Technical Another rear clunk saga

So it's fairly seldom where I am unable to find the cause of a problem, this is one of those times.... I recently installed a new 10 bolt rear, and built a truck arm suspension for my 51 Chevy hardtop and have a on again off again (more on then off) clunking noise from the rear end when I hit the brakes. The suspension is solidly fabricated and installed, trucks arms ran at an angle from the crossmember to the axle, frame width Panhard bar, air bags, shocks, all the parts to make it right. The clunking sensation sounds/ feels like the whole rear axle is shifting but after checking and re checking there is no way it's moving. I thought perhaps it was the brakes but I have rebuilt more drums than I care to admit so I know that they are right, the master cylinder is a cpp power deal, no prop valve (could that be my issue?) I am reluctant to believe its the slip yoke as the truck arms keep the axle firmly located. Any thoughts/ ideas/ solutions would be greatly appreciated!

 

I'm just wondering if your rear brakes are locking up. Check your universals, Is it possible your air in your bags could be shifting the weight of the car? Are your bags directly over your axle? Just a couple of things to consider. Maybe some more info could help.

 

Take an electric glue gun and run a small bead between anything that could possibly move. Let it set up a bit and take it for a ride. After the next clunk, crawl under it and see which beads have let loose.

 

My 2003 Toyota Tacoma has a very similar clunk when the slip yoke gets dry. The whole truck lurches when it breaks loose again on take off. Try a little silicon grease on the splines just to eliminate that part of the puzzle.

Joe

 

How is the clearance between the studs and the holes in the drum face? Tighten your lug nuts and report back.

 

My 92 Chevy pickup does the "dry slip yoke" clunk unless I grease it now and then. Good ideas so far.

 

So I greased the yoke this morning (there's a joke in there somewhere) and still no change! It happens anytime I press the brakes both high and low speed, and sounds to definitely coming from the rear. I had the rear diff completely gone through by s very experience local shop and it has a great bill of health... Rechecked all welds and everything is solid. The saga continues!

 

Brake backing plate to axle movement? Would be hard to notice.

 

The strange thing also is that it doesn't need to "reset" in between clunks, meaning if I am let's say coasting at 15-20 mph and hit the brakes it goes clunk, keep coasting and hit them again it goes clunk

 

Brake shoe motion impeded? White lube help?

 

Update, I had my pops drive slowly as I walked alongside the car, it looks like the right rear wheels stutters with the clunk... Bad brakes? Its definitely coming from the rear passengers side wheel area, lug nuts are tight and all that jazz...

 

I'd pull the brake drum and have a look. Sounds like a return spring is resetting "whatever", for the next clunk

 

Check the wear pads on the backing plate.
They wear, get ridges, then things snap and clunk over them. When the shoes over come the snag they grab the drum instead of ease into the drum. You should be able to find and hear this stationary too I'd think.

 

Something with the return springs if you ask me.

 

Also check to see if the sides of the shoes are hitting the inside of the drum.

 

get a professional opinion!

 

So I think I figured out the issue, I put the car up on my lift and had my lady inside pushing in the brakes with the car in drive, I narrowed the noise to the rear passenger drum, I took it apart and it all looked fine until I noticed that both brake shoes had the same length lining on them (the rear is supposed to be longer then the front) out of curiousity I pulled the driver side and drum and what do you know! The same two sizes of brake shoes! Looks like somewhere along the line Napa boxed up things wrong! I got some new shoes, installed them and voila! No more clunk! Thanks everyone for their input and ideas!

Alex

 

Good deal.

 

I'm not seeing how having the wrong length linings would cause a clunk though. I think that when you switched the shoes you probably fixed the real reason for a clunk without realizing it. Maybe a loose fit of the shoe against the top anchor pin, or a shoe catching on a groove worn into the backing plate. Maybe a spring wasn't seated correctly.

 

The diagnostics of this thread are most helpful. We've all been there, puzzled.