1991 Chevy Silverado '91 k2500 rear end clunking on accel &

JAYSONSTEWART78

MEMBER
1991 CHEVROLET SILVERADO
V8
4WD
AUTOMATIC
179,000 MILES

Hi, I need some opinions, I have a 1991 k2500 silverado with auto trans. Ive been getting some serious clunking in the rear, usually when shifting without a load.

-under hard accel. She shifts, sounds and feels good,
then when I get off the throttle she will shift again to drop the rpm's and then "CLUNK".

-same thing when getting off the hwy offramp an intermittant single down-shift clunk.

-also while coasting (say 35mph) give her a little throttle and "clunk"

-i grabbed the rear driveshaft and all feels tight in all directions. I dont hear any whinning, and the trans. Is rebuilt a year ago and shifts strong. In the driveway I went from drive to reverse a few times thinking maybe driveline lash between pinion and ring gear and didnt hear any big clunking. Ive lubed some of the rear output shaft splines on some of the newer gm trucks per the gm tech. Serv. Bulletin and this doesnt feel like that.

feels like some slop in the rear end, whats a good way to troubleshoot theese symptoms. Thanks!

3 Replies

DR LOOT

MECHANIC
2,311 POSTS

What you're describing sounds like the Bushing gone out of the transfer case driveline to the rear, get underneath the truck puts your hands on the joke at the transfer case pushing up and down, and tell me how much slop is in the Bushing on the transfer case.

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Thursday, May 14th, 2009 AT 10:38 PM

JAYSONSTEWART78

MEMBER
2 POSTS

Thanks for the reply, I checked the yoke and it is tight. Grabbed, shook, squeezed, rotated and pryed on everything.
I plan on flushing all fluids this weekend and inspecting the diff. I went for another drive and I think I can describe my issue a little more accurately now.

-the clunk occures more severe when heavy braking to a complete stop, for example, I step on it (i have a heavy foot), it goes through the gears 1st 2nd etc. Then I approach a stop sign so I brake, and as the trans. Makes its 2-1 downshift. CLUNK. Sounds pretty bad and the quicker I brake the louder it gets. Now if I brake really slow it may not do it. Hope you can help.
Thanks!

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Friday, May 15th, 2009 AT 9:53 PM

DR LOOT

MECHANIC
2,311 POSTS

I need to make sure you diagnose the rear end proper, did you:
1. Put the truck in neutral, before checking the backlash on the third member?
2. The driveline should not twist very far back and forth
3. There will be two adjustments to check
4. The first one will be played in the spider gears and wear on the axle shafts, that will be majored by how far the drive line twist back-and-forth before the tires move
5. The next adjustment to check is the backlash that will be a little harder to check, you will feel it through your hand by twisting the driveline back-and-forth very softly until you feel no contact with the gears that will be a backlash setting.
Let me know what you find out

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Saturday, May 16th, 2009 AT 10:54 AM