quickie ? on the clunk just before letting off brake going forward

Sprung Monkey

Original poster
Member
Oct 12, 2017
350
Al
quickie ? on the clunk just before letting off brake going forward
I beleive one of or both drive shafts probablley the rear splidesforward upon stopping then when tension of brakes is released there is a splipage of the driveshaft backward toward the rearend thus the clunk.

edit: this thread isn't about the 2 to 3 transmision upshift clunk I have felt a tad harshnessness there also but totalley difernt issue. I've read GM claims the clunk is normal.

am I wronge about this drive shaft slipage?

I personalley think it's another GM joke
?1 could I be wronge about the clunk maybe my U-jionts are worn?
?2.I have all wheel drive not sure what type of U-J the 97x requires?
1.at rearend driveshaft
2.at front of front drive shaft.
I think both slide into transfre case. @MRRSM

bottom line the clunk is annoying
any tip/advice here is appreciated SM
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
I have a similar "thunk" when braking coming to a stop uphill mostly. Don't hear it, just feel it in my butt. It's as if a rear caliper is moving backwards on the countershock when coming to a stop. Thought it was the shocks, replaced them, nada. Still there. U-joints are good.

Things to look at: u-joints, transmission slip yokes, brakes, suspension, trans. mount.
 
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HARDTRAILZ

Moderator
Nov 18, 2011
49,665
For years and years this has been discussed and most often a simple bit of grease on the slip yoke to the transfer case from the rear driveshaft fixes it.
 

xavierny25

Member
Mar 16, 2014
6,323
Staten Island, N.Y
I have spohn rear upper, lower control arms and panhard bar and the Clunk is still there. Sway bar bushings are 1 1/2 yr old, rear end links are fresh too. I'm going to try what @HARDTRAILZ said along with new u-joints.
 
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16vcabman

Member
May 10, 2018
113
Ortonville, Mi
Well, my concern is the fluid in the transfer case if set to the right level should lubricate the splines. So I checked the TC and low and behold the TC was low added up to fill line with correct fluid and the clunk went away. So check your tc
 
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Sprung Monkey

Original poster
Member
Oct 12, 2017
350
Al
Well, my concern is the fluid in the transfer case if set to the right level should lubricate the splines. So I checked the TC and low and behold the TC was low added up to fill line with correct fluid and the clunk went away. So check your tc
that's good you fixed a clunk however it's a differnt clunk. hardtrail is correct a tempuary solution is grease rear drive shaft spline w/ red grease.

I have new brakes, fluids trans/gear oil/ not sure about the 2 quarts of transfer case trac2?

I want to do all the maintenance at one time so transfer case oil is holding me up plus I can't find my second jackstand.plus I still need to adjust the trailer plugs taillights ect.ect.
 
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TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,047
Brighton, CO
Nope.. It just a thunk type sound, and it almost feels like someone gave you a love tap by lightly rear ending you.
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,047
Brighton, CO
Check you lateral arms to see if the bushings are still good. Check to make sure the rubber insulator above the springs are still present. Check the springs, although not likely to be the problem. Also check the pan hard arm bushing are still good. The stabilizer end links can make all kinds of noises, so check those as well.
 

smt 59

Member
All replaced in the last 2 years with Massive arms/pan hard bar and new end links last week with sway bar bushings as well. pulled the springs on Monday and all good. Shocks good as well. Transmission shop confirmed its not the diff. or U joints.

?????? this is why I am now stumped
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,047
Brighton, CO
How do your emergency brake shoes look?
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,047
Brighton, CO
While your under there, check the fluid level of the rear diff.
 

smt 59

Member
So I decided to pull the wheels after work today and found the parking brake shoes in good condition and all parts in tact, now I’m at a complete loss.
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,047
Brighton, CO
I only have 2 suggestions left

The backing plates for the brakes have been known to bend, or even rust out. One of them might be dragging against a brake rotor.

or..

If you have a selectable 4x4 system, make sure its in 2WD, and put the rear end on jack stands. Start the truck up, put it in gear, and see if you can track it down. If you only have AWD, than I dont suggest this unless its on a 4 post lift.

Beyond that, I am at a loss as well...
 

xavierny25

Member
Mar 16, 2014
6,323
Staten Island, N.Y
I'd check the Massive panhard bar,I do remember someone having an issue with one of the joints on one end. That was the cause of his mysterious clunk bang. It's really why I went with the Spohn pan hard bar. I didn't want to replace something that was working with something that might cause an issue. Just my :twocents:
 

smt 59

Member
All above noted suggestions have been checked and all is good, I’m now at a point after 14 years that a visit to the dealership is warranted.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Noooooooo!

Did you put some grease in the tranny slip yoke?
 

smt 59

Member
I have made arrangements with my friends shop to do that on Monday after work, the noise is so damned annoying it sounds like the back end is going to drop off.
 

smt 59

Member
The continuing saga of the unidentified clunk continues, the slip yoke was greased and u-joints checked while the shaft was out and it made no difference. The techs are now convinced that the rear diff is on it's way out and I tend to agree. So now some decisions need to be made. I will keep you posted.
 

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