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Old July 11th, 2019, 19:32
200k96 200k96 is offline
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AW4 transmission slipping: Torque converter possible?

Hi, bit of an odd question for the transmission experts:

Is it technically possible, even if unlikely, for the torque converter to be slipping badly while driving/accelerating but for it to also to pass the brake stall test at 2100rpm?

My transmission is slipping after making bad torque converter noises [drove around for a couple weeks and thought it was the bearings on the new alternator but it wasnt]. Then the noise got suddenly worse [loud high pressure air leak] and slipping that is now so bad I would be afraid to drive around the block. Shifts are still firm, so pump probably ok, but wont have a chance to check pressures til tomorrow.

It is of course possible that driving on the bad torque converter heated the fluid and fried the transmission - what I'm wondering is if it's possible, however unlikely, to be *only* the converter (i.e. should I try swapping it before moving on to jy trans if it doesn't work).
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Old July 12th, 2019, 04:04
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Tim_MN Tim_MN is offline
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Re: AW4 transmission slipping: Torque converter possible?

Diagnose first, then buy parts or begin repairs.

The AW-4 Service Manual is easy to find with a Google search. Inside are complete diagnostics.
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Old July 12th, 2019, 17:58
200k96 200k96 is offline
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Re: AW4 transmission slipping: Torque converter possible?

I had already ruled out fluid, solenoids, shift lag, and stall speed while waiting for my pressure tester to arrive. It has, and pressures are way to high in all gears, so while my original question is not definitively answered, it is not relevant, either.
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Old July 13th, 2019, 06:21
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ehall ehall is offline
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Re: AW4 transmission slipping: Torque converter possible?

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Originally Posted by 200k96 View Post
Hi, bit of an odd question for the transmission experts:

Is it technically possible, even if unlikely, for the torque converter to be slipping badly while driving/accelerating but for it to also to pass the brake stall test at 2100rpm?
Possibly. Could be some damage to the vanes that only work when pressure reaches a critical threshold. Could also have a damaged flexplate that is deflecting under torque.
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Old July 14th, 2019, 14:37
200k96 200k96 is offline
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Re: AW4 transmission slipping: Torque converter possible?

Thanks for the input .. did some additional testing today, and noticed that in addition to pressures being twice what they are supposed to be, manually manipulating the throttle cable has no effect on line pressure.

I'll just throw in here that in searching I've seen concerns about needing a banjo bolt to fit the pressure port - the otc kit I picked up came with a right angle adapter that worked fine once I found my Teflon tape.

Working hypothesis is that I've been driving around with regulator valve stuck open and it has finally damaged torque converter and possibly flex plate (I tightened the bolts a year ago and the worst of it went away, but still would hear the rattle on engine shutoff every now and again, even though I couldn't visually confirm a crack)

I'd wager my clutches are ok, and I could replace torque converter/flexplate to fix the problem and rebuild/replace valve body to keep it from happening again.. but since I have to drop the trans for the former, I'm not sure it's worth the trouble of dropping the transmission twice if I'm totally wrong, vs just swapping whole trans, though it would answer my question ... decisions, decisions
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Old July 14th, 2019, 14:48
lawsoncl lawsoncl is offline
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Re: AW4 transmission slipping: Torque converter possible?

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Originally Posted by 200k96 View Post
Thanks for the input .. did some additional testing today, and noticed that in addition to pressures being twice what they are supposed to be, manually manipulating the throttle cable has no effect on line pressure.

Just curious, what were your pressures? You do need to check the pressures with the trans fully warmed up, btw.
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Old July 14th, 2019, 15:08
200k96 200k96 is offline
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Re: AW4 transmission slipping: Torque converter possible?

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Originally Posted by lawsoncl View Post
Just curious, what were your pressures? You do need to check the pressures with the trans fully warmed up, btw.
I was seeing about 150psi in drive and neutral, 240psi in reverse once it warmed up. (160/300 on cold start). Neutral would go as low as 140 on recovery after blipping the throttle, but a couple shifts would bring it right back up.
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Old July 17th, 2019, 22:04
lawsoncl lawsoncl is offline
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Re: AW4 transmission slipping: Torque converter possible?

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Originally Posted by 200k96 View Post
I was seeing about 150psi in drive and neutral, 240psi in reverse once it warmed up. (160/300 on cold start). Neutral would go as low as 140 on recovery after blipping the throttle, but a couple shifts would bring it right back up.

That's ridiculously high, unless you're somehow reading kPA on that guage in which case that's pretty low.
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