4L60E torque converter shudder

Sal Lubrano

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Apr 26, 2002
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I apologize for posting this here. I know there are many knowledge transmission experts here who can give me some advice. Having problems with a 2008 Colorado 4L60e 175K miles. Transmission shifts perfectly firm, quick, no slipping or delays. I think the torque converter is having trouble staying locked (shuddering). When the converter locks the rpms drop to 1500, moving about 45-50 mph and a demand to accelerate. For a brief period there will be a metal rattle sound or maybe rumble sound heard and felt mildly to medium from the floorboard. Don't feel like it is slipping/grabbing. If it is going faster say 55 mph it will not happen. Only when the rpms are very low (as low as they can be for the trans to lock up the converter) and the gas is pushed lightly causing the engine to be in a lugging situation for acceleration. If the trans downshifts or unlocks it will not happen. It also, goes away after the truck accelerates about 5 to 10 mph faster. Hooked up a scanner and there are no codes or misfires. Checked the fluid level and it is full. If anyone can help me diagnose this or get me in the right direction it is greatly appreciated. Even if you might know a a site where knowledgeable 4l60e techs are would be a great help. Sorry it is not TR related. Thank you.
 

Chuck Leeper

8/10's of a century!
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May 28, 2001
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Probably get some responses at LS1tech.
You may be able to log the trans activity with EFILIVE, or HPT, if you have such available.
If there's metallic noises, it may be time to drop the trans pan, and see what may be lurking there.
There are some "for instances" here.
 

Pittguy

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Jul 7, 2019
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Ignition misfires can also give u the symptoms. Bad plugs.crossed or poor wires
 

Pittguy

New Member
Jul 7, 2019
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Does the vehicle have an aftermarket tune? Hows the trans mount since it's happening during lugging
 

Sal Lubrano

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Apr 26, 2002
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Just picked up this truck. Have absolutely no history on it. The sound is more of a rumble / grinding sound. I don't see any misfire counts on the scanner or engine codes. If I had to guess it is full stock, there are no visual modifications made to it. Transmission shifts perfectly which has me scratching my head with 175K on the clock. Maybe the transmission has been rebuilt along the way? I will check out the mount tomorrow, it is snowing here right now. As for the fluid being burnt, it does not look bad at all. I don't mind throwing fluid and a filter in there, if there is a chance that could solve the problem. I was also thinking of pouring this in https://www.amazon.com/Lubegard-19610-Tranny-Instant-Shudder/dp/B0002JMLQU. Not as a repair but to help with the diagnosis.
Thank you.

Here is a link to where I posted on the other board.
https://ls1tech.com/forums/automatic-transmission/1929443-4l60e-converter-help-please.html
 

gunzandgearz

gearzandgunz
Aug 24, 2015
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mustang oklahoma
Get it somewhere to simulate the problem and lightly touch the brake pedal while it's shuttering,not enough to apply the brakes,just enough to turn on the brake lights if it goes away it's the converter clutch, without a doubt,this is very common on these units, put some platinum lube guard in her and see if it fixes it, they make some shudder fix but try the other first