I just found out I have an A999 can I swap out guts into a A904?

[jogirob]

I'm driving some 5 hours round trip to pick up a "new" A904 from the transmission shop and to drop off my core with the royally screwed up rear servo bore and piston. I just recently found out that I had one of the more beefier A904 derivatives. A 1978 PN #4028878 with the 5 clutches up front and 4 in the rear. I'm pretty sure I'm going to be picking up a standard 3 clutch front/rear A904.

Am I able to swap out the front and rear clutch drums and keep everything else from the "new" rebuild? If so I think I'll just hold on to my core. They're offering $250 for it and am driving myself mainly to save on core shipping since shipping for the refurbished unit is already covered.

https://www.forabodiesonly.com/mopar/threads/a904-vs-a999.32114/

 

[wyrmrider]

not a core you want to give up
can they make it like new? just stick the guts in a new case

 

[jogirob]

not a core you want to give up
can they make it like new? just stick the guts in a new case

I'd be swapping out the guts myself. They only sell their own rebuilt units.

If i'd had known the 5/4 clutch drums weren't the standard I would've just bought a replacement case instead of the entire thing :-/

Another option, bring the rebuilt unit I bought home, swap out the good parts, and send the core back with the weak parts? I do have 30 days to send in my core. Again this is IF it's possible to do at all.

 

[66Satellite47]

A 904 case from the bone yard should be pretty easy. Swap in the good stuff you have, replace with new parts that are needed. An HD 904 is worth a lot.

 

[69 GTX]

How do you identify a 999?

 

[jogirob]

How do you identify a 999?

Here's a helpful snippet from the forum link I posted:
"The A999 has 5 clutches in the front drum and 4 clutches in the rear drum. The A904 has 3 clutches in both the front and rear drum. Not all A999 are a lock-up type transmission. The part number is found on the drivers side just above the pan. The following is years and part #'s for A999. 1974-75 #3681844, 1976-77#4028465, and 1978 #4028878. This info is from the direct connection chassismanual. Other than the part # you cannot physically tell a A904 from a A999 [from the outside]. The factory only put A999's behind the 360 engine. Hope this sheds some light on the subject."

 

[dvw]

Unless you are using the entire guts, you have to watch the clearance between the reaction shaft support and the front drum. If the 999 isn't a lock up this isn't an issue. If it is then there's some work to br done in order to use the 904 input and pump.
Doug

 

[jogirob]

Unless you are using the entire guts, you have to watch the clearance between the reaction shaft support and the front drum. If the 999 isn't a lock up this isn't an issue. If it is then there's some work to br done in order to use the 904 input and pump.
Doug

Yea I just read that these 999's have additional pinions in the planetaries for strength. Might as well take the entire input assembly. They're both non lockup units.

 

[dvw]

We had one long ago and made this swap. Machined the stator support for clearance. Also the front inner clutch hub lenghts are different for 3,4,5 clutch as I remember. Been along time ago.
Doug

 

[rmchrgr]

I wrote the post (see below) a while ago for FABO because there always seems to be confusion regarding these transmissions. It's more of a 'how to identify an A999' type deal but there is some other info in there.

https://www.forabodiesonly.com/mopa...on-lockup-a999-transmission-with-pics.307306/

Incidentally, I actually got some of the info from Moparts. DVW's son Dizuster posted a long thread where he detailed building one up several years back, They know what they are talking about with the clearances.

BTW, I have 6 frictions in my 5 clutch drum A999. I got them from A&A.

 

[Dipstick]

When swapping '78-later guts into anything earlier you have to use the pump that goes with the input shaft and rear clutch. They changed the sealing rings configuration so parts won't interchange with earlier.

 

[jogirob]

https://www.forabodiesonly.com/mopa...on-lockup-a999-transmission-with-pics.307306/

That is one juicy morsel of information! Thanks.

When swapping '78-later guts into anything earlier you have to use the pump that goes with the input shaft and rear clutch. They changed the sealing rings configuration so parts won't interchange with earlier.

Man am I glad I decided to bring my core back. The refurbished one I bought seems to be a 1977 unit. I cannot find the P/N in the tranny number guide. Only one way to find out! About to go out in the freezing cold just because I'm so curious. BTW p/n is PK4028483. 10,000 calendar# is 5751.(1977)

 

[jogirob]

Huzzzah! 5 clutch front 4 clutch rear and 4 pinion planetaries! As soon as I saw that bevel when I took the pump off I was like "Score!" Bad news is that I could've just dropped off my core since I didn't need to swap in anything. Oh well, I'm sure my old HD A999 is worth more than $250. If only I could un-seize that blasted rear servo and polish the bore...

 

[66Satellite47]

Get another case, re-use the quality parts.

 

[rmchrgr]

Get another case, re-use the quality parts.

Yep, per my thread on FABO, 904 cases are basically all the same.

When I built the trans for my Duster, I decided against using the OE 999 case because it was hammered. I got a 'race-prepped' case from A&A. No idea what year/application it was from but given the slim chance of it being an actual non-lockup 999, it was most likely a garden variety V8 904.

Regardless, it all fit together without issue. They clean the case to brand new, provide a cutout on the bottom for converter bolt access, weld a threaded fitting on the rail to be able to adjust line pressure without removing the pan and another threaded fitting for a Transbrake. They also tap the rear of the case for an external vent. Nice piece, worth the money if you're into it.

 

[dvw]

Now that I read the attachment we used the 1" clutch hub with the 5 plate front clutch. It kept smoking the clutches only when raced. Turns out the end clutch friction would slide off the splines and rotate. be careful if you mix and match. However the reaction shaft support can be machined for 5 plate drum clearance. I believe the 999 we started with was a lock up. Eventually if I remember (long time ago) we pressed the lockup shaft out of the 5 plate clutch hub and swapped it with the non-lock up shaft. Worked fine after that.
Doug