Clunk when accelerating after coasting at 80 km/h, and clunk when reapplying gas after coasting from 40 km/h to 60 km/h

[j91z28d1]

transmission mount?

 

[Geotrash]

Sorry I have a correction to make. The sound doesn't come from the engine bay, it comes from behind the drivers seat sort of around the transfer case location. Do you have any ideas what would make the clunking noise around there?

Sounds like that travel through the frame and you feel it in the seat. My money is still on motor mounts or front diff mounts. The transfer cases in these also develop play in the chain as the miles accumulate. My 2007 AWD XL Denali has a wicked clunk in the driveline from the play in the transfer case:

 

[Joseph Garcia]

Differential mounts, IMO. Been there, replaced them.

 

[RogerK]

Hello,

I own a 2008 gmc yukon and am experiencing some drivetrain issues.

First of all, when I am coasting at 80 km/h and floor it my yukon makes an alarming clunk in the front end. If I accelerate not as aggressively the clunk doesn't happen.

Also, when I take my foot off the gas going 40 to 60 km/h and let the rpms drop then re-engage the gas peddle I here and feel a slight clunk. I think of it as teeth grabbing after spinning or something like that.

My yukon has 244k kms and i already changed both rear u-joints. I did the engine mount check and they seem to be absolutely fine. Engine does not move around too much at all.

I also have the following engine codes:
P0430
P0455
P1153
Should I be fixing these? Are they pressing?

Not too sure what it could be, any ideas?

Probably a motor mount

 

[petethepug]

What you’re hearing is tied into a flow chart of fixing one particular thing can make fixing another thing you didn’t know about almost free.

It’s important to know when and how to spend dough on this drivetrain. Repairs & mandatory services done in the wrong order can cost you 3x as much.

Is there any past maintenance done on your truck?