Another clunk thread...

[Yo]

My 91 K5 is my second Blazer, so I've definitely had my share of clunks before.

My situation is slightly different though, because I have a series of clunks, not just a single defined CLUNK.

Upon a quick stop to a roll back, there's some wrap, so whenever I let off the brake, there's a "clunk" and a settling. However, when I roll forward ab 3-5 feet, I get another clunk.

I'm thinking the first series is wrap, but the truck suspension is factory with only a 1" zero rate, so axle wrap wouldn't seemingly be an issue?

The second clunk happens after I roll 3-5 feet, so I'm thinking the slip on my NP241 is binding, and not releasing from that bind until the driveshaft has turned over.

Any other areas you think I should check? Sorry for the tired subject.

EDIT: I forgot to mention I changed the tcase fluid last night with no change in performance.

 

[George_Pimpdaddy]

Well we sorta need to ask this but have you checked your u joints yet? also the rear bearing in the transfer case could be loose usually will drip outta the slip yoke if its that but try to give the drive shaft a good shake. Could also be worn or improper set gears in the rear axle.

 

[nvrenuf]

Checked the u-bolts lately? Since it's got Zero Rates it's been apart and may need to be retightened.

Also, can you duplicate the symptoms with the truck on jackstands?

 

[Yo]

Thanks for the response.

I initially thought the u-bolts were suspect, but I went through and retorqued, and the problem persists. They weren't even loose anyway though, I swore this would've solved at least one of the problems.

U-joints I have not checked, but I don't get a clunk when going from drive to reverse, which is usually how one could determine if a u-joint is bad, and they aren't making any noise. Driveshaft also has no play.

The slip doesn't leak, although when I bought the truck the original owner said it did sometimes.....I figured if it did leak, the tcase would be super low on fluid, but when I changed it last night, it was in surprisingly good shape, a little dark, but the case was at capacity.

I've have not been able to replicate this on stands; I haven't tried. I'm thinking it may not be the best way to assess the problem though because the bind up seems to be happening under weight, unless someone can provide some insight as to how I can replicate this without weight on the wheels.

I was planning on installing an SYE and upgrading to a standard slip 2-piece shaft w a CV, as I know this will knock out the binding issue if it does in fact exist. The "wrap" feeling I'm getting is strange bc the truck isn't lifted with the exception of the zero rate.

I will add that the fact that the secondary clunk doesn't happen until the truck has moved forward a few feet does lead me to believe the ring and pinion may need to be addressed. I was told the truck has a limited slip, but driving it around does not seem that way.

Anybody have any other suggestions or care to elaborate?

 

[George_Pimpdaddy]

Its a loose rear end i bet might wanna pop the diff cover and take a look, cant hurt to change the fluid anyway.

 

[blazer88]

I might know this one

I had a 91 before I sold it to my sister, and it had a clunk from the rear end. As the vehicle settled to a stop there was a clunk, and as you got on a throttle there was a clunk. You could not hear this noise from the outside of the vehicle, only the cab. Previous owner said it has done it the whole time he had it. Took it to my mechanic he said it was the pinion bearing, dont quote me on that. But I ignored it, just got used to it. He said it is no big deal and he had a mustang that did it. It is more annoying than anything. My blazer was 91 stock motor 5.7 and tranny the 4l60e, 4 inch procomp lift and 33x12.5x15 BFG AT's. If you send me a more detailed description the the clunk I bet it is the same exact thing.