I believe my front differential mounts are shot....got a quick question

[Mr T]

So I posted on another thread what could be the cause of a slight thud when off the power and the trans downshifts. Like 4th to 3r and even 3rd to 2nd or 1st. It's almost always power off that you hear/feel the low thud.

I have NO slipping on the trans. I've changed its oil every 30K (full flush). Denali has 203K miles. Gettin' up there.

I did get to the underside and the driveshafts seem fine. When wheels were up I could get the diff to move a bit when rocking the wheels.

Anyway, I would like to pull the front diff mounts and replace the bushings. My question to the fourm is can I replace just the bushings to save me some $$$ vs. buying all new mounts?

When I was shopping on Amazon to get some range prices ( I usually buy from an Online GMC store) I noted this. Can I pull my existing metal brackets and just put new bushing in them? This assumes the brackets are not cracked (unlikely). I don't know if those bushings need to be pressed in or if a urban home garage mechanic can do so easily without some special tool or press.

Thoughts?

 

[donjetman]

the thud could also be: motor mount(s), tranny mount, u-joint(s), sloppy/worn transfer case and or differential(s), or any combination thereof.

 

[Bill 1960]

I just replaced mine. The entire mounts, not just the bushings. One of mine was separated, so they definitely can fail. The bushings would require a press to get them in and out. Which I have BTW, I did the whole brackets for the sake of expediency.

 

[Foggy]

What Bill 1960 said !!!!!!

 

[Mr T]

Thanks. Due to the nature of the sound, I'm likely to "shop" stealerships to see what their diagnosis costs would be to help me land the real issue. With 203K miles, I'm not a fan of replace and pray. I want to nail the issue first try and unfortunately, I can't hang under the vehicle while driving......

If it is the bushings, I'll replace both myself with new units. Thanks for the feedback.

 

[Joseph Garcia]

I had a very similar thud, and after much searching for the source, it turned out to be the differential mounts. I replaced them, and the thud issue was resolved. They run about $150 for the pair at Rock Auto.