T350 help
 

Hopefully someone has some ideas about a tranny issue. Had to do a new case over the winter. My guy transfered all the guts over and had to replace the valve body gaskets. Said he copied them exactly. Started the car for the first time yesterday, and moves great in reverse and low. Nothing in 2nd or 3rd. Tranny guy came over today, and checked pressures. 200lbs at all 3 ports. Took it all apart, and air tested on the bench. Everything checked and looked great. Changed stator anyway just because he brought one. Still no good. It's locked so bad in 2nd and 3rd you can't turn the tires.
Help please!!!!
He's calling Hipster tomorrow (transbrake manufacturer). Do they have a special valve body gasket? Anyone ever run across this?

One more thing. The converter was just freshened. But there's nothing in the converter that could cause that, right?

Thanks a lot!
Mark

Re: T350 help
 

Mark, Sounds like the lo/rev piston is sticking on or being cross fed some how in 2-3.
Did your guy follow the instructions on the case mods to the tee ?

Try bypassing the neutral safety and start it in second or third...don't go near Low.

See if it works then.

http://www.autotransdesign.com/motor...ransBrakes.asp

Re: T350 help
 

Yes, Hipster has a special gasket, or at least the last 2-3 I freshened did. You need them. Do yourself a favor and order 2-3 spare sets, they should be priced low enough you can do that.

Reverse requires the high gear clutches and the low/reverse clutches. Low gear requires the low/reverse clutches and the forward clutches. Mark Y is correct, it sounds as though it may have the low/reverse piston hanging or being applied all the time. What does it do in neutral and park?

There are three seals on the low/reverse piston. Your builder should have used the inner and outer, but discarded the "middle" seal. If he installed that "middle" seal, it may cause a problem.

Re: T350 help
 

Mark,

Sounds like you have a bleed over between apply circuits. You certainly have enough line pressure. Any check balls missing that should be in the case when the valve body was removed?

If it was a C-4 I could nail the problem: not as familiar with T350. Been quite a few years since I built one.

And no, I wouldn't suspect any converter problem.

Good Luck!

Brian

Re: T350 help
 

Right...about converter

Re: T350 help
 

Thanks guys! Will order the gaskets tomorrow. The first time I fired up after reinstalling, went quickly from 1-2-3 and worked good. Then the problem reappeared and was there every time afterwards.
He said he did all the case mods exactly as directions said. Had a printed copy when he came over. And only one check ball used, which was in the correct position.

Re: T350 help
 

I'm not sure about neutral or park. Or the seals on that piston? He's gone home and took his gauges with. I'll copy all the replies and forward them to him.
Thanks again for the help :)

Re: T350 help
 

Did he air check the low/rev piston (in the back of the case)? You saw it go out and back?

Re: T350 help
 

No, I didn't see him check that

That's not the piston behind the tbrake solenoid, right?

Re: T350 help
 

Yeah, it's in the case behind the last set of clutches (also in case)

Re: T350 help
 

What your next plan? Pull the pan and v/b with the unit in the car?

Re: T350 help
 

I can't remember seeing him check that, but I'll pass it on. Thanks Mark

Re: T350 help
 

That was his next step probably. He wanted to make the call, and ask them some questions. I think you and Alan are onto the most likely solution.

Re: T350 help
 

Okay.. I had something you could check if you were going to work on it tonight


Call if you need anything

I'm easy to find


602-769- 0346

markyac@cox.net

Re: T350 help
 

I had an issue a few years ago with a TH-350,tranny worked great when cold,once it was warmed up it acted like it was bound up. Ended up being a leak between the case and the valve body. The valve body bolt holes were stripped out and allowed it to leak. Heli coiled several bolt holes and worked great afterwards. Not an expert,just giving ideas.

Re: T350 help
 

My trans guy here at the shop suggests the wrong separator plate might be there,and/or gaskets. Is that a' 69 case? Some of those had issues.

Re: T350 help
 

Same separator plate as previous case.
Where would I find what year case it is?

Re: T350 help
 

Mark, there's a date code cast into most cases, the location varies.

Re: T350 help
 

68-72 Turbo 350 I believe has the codes stamped in the accumulator cover--- vehicle ID numbers for the vehicle it was originally installed in can be in several places on that trans--that number is not the same as the trans code numbers

Re: T350 help
 

I pulled the trans this afternoon. He's going to do another case and double check everything. I spoke to Charlie at Hipster, and he said it's a stock gasket, but to make sure all the holes are correct. There's a couple that need to be added and/or enlarged.
I didn't check the date code on the case.
Thanks again everyone for the suggestions.
We'll see....

Re: T350 help
 

Best wishes to you and for the success of this project. That's why I gave up working on cars in a dealership a long time ago. One of these things on a warranty ticket could wast several days of your time, and for nothing.Every line mechanic's worst fear was a trans problem that eludes normal diagnosis and repair.

Re: T350 help
 

Got it fixed! Turns out the case had a very low spot by the transbrake solenoid/modulator valve area. Was over .010 low! He got it all flat and made the valve smoother and made sure the travel was exactly right between the passages. Apparently was passing fluid like crazy across that low spot. He usually doesn't miss anything, but this seemed extra crazy!
Thanks again for all the suggestions and ideas!!!! It all made sense, and did double check everything that was mentioned.
Mark

Re: T350 help
 

Glad to hear it's alive and well! Thanks for the update.

Re: T350 help
 

The stock case casting strikes again. Glade you got it fixed.