[tooski]

I am resurrecting a TH350 that lost all the gears (except park and neutral).
I have it disassembled up to the center support and low/reverse clutches.
The forward and direct drums are disassembled.

The reason for the failure became evident when I pulled out the input shaft and the two drums did not come with it. The splines at the bottom of the forward drum were in pieces.

I believe the cause of this was the bone jarring 1-2 shifts when not at wot. The wot shifts seemed fine.

Before I put this trans into service I installed a B&M shift kit set to high performance as to RV/towing. I do not know its previous history, but items made it evident it had been opened up.

There were flat steels instead of the wave steels in the intermediate and forward clutch packs. The direct drum return spring pack has 12 springs instead of 17. The forward drum return spring pack has 16 springs instead of 20.
Preliminary inspection shows the steels and frictions to be ok.

Would any or all of these cause the violent shifts? Is there anything else to look at, maybe trans fluid pressure?

[steve25]

Yes, line pressure would have a lot to do with it..
I would then be concerned that the converter might have been ballooning and applying excessive load on the motors thrust bearing.

I would check which can be done with the pan on and with the motor in the car.

[stevep]

Put it back to stock specs and make sure to keep the accumulator operating, so get an original valve body and use a Trans-Go-1&2 kit. It will come with the plate. Your VB may be OK too.
The forward and intermediate clutch uses 1 wave plate in each pack.
Very rarely have I seen a wave in the direct clutch and I have been rebuilding automatics for almost 50 years.

[chiphead]

A harsh shift shocks the internal parts and can cause breakage. The main line pressure, accumulators, orifice sizes in the separator plate, check balls, waved apply plates, clutch pack clearance, clutch spring number and type, type of frictions and steels, type of fluid, torque converter efficiency all works together to determine shift firmness and timing.

The B&M kits are known to be very aggressive, using large plate sizes and high pressure springs along with disabling the accumulators and removing flow check balls. This results in the super fast and hard "bang-chirp" type shifts that tend to break things.

[Schurkey]

Originally Posted by steve25

Yes, line pressure would have a lot to do with it..
I would then be concerned that the converter might have been ballooning and applying excessive load on the motors thrust bearing.

High line pressure WITHOUT ballooning the converter is also hard on the engine thrust bearing.

Often due to a restriction in the trans cooler plumbing, or in the cooler itself.

[tooski]

Thanks for the response, guys.
As I'm cleaning and inspecting I saw that the direct drum had 5 steels/frictions instead of 4. The pressure/backing plate has only a very small lip on the surface facing the clutch pack. The forward drum had a very noticeable lip in that area. I reassembled the direct drum to check the clearance. With the 5 steel/friction there was zero clearance between the last friction and the plate. One steel showed a slight bit of overheating, the rest showed a lot. I'm fairly sure the apply piston was not or inadequately cut. I don't recall changing a the pressure regulating spring. The one I just took out is a black spring, whatever that would indicate.

[tooski]

Originally Posted by steve25

I would then be concerned that the converter might have been ballooning and applying excessive load on the motors thrust bearing.

Th trans was short lived behind a mid performance engine. Maybe 2k miles. I took that engine out because of a broken ring land. I measured the thrust clearance @ 0.010" upon reassembly.