I'd like to stop the 904 transmission in my race car from leaking. It seems to be comming out of the shift/kickdown o-ring or seal. I have no experience building transmissions, but I have a book on order and an over-the-winter transmission build forming. I'd like to leave the existing transmission in place until the new one is ready, so I can move the car in and out of the garage over the winter if needed. (like to fix one of my other cars when it's only 10 degrees) It would sure be nice if the fluid didn't drip all winter.

The engine is about a '71 and I'm pretty sure the transmission has never been serviced or replace, but I'm only guessing. Do I need to verify the exact year of the 904. How do I id the vintage. It seems like the parts listings show some kind of change around 71-72. Was it a big change? I'm only looking for the one gasket if the repair can be made by just dropping the pan. Other than a fluid and filter change, should I adjust bands even if the transmission was working fine.

Also, I'll be finding a core 904 for rebuild over the next few months. Is there a specific year 904 that would be best to start with. I've been advised to swap in the low gears from a v-8 transmission into a /6 904 housing. Are there years or models cores that work best or should be avoided for all aspects of that build up.

I realize I'm asking 20 questions , so anything that you can explain with a good link might be better than trying to say it all in one reply, but I wouldn't mind any feedback you'll offer.

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1980 Aspen 225 super six

...not sure what the question was, but the KD and selector shaft seals are a pretty straightforward repair with the trans in car. Really need to drop the valve body which is not too difficult. Just make sure you have the wheels chocked and buy lots of shampoo/dish soap to get all of the trans fluid out of your hair afterwards...

D/W

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If it ain't broke, fix it!

Cat litter is also very nice in hair

First question is answered, Drop pan and valve body to fix KD shaft seals. Thanks!

It's sometimes hard to explain what i'm thinking, so I'll say it again hopefully more clearly.

How do I tell what year the transmission in my car is. It's came with the '71 motor, so it's not an '80 like the car. Is there an easy way to identify the transmission from numbers stamped on it? I think it's an early '70s 904.

I want to buy a rebuild kit for the transmission or at least the seals to fix the leaking shaft, but I keep seeing a choice like kit for '71 and down, or '72 and up. (ebay research) What changed in 71-72 that requires a different kit, or am I mistaken.

Additionally, I'm planning on building a 2nd 904 transmission for this car, but I am looking for suggestions of what to ask for at the junk yard or avoid. Thanks.

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1980 Aspen 225 super six

I know there is a difference between lock-up/non lock-up and early vs. late, but right off the top of my head, I think the "major" change was the input shaft splines which I think took place around '67-'68. I'll have to get near a book and let you know, if no one else solves the mystery first. I'm not sure just what changed in '72... Maybe part-throttle kickdown, but that would be just a small change to the valve-body. Lock-ups came later.

Anyway, not sure about all years, but you may find a VIN stamped just above the pan rail that will be for the car the trans came from. If not that, I'm not sure what to tell you for visual cues without dropping the pan.

D/W

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If it ain't broke, fix it!

By the way, can you tell I'm in an "unsure" mood today??

D/?

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If it ain't broke, fix it!

Stay away from lock-up. Also, the early fine-spline 904's will cause problems finding a T/C to match your crank pilot. Obviously you don't want a cable-shift (early 60's). The low gearset is not in all V8 904's... Look for an 80's Dippy, Gran Fury or 5th Ave. Technically, the low-gearset transmixer is an A-999 if I'm not mistaken.

D/W

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If it ain't broke, fix it!