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3rd gear slipping

1K views 5 replies 2 participants last post by  lassebre 
#1 ·
Hi, my name is Lasse and I am new to this forum. I live in Norway, so sorry upfront for any language or spelling issues. Ok, here's my problem. I bought a car with a broken TH 350 tranny (from around -80). The previous owner said that it had just been rebuilt by a professional, and that he had been kind of abusing it. You know, burn-out's etc. So I bought a rebuild-kit, pulled the tranny apart, and yes the clutches were toast. So I replaced all clutches and all gaskets. Changed the filter, changed the balls from plastic to steel, and replaced the band. I installed the tranny, and all looked great. First and reverse worked perfectly, and oil-level was perfect. So I took it for a spin, and it changed from first to second perfectly. But it wouldn't change to third until I let go of the throttle. Then it would stay in third, but only on minimum or no throttle. I do not have the kick down wire installed, but there is no problem from 1st to 2nd gear or no kick down from 2nd to 1st even with full throttle. So I don't think that it has anything to do with it. It won’t change to 3rd at all when it's warm. The question is: is this a modulator or governor issue? I pulled out the vacuum line from the manifold, and the engine revved up, and there were suction. What else should I check? I have a spare tranny, with broken bearings that I maybe could use the modulator or governor from. Don’t know if they work though.
 
#2 ·
Update..

A small update. I have changed the modulator and the O-ring. There is also suction down to the modulator, so I don’t think it’s a vacuum problem. But it may be the governor. How should I check if it works? Is there any sense in opening it and clean it?
 
#3 ·
lassebre said:
Hi, my name is Lasse and I am new to this forum. I live in Norway, so sorry upfront for any language or spelling issues.

Ok, here's my problem. I bought a car with a broken TH 350 tranny (from around -80). The previous owner said that it had just been rebuilt by a professional, and that he had been kind of abusing it. You know, burn-out's etc. So I bought a rebuild-kit, pulled the tranny apart, and yes the clutches were toast. So I replaced all clutches and all gaskets. Changed the filter, changed the balls from plastic to steel, and replaced the band. I installed the tranny, and all looked great. First and reverse worked perfectly, and oil-level was perfect.

So I took it for a spin, and it changed from first to second perfectly. But it wouldn't change to third until I let go of the throttle. Then it would stay in third, but only on minimum or no throttle.


I do not have the kick down wire installed, but there is no problem from 1st to 2nd gear or no kick down from 2nd to 1st even with full throttle. So I don't think that it has anything to do with it. It won’t change to 3rd at all when it's warm.

The question is: is this a modulator or governor issue? I pulled out the vacuum line from the manifold, and the engine revved up, and there were suction. What else should I check?

I have a spare tranny, with broken bearings that I maybe could use the modulator or governor from. Don’t know if they work though.

Sounds like you have full vacuum from the intake manifold to the modulator ?

To check the governor , remove it from the transmission. Then squeeze the weights together and watch for the inner valve to move up and down.

You may have a stuck / sticky shift valve in the v-body.

You may have the clutch pack clearance too losse in the direct clutch drum.

You may have a cut lip seal or sealing ring causing a low pressure situation in 3rd gear ... so the clutch does not hold properly.
 
#4 ·
Ok, now i've changed the modulator and the governor. Still no change. But isn't the reverse and the 3rd gear using the same clutch pack? If not, there's probably my problem. I just took out the old clutches(and steel's) and put in the new ones. But all other gears are super smooth/tight and fine. Revers, 1st and second works just fine. But how do i check (and maybe fix) the shift valve? Or how can i tell if it's causing the trouble? Is there any way of doing that without opening the v-body? I really don't want to rip down the transmission one more time :( Sorry for all the newbie questions..
 
#5 ·
lassebre said:
Ok, now i've changed the modulator and the governor. Still no change. But isn't the reverse and the 3rd gear using the same clutch pack? If not, there's probably my problem. I just took out the old clutches(and steel's) and put in the new ones. But all other gears are super smooth/tight and fine. Revers, 1st and second works just fine. But how do i check (and maybe fix) the shift valve? Or how can i tell if it's causing the trouble? Is there any way of doing that without opening the v-body? I really don't want to rip down the transmission one more time :( Sorry for all the newbie questions..
yes , direct clutch operates in rev and 3rd gear...

in rev the pressure is boosted , so a weak direct clutch may hold the power better than in a lower pressure 3rd gear
 
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