400hp and a lock up transmission ?

[ValerianMagnum]

Hi guys changing my 727 soon for a stock one with hduty parts , we will see but im pretty sure im gonna hate it ( had a 727 with a 2900 stall and s-kit ) i went crazy this summer and bought 4x 904 trans and 4-5 set ups of kickdowns ( oem + lokar ) my question is that 3 of my 4 904s are lock ups and my last one looks like a a999 if i compare the stamping numbers ( 80s vans ) can a 380hp crate engine kill this trans ? My duster is a street driven car and i heard with time that a 904 can hold up a 360 without a problem and its a lot lighter , 727s are getting very hard to find in my area ( montreal canada ) worth to rebuild a 904 for the next season or ?

 

[RustyRatRod]

4th one down is a slant 6 transmission, I believe. That said, hell yeah you can break one with a 380 crate engine. You'll need to build it to suit.

 

[ValerianMagnum]

Yes 4x from a 318 / 360 and one for the guts ( slant 6 trans lock up too

 

[Professor Fate]

Are you SURE those are lockups?
Lockup A999/32RH:

Your tailshaft housings look like standard 904, and I see no connector for the lockup override (tow/haul switch)...
Check your input shafts-
lockup (top) vs. non-lockup (bottom):

(pic borrowed from rmchrgr)
Also, the splines differ between the two- I forget the counts offhand, though.
As for your original question: will they live?
Just like any 904 based trans; they'll live if you build them for it.

 

[Professor Fate]

How to identify a non lockup A999 transmission with pics! | For A Bodies Only Mopar Forum
Worthy of note: not all A999s are lockup, nor are they all low gearsets...

 

[Murray]

Both 904 and 727 will handle big horsepower if built properly.

 

[Clelan]

Looking at the 2 photos above, the one below with splines all the way to the end of the input shaft is non lock up. The one with the rounded smooth end on the input shaft is the lock up.

Cley

 

[pt70]

Chrysler put 727's in 340 cars for a reason, they are rugged. 904's can be built to take more horsepower, but it's going to cost you. Talk to the guys at the drag strip, they would be a good source of information and maybe recommend a good trans man.

 

[mderoy340]

I've run a lockup 999 from a 84 diplomat behind my 340 for years. Stock internals, Trans Star rebuild kit, TF2 shift kit, lockup circuit plugged, A&A HD front band, TA 10" 3400 tight converter. The OEM front drum has 5 clutches and you can fit 6 thin ones if you wanted to. The lockup input shaft has worked for me with no failures. The weak point is the OEM converter hub design.

I sent my converter to Turbo Action and had them modify it to a slotted drive. They also modified the pump to accept the slotted oil pump gears. This modification has been working great. I drive my car 50 miles to the track, run 4-5 passes and drive home. I'm around 400hp and run 11.60s in the winter air, 11.80s in summer heat.