A998 Trans in '66 Dart

-
These are the part numbers from the Mopar Chassis book for A999 H.D. trans for 360( they first appeared in the 1974 360 4brl cars) All of the part# below had 2.45 first gear sets as far as I know, except the P parts trans that could have had the 2.74 gear set( I do not know for sure)
74-75 PN3681844 A999 non lock-up
76-77 4028465 A999 non lock-up
1978 4028878 A999 non lock-up
4028815 A999 lock-up
4058111 A999 lock-up
1979 4130515 A999 lock-up
4130645 A999 lock-up
P parts trans/ P4130400 A999 non lock-up(with man. v.b.)
PN3743382 A999 5 disc front clutch retainer, 1942403 front clutch plates(5 required) 2205203 front clutch disc(5 required)
My book only goes up to 1979 so this is all the part numbers I can give for the A999 and this same book says the A998 trans came out in 1968( I thought I was told 67 I was wrong) as an H.D. trans for the new LA 318. I had 3 of A999 transmissions back when I was racing my 69 GTS Dart W2 360(3681844) that was built by Turbo Action with a low gear set. I put that one in my 80 Mirada but the new W2 372 engine and the low gear set didn't like to play nicely together, so I found another(844) in a 75 360 Cordoba( which was a standard 2.45 gear set) and put it in the Mirada. Soon after I pick up a spare A999 part # 4028465(2.45 gear set) and If I remember right it came out of a 76 Plymouth Fury 360 2brl . My trans guy told me at the time what cars with 360 engines to look for transmissions in.
 
Since this low gear thing has been kicked around now a bit. I'd like to know what that 1st gear ratio is and how it compares to what other brands are running at the strip.
 
19DART66 said:
These are the part numbers from the Mopar Chassis book for A999 H.D. trans for 360( they first appeared in the 1974 360 4brl cars) All of the part# below had 2.45 first gear sets as far as I know, except the P parts trans that could have had the 2.74 gear set( I do not know for sure)
74-75 PN3681844 A999 non lock-up
76-77 4028465 A999 non lock-up
1978 4028878 A999 non lock-up
4028815 A999 lock-up
4058111 A999 lock-up
1979 4130515 A999 lock-up
4130645 A999 lock-up
P parts trans/ P4130400 A999 non lock-up(with man. v.b.)
PN3743382 A999 5 disc front clutch retainer, 1942403 front clutch plates(5 required) 2205203 front clutch disc(5 required)
My book only goes up to 1979 so this is all the part numbers I can give for the A999 and this same book says the A998 trans came out in 1968( I thought I was told 67 I was wrong) as an H.D. trans for the new LA 318. I had 3 of A999 transmissions back when I was racing my 69 GTS Dart W2 360(3681844) that was built by Turbo Action with a low gear set. I put that one in my 80 Mirada but the new W2 372 engine and the low gear set didn't like to play nicely together, so I found another(844) in a 75 360 Cordoba( which was a standard 2.45 gear set) and put it in the Mirada. Soon after I pick up a spare A999 part # 4028465(2.45 gear set) and If I remember right it came out of a 76 Plymouth Fury 360 2brl . My trans guy told me at the time what cars with 360 engines to look for transmissions in.
Click to expand...

Cool, thanks for this. I actually "learnt" me a couple of things. I didin't know the 998 and 999 ever came as a non lockup, nor did I know they were introduded that early. Thanks.
 
The 999 I'm going to put in my 65 Barracuda must be a 80's model. My book doesn't list it, and the number is beyond any listed here previously. I've Googled it to death, but must be wording the search wrong! :realcrazy: It's P4295887 7966 5768. It's a lockup for sure, and I'm hoping it's the low 1st gear.
 
Get the convertor hub changed to your 65 small hub crankshaft or change your crank to a >67. Can adapt an early trans to fit a later motor with hub bushing but not the other way around.
 
roccodart440 said:
Since this low gear thing has been kicked around now a bit. I'd like to know what that 1st gear ratio is and how it compares to what other brands are running at the strip.
Click to expand...
904/727 ratios are 2.45-1.45-1.00; some 998s are this as well
some998/all999 are 2.74-1.54-1.00

The standard ratios could be considered "close ratio" compared to the 999 ratios.
 
pishta said:
Get the convertor hub changed to your 65 small hub crankshaft or change your crank to a >67. Can adapt an early trans to fit a later motor with hub bushing but not the other way around.
Click to expand...

I have a 273 block, and if I use it....it will be with a 318 or 340 crank. I'm pretty much leaning towards building a 318 or 340 though. "Somebody" has a sig line that makes pretty good sense.....lol. Now, back to our regularly scheduled tranny :eek: discussion!
 
JDMopar said:
The 999 I'm going to put in my 65 Barracuda must be a 80's model. My book doesn't list it, and the number is beyond any listed here previously. I've Googled it to death, but must be wording the search wrong! :realcrazy: It's P4295887 7966 5768. It's a lockup for sure, and I'm hoping it's the low 1st gear.
Click to expand...

I found out it's from an 84 5th Avenue or Diplomat. :thumbsup:
 
was the A998 ever used in a Mopar? I thought they were all A999's. 998 lists for AMC but could be wrong.
 
I have at least one example of each, in one of my sheds. They all came out of Mopars that I stripped many years ago.
As far as I can tell , the A998 is mostly a non-lock up A999, but could have 904 ratios.It appears to be hybrid,lol.
I have not studied it out.
 
pishta said:
  • looks like the 998 was rated lower in torque capacity. often wondered why a trans maker would make a lower rated trans when the design is 99% the same.
Click to expand...
$$$$$$$ It looks like there's a difference in the gear ratios between the two depending on the application and the A999 has a 5 disc direct clutch.
 
I think that the gear ratios might be the torque handling difference.
So, to me ,I'm guessing the torque handling difference was the fall-out of the gearchange,not the other way around.

That 2.20 rear gear of the Chryco's needs the 2.74 low in the 999, for a starter gear of 6.03
But 2.45gears can use either ratio depending on 225 or 318, so starters of .....6.00 and 6.71
And by 2.76 rear gear, the 904 is fine, with a starter of .............................................6.76.
Thus it is possible to have similar starter gears but vastly different cruiser gears, namely;
2.76,2.45,and 2.20. Kindof a poor-man's overdrive, when performance is not required.

Long ago, I pulled the 2.74 ratio stuff out of a slanty case and stuffed it into a 904 case to get a wide ratio 904 without loc-up. With 3.55s, this makes a starter of 9.73, which is the equivalent of a 904 with 3.97s.
To that,I added; a 2800TC, headers, a TQ on a small-port intake, and 5500 rpm valve springs. This worked great behind an otherwise stock smogger318, in my Barracuda, and was a funtastic combo.
I also ran that combo with gears down to 2.76s, and with the 2800TC, they were all doable.
I had all this stuff laying around for decades,so no extra cost to me.

There is one caveat; you must not mix 904 planetaries onto 998/999 output shafts; or vice versa. The spline count is the same, so they do fit; but the shape of the splines are different, and the 904 shaft will strip the splines out of 998/999 aluminum planearies in just a few shift cycles. and Zing!, yur walking.
 
OP,
I gotta tell you something, in case you don't know it.
The way that the TC works is that it multiplies the torque coming into it , to a higher number and sends that into the trans. This is called Torque Multiplication.
The ratio of torque in, to torque out, can be as high as 1.8 or more. The ratio is highest at zero mph, and diminishes rapidly as the car gains mph, and usually ends up at around 1.1 to 1.05, at some higher mph in top gear.
If you think about this, the TC is a completely autonomous device automatically varying it's "gear ratio" between 1.8 and 1.05, as load dictates. It's like a 2:1 transfer case but with infinitely variable inbetween ratios, and you don't have to yank the lever.

Ok so, if you compute the gear ratios to get TM numbers into the rear axles, with a wide ratio box, and include a lock-up, this is what it might look like, with 2.94 rear gears.
First gear at zero mph; ........... 2.94x2.74x1.8=14.50
same but at the top of first; ...... 2.94x2.74x1.2=9.66
Second gear; .......................... 2.94x1.54x1.2=5.46
Third gear; ............................. 2.94x1.00x1.1=3.23
Third, in loc-up; ...................... 2.94x1.00x1.0=2.94
How many actual gears is that?
Yeah, I count 5 too.

As to the torque multipliers, I did the best I could at guessing them. They could be wrong, but the point is the same, namely; that you end up with 5 working ratios; well actually 4 plus the magical autonomous TC.

As to 2.94s; I choose them, for this exercise, cuz
Firstly; 65=2375 with 27" tall tires. This is a reasonably comfortable rpm that still allows 75=2740, and I know how Americans love to open it up on their great hiways. and
Secondly; I also chose it for use in the lightweight-A cuz with a 2800TC, and any V8, this is all you need. More gear equals longer tirespin.
Thirdly; rear gears are cheap and easy to change.

I have driven this combo with a smoggerteen and a 2800TC and never lacked for power. The teener was stock except for headers and a TQ on a smallport cast iron factory intake. I admit 3.23s were a lil more fun. My combo did not have a loc-up feature, and 3.55s were the limit for me.
As to stall;
Next, by experience, I can tell you that with used 295/50-15 BFG tires, you will need about 2200 to 2500 ftlbs to the asphalt, to break them loose, and once spinning,less.
That means we can now back-calculate the crank torque required to do that.
So , I know you can't fit 295BFGs into your stock tubs, so lets go with 27" tall whatever fits, and a requirement of 2200.
2200/14.50 (with these 2.94s)=152 crank footpounds. So now all you gottado is choose a Stall-speed that will get you 152 ftlbs, and you are guaranteed to be able to break the tires loose. This does not guarantee how far they're gonna spin tho,lol.
The stall rpm will vary by engine displacement, and engine efficiency.
Generally; the bigger the engine,or the higher the efficiency; the lower the rpm can be.
As to the loc-up
But hang on, the above combo includes a loc-up feature, soooooooo, you don't "have to" select the lowest possible stall that will still spin the tires.
Now, you can bias the stall for performance somewhere else, and
#1) I like the power to be at ~32 mph .
So in the above case, with 2.94s; 32mph will be 3200rpm in first, 1800 in second. Say you are cruising along at 32mph,in second, cuz 1800 is very comfortable; but you want to increase your speed briskly, without the trans downshifting. 1800rpm will not give you much acceleration power; at least not to satisfy your requirement at this time. But if you had say a 3200TC, then your engine would be at the same power level, as if it had downshifted. She'll still be stuck with a 1.54 ratio versus 2.74, but now the torque difference at 3200 versus 1800 may satisfy the need. How sweet is that!
#2) Another time, is to overtake a slowpoke, on the hiway, who is doing say 58mph. In loc-up, you are doing 2100.Disengaging, your engine pops up to 2330, which, with a regular stall TC, will take a mile to pass that guy. If you downshift into second, the Rs pop up to ~3400, and away you go.
But if you had a 3400TC maybe your engine might have enough torque to pull off the pass in top gear, cuz instead of 2330, you are now at 3400. How sweet is that!

Of course, you might have other than 2.94 gears with different rpms; but the point is the same; with the loc-up feature, you are no longer married to a crappy stall.

And with the patterns here provided you can dial in your combo to suit your needs, with a pseudo 5-speed automatic.

BTW;
With this kindof thinking, your lightweight-A doesn't need the wide ratios. If you used a a regular 904 with loc-up, and a 2800TC, this would provide all the same benefits with the advantage of the closer ratios. The new numbers , still with 2.94s are;
A)12.97-8.64-5.11-3.23-2.94.. splits of .67-.59-.63-.91 Compare to the wide
B)14.50-9.66-5.46-3.23-2.94...splits of .67-.56-.59-.91
If you really need a deep low, then try 3.23s with a 904 at;
C)14.24-9.50-5.62-3.55-3.23 splits same as A) This would allow less stall but a higher cruise rpm. As for me, I am willing to cruise at 60=2400, And my cam sorta requires it, so this last combo is what I would run, still with the 2800TC; I love that thing.

If you're sharp, you will have noticed that the loc-up is worth one gear size or ~9% . So it will drop your cruise rpm that same 9%. This is not a fixed number.If you're cruise rpm in non-lock up is 2500rpm, then the lock-up is worth ~225rpm, if 3000, then ~270

Happy discovery Trails

EDIT; I may have mis-estimated the TM in the TC, so I'm gonna go back and do some re-calculations, to better illustrate the ratios. Not much is gonna change, but in the interest of accuracy, I'm gonna change it . And done.
 
Last edited:
Wow. So what i am getting from this is that the 998 and 999 are the same dimensions as the 904, with the later (post74/75 or so) having lower gear ratios. My questions are; Does the lower 1/2 gear ratio create a extremely large split between 2/3?? Is that really a bad thing, having the lower gear ratios concerning acceleration?(say 1/4mi.). I built a 318/331 using the format from the Hot Rod magazine (approximately - with a few of my own touches) and am pretty certain it makes close to 400hp (no affordable local dyno). With the small wheel wells in the early A body, it may be beneficial to have the lower 1/2 to get the tires to hook more quickly? (i have a car that I do NOT want to mini tub or hack up!) Last questions - how do I identify the early/late 998/999 trans without disassembly and does anyone within a 500 mile drive from Seattle have one they want to part with! :) Thanks! Major0014/Cheech14
 
AJ/FormS said:
OP,
I gotta tell you something, in case you don't know it.
The way that the TC works is that it multiplies the torque coming into it , to a higher number and sends that into the trans. This is called Torque Multiplication.
The ratio of torque in, to torque out, can be as high as 1.8 or more. The ratio is highest at zero mph, and diminishes rapidly as the car gains mph, and usually ends up at around 1.1 to 1.05, at some higher mph in top gear.
If you think about this, the TC is a completely autonomous device automatically varying it's "gear ratio" between 1.8 and 1.05, as load dictates. It's like a 2:1 transfer case but with infinitely variable inbetween ratios, and you don't have to yank the lever.

Ok so, if you compute the gear ratios to get TM numbers into the rear axles, with a wide ratio box, and include a lock-up, this is what it might look like, with 2.94 rear gears.
First gear at zero mph; ........... 2.94x2.74x1.8=14.50
same but at the top of first; ...... 2.94x2.74x1.2=9.66
Second gear; .......................... 2.94x1.54x1.2=5.46
Third gear; ............................. 2.94x1.00x1.1=3.23
Third, in loc-up; ...................... 2.94x1.00x1.0=2.94
How many actual gears is that?
Yeah, I count 5 too.

As to the torque multipliers, I did the best I could at guessing them. They could be wrong, but the point is the same, namely; that you end up with 5 working ratios; well actually 4 plus the magical autonomous TC.

As to 2.94s; I choose them, for this exercise, cuz
Firstly; 65=2375 with 27" tall tires. This is a reasonably comfortable rpm that still allows 75=2740, and I know how Americans love to open it up on their great hiways. and
Secondly; I also chose it for use in the lightweight-A cuz with a 2800TC, and any V8, this is all you need. More gear equals longer tirespin.
Thirdly; rear gears are cheap and easy to change.

I have driven this combo with a smoggerteen and a 2800TC and never lacked for power. The teener was stock except for headers and a TQ on a smallport cast iron factory intake. I admit 3.23s were a lil more fun. My combo did not have a loc-up feature, and 3.55s were the limit for me.
As to stall;
Next, by experience, I can tell you that with used 295/50-15 BFG tires, you will need about 2200 to 2500 ftlbs to the asphalt, to break them loose, and once spinning,less.
That means we can now back-calculate the crank torque required to do that.
So , I know you can't fit 295BFGs into your stock tubs, so lets go with 27" tall whatever fits, and a requirement of 2200.
2200/14.50 (with these 2.94s)=152 crank footpounds. So now all you gottado is choose a Stall-speed that will get you 152 ftlbs, and you are guaranteed to be able to break the tires loose. This does not guarantee how far they're gonna spin tho,lol.
The stall rpm will vary by engine displacement, and engine efficiency.
Generally; the bigger the engine,or the higher the efficiency; the lower the rpm can be.
As to the loc-up
But hang on, the above combo includes a loc-up feature, soooooooo, you don't "have to" select the lowest possible stall that will still spin the tires.
Now, you can bias the stall for performance somewhere else, and
#1) I like the power to be at ~32 mph .
So in the above case, with 2.94s; 32mph will be 3200rpm in first, 1800 in second. Say you are cruising along at 32mph,in second, cuz 1800 is very comfortable; but you want to increase your speed briskly, without the trans downshifting. 1800rpm will not give you much acceleration power; at least not to satisfy your requirement at this time. But if you had say a 3200TC, then your engine would be at the same power level, as if it had downshifted. She'll still be stuck with a 1.54 ratio versus 2.74, but now the torque difference at 3200 versus 1800 may satisfy the need. How sweet is that!
#2) Another time, is to overtake a slowpoke, on the hiway, who is doing say 58mph. In loc-up, you are doing 2100.Disengaging, your engine pops up to 2330, which, with a regular stall TC, will take a mile to pass that guy. If you downshift into second, the Rs pop up to ~3400, and away you go.
But if you had a 3400TC maybe your engine might have enough torque to pull off the pass in top gear, cuz instead of 2330, you are now at 3400. How sweet is that!

Of course, you might have other than 2.94 gears with different rpms; but the point is the same; with the loc-up feature, you are no longer married to a crappy stall.

And with the patterns here provided you can dial in your combo to suit your needs, with a pseudo 5-speed automatic.

BTW;
With this kindof thinking, your lightweight-A doesn't need the wide ratios. If you used a a regular 904 with loc-up, and a 2800TC, this would provide all the same benefits with the advantage of the closer ratios. The new numbers , still with 2.94s are;
A)12.97-8.64-5.11-3.23-2.94.. splits of .67-.59-.63-.91 Compare to the wide
B)14.50-9.66-5.46-3.23-2.94...splits of .67-.56-.59-.91
If you really need a deep low, then try 3.23s with a 904 at;
C)14.24-9.50-5.62-3.55-3.23 splits same as A) This would allow less stall but a higher cruise rpm. As for me, I am willing to cruise at 60=2400, And my cam sorta requires it, so this last combo is what I would run, still with the 2800TC; I love that thing.

If you're sharp, you will have noticed that the loc-up is worth one gear size or ~9% . So it will drop your cruise rpm that same 9%. This is not a fixed number.If you're cruise rpm in non-lock up is 2500rpm, then the lock-up is worth ~225rpm, if 3000, then ~270

Happy discovery Trails

EDIT; I may have mis-estimated the TM in the TC, so I'm gonna go back and do some re-calculations, to better illustrate the ratios. Not much is gonna change, but in the interest of accuracy, I'm gonna change it . And done.
Click to expand...

Really cool calculating. I however, have read someplace (probably on the internet, so you know it has to be true) that if you run a stall speed higher than your cruising rpm that the TQ generates an unacceptable level of heat. Hmmm. Heat is not our pal. Now, I know that it is not always the "Great White North" in Manitoba (dad was born in Sask.) so this has to be at least a seasonal concern! Thanks, Cheech/ R/T / Major0014
 
The 999 ratios allow the next smaller rear end to be used for the same starter gear. This allows about 10% less cruise rpm for the same speed.

In the lightweight As, I don't see a point for the lower gears,except for the cruise advantage.

If you don't tub your car, you cannot run a big enough tire to not be spinning with 400hp, for most of the Eighth or more anyway, so I wouldn't worry about the difference in the trans ratios.
But, in your case, yeah, the power band might be a ill narrow 7
The transmission has a PN stamped on the panrail that someone here can look up for you. I have heard that some to most of them have the model number cast on the top of the bellhouse.
ict
I have heard it said on FABO that modern TCs don't suffer those overheating woes. But I imagine if the stall is very much higher than the cruise, I would still run a cooler.

The thing is, that with 400hp, in a stock body, for a streeter, I see no good reason to run race gears, nor a very high stall., because the engine is way overkill anyway and is gonna commence spinning the skinny donuts almost right out of the gate.
Oh wait, you said 331 cubes. To get 400 from just 331 means that you are running a very big cam and a Lotta compression, which sorta forces you to run those big rear gears, so, ok, I get it. And the bottom end will be soft, forcing you to run a big TC, I get that too. So then the A999 is making sense. But with a 3000/3500 stall you are still gonna blow the launch with whatever skinny tires you manage to fit in the back. So then, you can get a loc-up in those A999s
But in your case the power band might be a lil narrow to properly pull those A999 ratios,.IDK., unless you do in fact run a very high stall. But again, I just don't get why you would build a combo like that and then put skinny tires on it.
What am I missing



.
 
Last edited:
All of the above is very interesting BUT no one mentioned that the ‘66 crankshaft pilot hole is smaller then the later lock up converter snout .
So one would have to machine the pilot hole out to except the T .C .snout .
 
GGs66GT said:
All of the above is very interesting BUT no one mentioned that the ‘66 crankshaft pilot hole is smaller then the later lock up converter snout .
So one would have to machine the pilot hole out to except the T .C .snout .
Click to expand...

Precision of New Hampton will put any converter front on it you want. Even a Chevy or Ford. lol
 
GGs66GT said:
All of the above is very interesting BUT no one mentioned that the ‘66 crankshaft pilot hole is smaller then the later lock up converter snout .
So one would have to machine the pilot hole out to except the T .C .snout .
Click to expand...

JDMopar said:
I have a 273 block, and if I use it....it will be with a 318 or 340 crank. I'm pretty much leaning towards building a 318 or 340 though. "Somebody" has a sig line that makes pretty good sense.....lol. Now, back to our regularly scheduled tranny :eek: discussion!
Click to expand...

Post #31 quoted in #34. :)
 
You must log in or register to reply here.
-

Back
Top