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MM/D50 "Baby A904" Narrowblock Auto?


Dave-O
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I'm chasing my options for automatic transmissions that bolt up to narrowblock 4G63s/G63Bs and have somewhat of an aftermarket. I didn't want an automatic for the track car, but it's perfectly acceptable [and somewhat preferred] for a big-turbo street/strip daily-driver.

 

I've been told, and have read, that the baby A904 can be built just as stout as the slant-6 and V8 versions of the Torqueflite. I'm also looking at higher-stall converter options [3000+rpm] and possibly a trans-brake or manual valve body.

 

Anyone have some insight to building/sourcing one of these? I'm under the impression they came in pre-'86 Mighty Maxes and D50s with the G63B.

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I'm chasing my options for automatic transmissions that bolt up to narrowblock 4G63s/G63Bs and have somewhat of an aftermarket. I didn't want an automatic for the track car, but it's perfectly acceptable [and somewhat preferred] for a big-turbo street/strip daily-driver.

 

I've been told, and have read, that the baby A904 can be built just as stout as the slant-6 and V8 versions of the Torqueflite. I'm also looking at higher-stall converter options [3000+rpm] and possibly a trans-brake or manual valve body.

 

Anyone have some insight to building/sourcing one of these? I'm under the impression they came in pre-'86 Mighty Maxes and D50s with the G63B.

 

To my knowledge, the little Torqueflite differed only in bell pattern, and the internals were identical to those of the Chrysler-badged products as was the length from the rear engine (trans) mount to the output (main) shaft, since they used identical mainshafts and tailshaft housings. I'm not sure about the Mitsu stuff, but the A904 was dead by '81, leaving the A998/A999 as the sole light-duty trans. This isn't such a bad thing, since they used a deeper 2.74:1 low gearset, but most of them were lockup, and a true HD lockup converter still hasn't been developed. I helped swap a 340 into an '84 D50 as well as putting a 360 into an '83. In both cases, we used the rear trans mount as a locator to get the front motor-mount brackets into place. The '84 was a 4WD, the '83 a RWDer (and a damned rocket, I might add). Both the shift and the (engine-correct) kickdown linkage dropped into place as if the V8s were born there.

 

In similar years, the A727 and the A904/A998/A999 used the exact-same valve body, assuming they had the same converter style (lockup or non-lockup).

 

Yes, the A904/A998/A999 transmissions can be built to be extremely strong. In fact, virtually every competing SS/A auto car uses A904 internals in an A727 case (1968 Hemi Dart/Barracuda). Stout? Yes. Cheap? Not even close! Then again, those cars run mid-8s. Depending on your build, a sturdy A904-based trans can be built for a lot less money. As always, how fast you want to go is dependent on your wallet. The parts are there if you can afford them.

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I mentioned the valve-body similarity so you'd know that a trans brake for an A727 will fit a similar-year A904/A998/A999 and work perfectly. Also, it appears that for what you're doing, the A998/A999 gearset would be preferable with its 2.74 low gearset (as opposed to the A727/A904 2.45 first gear). Launch, baby!

 

The A727 internals are idental between big-block version (A727B) and small-block (A727A), with the exception of the Hemi and truck transmissions which used a 4-pinion planetary and a 5-disc front drum.

 

Here's something worth investigating: because of their similarity, I'm thinking you may be able to use the D50 forward case on an A500 (the A904-based overdrive transmission used in light-duty 2WD trucks). I don't know if it works because I've never tried it, but how cool would it be to have that .69:1 overdrive at the flip of a switch? Hit the button and a 4.56 gear suddenly becomes a 3.15. Though the A500 is a lockup trans, changing the valve body, forward case, and converter might circumvent that, leaving your high-stall converter options open... of course, even with the overdrive your highway RPM would still be at your stall RPM. It's definitely worth researching.

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  • 3 months later...

I mentioned the valve-body similarity so you'd know that a trans brake for an A727 will fit a similar-year A904/A998/A999 and work perfectly. Also, it appears that for what you're doing, the A998/A999 gearset would be preferable with its 2.74 low gearset (as opposed to the A727/A904 2.45 first gear). Launch, baby!

 

The A727 internals are idental between big-block version (A727B) and small-block (A727A), with the exception of the Hemi and truck transmissions which used a 4-pinion planetary and a 5-disc front drum.

 

Here's something worth investigating: because of their similarity, I'm thinking you may be able to use the D50 forward case on an A500 (the A904-based overdrive transmission used in light-duty 2WD trucks). I don't know if it works because I've never tried it, but how cool would it be to have that .69:1 overdrive at the flip of a switch? Hit the button and a 4.56 gear suddenly becomes a 3.15. Though the A500 is a lockup trans, changing the valve body, forward case, and converter might circumvent that, leaving your high-stall converter options open... of course, even with the overdrive your highway RPM would still be at your stall RPM. It's definitely worth researching.

 

 

i've done it, my mighty max has the 90+ mighty max auto tranny and it is indeed an a500 and can use all a500 chrysler parts inside. mine is in the shop being built as we speak, as for the torque converter i have to have one custom built, but that's worth it to me so i can stop taking the teeth off the manual mighty max gears.

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i've done it, my mighty max has the 90+ mighty max auto tranny and it is indeed an a500 and can use all a500 chrysler parts inside. mine is in the shop being built as we speak, as for the torque converter i have to have one custom built, but that's worth it to me so i can stop taking the teeth off the manual mighty max gears.

 

the pre '89 trannys are a904 and can be built the same way btw.

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  • 3 weeks later...
I was building a 4g63/a904 conquest. When i traded off the project I had just had the trans done. I did 727 manual valve body with trans brake, and a 5000 stall. The baby case 904 is the only one i know of the will bolt to the 4g. I research all my options at the time and elected to run that trans instead of doing an adapter plate. I was shooting for 1000hp. The turbo was a 372BW and has proven to be streetable to some people :blink: If you are interest in the a904, I may be able to supply you with a useable unit. PM me if you are interested. Good luck with your build.
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  • 2 weeks later...
Hey mighty max who's doing your a500 trans and how much power will it hold? I've got a 4g64 thats making some power, maybe 400 plus and i'm thinking of putting an auto in. I was thinking of a built 700r and bills adapter but this might be an option. Thanks for any info....
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