'90 burb "klunk" question

[da-burb]

I stepped into the 90's with my latest winter-beater. It is a GMC K1500 burb. When I come up to a stop sign I will get a klunk that I can feel and hear. That is when it is in gear. If I do the same thing and slip it into neutral before I stop there is nothing. Tranny is an automatic with O/D so I assume it is a 700. Anybody have this happen to theirs and know what the fix is?

[perry]

hello
kind of feels like a small carhit your rear bumper at a stop.
it has something to do with the trans mission with the OD, i switched mine to a th400 and it went away

[jeffspower]

A lot of 88-up chevy trucks do that. Mine does. It is in the fit of the driveshaft slipyoke. The rear end moves slightly when you hit the brakes, & bounces back once you stop- making the slipyoke "jerk".

[jimfulco]

Subs with one-piece drive shafts do this all the time. My '79 with Turbo 350 does it sometimes. If you grease the yoke splines (Chevy place said use anti-seize compound), it will stop for a week or so, maybe a bit longer. Except for being annoying, it won't hurt anything.

[Krosati]

Does it seem to only do it if you stop kinda quick?
Mine does the same thing and I have tried seveal different methods of stopping. If I ease on the brakes and come to a gentle strop, I get nothing. But if I firmly apply the brakes and stop short it does it.

[da-burb]

We have the same problem Krosati. I have yet to have the noise when I do a hard stop in neutral though. I didn't think it was anything serious, but if it was fixable I want to do it. With over 200,000 miles I expect some noises, but this one is getting to me.

[chiphayes]

i worked at a local college and all of our trucks were88-94s,allof them did it after a few years of use,my 92 blazer does it.anyway our mechanic at the college,old man very intelligent,says it was the rear leaf springs,the plastic,in between the leaves wear out.just an idea,gm here locally even agreed.

[eaglelox]

check out bushings in rear springs.if thay are worn it will allow movement. check also u-joints, trany mounts, pinion nut

[Grim Reaper]

My 75 Jimmy, My 79 Blazer and my 88 R20 burb all do it. All fixed yoke (yes, even the TH400 burb). Brakes seem to make the biggest change in it. New brakes front and rear and it seems to do it the least.

[Sonny]

I haven't done this and it sounds silly, but a long-time GM mechanic said to put a super ball in the yoke. He said this helps the yoke to move easier on the spline shaft. Anyone else heard this because my 94 burb does the same thing.

Sonny

[Ryan Flowers]

My 85 did it and my 90 started doing it. I lifted them both and it stopped. Asked around and got two answers from about 5 different guys:

1. The poly urethane bushings in the leaf springs wear out or loose or broken shackles. When I put the lifts on the Burbans I put in new bushings and it stopped. (Didn't want to believe this one but when I lifted my 90, one of the front driver side shackles was completely sheared in two. As much as I crawled up under that front end and looked I never even saw it was broke until I took it all apart for the lift).

2. Was axle wrap (which I personally think was the cause). After installing the lifts and putting shims between the axles and springs it cut out the klunk.

Who knows if we will ever know? I say start with the cheapest fix first!

There are allot of better qualified gear heads in here that could probably pin point it.