2017 Yukon XL Denali V8 6.2L 8L90 Transmission or Rear End?

[YukonGirl2017]

Hello, I am looking for advice. I have a 2017 Yukon XL, with selectable 4WD I just purchased it not long ago. It currently has 87,639miles on it. I am trying to figure out if it is my transmission kicking or my rear end when changing gears; you can feel a clunk when your foot is on the break and shifting from park to drive and back to reveres and sometimes but not all the time when your stopped and try to get on it you can feel a clunk/jerk when accelerating but it feel like its coming more from the back the transmission cooler lines were just replaced, by the selling dealership but my fiance put it on the lift we found that the rear ends seal that is right at the yoke and Ujoint is leaking and seems to have been for a while so I'm wondering if it is possibly the rear end and not the transmission and note you can also feel the cluck when shifting through PRND and or trying to step on it when you are stooped. While my fiancé has been driving I’ve felt it happen a couple times while slowing down as well. According to the service history the vehicle has been very well maintained. When the technician who replaced my transmission cooler lines did the test drive they claimed the transmission is good and did not feel this issue that or they just don’t care. Their is no check engine light etc. Also if I go into myGMC app and look at the diagnostics for the vehicle it all checks out.

Note: it does have a tow package but doesn’t look like it was ever used.

I’m just looking for some insight. Any advice on what to do at this point. I do have a 3,000mile drivetrain warranty but with them stating it’s running okay I do not know how to approach this?

 

[RoadTrip]

That clunk could be a broken engine mount or even worn bushings in the lower control arms.

You can check for excessive engine movement hy having your partner start the vehicle and put it in drive, keeping her foot heavy on the brake. Keeping the vehicle braked, have her give the engine a couple quick throttle blips. You should observe the engine to see if it tilts or lifts. If so, at least one engine mount is bad.

The lower control arms can be tested from a stop by a brief acceleration for a few feet and then another stop. The clunk will happen more often when braking.

Replace that seal and try these tests before getting a new trans or diff.

 

[YukonGirl2017]

That clunk could be a broken engine mount or even worn bushings in the lower control arms.

You can check for excessive engine movement hy having your partner start the vehicle and put it in drive, keeping her foot heavy on the brake. Keeping the vehicle braked, have her give the engine a couple quick throttle blips. You should observe the engine to see if it tilts or lifts. If so, at least one engine mount is bad.

The lower control arms can be tested from a stop by a brief acceleration for a few feet and then another stop. The clunk will happen more often when braking.

Replace that seal and try these tests before getting a new trans or diff.

Have you seen this issue before?

 

[RoadTrip]

Yes. This is from personal experience. There are threads on here which go into detail about the engine mounts, but less so about lower control arm replacement.

 

[YukonGirl2017]

Yes. This is from personal experience. There are threads on here which go into detail about the engine mounts, but less so about lower control arm replacement.

I really appreciate it I will see if we can do this procedure and let you know, I’m really hoping it’s not a transmission or a rear end.

 

[RoadTrip]

P.S. Do not drive your vehicle in “Auto” on the 4WD selector knob. It will prematurely wear out your front driveline components. Keep it in 2WD unless you need it.

 

[YukonGirl2017]

P.S. Do not drive your vehicle in “Auto” on the 4WD selector knob. It will prematurely wear out your front driveline components. Keep it in 2WD unless you need it.

My husband said to never use it, to treat it as our old Chevy 1500 with selectable 4WD, to keep it in 2WD and only go into 4WD when needed and only use 4LOW if I’m stuck. So thank you!

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

The truth is that it could be caused by any number of factors. You need to narrow it down to the source of your issue, before firing the parts cannon and wasting a lot of money.

Find a trusted local repair shop, and do the standard test for broken motor mounts, particularly the driver's side motor mount. If the motor mounts test out OK, then get the truck up on the lift with a person in the driver's seat, and shift into Drive and give it some gas. Another mechanic with a mechanic's stethoscope will be under the truck, tracing down the source of the sound. When I had this done with my truck, they found that the front differential mounts' bushings were shot, and after replacing the mounts and their bushings, the sound went away.

 

[YukonGirl2017]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

The truth is that it could be caused by any number of factors. You need to narrow it down to the source of your issue, before firing the parts cannon and wasting a lot of money.

Find a trusted local repair shop, and do the standard test for broken motor mounts, particularly the driver's side motor mount. If the motor mounts test out OK, then get the truck up on the lift with a person in the driver's seat, and shift into Drive and give it some gas. Another mechanic with a mechanic's stethoscope will be under the truck, tracing down the source of the sound. When I had this done with my truck, they found that the front differential mounts' gaskets were shot, and after replacing the mounts and their bushings, the sound went away.

I appreciate all the advice! Here is a picture of my Yukon

 

[Blackcar]

If dealer didn't do repairs to transmission issues these transmissions take a what they call Mobile one blue label trans fluid and fluid level needs to be correct which is also needs to be done correctly.

Here is TSB on vehicle you have.

https://static.nhtsa.gov/odi/tsbs/2019/MC-10163890-9999.pdf

https://static.nhtsa.gov/odi/tsbs/2019/MC-10169298-9999.pdf

 

[YukonGirl2017]

If dealer didn't do repairs to transmission issues these transmissions take a what they call Mobile one blue label trans fluid and fluid level needs to be correct which is also needs to be done correctly.

Here is TSB on vehicle you have.

https://static.nhtsa.gov/odi/tsbs/2019/MC-10163890-9999.pdf

https://static.nhtsa.gov/odi/tsbs/2019/MC-10169298-9999.pdf

Thank you!

 

[Bigburb3500]

Check the driveshaft/u-joints as well. If you are hearing. The noise could be play in the driveshaft and why you hear it towards the “back” of the vehicle.