OK- I am tearing into my first 904 rebuild. The transmission is a completely stock A-904 out of a 1979 Aspen. The history of the transmission is that it was pulled from the Aspen, given to me (thanks again sixshot!) and I installed it in my brother's van. It worked beautifully until one of the rubber hoses between the transmission and the cooling lines developed at crack while my brother was driving it. It must have been in the supply line because the transmission fluid sprayed directly onto the exhaust pipe and made quite a smoke show as my brother drove down the highway. The transmission started slipping worse and worse until it barely moved the van at all by the time my brother got it home. When I pulled the transmission off the van it was totally empty of fluid.

Surprisingly, despite the fact that the transmission is a 1979 version with the early lockup module, the lockup feature never had a problem.

i am rebuild this transmission for use in my brother's 1974 Duster project car. I am doing a stock rebuild for now, not even a shift kit installation. I just want to rebuild this transmission totally stock and plain. Depending on how it works out, I might pull the valve body and install a shift kit later. I just want to rebuild it and make sure it works in stock form before I go modifying it.

Today I began disassembly of it and I have a few questions.

FRONT CLUTCH ASSEMBLY



This is the front clutch pack as pulled from the transmission. Things to note: (1) there are only three clutch plates; (2) the first clutch plate has nearly all the clutch material stripped off of it and the middle clutch plate has all the clutch material stripped off (I guess that is why the van wouldn't move!); and (3) you can't really tell, but the third clutch plate is actually cupped.

Questions regarding front clutch assembly:

(1) I have read that more clutch plates are better, and that sometimes you can just add more discs during a rebuild. The rebuild kit I am using has at least one extra clutch disc and driving disc, possibly two. Can I just stuff an extra one or two clutch plates and driving discs into the piston retainer assembly or would I need to get a different retainer? (See the third picture to see how much room I have between the snap ring and the top of the first pressure plate)

(2) The rebuild kit I purchased has two separate stacks of new clutch plates and driving discs- presumably one for the front assembly and one for the rear. however, the kit does not indicate which stack is which. Should I match the replacement clutch plates to the application by the texture of the clutch material? The front clutch plates have a tight orthogonal/checkerboard pattern of grooves in the clutch material and the rear plates have a much broader series of lines. The replacement clutches have a stack of each pattern clutch plates.



I suspect the replacement front clutches are on the bottom and the rear clutches are on the top. Do I just match the texture pattern to the old clutch discs?

(3) The front clutch retainer bushing appears to be scored and worn. What do you think?



Should I replace it?

(4) In a stock daily driver transmission is it worth it to replace the wavy front clutch snap ring with a flat one?

REAR CLUTCH ASSEMBLY



Surprisingly, the material on the clutch plates looks fine.

Questions regarding rear clutch assembly:

(1) Is there any reason to try and shove in a fifth clutch plate on the rear clutch assembly?

(2) I noticed that housing around the piston spring that holds in the piston in the rear clutch pack appears scored like something is malfunctioning inside the rear clutch pack:



Is this sloppy manufacturing and should I ignore it or is it a problem and should I replace the clutch retainer?

(3) I know I need to pull the tailshaft housing to get the rear band out, but is there anything else I should do back there? Should I mess with the governor at all or just leave well enough alone?

GENERAL QUESTIONS:

The transmission was shifting fine and at good MPH points when the transmission was working last. What areas should I inspect for damage if the transmission was driven on the highway with decreasing a fluid level until it finally ran dry and burned itself up? How far should I disassemble it and is there a point where it isn't worth taking it apart any further?

Thanks for any help and input that can be offered. I am trying to do a good job rebuilding a stock transmission before I start my next project of combining a 1983 slant six lockup A904T with a 1968 318 nonlockup A904.

Reed, with this trans run untill it wouldn't have enough fluid to function.
I would replace every bushing and the spring plate you pictured is toast.
The pump is also quite suspect for wear on it's internals.

Richard

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Part of Tyrde-Browne Racing

Dang it. OK, so I should really be doing an absolutely complete teardown and rebuild. Or looking for a different transmission. D'OH. Maybe I can scavenge a pump and a spring plate from the rebuilt 68 904...

I would do a complete rebuild, including taking the pump apart and inspecting the parts for wear. Bushings should be replace for "piece of mind" if nothing else.

Mike

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An officialis Tyrde-Browne Racing membrum

The only way to "add" clutch plates is to use different clutch drums. High capacity drums (think V-8 trans) have the snap ring groove further out in order to fit more clutch discs & steels.

Be sure to soak the new friction discs in trans fluid for 20 min before installing them.

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63 Valiant Wagon
225 - 4 bbl

Well, OK- change of plans.

My end goal is to have two rebuilt transmissions- one for my brother's 74 slant powered Duster, and one for my brother's 83 slant powered van. To achieve this goal, I have the following materials:

one 1979 slant six transmission (the one that was run without fluid and is a total write-off));

one 1983 slant six lockup 904T that has the wideratio gearset and was rebuilt by a shop but has a nasty shudder around 35 MPH (I believe it is a lockup problem, but I haven't pinned it down); and

one rebuilt 1968 smallblock 904 that was rebuilt and supposedly works perfectly, according to the guy I bought it from.

Here is my new plan, if all the parts will swap around and work:

Duster transmission- Take the guts of the rebuilt 1968 smallblock transmission and drop them into the 1979 slant six case. I would swap everything over but add the part throttle kickdown from the valvebody of the 1979 slant six transmission. All the original 1979 guts in the 1979 slant six transmission would just go away, not to be used. The only part from the the slant six transmission that would be kept would be the part throttle kickdown. I would have to get a new non-lockup torque converter, but that is a small price to pay.

Van transmission- take the rebuilt 1983 904T with the wide ratio gearset and remove the lockup hardware from the valvebody. That should take care of the shudder problem and give me a decent working rebuilt tranny. The transmission works great other than the shudder (probably caused by lock problems).

Can anybody see any problems with this plan of action?
Any compatibility problems with using the 1968 v-8 904 guts in a 1979 slant six 904 case?
Attaching the part throttle kickdown from the 79 VB to the 68 VB?
Removing the lockup provisions from the 83 tranny and running nonLU converter?

Thanks.

The V-8 internals will be a direct swap might have to use the low/reverse band if they are not the same type (anchor points) from the /6. Either valve body will work, but there are two types of part throttle kick downs. Before you do the change of the part throttle post pictures of both valve bodies.

Richard

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Part of Tyrde-Browne Racing

Will do. I'll try to do it tomorrow or the next day. Thanks.

Got the V-8 trans on the workbench, drained, and pulled the valve body.

Picture 1- 1979 Slant six 904 valve body:


Picture 2- 1967 (so says the date code) 318 904 valve body:


Picture 3- a screw that was loose in the trans pan when I pulled it. It is too complex to not be a critical component. Any ideas where it goes?

The loose screw is the throttle lever stop screw. You will also have to use the nonlockup valve body. For where that screw goes look at both valve bodies, it will be self explaining.
Take the 3 screws out of the side away from the selector on both valve bodies and post views of the part that you will expose on the valve bodies.

Richard

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Part of Tyrde-Browne Racing

Ah, thanks! Any input about the part throttle kickdown?

Reed,

I have some 904 bushings and sealing rings here if you want them.

Josh

Thanks. I was actually just reading your post about rebuilding the 904 for your old 67 Valiant in your kitchen! I'll have to wait and see what the clearances look like on this V-8 904. I haven't measured anything on it yet, just pulled the valve body for some pictures. I am still trying to make sure I can install the part throttle kickdown from the 79 valve body onto the 67 valve body.

Reed, look at the rest of my post as some valve bodies use different part throttle kickdown parts.

Richard

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Part of Tyrde-Browne Racing

OK- I think I get what you are saying Fopar. Im not trying to be dense, this is just my first rodeo, so to speak.

Another question: I am disassembling the 1979 slant six 904 case to give it a good scrubbing, but how do I get the low/reverse band out? The pivot pin is not threaded, there is no head out flats of any kind, it just spins freely in the case of the transmission.

The pivot pin is circled in this photo:


Also, will the overrunning clutch in the 79 case work with the 67/68 guts? Mine is staked in with rivets and I would have to press the rivets out to get the overrunning clutch housing out.