There was a GM TSB that came out that sounds like your symptoms. The summary is: "Clunk noise felt through floor pan". By Googling that phrase I came up with this forum thread: going crazy over clunking... - Car Forums and Automotive Chat

About half way down is a post by a "blazee" where he quotes the language from the TSB. He then describes his fix after the quote. It talks about the torsion bars.

Scroll further down near the end of the page (the thread seems to go off topic) and you'll find a post by "herkyhawki". He describes his fix which involved the stabilizer bar.

Hope this might help.

 

I went to see my auto parts guru for price on cv joints as I had clunking going on and he said before doing that go to a Dodge dealer and get some differential additive which surprisingly fixed it.

 

it does it in 2hi.. .. when the front tire is free of the differential only when turning full lock right and moving forward...

 

There's some good information in that post from the Automotive Forum. I'm going to add those checks to my diagnostic list!

 

Here's what's new with the Jimmy:

I had the day off today so I was able to spend some quality time in the shop with my vehicles. I changed oil in my '93 Sonoma pickup which was straightforward and easy. I like both of those qualities.

I also did a quick oil change on the Jimmy. Since I had it up in the air I was able to do a little bit of checking. The sway bar isn't hitting anything. It doesn't look like the lower control arms are hitting anything. I had my friend turn the steering wheel back and forth and it didn't look like anything was hitting or rubbing on the control arm or steering linkage. Also good to know, the Pitman arm and steering gear box didn't have any slop. I didn't get to checking the torsion bar mounts in the rear.

The upper control arm bushings look suspicious to me. I don't know what they're supposed to look like but the rubber in the bushings was all cracked. The control arm didn't move in and out when I tried to move it but it did move forward and back by almost a quarter inch.

Do the bushings sound bad enough to warrant replacement?

Also, since my friend was over, I had him watch the front tire as I backed up during a tight turn. He told me the camber looked like it was off and the tire was scrubbing badly. I wondered if for some reason the front axle might have been locked causing it to bind. I jacked up the right front tire and tried to turn it. It spun several times freely. With the right front tire still up in the air I put it into 4WD and the tire still turned just fine. I thought that when it's in 4WD the right front tire shouldn't turn because the axle should be locked and the differential would keep it from turning while the left tire was still on the ground.

That leaves me with a whole new set of questions. Is it really in 4WD or is it not in 4WD? If it is in 4WD is that what's causing the tire to scrub on the hard turns in reverse? If not then is it just a bad alignment? I just had it aligned last month after I replaced the ball joints, idler arm and outer tie-rod ends.

 

I dont know much about the 4wd but I can tell you by the description of your bushings they need to be replaced.They should be no play in them and the rubber should be solid with no cracks what so ever.Be glad its the upper ones that are bad and not the lowers.I would check those out though cause It would cause the symtoms you are describing.

 

Thanks for the info. I'll definitely order a new set of UCA bushings from RockAuto and replace them over the holidays when I'm not busy earning money.

If anyone else has thoughts about what may be going on with the 4WD I'm open to all input.

 

Just so you know you have to disconnect the upper ball joints to change them.You may and its a good possibility you may damage them.You might be better off ordering both control arms.They have the bushings and ball joint already in them.

 

Also, since my friend was over, I had him watch the front tire as I backed up during a tight turn. He told me the camber looked like it was off and the tire was scrubbing badly. I wondered if for some reason the front axle might have been locked causing it to bind. I jacked up the right front tire and tried to turn it. It spun several times freely. With the right front tire still up in the air I put it into 4WD and the tire still turned just fine. I thought that when it's in 4WD the right front tire shouldn't turn because the axle should be locked and the differential would keep it from turning while the left tire was still on the ground


Have you checked all the vacume lines going to the transfer case and front differential?

 

Just did my uppers today... disconnecting ball joints is simple.. merely use a prybar to pry between uca and spindle and smack the spindle at the taper with a 3lb sledge... pops right out, no damage... Lowers are next... but only in the spring.. too damn cold in the winter.