Torque converter - rattle and lock up jammed on.

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Apr 29, 2022
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Hi all - an odd one here, and am hoping a US based forum will have way more experience with torque converters than a european one!

I've just done an overhaul on a Renault DPO 4 speed auto. Its a pretty conventional unit made by Siemans and based on a VW design. Bog standard planetary 4 speed with a lockup converter.

This was a budget build using a nearly new donor trans for parts, but I did all the right things with fully dismantling it and cleaning everything.

I used what i thought was a known good converter with very low kms on it since it was reconditioned. Not that there was anything wrong with the converter in the trans that failed with a burnt out E2 pack at 130K kms - most likely due to the pressure modulation solenoid failing about 30K kms prior. The solenoid was replaced then, but I suspect the damage was already done.

Anyway, the rebuild went well I thought - I was OCD with cleanliness and all the right things were done I think.

Start up was good and pressure built straight away and it engaged drive happily pretty much immediately. I have the Renault specific interface and can read pressures as normal and no codes thrown.


But. There is a nasty rattle from the converter at idle and it stalls when you put it into drive or reverse - the converter is locking....

I got it to a brief drive once i managed to get it going past the small amount of slip the converter would give and it drive ok above a certain speed and changed gears well - so its not trying to engage two gears at once.

My main question (if you've made it this far and thank you!) - if the converter is locked because of a stuck on lock up solenoid, would the converter rattle at idle? I'd like to think its a lock up control problem. The computer tells me its not asking for converter to be locked and its not throwing code, but the solenoid could be jammed on mechanically. But the rattle makes me think the converter has a mechanical fault internally thats causing the clutch to jam on.

Anyone heard of a converter failing internally like that...? Or should I really be focusing on solenoids/control circuits?

Cheers from a Renault nut in Australia :)
 
It sounds like a mechanical failure of the converter if it is not being driven electrically to lock up prematurely. You will have to determine that.. The rattle and the locking up issue likely are related due to a mechanical issue.. Sadly, I think your going to have to disassemble and probably replace the converter.
 
Definitely worth trying to ensure the solenoid and respective valve body/hydraulic circuit is clear before a trans removal. If the converter is locked at idle it’s turning the trans input shaft one to one like a manual trans with clutch engaged. The rattle could be whatever the trans input shaft is spinning, not necessarily inside the torque converter.
 
I'm not surprised by a rattle with a locked up converter at idle. It's just a mechanical device with some play on the splines and springs on the clutch. Converters were never designed to be locked up at idle, so maybe the sounds are normal "if" it's being commanded to lock up at idle.

I'm not familiar with your setup, but I believe some converters use pressure to hold the lock up clutch open. And when the solenoid is powered, the fluid flow stops and the converter clutch locks up. Can you de-power the solenoid?

I wish you luck, what ever you find. I hate problems like this. So unnecessary.
 
I’m not sure but this could be a sprag type clutch. That would definitely be prone to rattle when loosely engaged due to low engine RPM-idle.
 
I'm not surprised by a rattle with a locked up converter at idle. It's just a mechanical device with some play on the splines and springs on the clutch. Converters were never designed to be locked up at idle, so maybe the sounds are normal "if" it's being commanded to lock up at idle.

I'm not familiar with your setup, but I believe some converters use pressure to hold the lock up clutch open. And when the solenoid is powered, the fluid flow stops and the converter clutch locks up. Can you de-power the solenoid?

I wish you luck, what ever you find. I hate problems like this. So unnecessary.
Extremely unnecessary! :)

Yes, that’s exactly how the lockup here works. Page 19 of this http://www.kit-group.ru/sections/AL4 Transmission.pdf

No way of depowering… It’s internal and on a single loom with the rest. You can run an actuator test with the laptop that makes the two main (pressure regulation and lock up) solenoids buzz and it did make a buzz. Not sure if it supposed to mAke one buzz or two here. I actually have another renault here with the same auto, time to plug it in and see what that test does on it….

It’s a bit of pain getting the solenoids out, the whole valve body has to come out and it’s awkwardly on the front of the transmission up against the radiator fans… But easier than removing the trans!
 
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Definitely worth trying to ensure the solenoid and respective valve body/hydraulic circuit is clear before a trans removal. If the converter is locked at idle it’s turning the trans input shaft one to one like a manual trans with clutch engaged. The rattle could be whatever the trans input shaft is spinning, not necessarily inside the torque converter.
The sound is very much in the converter I believe. Quite distinct in the bellhousing….
 
I’m not sure but this could be a sprag type clutch. That would definitely be prone to rattle when loosely engaged due to low engine RPM-idle.
There is a freewheel on the stator apparently, although not on the clutch assembly itself.
 
It’s probably not throwing a code for the lockup solenoid because it’s never made it to conditions where the ECU would want to engage it - ie cruising in a higher gear. If it’s faulty it would throw a code then.

But don’t want to drive it again to find out… I shouldn’t have forced it up the drive for that one run around the block, if it is a control problem with a locked on solenoid i didnt do the converter clutch lining many favours!!!!
 
FYI - the car is one of these. My friend (whose car it is) loves it. Very very rare in Australia (hence the home build on the trans, no one around here wanted to touch it…) but a very good and practical car amongst a sea of bloody SUVs… Sadly Australia has also gotten on the suv bandwagon :(
 

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Are you saying the converter rattles in Park? Even if the converter clutch was stuck on.....It wouldn't normally make noise in park. Though I'm not familiar with the unit.
 
Are you saying the converter rattles in Park? Even if the converter clutch was stuck on.....It wouldn't normally make noise in park. Though I'm not familiar with the unit.
Yes - it appears to be locked up in park and neutral as well as driven gears. with the associated rattle.
 
Back in the day, GM TH125's were notorious for stuck on converter clutch solenoids. They made zero noise in Park/Neutral but the engine would stall immediately when shifted into gear.
 
I wish the solenoid was as easy to get to as those old GM transmissions!!

I should have put new pressure and converter modulating solenoids in when I assembled it. They’re only $100 for the pair and assuming they were ok because they were replaced 30,000kms before the clutch pack died was perhaps foolish. A false economy given how annoying a job it is getting the valve body removed with the transmission in the car…
 
So the Renault auto trans I rebuilt shifts incredibly well. Probably the best shifts I've felt in these things, they're notorious for hard shifts.

I did change out the valve body and replace the main pair of solenoids that control line pressure and the converter lock up. I had used the old one's stupidly as I'd been told they were not that old. So when I went to start it last week it kept bogging down and missing when put in drive.

I had thought it was an engine issue long enough that I forced it past the bogging to do a quick test drive. Bad move. As suggested on here, it was indeed the converter lockup locked - the control solenoid was stuffed and stuck open.

The scary part is when I dropped the fluid to change the solenoid it has a very metallic sheen to it...

But - it drives perfectly and the converter lockup works on the cruise, so I've left instructions to keep changing the fluid until it stops being metallic looking and see how long it goes for!

But, ****up aside on not joining the dots on why it was stalling quicker, it seems I successfully assembled it!
 
And yes, as it turns out a healthy converter that is being kept locked on by a control problem will rattle like a bastard at idle.
 
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