Which mounting brackets do I replace?

[Mr T]

Wife’s ‘08 with 200k has been making a consistent downshift thud for over 4 years. Sound like it may be a transmission mount.

Both motor mounts have been replace(2 years ago). Wondering how many mounts the transmission has and if it could also be from the transfer case.

you mostly hear it when the motor downshifts as you approach a light.

 

[CaptainAmerica1]

Should just have one transmission mount. May be ujoints in the driveshaft as well.

 

[Chert_Detective]

Is it every downshift or when rolling to a stop?

I remember browsing past a thread on here that mentioned something about the slow rolling 2 to 1 downshift being in the valve body of the trans.

 

[wjburken]

Other things to look at in addition to what’s been mentioned, assuming your Denali is AWD, is:

Excessive play in the front differential
Excessive play in your transfer case
Bad CV Shafts

 

[Mr T]

Good points. I recall, when I was changing oils (front diff, transfer, tranny, etc) I did have play in my front diff. I also inspected my drive shaft u-joints and they have no slop.

I recall being able to get the front to move up and down so maybe its mounts are gone. I’ve removed it completely 2 years ago when I did the oil pickup tube replacement. That was a joy. Sucker is heavy and with no lift and no help, it took me forever to get it in place.

CV shafts are good. I replaced them with front hubs/bearings about 1 year ago.

So I have 1 mount on the tranny.
1 on the front diff?

As for throttle body between 2 and 1, maybe but it really sounds like a mild thud, as if a mount is gone or bad and not a hard shift. It is subtle but there. More felt through the body than heard. Also it is not on every shift, that’s for sure

I’ve changed tranny oil every 30 K as well. So its been well maintained. I’m happy I’m at 200K thus far but it has taken lots of oil changes to get it there.

 

[Joseph Garcia]

I had a clunk that turned out to be the front differential support mounts. Once they were replaced, the clunk was gone. I've listed the URL of my forum post below, if you want to explore it.

https://www.tahoeyukonforum.com/thr...-not-the-drive-shaft-slip-yoke-solved.119545/

 

[Mr T]

I had a clunk that turned out to be the front differential support mounts. Once they were replaced, the clunk was gone. I've listed the URL of my forum post below, if you want to explore it.

https://www.tahoeyukonforum.com/thr...-not-the-drive-shaft-slip-yoke-solved.119545/

I have a hunch those are the cause. I remember looking them over and when I would rotate the tires they would let the diff move a bit. I don't know HOW much is TOO much but it moves and I could get it to almost hop a bit...which is probably the cause of my clunk.

I'll check out the cost for parts and likely do a replacement soon.

Thx.