Transmission issues need help asap! Please!

Javenged1007 · June 29, 2018

Someone help me! In the process of troubleshooting my 2006 gmc Yukon Denali xl 6.0. It's my work truck and need to get it going asap but single income currently. So he it is

2006 GMC Yukon Denali Xl 1500. 6.0l

AWD about 189000 miles

First sign of problem, may not be related, but got home, went to put in park and could not get it into part. Kind of had to force it in place but gently.

Drove fine next day and did not have issue after that. Few days later, took off at light and when shift into 3rd I think....it kicked really hard then revved up to 5000rpms. I got off the gas and it went back into gear. Drove it home about 10 miles carefully and if I lightly press the pedal it would advance. Got home and it made a weird wind noise drive side area.

Check fluid, normal. Temp on gage for trans was at normal. Took around block and it goes into reverse no issue and then neutral then 1st, but when in 1st it seems the breaks are being pressed and its lags like crazy. Goes into 2nd hard then from 2nd to 3rd it slips. My question is where do I start? Is there something I should look for first? I was ase cert 22 years ago, so know my basics and do all my repairs but awd is not my cup of tea. I want to check my transfer case and see if there's fluid. Also going to do a visual inspection and check for any logical issues.

Please any help would be greatly appreciated.

Doug_Scott · June 29, 2018

I would start at the first issue. Check the shifter linkage for any looseness or binding.

The issue where you were pulling away in 1st but felt like the brakes were holding it back was very likely the transmission not being in 1st, but likely in 2nd gear. That could also be a linkage issue. I have exactly zero hands on experience with any of the recent GM transmissions, so cannot help with anything inside the case. Your first issue really sounds like something being either loose, or broken.

If this was a Torqueflyte I would say the rooster comb(shifter detent) has become loose on the shifter lever. It's held in place by being a tight fit and peened over to retain it. Try shifting the shifter into 1st or L position and then into park with then key in the off position, or better yet with battery ground cable disconnected. Once the shifter is in park see if the truck will roll. Move the shifter fast and slow, you are trying to duplicate the shifter not going into park. I always try the free things first, and also start at the first symptom.