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Hello, I have the shuddering issue on my 08 XC90 V8 AWD, the same indicated in this thread: https://forums.swedespeed.com/showthread.php?573730-2007-Volvo-XC90-3-2L-Transmission-Shudder

It is very likely the torque converter (TQC) - I loaded up the TCM in Vida and had a friend read it off while driving, and the shudder only occurs when the TQC is in "slip" mode. When the SL solenoid is around 600mA. The shudder does not occur when the TQC is fully locked or fully unlocked. I added ShudderFixx and there was no change. There are no codes outside the regular audio system\bulbs\tire sensors stuff. I flushed the trans a year\10,000 miles ago.

I read that some people replaced the valve body and had no effect, some replaced the TQC and it fixed the problem, others it only resolved the problem for a short time.

My driving is 95% sitting at or between stop lights, I almost never go over 45mph, so the shudder is near constant in normal driving if I don't drive to specifically avoid slipping lockup.

So here is my idea: If I cut the signal (for example, by disconnecting the SL (lockup) solenoid, or even installing a switch to break signal) to disable lockup entirely, is there any risk of damage besides the additional heat and possible 6-8% loss of MPG if I do go on the highway? The switch would only be an interrupt so there is no risk of locking up when it shouldn't be.

The other option I figured was a small IC that would only allow signal once it hit a threshold of something like 950mA ((0mA being fully unlocked and 1000mA fully locked) thus removing the slipping lockup mode entirely. I don't care if it throws a code unless it's causing the car to go into a limp mode.


Please let me know if this is a bad idea.
 

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Hi! I have the same problem, and have thought about doing the same thing. Want to bump this thread--anyone have any experience doing this?
 

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I'm not one for magical fluids, but this significantly helped the shudder in my old V8 TF80: https://www.amazon.com/Lubegard-19610-Tranny-Instant-Shudder/dp/B0002JMLQU

I went as far as replacing the valve body, which didn't fix the issue, so you're right on the money, it's very likely the Torque Converter.

I would be interesting to see the results if you disable/disconnect that solenoid. I don't see any harm in preventing lockup, except maybe a CEL or two. Why not try disconnecting that pin at the TCM and report back with results?
 

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I have the same issue in my 3.2 , would be curious to see how this works as well. Right now in the city I drive it in manual mode to keep the rpms above 2k to avoid the shudder.
 
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