The weird clunk

[83GMCK2500]

I too had a '99 Tahoe with a strange clunk. I researched it and researched it and came up with rear output shaft in the transfer case. There was a special grease for it, as well as a higher nickel content replacement slip yoke from GM if it was really bad. Mine almost sounded like a quick "vup-vup" when leaving the line/light/stop hard. If I drove normally, which is pretty light, it didn't do it.

 

[TurboTahoe]

Well, I've taken Tim's advice and purchased mounts from NAPA. They are made in India! Look beefy enough. Now I have to figure out how to swap them out...

-Rob

 

[3500GMC]

A pinion crush sleeve can fail and cause a clunk. Grab the d-shaft at the rear yoke while there is no tension on the drive system and give a good tug and note any movemant in and out.

1/2 ton Dodge corporate rears were bad for this too.

Just a thought.

 

[jmiller]

My last drive line clunk besides u joints was excessive backlash in the rear gear.

The pinion turned quite a bit from clockwise to counter clockwise.

Found the carrier bearing inner race started to spin on the carrier. This changed the back lash. I had 0.025" backlash and a side to side movement of the carrier of 0.020".

The carrier and bearings need to be replaced, (not to mention the gear set) but other bills needed to be paid first. The gear face looked great, so I reset the backlash and carrier preload back to specs. In the last year I've put over 10K and a one winter of plowing. Sounds like it might be coming back. I need to check for play when I grease the U joints.

 

[Odlaw]

My 99 Tahoe did just that pretty much every day of its life. I brought it in to have it "fixed" numerous times and within a few weeks, it always came back. Its supposedly called gear lash and its from lube drying out prematurely between the axle/u joints and rear end. There are splines inside there that get dry and the clunk is the complete lack of lube. Its plagued GM trucks for nearly 20 years that I know of. Every fleet GM truck, 90-99 has done it to include burbans and Tahoes. In fact, my 04 GMC DMAX did it and my 07 clunks too and has done it since 2500 miles. Its gotten worse over time and so did my Tahoe. I've had my 07 in the shop twice to get it fixed and it keeps coming back. In fact, I get it in reverse too and so did my 99. Its a poor design if you ask me.

What he said. Except, I don't know how this could be possible between the rear end and the u-joints - on my 01 Z71 it was the slip shaft that slides in the tail of the tranny. GM recall said they would replace the slip shaft with a different one that contained nickel and would not rust and therefore prevent this problem.....but, due to the millions of recalls they were all out of the shafts so in the meantime, I could bring it to any GM dealer and they would apply a "special" lubricant until it could be replaced. About six months later, got a call, part was in - they swapped it and I haven't had the clunk to date.

So, long story short, slide that shaft out of the rear of the tranny and apply your own brand of lubricant and see if it stops.....my guess is that this is the problem.

Smitty

 

[TurboTahoe]

If all else has failed to correct this clunk, try removing drive shaft and putting a small amount of grease on the slip yoke splines. I think that may have been what UNIT453 was talking about. Has been a thorn in GM,s side for many years. Was a grease released for this many years ago but no clue what part number.

I looked at what it would take to do this, and I can't quite figure it out.

I read this article: http://www.agcoauto.com/content/news/p2_articleid/144

and looked under the Tahoe. It appears that one could simply unbolt the U-joint going to the differential, pop the drive shaft out, pull it back, grease the splines, and then replace everything. Is it that easy? I unbolted the U-joint, but could not get the U-joint to budge out of its cradle....

-Rob

 

[ak diesel driver]

pry bar

 

[Dieseldad97]

Still chasing the clunk eh Rob? I also had the clunk and after finding out the tranfer case was low on oil and filled er up my clunk is 100% gone. Who knows? Have you checked your oil level in your case? Just a thought.

 

[94K30]

Jan 12th, we had a huge snowstorm here, 27" in 14 hrs, during the middle of that plow session, my tranny mount decided to come apart.... when the tranny started moving around, it cracked a cooling line, and whacked the harness where it goes into the tranny. ( that Harness is a GM only part and very pricey) I ended up having to have it towed, Checking those mounts seem to me to be a great PM item, all of the sudden....