2nd gear slipping. TH400 - Pontiac GTO Forum
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post #1 of 22 (permalink) Old 08-26-2018, 12:42 PM Thread Starter
 
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2nd gear slipping. TH400

Rebuilt my motor and put everything back in.

Car runs great but I can't shift into 2nd manually. It just revs up. When driving and it shifts by itself, it will go into 2nd but I can feel it still slipping. I replaced oil and filter and module to see if it was that easy, but no luck.

You guys think it is the sprag? It was fine before i pulled the motor. But now just doesn't go into 2nd manually and just slips.

What do you guys think?
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post #2 of 22 (permalink) Old 08-27-2018, 09:56 AM
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I'm not that versed on TH400's, but something's amiss. Make sure the fluid level is correct, that you don't have any leaks in the vacuum line to the modulator, etc. You might also pull the modulator and examine the bit of fluid that will drain out to see if it looks brown or smells burnt. If that's the case it's a sign of internal problems.

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post #3 of 22 (permalink) Old 08-29-2018, 12:44 AM Thread Starter
 
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Fluid is good and new. Vacuum line and modulator are new as well.

If i am in 3rd gear driving and go WOT, it does kick down to 2nd gear and pulls like hell. No slipping. If i am cruising at light speed or coming to a stop and manually shift to 2nd, it does absolutely nothing. Almost goes into neutral.

I do have a squeal noise if i floor it real quick. It happens for a few seconds. Also happens if I am in park with the hood popped and snap the throttle from the carb. Sounds like a belt but can't tell.
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post #4 of 22 (permalink) Old 08-29-2018, 06:27 AM
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That's a strange one. So it acts like it's going into neutral on upshifts but works fine on downshifts? That makes me suspect a problem in the valve body, servo, piston, hyrdraulic passage, etc that doesn't fully apply the second gear clutch on upshifts. This is a problem for someone who knows way more than I do.

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post #5 of 22 (permalink) Old 08-29-2018, 09:32 AM Thread Starter
 
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The opposite of what you said

Up shifts fine, down shifts fine under WOT throttle with the kick down and 2nd gear pulls.

I just can't manually shift into 2nd without it feel like its just slipping. Also, slowing to a light i dont here it downshift into 2nd either.
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post #6 of 22 (permalink) Old 08-29-2018, 01:03 PM
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So it's only on manual shifts? Sorry for misunderstanding. In that case, if start with the cable adjustment. At the point where the cable connects to the transmission, there's a slotted adjustment point.

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post #7 of 22 (permalink) Old 08-29-2018, 02:49 PM Thread Starter
 
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it will actually shift into that gear but the gear slips.

basically 2nd gear is slipping and not acting properly.
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post #8 of 22 (permalink) Old 08-29-2018, 03:20 PM
 
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Originally Posted by Charlie Ashby View Post
Fluid is good and new. Vacuum line and modulator are new as well.

If i am in 3rd gear driving and go WOT, it does kick down to 2nd gear and pulls like hell. No slipping. If i am cruising at light speed or coming to a stop and manually shift to 2nd, it does absolutely nothing. Almost goes into neutral.

I do have a squeal noise if i floor it real quick. It happens for a few seconds. Also happens if I am in park with the hood popped and snap the throttle from the carb. Sounds like a belt but can't tell.
Suggestion to check;

For grins, un-bolt the torque converter from the flex plate and see if it moves back away from the flex plate about 1/2". If it's tight to the flex plate it did not seat into the front pump. That will cause problems and can cause a squealing noise. Just figured since it was working before and now you have a problem, might be the torque converter did not get back in the right slot. Good luck.
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post #9 of 22 (permalink) Old 08-29-2018, 03:47 PM Thread Starter
 
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Suggestion to check;

For grins, un-bolt the torque converter from the flex plate and see if it moves back away from the flex plate about 1/2". If it's tight to the flex plate it did not seat into the front pump. That will cause problems and can cause a squealing noise. Just figured since it was working before and now you have a problem, might be the torque converter did not get back in the right slot. Good luck.
Once I bolt it to the flex plate, wont it come right back forward again?
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post #10 of 22 (permalink) Old 08-29-2018, 04:01 PM
 
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Yes, but the idea is that the slots in the torque converter align with the teeth in the pump. You can have the torque converter pushed on top of the gear and that won't turn the pump gear properly.
I'll post a picture of what the pump gear and slot in the torque converter look like.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Undercarriage, Frame, Transmission and Differential Discussions.

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