad.
The only thing you got going for you with this combo, is the cubes and the lighter weight body style.
As a cruiser this might work, but I don't think there will be much fun in it until you get the Rs up; Ima thinking she will begin waking up around 3500rpm/33 mph, in first gear, and start pulling at 4000/38 mph.
If you're OK with that, then have at her, but you'll
probably want to paint it red,and tell your friends it's a 273.
Because;
Here is what a 273 looks like in terms of low rpm performance;
Static compression ratio of 8:1.
Ica of 48*, 640 elevation
Effective stroke is 2.89 inches.
Your dynamic compression ratio is ................ 7.10:1 .
Your dynamic cranking pressure is ................ 136PSI.
V/P (Volume to Pressure Index) is .................. 98VP
Notice the VP is higher than your 340 is, and the 273 with it's tiny cam, is making more pressure than the 340. An additional penalty with the 340cam, is lousy fuel-economy.
But the good news is a new smaller cam can be slid in at any time into a low-compression engine, with nothing but good results.

Here is a 360 2bbl type cam, with no other changes
Static compression ratio of 8:1.
Ica of 54*, still 640 elevation
Effective stroke is 2.78 inches.
Your dynamic compression ratio is 6.87:1 .
Your dynamic cranking pressure is ................... 130PSI.
V/P (Volume to Pressure Index) is..................... 112VP

112VP is still nothing special ; in comparison, a 5.2 Magnum makes over 124VP. But it is an improvement of; 112/94= plus 19%, which is about the same percentage as going from 3.07s to 3.66s, in terms of bottom end performance improvement.
I know you're on a budget, but since you do not yet have a rear end, there is no way I would suffer this combo with 3.07s. I would leave the 7.25 in the back with whatever gears are in it (but with an oil change); your 340 at this point cannot hurt it unless you start peg-legging it. Don't do that! And I would take that money you saved and get yourself a higher stall TC; at the very, very least a 2600.
If that 7.25 is a 2.76, your combo will still be real soft off the line, but at least you can cruise 70=2570 at zero-slip.

Here is my reasoning;
Lets say your 94VP bring 240 ftlbs to the crank at 1800/2000 stall. By the time that gets to the rear axles, And at zero mph, it might be an instantaneous;
240x1.6TC x2.45x3.07=2890 ftlbs@zero mph out the back, and 70=2890@zero-slip.
whereas;
at 2600, I'll guess the 340 brings 280ftlbs to bear, then with 2.76s
280x1.7TC x2.45x2.76= 3220ftlbs@zero mph out the back, and 70=2600@ zero-slip.
Notice the instantaneous ftlbs has risen from 2890 to 3220, WITH a cruise reduction of 290.
So if my guesses of 240 and 280, or even just the ratio of 240 to 280=1.166, is anywhere close, then you can see that the 2600 is gonna be a big improvement;
3220/2890= plus 10.7% in take off, and
2890 less 2600, is a 290 rpm improvement in cruise rpm.
These are big deals.

But if your current 7.25 happens to be a 3.23, well; there is no saving the cruise rpm cuz 70=3040@zero slip. Your best solutions are taller than 25" tires and slowing down. All my calcs thus far have been with 25" tires.
In this case,(with 3.23s) you can keep your current TC which I'm guessing is gonna be between 1800 and 2100tops, and your new take-off could be
240x1.6TC x2.45x3.23=3040@zero mph; that's bearable with a 340, now you can at least spin the tires for a lil ways (get a SureGrip asap); and now, you can
paint your 340 turquoise.
With the money you saved by not buying a Jeep rear, nor a hi-stall, treat your car to an A999. and hope for 2.76s in the 7.25. Thus;
240x1.6TC x2.74x2.76=2900ftlbs@zero mph, and 70=2600. Compare this to the first math I did above, in blue.
240x1.6TC x2.45x3.07=2890 ftlbs@zero mph out the back, and 70=2890
Notice the take-off is about the same, but the cruise Rpm is down to 2600 from 2890, being 290rpm.
And you don't have to beat the snot out of your tunnel. The A999 bolts right in. Physically, the A999 is practically identical to the A904, just with all the best Mopar guts in it, the new ratios of 2.74-1.54-1.00, and the loc-up TC which is good for between 220 and 280 cruising rpm reduction. And the TC stall is usually slightly higher than a 904. The early models had a hydraulic loc-up, controlled by the VB,automatically.
The only thing you have to remember is the engine balance, which has to be transferred to the new flexplate. Rebuilding these A999s is easy-peasy.

I hope you realize that these changes are a direct result and correction for the very low cylinder pressure in your 8/1 Scr 340. If she was the earlier model 340, you could just slam anything together.

By the way, about 1975, I slammed a 340 short block together with a 318 cam and top end; heads and 2bbl. Hey, its what I had and I was ~21 years old. I dropped that into a 65 V100 wagon, I think you Americans called that a Dart. I had to get fenderwell headers to make it work, which was my major cost. This was my all-time favorite swap. I used an A904 from a 273, and the wagon's oem 7.25 with 3.23s. The trans went out first, with me driving the crap out of it. I think I got three summers out of it.
That 340 tho, was the hi-compression model. I still have it, but in boxes now,lol. I still got the trans too,lol. In any case
just trying to help.
 
Last edited:
AJ Even I don't under stand what you said, it makes me wanna agree..
 
AJ/FormS said:
Chris; I think you might be in a bit of a pickle
The Wallace Calculator says; if your
Static compression ratio really is 8:1, and
Ica of 64*(268/276/114 cam); and 640 ft elevation
Effective stroke is 2.57 inches.
Your dynamic compression ratio is ............ 6.43:1 .
Your dynamic cranking pressure is ............ 119 PSI.
V/P (Volume to Pressure Index) is ............... 94VP
read about VP here; V/P Index Calculation
At VP of 94 your 340 is gonna come off idle, feeling just about like a 273.(see below)

With 3.07 gears it will be even worse, and the unknown stall speed is probably gonna hurt real bad.
The only thing you got going for you with this combo, is the cubes and the lighter weight body style.
As a cruiser this might work, but I don't think there will be much fun in it until you get the Rs up; Ima thinking she will begin waking up around 3500rpm/33 mph, in first gear, and start pulling at 4000/38 mph.
If you're OK with that, then have at her, but you'll
probably want to paint it red,and tell your friends it's a 273.
Because;
Here is what a 273 looks like in terms of low rpm performance;
Static compression ratio of 8:1.
Ica of 48*, 640 elevation
Effective stroke is 2.89 inches.
Your dynamic compression ratio is ................ 7.10:1 .
Your dynamic cranking pressure is ................ 136PSI.
V/P (Volume to Pressure Index) is .................. 98VP
Notice the VP is higher than your 340 is, and the 273 with it's tiny cam, is making more pressure than the 340. An additional penalty with the 340cam, is lousy fuel-economy.
But the good news is a new smaller cam can be slid in at any time into a low-compression engine, with nothing but good results.

Here is a 360 2bbl type cam, with no other changes
Static compression ratio of 8:1.
Ica of 54*, still 640 elevation
Effective stroke is 2.78 inches.
Your dynamic compression ratio is 6.87:1 .
Your dynamic cranking pressure is ................... 130PSI.
V/P (Volume to Pressure Index) is..................... 112VP

112VP is still nothing special ; in comparison, a 5.2 Magnum makes over 124VP. But it is an improvement of; 112/94= plus 19%, which is about the same percentage as going from 3.07s to 3.66s, in terms of bottom end performance improvement.
I know you're on a budget, but since you do not yet have a rear end, there is no way I would suffer this combo with 3.07s. I would leave the 7.25 in the back with whatever gears are in it (but with an oil change); your 340 at this point cannot hurt it unless you start peg-legging it. Don't do that! And I would take that money you saved and get yourself a higher stall TC; at the very, very least a 2600.
If that 7.25 is a 2.76, your combo will still be real soft off the line, but at least you can cruise 70=2570 at zero-slip.

Here is my reasoning;
Lets say your 94VP bring 240 ftlbs to the crank at 1800/2000 stall. By the time that gets to the rear axles, And at zero mph, it might be an instantaneous;
240x1.6TC x2.45x3.07=2890 ftlbs@zero mph out the back, and 70=2890@zero-slip.
whereas;
at 2600, I'll guess the 340 brings 280ftlbs to bear, then with 2.76s
280x1.7TC x2.45x2.76= 3220ftlbs@zero mph out the back, and 70=2600@ zero-slip.
Notice the instantaneous ftlbs has risen from 2890 to 3220, WITH a cruise reduction of 290.
So if my guesses of 240 and 280, or even just the ratio of 240 to 280=1.166, is anywhere close, then you can see that the 2600 is gonna be a big improvement;
3220/2890= plus 10.7% in take off, and
2890 less 2600, is a 290 rpm improvement in cruise rpm.
These are big deals.

But if your current 7.25 happens to be a 3.23, well; there is no saving the cruise rpm cuz 70=3040@zero slip. Your best solutions are taller than 25" tires and slowing down. All my calcs thus far have been with 25" tires.
In this case,(with 3.23s) you can keep your current TC which I'm guessing is gonna be between 1800 and 2100tops, and your new take-off could be
240x1.6TC x2.45x3.23=3040@zero mph; that's bearable with a 340, now you can at least spin the tires for a lil ways (get a SureGrip asap); and now, you can
paint your 340 turquoise.
With the money you saved by not buying a Jeep rear, nor a hi-stall, treat your car to an A999. and hope for 2.76s in the 7.25. Thus;
240x1.6TC x2.74x2.76=2900ftlbs@zero mph, and 70=2600. Compare this to the first math I did above, in blue.
240x1.6TC x2.45x3.07=2890 ftlbs@zero mph out the back, and 70=2890
Notice the take-off is about the same, but the cruise Rpm is down to 2600 from 2890, being 290rpm.
And you don't have to beat the snot out of your tunnel. The A999 bolts right in. Physically, the A999 is practically identical to the A904, just with all the best Mopar guts in it, the new ratios of 2.74-1.54-1.00, and the loc-up TC which is good for between 220 and 280 cruising rpm reduction. And the TC stall is usually slightly higher than a 904. The early models had a hydraulic loc-up, controlled by the VB,automatically.
The only thing you have to remember is the engine balance, which has to be transferred to the new flexplate. Rebuilding these A999s is easy-peasy.

I hope you realize that these changes are a direct result and correction for the very low cylinder pressure in your 8/1 Scr 340. If she was the earlier model 340, you could just slam anything together.

By the way, about 1975, I slammed a 340 short block together with a 318 cam and top end; heads and 2bbl. Hey, its what I had and I was ~21 years old. I dropped that into a 65 V100 wagon, I think you Americans called that a Dart. I had to get fenderwell headers to make it work, which was my major cost. This was my all-time favorite swap. I used an A904 from a 273, and the wagon's oem 7.25 with 3.23s. The trans went out first, with me driving the crap out of it. I think I got three summers out of it.
That 340 tho, was the hi-compression model. I still have it, but in boxes now,lol. I still got the trans too,lol. In any case
just trying to help.
Click to expand...


Thank you again for your help, AJ.

The reason I am looking to install this 340 in is because the slant 6 currently in the car is in need of a rebuild - it has extreme blow-by and low numbers when I did the compression test (90-100). Plus the 340 just sits in my garage with no use.
The 727 is also sitting in my garage, but I am more than likely keeping it there. I'll get a A999 from the junkyard and refresh/rebuild it myself, and maybe add a higher stall TC to it. This will fit the Dart tunnel better and have a better 1st gear ratio than 727.
On the rear end, I have to go with a 8.25 unit. The current 7.25 has the small bolt pattern and the front is converted to disk with large 5x4.5 bolts. So I have to keep 2 spare tires in the trunk - one for the front and one for the rear. Still have time to shop around for the right 8.25 rear end....

It is not just a budget constrain, even thou this corona mess made it more of an issue. There is also a question of car value. I just don't like loosing money if I want/have to sell it later on. These Darts are not that valuable to start with. And people buying a 65 dart convertible more than likely are looking for a "parade" cruiser kind of car. The 340 will make it a bit preppier and sounding "tough" out of the rear pipes.

So, the current 340 will go in the car along with the A999 transmission and higher stall TC. The only unknown is the rear end. What ration???? to get to the right balance. Will do some more number crunching using your suggestions.

You mentioned that the early 904/a999 had hydraulic type Lock up? Do the newer models have an electrical, solenoid type switch, like the A500/A518? What should I look for at the junkyard? year, external plug connector?
 
ChrisRom said:
You mentioned that the early 904/a999 had hydraulic type Lock up? Do the newer models have an electrical, solenoid type switch, like the A500/A518? What should I look for at the junkyard? year, external plug connector?
Click to expand...
You are making the right decision.
The Locup trans already comes with a slightly higher stall than the regular 904. I'll guess ~300rpm.
The later A999s, I have read, had the loc-up electrically controlled by grounding the internal solenoid. You can install a dash switch to do that. So that opens up your choices to all A999s. The TC for the A999 is different from an A904, and they do not interchange. So you kindof need to get them together, else you will have to buy one. Hi-stall lock-ups are sortof a specialty, so not cheap. Better to get the TC with the trans.
Another option is the A998, non loc-up, then a regular A904 TC fits. But you have to be really careful when buying an A998, because they can have either ratio in them, and in your case you want the 2.74-1.54-1.00 ratios because the low gear is 2.74/2.45= plus 12% lower..... so you can run plus 12% less hiway gear to break even, and thus help the low-C 340 get off the line/etc, as previously discussed.
 
AJ/FormS said:
You are making the right decision.
The Locup trans already comes with a slightly higher stall than the regular 904. I'll guess ~300rpm.
The later A999s, I have read, had the loc-up electrically controlled by grounding the internal solenoid. You can install a dash switch to do that. So that opens up your choices to all A999s. The TC for the A999 is different from an A904, and they do not interchange. So you kindof need to get them together, else you will have to buy one. Hi-stall lock-ups are sortof a specialty, so not cheap. Better to get the TC with the trans.
Another option is the A998, non loc-up, then a regular A904 TC fits. But you have to be really careful when buying an A998, because they can have either ratio in them, and in your case you want the 2.74-1.54-1.00 ratios because the low gear is 2.74/2.45= plus 12% lower..... so you can run plus 12% less hiway gear to break even, and thus help the low-C 340 get off the line/etc, as previously discussed.
Click to expand...

Thanks,

I installed an A518 in my challenger couple years ago, with a higher CR 340 and a lot of upgrades - cam, airgap intake, etc.
I got some adjustable pressure switches for OD and Lock up with an override on the console. Nice setup and good running car.
I am happy with that build, but there is no room for such thing in the Dart without major tunnel modifications, and not ready to tear this car apart yet.
 
ChrisRom said:
On the rear end, I have to go with a 8.25 unit. The current 7.25 has the small bolt pattern and the front is converted to disk with large 5x4.5 bolts. So I have to keep 2 spare tires in the trunk - one for the front and one for the rear. Still have time to shop around for the right 8.25 rear end....
Click to expand...
As to dual bolt patterns;on a budget, and for a city car, you gotta think about this.
Firstly; as yourself how often in your lifetime, have you had to install a spare? How much would a tow-call cost you? And what is it a bbp rearend gonna cost you?
As for me; I have had one tire go down on my Barracuda since 1999, thankfully just 3 miles from home. I do not carry a spare. I do have 5 on 4 in the front and 5 on 4.5s on the back.
Our roads are not like they were in the 50s .
And our tires are not 60s technology.
And I don't drive on junk tires anymore.
So I assessed the risk and went with no spare at all.
But if you just want the peace of mind, there is no argument against that. Nor against what brand 4.5bc axle you install.
So that just leaves the ratio.
In your case, you probably want decide what is more important to you; is it
cruising at low rpm, or is it
a snappy take-off, or is it
the kick-down into first at 30 mph?
Cuz with the low cylinder pressure of your 340, IMO, it will not be possible to cover all three bases.
But yaknow, I should restate that somewhat; I know that for me, I would have to bias MY decision for MY desired outcome. You may not be as particular as I am. And for me, it would be hard to let go of a snappy take off.
And if you are buying at the pickNpull, you might not have a lotta choices.
Here is a lil chart to help you;
ratio....mph@70.... take-off... KD@32.... mph@60
2.76 ....... 2600 ...... 7.56 ..... 3255 ..... 2210
2.94 ....... 2770 ...... 8.06 ..... 3470 ..... 2355
3.07 ...... 2890 ...... 8.41 ..... 3620 ..... 2485
3.23 ....... 3040 ...... 8.85 ..... 3810 ..... 2614
3.55 ....... 3340 ...... 9.73 ...... 4190 ..... 2872
3.55 ...... 2410 ..... 10.97 ..... 4360 ..... 2065
>mph@70 is in loc-up or zero-slip and with 25" tires. These can be reduced to 86% by cruising at 60 (per the last column), the sacrifice being your travel-time will be increased by 1/.86, or plus 16%, or about 10 minutes per 60 miles.
With a 904 the Rs could be between 5 and 10% higher.
> take-off is your starter gear; 7.56 is pretty sucked out, while 9.73 is really snappy.
> KD is into 2.74 low gear. That 340 cam is gonna Torque-Peak at around 3800/4000, so I would like to be about there for the excitement factor.
> the bold numbers are the lowest that I would recommend in each decision, for myself.
> I set it up with 3.07s in the middle, so you can easily compare.
> stay out of the red; try to stay out of the Orange; Green means go; and black is ok too. The violet is what I am enjoying, with a 367, a Commando 4-speed, and A GVod

> As yoi can see the 3.07s at 60 mph are hitting 3 bases.
 
I did look at the GV unit for my challenger.
Thinking that if it doesn't sell and the economy bounces back up, I may want to switch to a manual transmission.
I also talked to a company here in TN about a Tremec 5sp kit.... will see.

Back to the Dart, I will keep an eye on a 3.07 Jeep 8.25 rear end. They run around $150 at the local yard, another $100 to relocate the perches and shock mounts (my welding skills are not that evolved). Not bad. I think it will pass the wife imposed "financial austerity" rules....
Thank you for your help again.
 
ChrisRom said:
think it will pass the wife imposed "financial austerity" rules....
Click to expand...
Oh-oh,lol.
All the best to you

BTW
As a point of interest; If I had it to do over, I would not put a GVod on a Mopar 4 speed again, for any other reason that to use as an overdrive.

What I would do is use a 700R4 with a hi-stall of about 2800, and a lock-up. This makes it a 5.5 gear combo, namely; 4 in the trans, a hi/lo in the TC, and a half-gear in the lock-up.
This GM trans boasts slightly wider splits than the A500,
bolts right in to the 67 up floor pans,and
adapters and rear mounts are available.
The ratios are 3.06-1.63-1.00-.70 overdrive; splits of .53-.62-.70
How does it make 5.5 gears? Glad you asked.
First, you have to understand that the TC is more than just a fluid coupling. It is also a Torque Multiplier. It takes whatever torque is coming into it,and multiplies it to a higher number going out. This is expressed as a ratio. The ratio is highest at zero mph, and it diminishes as the speed goes up.
The highest starting ratio I have heard of is 2.0, but more typically it is about 1.8. At the lower end, at around a hundred miles per hour, it may have diminished to 1.1 or a bit less. So that makes a range of 1.8 to 1.1. expressed as a gear it would be 1.1/1.8=.61, which is a very fine split, about the same as is in the automatic; 1.45/2.45=.592, in the case of the A904/A727
So right there you have an automatic 2-speed in the TC, continuously and automatically variable, between 1.8 and 1.1.
Then the 4 in the main box including overdrive. and finally the lock up which is usually good for a 10% rpm reduction. So 2 plus 4 plus 1/2=5.5 gears.
Let me show you what the rear tires will be seeing. And I'll gear it for ~2400@70 with 25" tires, in loc-up; so, that would take a 3.64 rear which I will round down to 3.55s.
Ok.
So how this works is TC ratio, times trans ratio, times rear ratio equals a number that you can multiply your engine torque by, to get what I call "road torque" And you do it with each gear. Remember this is with the 700R4
So in first gear @zero mph;
1.8x 3.06x3.55=19.55 out the back.This number will automatically diminish by the shift rpm to something like
1.2x3.06x3.55=13.04 at shift rpm.Then into Second
1.2 x1.625x3.55=6.92 ; and into third
1.1x1.00x3.55=3.91, and into overdrive
1.1x.70x3.55=2.73 and finally into lock up
1.0x.70x3.55=2.485

Lets line them all up;
19.55-13.04-6.92-3.91-2.73-2.485 count them; I get 6 ratios.... from a 4 speed.
The splits are .67-.53-.56-.70-.91
Ok so;
70=2340, very nice
starter gear is 10.86, very nice!
KD @28mph is 4100 ,OOps a lil high, but not for a 268/276/114 cam, it will go to 5500/38mph.
2 out of 3 is pretty good!

This trans could be run with a 3.23, but then the cruise rpm will be excessively low at 60=1825, for that 340 cam. Low because that cam is dirtying up the intake because of the 64* Ica advertised , which, seat to seat ,is probably another 15 degrees later, or more. In other words the intake valves will be closed, finally, just about the time the pistons are half way up the bores. And we haven't even talked about the overlap period of 44*, which actually ain't that bad,lol.
Dirtying up means, reversion; the the pistons are pushing a portion of the just ingested fuel/air charge, back up into the intake plenum. This makes the low-speed circuit hard to tune, and it invariably runs rich. The slower the rpm the worse it is. It usually takes 2200 to maybe 2400, and lots and lots of ignition cruise-timing, to clean it up. This all means that there is not much point to lower the cruise rpm of a 340 with a 340 cam, in an attempt to find fuel economy. With just 104* advertised power duration, a lot of energy is going straight into the tailpipe, sent there by the early opening exhaust valves. There are not a lot of street cams that get below 100*, But again seat to seat, the 340 cam will be waaay down there. For this reason, I see no point in cruising any slower than 2400 with that factory 340 cam.
I got off track again, didn't I,lol.
Oh yeah, I remember;
count them; I get 6 ratios.... from a 4 speed.
I call it a 5.5 cuz lock up is only gonna be about 250 rpm.

The A904 with a GVod could be used with 3.55s for 70=2740@5% slip,
and a starter of 2.45x3.55=8.70x1.8 in the TC=15.65 at zero mph,
and 30 @ KD into first is ~4120, shazzam!
That would be 3 for 3!
But I think you would have to cut the floor open just a little, to make a space for the GV unit.
This combo would have ratios of
2.45-1.45-1.00-.78od and splits of .59-.69-.78 nice but no lock-up, so just 5.0 gears. Geared for 70= 2740 slipping 5% requires a rear gear of no more than 3.55s . So
1.80x2.45x3.55=15.65; and
1.20x2.45x3.55=10.44, and
1.20x1.45x3.55=6.18, and
1.10x1.45x3.55x.78=4.42, and
1.06x1.00x3.55x.78=2.94, and
no lock-up, and
15.65-10.44-6.18-4.42-2.94
with splits of .67-.59-.72-.665, pretty sweet!
and now you have unlimited A904 TC selection.

With 3.23s it would be
70=2490,
a starter of 14.24>9.50, and
KD into first at 32=3750
Oh yes I'm liking those numbers.

Fun with math
 
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