73-87 Chevy _ GMC Trucks > Engine/Drivetrain

TH 350: Trustworthy or Toast..?

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Mr. Machanic:
To my short comings, I did not take any pics. And I'm kicking myself.

78 Big 10. TH350 90,k on the clock.
As soon as I got it in the driveway, I dropped the pan and changed the filter and fluid.
At the deepest end of the pan there was at least 1/8" of sludge that looked like old gray paint. The actual shiny metal flakes were not visable in the sun light. Fluid did not smell burnt, but was a tad cloudy.
I have read the gray krap is friction material.
The top of the filter was not plugged up.
There was no maintance records available, so no idea when the last change was done...if ever.
After the oil/filter change: it will now coast out of the level drive, at idle. (That was an improvement)
It seems to go down the road well enough and shifts as it should. If I stick my foot in it, it will downshift as it should...3-2 going up a hill and 2-1 if I really stomp on it.
I have not tried to burn the tires or a brake tork. This is a 6200lb truck. I wouldn't hesitate if the tranny was new.
Some things I've read suggest it needs rebuilt, but an old mechanic sayes it should be fine.

So, as I was watching "Roadworthy Rescues" this morning, they dropped a mopar powerglide tranny pan and man, the sludge in the pan sorta gave me flashbacks, and they got a rebuilt one to replace it. Their comments on the amount of sludge got me to wonder about my tranny.

Back story, I've had stick shifts all my life. Wife has had automatics and I've maintaned them but never tore off a pan. So, this is kinda new territory for me.

I am very mechanically inclined and have no reservations about rebuilding this tranny.
I just don't want to tear into something that doesn't need it.
We plan on using this truck to go camping with and pull a small pop-up camper.

So to the Collective:
Do you think it's Trustworthy?
Or,
Rebuild it, for sure...

If you have any questions, please ask.
Thanks in advance.

Mike81K10:
I had a TH350 in a 77 Monte Carlo that had a HP engine. It ran great and was reliable, however I did have it rebuilt with a shift kit. It did not have overdrive and the 700R4 has that replaced the TH350. The 700R4 would be better for fuel economy thanks to the Lower RPM with the overdrive. I believe the TH350 is a shorter transmission than the 700R4. The lower RPM will be less noisy on the highway from what I understand.

My knowledge pretty much ends here because like I said, I had my TH350 rebuilt with a shift kit. Transmissions is the one thing I have never rebuilt except for fluid and filter changes. However owning a car with the TH350 did not disappoint. Would have still owned the car if it were not stolen. Others on the forum will have much more knowledge and more to add.

Mr Diesel:
Drive it until it starts to slip. Might get 50k more miles, might get 10. Unless you plan to make a lot of long trips with it I would just drive it and not worry.

Captkaos:
If it didn't smell burnt I would just run it.

bd:
Dark sediment in the pan is the result of normal wear.  The time for real concern is when you discover ferrous (magnetic) and/or non-ferrous (aluminum or brass) metal, discernible pieces, rubber fragments, paper flakes, and/or engine coolant.  I agree, without symptoms, drive it.

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