leaf spring bushings and popping noise

[old cool]

About the only bushings or mounts that were not changed on my 66 gmc were the cylindrical bushings at each end of the leaf springs. On occasion, when I corner, I hear a popping noise in rear of truck. Would these dryer, shrunken bushings be the culprit. Or, are there other common causes to make a popping noise. Everything looks snug, including, but not limited to, shock absorbers.

[padresag]

are they not metal bushings back there; greaseable?
ron

[old cool]

rubber inserts that show cracking and shrinkage. all else (possibly called bolt sleeve) is metal. hope we're talking about same item

[padresag]

spring pins and shackles as in the attached link from LMC. the one illustrated is a 4 x 4 rear end but should be similiar to a 2 whl dr rear suspension(which they don't appear to show)
ron

[old cool]

Ron,
Does shackle bushings sound right? I see them on internet; even utube. Looked again and the bushings are somewhat dry rotted. I'm hoping someone can tell me that old bushings are the reason a truck would pop when cornering or, is there is another part to look at. Can't find anything loose. If the bushings aren't an issue, I can live with a little dry rot and take care of other issues, lol.
FYI: no grease zerts on rear leafs that i can see. I have seen them pictured on later trucks.

[padresag]

here is a better link http://www.classicparts.com/Chassis/products/224/
there should be zerk fittings on the end of the pins. if they haven't been geased in who knows how long and are seized or worn out they will make a noise, same as a broken shackle or pin. do not believe that they went to rubber bushings until 67. there could also be other reasons such as a brken centre bolt in the springs, frame, even bed bolts can cause noises. are you sure that is not just dried out old grease that you see instead of dry rot
sometimes a little grease will do wonders. I remeber , in 1975 I had a Hayes truck on logs out of Mackenzie,b.c.. I had a driver on and we were hauling nights off highway to save the roads at break up in March. diver complained that the truck was having difficulties steering around corners loaded* carrying about 105,000 lbs net with just a tandem axle trailer. I asked him if he was using that thing that was behind the seat. he said no what is it and I replied ; the grease gun and you should be greasing the frt bunk periodically and that will stop it from binding. that was the end of his driving career with me
ron

[Shorty63]

If the popping noise if coming from those bushings you should be able to recreate the noise by jumping in the box. I would start by making sure that is where the noise is coming from.

[old cool]

Ron i guess i have later model set up as I do not have zerks where the leafs bolt into brackets. Also, (FYI) frame is not believed to be orig. Though, I will say, from looking at a frame picture in a 1964 shop manual, my brackets and leafs look the same. As I do more reading on the 60's gmcs, it does seem that 63-66 are not much different underneath if at all.

Shorty, I can make it pop when I push to box side to side. It does not happen on every push. It's as though it pops is a certain position and then stays there for a while. Maybe it readjusts after driving (r and l turns, etc.). I will need a helper with a stethascope before i can track it down. I was just wondering if that's the most common place where they pop.

[padresag]

you should also be able to tell by jacking the the frame up by either seeing the slack in the bushings or hear it. also if the leafs are badly worn or rusted that can also cause a popping noise. it it was sitting for a good period of time the leaves could have rusted and etched a notch where the ends of the leafs are and can click across that edge with movement. they do not stay new forever
zerks if there are any would be on the outside end of the pins
ron

[old cool]

No weakness in springs. Most bolts, mounts, and bushings have been changed. New wood and rails. ONLY noticeable compromise are the shackle bushings. There all there, just showing some cracking. U-blots surrounding springs are tight. (I can't turn the nuts any further). Lastly, I fastened tailgate chains to make sure that wasn't the clunk.
Something is either overtightened or undertightened.
Like other posts I've read, there are just many, many possible answers. But, it's always good to hear ideas. Thanks, thanks, thanks...

[padresag]

on some GMC the upper rear shock bolt goes through the frame from the outside in. somehow if I can remember the shock itself can be tight on the bolt, but the bolt can be loose in the frame. difficult to find these noises on the internet. this is where experience comes into play and diagnosing the problem. it is just a systematic set off checks usually to find these thing and in about 15 min your done
ron

[old cool]

I'll have to check it out.