Welcome to my thread, I have some weird braking action in my old pickup that I want to fix but haven't been able to figure out the what or why.
It's a 1991 Dodge W150, extended cab long bed. 318, 727. I had a build thread at one point but stopped keeping track of it and now PB has tempered my picture posting.
So; under braking I get a rear to front bounce. Quick like pulsing but not coming through the pedal. Hard stops or easy it is ALMOST always there. It has new brakes front and rear, bushings in the rear, shocks all around and rear springs. I've had the rear drums apart ten times and don't see anything wrong and the pads are not wearing oddly. It's pretty violent under hard stops so I'd like to hear some ideas I could test. Who's first?
Are the shoes installed correctly? There is a front shoe and a rear shoe and it can be hard to tell the difference between the two. Swapping them around can make the rear brakes more grabby.
Also, if the drums aren't round, they can act strangely. If you've had them turned, they may not have cut them properly or hit some hard spots that their tool skipped over.
That year didn't have ABS in the rear, did it? No load level based brake bias setup?
How tight do you have them adjusted? Maybe try backing them off a little to see if that helps at all?
It had rear abs but the parts are nla and were bypassed. I will adjust them in further, pads are on correct I've done dozens of first gen dodge brake jobs. Drums were new, decent quality but perhaps OOR from the box? It does it evenly, no side to side just back to front.
You replaced the hardware kit on both sides? Worn or under strength return springs have an elastic effect that can cause a pulsation. This could be either worn old reused springs or chinesium new springs.
The shoe lands are smooth and well lubricated? Sometimes they get grooves worn in them that cause the shoe to stick a little at initial application.
The shoes have a mild bevel or taper on the ends of the friction surface? I've seen where the leading edge of the shoe will grab and then kick off the drum instead of engaging smoothly.
You verified the wheel cylinder is expanding evenly? Hydraulics will take the path of least resistance and sometimes that means one side of the cylinder will expand faster then the other, or if rusty and old, not smoothly at all.
Outside of that, the aforementioned oval drums or the RWAL somehow how still trying to function is all I can think of.
I'll second the OOR drums, even straight OOB. The chicoms are 50/50 for drums being right.
But I'll also say look at the brake pad slide area on the spindle. Those have a nasty habit of having a groove worn in and delaying the front from applying. Most everyone misses this area and wonders why it doesn't stop any better than before.
Pinch off the rear brake hose, gently, with a vice grip, then drive it and confirm the problem is gone. That limits it to rear brakes
Then turn the drum that got dropped in shipping.
