Not best, but optimum Transmission?

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7milesout

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Trying NOT to open a can of worms here, boy I hope it doesn’t. My 727 (or more likely the torque converter) is making some rattling noise and seems to be slipping into neutral when I come to a stop before everything gets warmed up.

So I’m thinking the transmission may have to dealt with before too long. Here are my thoughts, but I’d like to hear from “the experts” (you guys) before I actually do anything. I'm sure it is obvious, but I am very weak when it comes to transmission knowledge. It is something I have never had to deal with.

I have a 72 Scamp, with an LA360 and 727, column shifter. 14” wheels and tires (very close to 24” O.D. on the tires), 3.23 rear gear and Eaton TrueTrac differential. It turns in the vicinity of 3,000 rpm at 60 mph. Sure, I’d love a 4 speed manual, but I’d rather leave the car as close to stock as possible, within reason. Plus if I had a manual I would probably stay away from the dragstrip, not wanting to burn up a clutch.

If I’m going to futz with the transmission anyway (due to a problem it may be having), I would want to go back with a 4 speed (3 speed + O.D.) transmission. So, the discussion I would like to have is, what is the optimal transmission to go back with? I can hear the cans opening… Base your feedback on the below.

After what level of reading I have done, it seems like maybe my best option is to go with an A500 (42RH). As I gather, the advantages (for me with the 72 Scamp) with an A500 transmission is:

  • Less modification to the tunnel for fitment.
  • 1st and 2nd gears will put me up in the power quicker for better strip performance (I will run it down the strip a couple/few times a year).
  • The overdrive is the same 0.69:1 as most (or all?) other torqueflites.
  • The A500 / 42RH can be “built” to be very stout, just like most other torqueflites.
    • I'm not likely to every have more than maybe 500 hp max anyway.
  • An A500 is not some damn GM transmission. :D
 
Trying NOT to open a can of worms here, boy I hope it doesn’t. My 727 (or more likely the torque converter) is making some rattling noise and seems to be slipping into neutral when I come to a stop before everything gets warmed up.

So I’m thinking the transmission may have to dealt with before too long. Here are my thoughts, but I’d like to hear from “the experts” (you guys) before I actually do anything. I'm sure it is obvious, but I am very weak when it comes to transmission knowledge. It is something I have never had to deal with.

I have a 72 Scamp, with an LA360 and 727, column shifter. 14” wheels and tires (very close to 24” O.D. on the tires), 3.23 rear gear and Eaton TrueTrac differential. It turns in the vicinity of 3,000 rpm at 60 mph. Sure, I’d love a 4 speed manual, but I’d rather leave the car as close to stock as possible, within reason. Plus if I had a manual I would probably stay away from the dragstrip, not wanting to burn up a clutch.

If I’m going to futz with the transmission anyway (due to a problem it may be having), I would want to go back with a 4 speed (3 speed + O.D.) transmission. So, the discussion I would like to have is, what is the optimal transmission to go back with? I can hear the cans opening… Base your feedback on the below.

After what level of reading I have done, it seems like maybe my best option is to go with an A500 (42RH). As I gather, the advantages (for me with the 72 Scamp) with an A500 transmission is:

  • Less modification to the tunnel for fitment.
  • 1st and 2nd gears will put me up in the power quicker for better strip performance (I will run it down the strip a couple/few times a year).
  • The overdrive is the same 0.69:1 as most (or all?) other torqueflites.
  • The A500 / 42RH can be “built” to be very stout, just like most other torqueflites.
    • I'm not likely to every have more than maybe 500 hp max anyway.
  • An A500 is not some damn GM transmission. :D

If you don't do freeway a lot I think you might stick with the 727.
 
Out of curiousity, what is the fluid level at? The trans in my Dakota would slip into neutral when the fluid was low. I had a rusted out pan. Be the first thing I check. I don't know on the rattling though.
 
If you are'nt handy with the tools on the more delicate stuff like trannies, then if I were you, I'd look at your pocketbook, decide how much you can throw at it. Then call A&A or Cope and tell them you want to spend X amount of dollars on the most bada** trans they can build you. You don't have to tell them how much $$, but I would start a conversation with them about what you desire and see if it works into your budget. I'd lean towards sticking with the 727 myself.....you can do a lot with them.
 
Clutch problems are not an issue, with your tires

Optimum trans for what?
Street? Street is all I know.
There are several points to consider;
They are arranged according to my preferences.

low-rpm torque, and stall
rear tires and gears
Starter gear requirement
hammer down at 32mph
zero to 60mph ET
rpm at cruising speed
engine powerband
Rpm of peak power
rpm at TrapSpeed
there may be more

Re-arrange to suit your preferences.

I can tell you what doesn't work;
a 292/292/108 cam in an 8/1 scr 360 cuber with 3.55 gears, any tires, and a 2.66low A833. This is guaranteed to make you pout. If you put a 727 into the mix with a stock TC, You will cry buckets of tears.
I can tell you what is guaranteed to tickle your innards and make you smile every time you stab the gas;
a 220 to 223 (at .050) fast rate hydraulic cam, in an 11/1 Scr aluminum headed 360 with any gears, any tires, any trans and, any TC.
On the street, Torque and TM (Torque Multiplication) are king.

General observations;
>The more torque you have at 32 mph at Kickdown, the more you are gonna need tires and traction. That is to say; with street tires and street suspension, it is easy to annihilate the tires, which results in lots of tirespin and slow ETs. If that's your thing, perfect.
> For me, I care almost nothing for dragracing, so I will never optimize my rear gears for that. But I do care about low-ET for zero to sixty. To that end, I gear my car to run outta revs, at or near the power peak, at or near 60 mph, in SECOND gear, having gone thru the power-peak twice. And so, I have to use a manual trans, cuz you can't do it with an automatic, even with wicked race gears in the back.
For example; say you had 3.55s, and a powerpeak around 5000, shifting at 5400, with 27" tires. Ok. the 727 will get 60=4000, just getting up on the power. Whereas the MT will be at 5100, right on the power-peak, for the Second time. So the M/T will put more average power into the exercise. If you can make it hook, you will generate a low-ET. But if you spend 2.44 seconds in the 60ft window, well then, the 727 car might smoke on by you.
With a stout 360, first gear is sortof a throw-away gear, only used to get into second. So for me, hammer down at 32 mph is a big deal. My A833 has the Commando 3.09 low in it, so 32mph is 4300, about at the top of the torque peak, but already on rising power curve. But in second gear, she cruises at 2700, so sorta quiet and relaxed, and un-assuming and the cops don't notice me. But when the mood hits and I downshift, it is instant tirespin, and bouncing off the rev limiter. I can only hold it there for 1 or 2 seconds, before grabbing second, which also goes straight to the limiter. By now the tires are warmed up, and the car is rocketing to my self-imposed speed limit of 60 mph, and perhaps 3 seconds has elapsed, maybe 3.5. Then it's hard on the brakes, and slam it into third. For me that is a rush.
>If you have a 727 with the same 3.55s, and a typical 2500TC;
32mph will be ~3800 in first gear at WOT; and ~2000 cruising in second. So at KD you might be right on the torque peak, ............ but you can't make it to 60 in first, shifting into second at about 45 mph. At which time your tires will have grabbed, and now your revs will fall to 3200, and your smokeshow is done. Yur gonna need one of four things; 1) more torque, 2) more stall, or 3) more TM.
>These lead straight to 4) an overdrive. The od will let you run; more gear, less stall, and make your engine perform like a bigger one. And the bonus is; a lower cruise rpm.

If you look on the bottom of the list you will get to the engine. I put them there cuz, for a streeter, the absolute power of your engine is not real important. When properly geared for zero to sixty, first gear is a smoke-show. So your engine needs to be on the power when it hits Second gear, and then you stretch second out to Sixty ( or wherever you decide to quit). So yeah, cubes are gonna make a difference, cuz they bring more average power to the table, if you can make the car hook. But power at 6000 is never gonna mean anything but nothing, if you don't get there. And in the meantime, you rob powerband and fat-midrange, to get that power at 6000.

So, IMO, forget the 292/292/108 cam! with 3.55s. The second-gear power peak comes at ~80 mph with an auto, ~83 with a manual.
And it makes waaaaaaay more power than your stock chassis can deal with. and you just end up with tirespin all the way there. If you gear it down to peak at say 60mph, this will take 5.38s.... and now you have two useless tire-frying gears. Ok, you like that cam? put it in a 273, to try and tame the tirespin. Or spend the coin on the suspension,to make it stick. But of course, that cam brings other limitations with it.

Ok I'll spill the beans, I have the optimum transmission.
For me,
And for my combo.
This comes after running just about every Mopar trans available before the A500/518s, and with just about every rear gear, and after hammering thru 3 different cams.
I have settled on; a 3.09low Commando box, with a GearVendors overdrive behind it, and 3.55s out back
The Commando ratios are 3.09-1.92-1.40-1.00 and the GVod is .78.
Splitting gears, I get a bunch of gear ratios that I can use in different ways, like this;
3.09-2.41-1.92-(1.50-1.40)-(1.09-1.00)-.78od,( GV ratios in red). That's 8 gears, but 2 of them,as you can see, are too close together to be both used, so I use one or the other as a 4+1 most of the time, and occasionally as a 5+1
So usually,I shift 3.09-1.92-1.40-1.09-.78; splits of .62-.73-.78- and .71into od
When showing off; 3.09-2.41-1.92-1.50; splits of .78-.80-.78
With 3.55s that 1.50 ratio gets me 93mph @6150rpm, in the Eighth.
The starter gear is a delightful 10.97. I have tried every imaginable starter gear from 8.59 to 15.08; and 10.97 is just right for my engine.
As for my engine; She is not built for absolute power. Nor even for a lotta power. She was built for monster low-rpm torque, a big fat midrange, modest power at peak, and the ability to rev out to 7200.
 
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my engine
is nothing special.
4.04x3.58 KB 107s at .005 out of the hole. OOTB Aluminum heads, with .039FelPros making 10.95 Scr and .034Quench. Adjustable valve gear, Airgap and ancient 750DP. TTI headers and dual full-length TTI 3" mandrel-bent pipes.
The cam I was most happy with was a Hughes HE2430AL spec'd at
270/276/110 +2/53overlap(52effective)/116comp/110powr/Ica of 64*
.050s of 223/230; lifts of 538/549
The current cam is a Hughes HE 3037AL
276/286/110+2/61overlap(60 effective)/114comp/105powr/Ica of 66*
.050s of 230/237; lifts of .549/.471
This cam lost low-rpm torque, which I solved with the Commando box.
This cam makes lousy fuel mileage as compared to the previous one; Which I solved by retiring it from being a DD. Now I could care less how much fuel it burns; actually the more the better,lol.
This cam puts a lil top-end rush back, which I missed after retiring the first cam,which was the 292/292/108.
Otherwise the midrange seems about even
If you can, run a cross-over pipe; I lost quite a bit of low-rpm torque when I had to cut mine out to fit the GVod.
Knowing what I have come to learn from the FABO gang, my next cam will be a Solid lifter, tight-lash FT with a really tight LSA to work with my GV splitter. But maybe only same after lash specs as the current cam, or perhaps one size smaller.
 
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My GWAD. At the risk of writing a book, I'll just say the most economical thing you can do is stick with what you have, even if it means having it completely overhauled. As long as you don't "need" an overdrive, you HAVE the best three speed transmission on the planet.
 
(I will run it down the strip a couple/few times a year).
If that's true;IMO, for an SBM;
I wouldn't bother setting my streeter up for the strip to aim for low-ET.From optimum track set-up, to right-off-the-street is about a half second in ET. Maybe a lil more. Instead, I was content with the TrapSpeed of 93 mph@7.92 seconds, and knowing that there was probably over a half a second left in it, should I ever chose to pursue it.
If you bias your combo for the quarter, you will be way off optimum for street.
You can bias for Eighth, and be pretty close for street.
It's hard to beat a good TC at the track.
It's hard to beat a Commando box on the street.
A modern PP will take anything your streeter can dish out. With the skinny tires on your ride, so will a modern disc. Heat is mostly what kills the disc. And heat is mostly caused by; dragstrip starts with a crappy starter gear, or trying to drive too slow with said crappy starter gear slipping the clutch,and/or just plain having a weakazz PP. Avoid those and your clutch can last for many many years.
 
If you don't do freeway a lot I think you might stick with the 727.
Tis a sticky thing to consider. Every now and then I like to drive it up to my Paw's house. 120 mile ride on the interstate. I keep it to 60 mph (3,000 rpm). It still feels like I'm abusing it. I would just like it to feel more comfortable under all conditions.

Out of curiousity, what is the fluid level at? The trans in my Dakota would slip into neutral when the fluid was low. I had a rusted out pan. Be the first thing I check. I don't know on the rattling though.
Good question. I checked it just a few days ago when I rolled back into the driveway. It was about 20% down from the top line. I replaced the pan and pan gasket last year. And the fluid is as pretty and healthy as a horse.

If you are'nt handy with the tools on the more delicate stuff like trannies, then if I were you, I'd look at your pocketbook, decide how much you can throw at it. Then call A&A or Cope and tell them you want to spend X amount of dollars on the most bada** trans they can build you. You don't have to tell them how much $$, but I would start a conversation with them about what you desire and see if it works into your budget. I'd lean towards sticking with the 727 myself.....you can do a lot with them.
Lefty - I'm good with my hands, if I have the right tools. A) I don't have the right tools for a trans, and B) I know very little about a trans. Really considering taking a class specifically about automatic transmissions this summer at the local tech college. But even at that, I just have a normal house and garage. No lift. Pulling and replacing would be VERY difficult for me. I happen to have a few dollars available to waste on this kind of crap, so I'll take a look at A&A and Cope and see what's up with them.

My GWAD. At the risk of writing a book, I'll just say the most economical thing you can do is stick with what you have, even if it means having it completely overhauled. As long as you don't "need" an overdrive, you HAVE the best three speed transmission on the planet.
RRR - That makes TONS of sense. Maybe too much sense. I dream (and will start to put my dream in motion) of building a very nice engine on the side. So I can keep chugging along with the 360. Then when I have my dream engine built, swap it. Would want to have an ideal transmission ready to go at the same time. The 727 would be fine if I could turn 70 mph at say, 2,400 - 2,500 rpm. In the end, it's likely I'll just live with it.
 
"20% down from the top line"?!?!!? WTH does that even MEAN?? LOW is LOW. You've probably been running it low all this time. FULL means FULL. That means AT LEAST to the FULL mark. It's like a floor jack, not a motor.
 
"20% down from the top line"?!?!!? WTH does that even MEAN?? LOW is LOW. You've probably been running it low all this time. FULL means FULL. That means AT LEAST to the FULL mark. It's like a floor jack, not a motor.

Garsh ... settle down. My trans dipstick has 2 lines, or 2 dots. Indicating a full level, and an "add" mark. At the add mark it is supposedly 1 pint low. And for a torqueflite it is recommended to NOT go above the full mark. Mine was roughly 20% below the full mark.
 
Garsh ... settle down. My trans dipstick has 2 lines, or 2 dots. Indicating a full level, and an "add" mark. At the add mark it is supposedly 1 pint low. And for a torqueflite it is recommended to NOT go above the full mark. Mine was roughly 20% below the full mark.

What happens if you over fill a little?
 
What happens if you over fill a little?
The vehicle detonates immediately, like it was hit with a MOAB. :D

A little I suppose nothing. But something negative must happen at some level of overfill. I don't know what. Just what I read in some torqueflight info.
 
I rebuild these, and I'm shocked by how many people think a trans can operate just fine while it's low on fluid. They understand that it's a hydraulic unit, but think it's like a motor (which can run with NO oil). Their motor still runs when it's three quarts low, so why not the trans? Because the trans sucks air and burns up. Some think they don't have to have ANY fluid in it if it stays in Park. "Do Not Overfill" means so far up the stick that the spinning drums can aerate the fluid. Probably half of the transs that come in were destroyed by low fluid level. I've seen plenty of transs "20%" low that took a gallon to reach the full mark. I would overfill it half an inch.
 
Make sure the converter is full.... you just may be lower than you think.
 
If the trans is fried anyway, what can it hurt to dump another quart into it at least for testing?

Here's the dipstick pulled out and wiped from my 727.
What were you saying about low is low, full is full, and 20% down from the top line"?!?!!? WTH does that even MEAN??

Let me explain. The word that says FULL on the dipstick in the picture, it is just to the right of a stamped rib that forms a line. That stamped line indicates full. 20% down from that means that the trans fluid capacity was less than full and the top edge of the fluid was just to the left of the FULL line mark. Not as far down (to the left) as the ADD 1 PINT line. 20% down would be 1/5th of the distance toward the ADD 1 PINT line, but more close to the FULL line than to the ADD 1 PINT line. If the fluid level were at or very close to the ADD 1 PINT line, I personally would not add a quart (you might however or more), no ... I would not do that. I would add ... a pint. Now a pint is 2/4ths, or 1/2 of a quart. It's also very close to 6/12ths of a quart, or roughly 50% of a quart. And that's how much I would add, a pint. I wouldn't add 2 pints either, especially since the dipstick says add 1 pint.

But since I measured it, and it was between those 2 lines (closer to full line than the ADD 1 PINT line remember), that indicates to me at least that it was not low. Maybe I should have gotten a teaspoon and "topped off." But I did not. And I'm pretty sure the trans is not "fried" because the level was between the two marks and not at or above the FULL line on the dipstick.

Lastly, when I pulled that dipstick out of the trans cold, it was above the full line (to the right of the full line as pictured). I hesitate to mention an estimate of how far to the right so I don't get lambasted and have to explain that amount too. Let's just say, "it was way far above (to the right) of the FULL line.

I realize I may be wrong in this explanation since I have never rebuilt a transmission. FWIW.


7milesout
20200216_175850.jpg
 
FWIW; I got it when you first said it. And I have used the same terminology so, IMO, yur in good company.
It's the same way I mix 2-cycle gas; as 4% instead of 25:1.. If the tank only holds say 700 ml; I put 600 gas and 4% oil =28mls of oil. It cannot be any simpler.
Yet customers get so caught up in the method, I have to explain it almost every time.
It's like the
1260 days/ 42 months/ 3.5 years end-times tribulation period. Last week I heard a pastor say the tribulation started in 1975.... well waitaminute, that's 45 years ago,lol. I'm outtahere.
 
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You should be at 2800 rpm @ 60mph with the 24" tires. Why not slap on some 26" tires and slow her down to 2600 rpm? Also, FYI, at these RPMs you are not "abusing" anything.
 
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making some rattling noise and seems to be slipping into neutral when I come to a stop before everything gets warmed up.
And I'm pretty sure the trans is not "fried" because the level was between the two marks and not at or above the FULL line on the dipstick.
Maybe I should have gotten a teaspoon and "topped off."
Step 1: Learn all about fluid levels. Step 2: Become transmission expert. Step 3: Go racing!
 
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