TH350 slips in 1st gear when cold
 

I have, what I believe to be the original th350 in my '72 Luxury LeMans and it has started slipping when taking off. It slips in 1st gear only, not from 1st to 2nd or 2nd to 3rd. It started by slipping for a brief moment when I eased on the gas one morning when it had not been driven for three or four days and I chalked it up as a fluke. Lately it seems as though every time I get in and go, in weather below 55*F, for the first run of the day, it slips for a few seconds. The fluid level is good and it smelled normal a few days ago when I last checked it. I've only had this car for two years and 30,000 miles and it isn't raced. It mostly gets highway driving at between 60 and 75mph. Any ideas or experience with this? Tranny or torque converter?

Thanks,
Karl

:usa2:

Im no tranny expert by no means, but i would try changeing the filter first...It is possible that the filter is clogged just enough to make it slip until it gets the fluid warm and up to pressure...

I would start out like stated above. Maybe just a blocked filter. Pull the pan and do a filter change. Look for crap in the bottom. That might tell you something.

Does it do the same thing in reverse when it's cold? If its a fluid problem, it should slip in reverse as well. It could be a sticking valvebody spool valve. Check the fluid, filter and valvebody. Also check for restricted cooler circuit.

What I really suspect is that the tranny is high mileage and the seals have gotten hard in it. This allows fluid to blow by the apply piston and the clutch wont apply until the fluid warms up. Since the complaint is slipping in 1st I suspect the fwd clutch pack.

The forward clutch is the only clutch used for 1st gear. If the tranny is slipping in 1st, that's the fwd clutch that's slipping. It's also used with the intermediate clutch for 2nd gear and the Direct clutch for Drive. If the FWD clutch is slipping, eventually it will fail and you'll lose all forward gears, but reverse will still work. Reverse uses low/reverse clutch and direct clutch.

If you heard any squealing, squalling in 1st or reverse, or found broken sprag parts in the pan, I would suspect a low sprag failure. The low/reverse sprag (different from the low/reverse clutch) is a spring loaded gizmo with rollers used only in low and reverse, to hold the rear planets stationary. But it doesn't affect 2nd or 3rd unless it totally comes apart. If it was the reason, it would slip in 1st and reverse, but the tranny would make noise and put metal in the pan.

The best thing to do is to let the fluid warm up before you try to drive it. If it tries to slip in 2nd or Drive, park the car because the tranny is on the verge of failing the clutch plates and stranding you.

Unless you find something simple, a slipping tranny indicates impending failure.

This has been my experience with most transmissions too. If it slips, it's going to fail in the future and get worse.

I think it would be what I highlighted in red above. So far there is no noise and only occurs when it is really cold and only when taking off from a dead stop. I have since made sure to warm the engine up thoroughly and shift through the gears a few times with the brake depressed before leaving the house. I depress the gas slowly and if it slips I stop and try again in a few minutes and have had little trouble since.

Thanks,
Karl

:usa2:

Karl,

What's the mileage on the car and do you know if the tranny had ever been into?

I'd be very apprehensive of it, afraid to do more damage. A fluid and filter change sounds like something I'd consider right about now, at least.

Charles

Charles,

The odometer reads 85,000 miles but I'm the third owner so who knows if that is actually 185,000 or even 285,000. I am going to change the filter soon if just to see if there are any spare parts in the pan. Meanwhile I am trying to decide weather to buy a 2004r or another th350 when this one dies. http://www.jakesperformance.com/Home_Page.html has their base th350 at $950 and the base 2004r at $1,550.

Karl

Don't think you can go wrong with Jake.

I believe you'd be very happy with the 200-4R.

Let me know if I can help.

Charles

I can highly recommend Jakes Performance. Very knowledgeable tranny man. One of the better builders for the 2004r IMO.:2cents: He has posted helpful info on this and a few other sites before. Goes by Jakeshoe.:)

just rebuilt mine
 

Bought the th350 handbook and had the trans man help, got a donated converter (rebuilt), rebuild kit and help removing and replacing and got out for a lot less. I got some really good help from posters in this section. Took pics of the teardown, but the trans man put it all together.

See the link below for leaking th350 teardown.

Not quite done, but looking forward to it.

Greg