99 Yukon - Transmission quits when warm

[flyinghat]

Hi everyone,

I've done my best to search around the forum for an answer to this, but I'm afraid I wasn't able to find one.

I've got a 99 Yukon with a 5.7 and the 4L60E, my issue is this: the transmission functions perfectly when cold, but when it warms up it completely ceases to function. As soon as I start the car I'm able to shift through all 4 gears and reverse and even drive it... but when it gets up to operating temperature it basically feels like I'm in neutral.

Any idea what might be causing this? My line of thinking is that there's some debris that's floating around, and when the transmission warms up that debris comes up from the bottom of the transmission and gets stuck in a line somewhere.

Any insight would be greatly appreciated! Thanks.

 

[lesterl]

Start by checking electrical connections/ grounds, then PCM, Fluid level, fluid condition burnt/ black....

 

[flyinghat]

I actually figured it out, the trans fluid was dark but not black or burned... what happened was what I thought, some very fine metal shavings (became the consistency of sludge) were collecting on the bottom of the pan on the magnet, when the fluid heated up the metal circulated and clogged the filter up. I cycled about 4 quarts of the fluid out through the trans cooler line out of the radiator, then dropped the pan and dumped the rest out. Swapped out the filter, threw some new fluid in, and lo and behold she ran.

Either way, thanks for the feedback. I figure I'd update the thread for anyone searching for this issue, I had a really difficult time coming up with anything to back my suspicions up online.

 

[lesterl]

NICE FIND!!!!! Hope it stays...... where did all the metal particles/ sludge come from ?