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Torque converter not staying locked up on highway


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Hey guys, I took this drivetrain from a 92 legacy turbo wagon and put it in my 94 legacy turbo sedan. Now in the wagon had the same problem keep in mind, and I have tried swapping TCU's. So when I am on the highway 4th gear, it will lock up for a minute or so, then it will stay unlocked the rest of the drive. If you stop and restart the car will work repeat, lockup for a minute on the highway then unlock. So RPM's are obviously higher because of this and I get ************ty highway fuel economy of course. Now if I look at the oil pan, there is a nice big dent and after looking at some FSM's it appears right where the dent is, the lockup solenoid is there. Possibly got hit and damaged so can not hold pressure for long period? What are your thoughts? Consider I have done a tranny fluid change as well :)

 

I am going to be pulling the pan ASAP to replace with a non dented one, and I have 2 parts tranny's so if I see a damaged valve body or something I can replace the part.

 

So main question is, dented pan creating a issue? or probably more serious? Keep in mind it will lockup momentarily.

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Have you checked fo trouble codes?

 

It could also be the temp sensor?

 

While you are in there you could check all the pipes and retorque the valve bodies. They can work loose(or perhaps they don't get tightened properly). Preferably remove the bodies and tighten the bolts on top as well, or, just check the ones from the bottom and if there were several loose then pull the valve body and do the lot.

Edited by Log1call
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  • 4 weeks later...

Just a update. When I removed the oil pan I could obviously see that the pickup has been hitting the pan. Although no other damage. Replaced the sensor for the hell of it. Seems the same though and still no lockup on the highway. It locked up one time like usual for the few seconds or so, and I can be jumping into boost etc without it slipping, then while crusing steadily jumps out of lockup!

 

So confused, what the heck is the issue? Could it actually be the torque converter ? Why would it work one time? I checked out all the bolts nothing loose. There is 1 solenoid I can see but I don't think the solenoid is for lockup.

 

Any other ideas as to what is creating this issue?

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Your going to have to get some pressure gauges on the tranny to see what the issue is. I wouldnt fault the torque converter, but maybe your front pump cant develop enough line pressure to keep it engaged. Another possability is a worn internal seal someplace.

 

 

nipper

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Hoping that trans-x will swell a leaking seal, allowing it to build pressure again for a steady time. It's just odd how it will lock up for a bit, then after that bit there is no lockup till the car sits and it goes for a drive on the highway.

 

The oil pan was dented to the point where the pickup made a perfect square indent in the pan indicating it was restricting flow, and my mechanic believes it damaged something.

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Hoping that trans-x will swell a leaking seal, allowing it to build pressure again for a steady time. It's just odd how it will lock up for a bit, then after that bit there is no lockup till the car sits and it goes for a drive on the highway.

 

.

 

Its loosing internal pressure someplace. Use trans-x cross your fingers and start looking for a replacement.

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Its loosing internal pressure someplace. Use trans-x cross your fingers and start looking for a replacement.

 

I have a replacement ready just didn't feel like replacing the tranny, but it realistically doesn't seem like a difficult job. Guess I can't win, original tranny had no awd, added lucas, lost 2nd then got back 2nd and lost 3rd and 4th of course while I was on the highway :) Put this tranny in have all 4 gears and awd with slight delay, yet no lockup on the highway = crappy fuel economy on the highway.

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For me i had the same problem (no dented pan though) but it was over filled with 100 ml. THat is what i took out and from then it started to lock up normally.

But you have refilled it after replacing the pan so that should be right.

 

Actually that's a possibility! Let me check that out!

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I haven't even checked. I am just saying it makes ticking sounds. I thought it was a exhaust leak because it is sort of popping like. Rolled under the car and noticed it was the transmission almost sounds like a solenoid flickering.

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Hmm, I don't think I had enough oil. When I checked this morning on a cold start, I see like a thin line, then there is a thick line. I am thinking the other line is from oil splashing, and the other one is the real line! So it appears the transmission is very low still hmm. I will get another jug of oil, I think it is 1L short.

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  • 3 weeks later...

Still doesn't seem to be locking up for a long enough period. I swapped TCU's to one that I know was locking up perfectly. Haven't done any highway driving yet, will do so though, last drive seemed to lockup for a very long time at 80km/h yet I had to slow down.

 

I am debating replacing the whole tranny. Seems like such a waste. Is it possible its just the valve body? The oil is always a nice red with no burnt smell.

 

Thing's i have done so far, replaced bent oil pan, replaced shift solenoid, replaced oil a few times, and added trans-x recently which made it definitely shift better.

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How warm is it over there. I remember it took me 15 to 20 km to get it locked when temperature was around 0 C. (Of highway driving). And that was normal operation.

I used to check it by giving little press on the accelerator the rpm would just increase 50 to 100 when not locked. When locked it just stayed where it was.

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Well, it was 15+C today. It locks up, but only for a period of time, then jumps out of lockup and doesn't lockup the rest of the drive on the highway. With my car is is like a 800rpm+ difference when I hit the gas on the highway. Someone said maybe the torque converter is locked up, but the gear itself starts to slip.

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