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TH350 Output Shaft Locked in Place When Running

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New User

Jun 25, 2016, 10:52 AM

Post #1 of 3 (960 views)
TH350 Output Shaft Locked in Place When Running Sign In

I've never run into nor heard of this problem. I broke in a new stock SBC with the transmission, (unknown year), installed but did a bonehead move and didn't fill it with fluid. It was run about an hour this way. There was maybe a a pint or so in the converter but the rest of the transmission had been completely drained about 4 years ago. After adding 9 quarts as a start, I noticed I couldn't turn the driveshaft when the engine was running. This is in all gears. Once the engine was stopped I can turn it.

If I start the engine in gear or in neutral, it the driveshaft turns a few revolutions and stops. The direction is always in reverse. It's a "soft" stop. It seems like once the pressure builds up it's like it's in two gears at once. If I try this in park it will also turn in the same direction until the pawl locks.

The transmission ran fine from what I can remember prior to removal. I also don't remember doing any work to it other than probably changing the filter.

I'm sure I am going to have to pull the pan but I'm not sure what to look for. Maybe one of the linkages to a piston/valve has become disconnected in the valve body.

Also, is it possible I hurt something by running it without fluid?

I can completely restore/build a car but I don't tear into transmissions other than the pump or valve body so I am considering myself a newbie on this.



Jun 25, 2016, 12:34 PM

Post #2 of 3 (951 views)
Re: TH350 Output Shaft Locked in Place When Running Sign In

If this turns with the engine off and not while running, something is locked up. You could start by dropping the pan, but this trans may have to come out. Gary

New User

Jun 25, 2016, 1:44 PM

Post #3 of 3 (944 views)
Re: TH350 Output Shaft Locked in Place When Running Sign In

I solved one problem! I neglected to connect the link to the valve closest to the selector input shaft when I was replacing all the seals. duh...

Now, the running it dry issue. It's shifting now. I can't tell if the clutch plates are holding well enough to move the vehicle. It's just the chassis on jack stands. I'll have to wait until it's driveable to see if it's mortally wounded.

If it is, then a 200R4 sounds like a good idea!

Thanks for the advice everyone!

(This post was edited by 69-er on Jun 25, 2016, 1:46 PM)

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