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

[Sprung Monkey]

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]

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.

 

[HARDTRAILZ]

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.

 

[16vcabman]

I thought it might be some of the rear control rods having bad bushings that is what it feels like?

 

[xavierny25]

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.

 

[16vcabman]

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

 

[Sprung Monkey]

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.

 

[smt 59]

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.

Does this noise sound like a broken spring or metal binding???

 

[TollKeeper]

Nope.. It just a thunk type sound, and it almost feels like someone gave you a love tap by lightly rear ending you.

 

[smt 59]

Damn, I guess I need to keep investigating, mine is a sound like described above.(Spring breaking or metal binding) Thank you.

 

[TollKeeper]

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]

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]

How do your emergency brake shoes look?

 

[smt 59]

Good question, I will pull wheels on the weekend.

 

[TollKeeper]

While your under there, check the fluid level of the rear diff.

 

[smt 59]

Will do, although I changed it about 2 years ago when the seals where replaced. Doesn’t hurt to check.

 

[smt 59]

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]

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]

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

 

[smt 59]

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]

Noooooooo!

Did you put some grease in the tranny slip yoke?

 

[smt 59]

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]

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.