rear differential "klunk"

[rmtech02]

Hey all,

I hate doing this, but i cant find a thread i saw a few days ago about my problem, maybe someone knows off hand where the info is???

!993 GMC Safari Automatic

My problem:The rearend differential makes a "klunk" when shifting from 2nd to 3rd(around 30mph), if its under torque, like going fast its not so bad, but traffic light to traffic light its loud,irritating, and sounds like the rear end is gonna fall out....(it also "klunks" in other gears but not as bad, and is slow to "grab" going from P to D or D to R.

I have replaced the u-joints in the rear previously due to "rustage"

I took it by a transmission shop, and after a test drive and ruling other things out, motor mounts etc. he had me brake torque it(gas,let up,gas,let up,gas,let up)....3 times in drive, then to reverse three times, then a second time...drive, then reverse...the second time i did reverse he said the entire driveshaft turned 1 full turn then "caught" and grabbed a hold like it should....



1.What in the world could that be specifically????

2. I have a "Pick n pull" i frequent, but if i was to grab a rearend how could i tell if it was ok while its sitting there in the van unable to drive?

3. Is there a way to tell its the differential while im under it and have the driveshaft out?

4. Any other suggestions?

I'm not afraid or worried about rebuilding it, or working on it i just dont want to go at it blindly, and replace unneccesary parts, also.. i had surgery on left hand today, please forgive any spelling, and i wont be messing with the van for 2 weeks, but i wanted to get this in and get ideas before i can work on it.

Thanks,
Randy

[astroturf]

Have a look here RMTech... viewtopic.php?f=108&t=4572&hilit=rookie#p31898 How old are the shocks? Jim

[chevy57bert]

Crawl under your Van, and try to turn the driveshaft. look if you have to much play.

[rev_les]

Crawl under your Van, and try to turn the driveshaft. look if you have to much play.

In addition to turning it....grab the differential yoke and see if it moves up and down.

[Big_kid]

Crawl under your Van, and try to turn the driveshaft. look if you have to much play.

Chock the wheels & set the parking brake, and put the transmission in neutral first. Otherwise the trans being park will keep the shaft locked up. If the driveshaft is spinning, at least one wheel should be turning. If not, you've got a problem.