Sanity Check: 15-Year-Sat 904 Swap Plan to Get Me to MoParty

[Tuesday]

Hey guys, looking for a sanity check on my plan. Spending as little money as possible….

I blew the clutch in my 904 and picked up a used transmission to get me back on the road. It was rebuilt back when it was pulled to go into a ’Cuda, but that project got sold off and the trans has been sitting for about 15 years. I trust the guy I bought it from — he had it rebuilt and kept it stored — so I’m hoping it’s solid enough for now.

Long-term, I’m planning to go Tremec 5-speed, so I don’t want to sink the time or money into a full rebuild right now — I just need to get to MoParty (555 miles away) and hopefully squeeze a year or two out of it.

Here’s my bare-bones install plan:

• Drain & flush the torque converter, pre-fill before install
• Replace front pump seal
• Replace rear output shaft seal
• Replace dipstick tube O-ring
• Drop the pan, clean it, install new filter & pan gasket
• Fill with ATF+4
• Optional if I have time/parts: shifter shaft seal, kickdown shaft seal, neutral safety switch

I understand there’s a risk the old internal seals could be dried out and give me delayed engagement or failure, but I’m hoping this light refresh will be “good enough for now” to get me to MoParty and buy me some time until the 5-speed swap.

Is this a reasonable plan for a temporary fix, or am I mad to think it’ll last 2 years with the odd Autocross? Will it even get me to MoParty?

 

[toolmanmike]

 

[Demonracer]

Do your planned maintenance and send it.

 

[Tuesday]

Do your planned maintenance and send it.

You’re sharing my inner thoughts!! Am starting to feel much better !

 

[volaredon]

What converter? I hope not the one out of the dead trans or that is guaranteed death for the new transmission. No way to flush all the old crap from the dead trans out of there. Years ago there was a trans parts warehouse not far from me that had a machine to flush converters out of the trans. But they're gone now

 

[Tuesday]

What converter? I hope not the one out of the dead trans or that is guaranteed death for the new transmission. No way to flush all the old crap from the dead trans out of there. Years ago there was a trans parts warehouse not far from me that had a machine to flush converters out of the trans. But they're gone now

I’ve also got the converter from that new transmission - am dumping my existing one - will clean and flush this replacement one out. Car’s still at the shop following the inspection, but there were big pieces of clutch in old trans and I had no third gear.

 

[413]

Was it in a heated mostly dry shop? Should work fine really. Be surprised if it has a problem.

I rebuild a trans for a guy. He never installed it. 10-12 years passed. I bought it and used it as is, works fine, shift seal started seeping after a few years.

Your plans is good.

 

[Dana67Dart]

I would pull the pan first. That will tell you a lot about the transmissions condition

 

[volaredon]

I’ve also got the converter from that new transmission - am dumping my existing one - will clean and flush this replacement one out. Car’s still at the shop following the inspection, but there were big pieces of clutch in old trans and I had no third gear.

Then I definitely wouldn't use the converter from that trans no matter how much "flushing" you think you did

 

[1WildRT]

Was it in a heated mostly dry shop? Should work fine really. Be surprised if it has a problem.

I rebuild a trans for a guy. He never installed it. 10-12 years passed. I bought it and used it as is, works fine, shift seal started seeping after a few years.

Your plans is good.

I'd be more concerned about dry... It wasn't outside on in a flood was it? Beyond that do your maintenance & run it...

 

[Detroit Iron]

Sounds like you know what needs to be done. Only thing I'd change is the tailshaft bushing. Easier done out of the car than in. I currently have a thread on that subject.....

 

[1WildRT]

Sounds like you know what needs to be done. Only thing I'd change is the tailshaft bushing. Easier done out of the car than in. I currently have a thread on that subject.....

I change that bushing in car fairly often... Easy, if you have the tools...

 

[Tuesday]

I would pull the pan first. That will tell you a lot about the transmissions condition

- will do this, for sure!

 

[Tuesday]

Then I definitely wouldn't use the converter from that trans no matter how much "flushing" you think you did

Yep - no way!!! I’m going to make sure donor is sound!

 

[Tuesday]

I'd be more concerned about dry... It wasn't outside on in a flood was it? Beyond that do your maintenance & run it...

I’ll let you know how I get on !!

 

[413]

Only thing I'd change is the tailshaft bushing. Easier done out of the car than in. I currently have a thread on that subject.....

How did the tailshaft bushing go bad sitting there?

 

[Detroit Iron]

How did the tailshaft bushing go bad sitting there?

Not saying it goes bad sitting, but you never know 100% it wasn't run. Cheap insurance.

 

[413]

Put a slip yoke in the back and see how it fits. Automatically condemning a bushing that wide that rarely fails is silly, how can you use ever used any used parts at that rate?

 

[Tuesday]

I would pull the pan first. That will tell you a lot about the transmissions condition

Yep - 100%. Will do that today and just checking that I get this right before going further - done some research and looks like when I pull the pan from the 904 transmission, I should be looking at:

• Fluid condition - presuming red is good, but brown/black or burnt smell is a bad sign (will this be the case even in an older transmission that hasn't been opened/used for a while)
• Debris in the pan - bit of sludge is normal, but if there is shiny metal or lots of clutch dust that could mean internal wear
• Valve body - check bolts, look for buildup or anything gummed up
• Bands and servos - guess I can test some of the band movement with a screwdriver?
• Manual valve - I should move the shift linkage and make sure the manual valve moves freely - is this something I can do without anything connected to it?
• If needed, I looks like I can drop the valve body to inspect further - is that straightforward?

Does that sound correct to you? Feel free to let me know if I’m missing anything important - any red flags I should be looking for?

 

[413]

Checking the original story, isn't this a rebuilt trans that was never used?

I'd look for rust and what kind of fluid or lube you find in there. Clean out anything that may have come into the dipstick area.

When you turn the input shaft it should feel. Different turning it different directions.

Pulling the valve body won't tell you much at all. Leave it alone.

 

[Tuesday]

BINGO!!! It’s great inside - photos attached - going to leave it well alone - looks like it was put together yesterday! Next check is the torque converter. Do you think I should try and swish it around with ATF at home today or take to shop and hope (and expect) they’ve a flush machine?

 

[Tuesday]

Checking the original story, isn't this a rebuilt trans that was never used?

I'd look for rust and what kind of fluid or lube you find in there. Clean out anything that may have come into the dipstick area.

When you turn the input shaft it should feel. Different turning it different directions.

Pulling the valve body won't tell you much at all. Leave it alone.

It was and is - always unsure of these things until you 100%. But have checked now and it looks amazing in there!! HUGE result.

 

[413]

Same on the converter, isn't that new also? If so it doesn't need flushed, and a shop will just flush money from your pocket.

Pour some fluid inside before installation and go with it.

 

[transman]

What converter? I hope not the one out of the dead trans or that is guaranteed death for the new transmission. No way to flush all the old crap from the dead trans out of there. Years ago there was a trans parts warehouse not far from me that had a machine to flush converters out of the trans. But they're gone now

And those old converter flushers weren't all that good. Flushing with cold solvent only gets some of the junk out.

 

[Dartswinger70]

Put it in run it make band ajustments etc.