chukarhunt

iTrader: (1)

Good Day All!

This is my third attempt at this same posting… Yotatech would log me out after a very long and thought out post, and lose everything… so I am typing in word first, then try it again….

I figured the pulsing/surging from the brakes was due to the rear drums after doing the parking brake test while moving along. I bought new drums and installed them. Took the truck out for a drive and everything felt fine until the truck started shaking. I pulled over only to find out that the parking brake self adjuster had pushed the pads to full time contact with the drums, thereby overheating them and from what I can gather, warping at least one of the new drums.

I replaced the front rotors and pads and one caliper. I bled the brakes to the best of my abilities, but I will come back to that…. I also took the “new” drums in and had them turned. Some say don’t do that, but I took a chance. If anything the drums are worse now, resulting in very bad diff gear backlash when braking. I am not happy…

I cannot feel the surging/pulsing in the steering wheel or the pedal, only the truck. It does the same thing when I apply the parking brake, so my only consensus is it is coming from the rear. This may have nothing to do with it but it might help with diagnosis: My pedal does not have full power until about 50% of the way to the floor. It barely works on initial braking, but then I get what feels like full engagement after halfway. It is night and day difference. I also replaced the master cylinder, same output… In my opinion, the front is still engaging before the rears, because the surging doesn’t really start until the halfway point. Will need to drive some more to really make sure….

SO… Any input would be great. I feel like I am overlooking something. The driveshaft feels tight, but the middle rubberish section of the two piece driveline does concern me. Should I spend the money and buy new drums? Sorry if I lost some of ya…

MudHippy

I'm having a similar issue with this 90 long bed PU I just bought. My first inclinations are towards the LSPV. Second, since it feels like the opposite of axle wrap, maybe it has something to do with the PO putting the add-a-leafs under the overload springs. I dunno. But I need to put this new clutch in it before I can move on to solving the braking issue. Which I will. One way or another. I'll get back to you when I do. Don't hold your breath. I've got about 1.5 million things I'm trying to fix at the moment.
The single worst thing about this website. So many people have lost out to such good advice given by me. Due to the fact that after I type it up and try to post it...IT'S GONE!!! Sometimes I take the time to rewrite it, a lot of times I simply give up and don't. You have no idea how many times I've cussed my computer screen out because of it.

ANSWER: NEVER CLICK ANYTHING HERE WITHOUT COPYING WHAT YOU'VE WROTE FIRST. LEFT CLICK AND HOLD, SCROLL OVER THE WORDS WRITTEN TO HIGHLIGHT THEM, THEN RIGHT CLICK, AND THEN LEFT CLICK COPY(FOR PASTING IF/WHEN/WHERE NEEDED). Then, with any luck(since even this doesn't always work for me), you don't have to suffer a total do over.

BTW, it just happened again when I tried to post this. Luckily, my preservation technique worked.

osv

there isn't any connection between the diff and the brakes.

if anything, you are describing multiple failure modes, that don't appear to be connected: 1)pedal travel/effectiveness, 2)driveshaft carrier bearing question, 3)pulsing of the pedal, etc.

the suggestion that one issue could be lspv-related could be a good place to start troubleshooting #1 or #3, but it's not relevant to #2... can the lspv arm be wired into the open position, so it's not functioning, as a troubleshooting step? it was permanently setup that way on my truck, but it also looks like some of the rear brake lines were re-routed... I need to figure out what was done there.

driveshaft issues... have you tried disconnecting the rear driveshaft at the diff, and inspecting the ujoint? you can also check for diff play easier, and see what the carrier bearing is doing.

chukarhunt

iTrader: (1)

Quote:

You have no idea how many times I've cussed my computer screen out because of it.

LOL, if I wasn’t at work I probably would have done the same thing! I do appreciate you posting though, MudHippy, with your preservation technique! I will give it a go…

Quote:

Second, since it feels like the opposite of axle wrap, maybe it has something to do with the PO putting the add-a-leafs under the overload springs.

I had no idea what axle wrap was until I just looked it up, and yes, my truck does do that! I was following my wife home and as she took off from a stop and I was like… ?!?!?! lol. It is a good 2-3 inches of pinion rise. But that being said, the PO had put helper springs on the rear, between the frame and leafs. He said that it helps the driveability of the truck on the street, which I have no complaints. Definitely has helped me with the 1 ton pellet loads! But, as you say, could the extra spring rate and height be doing something to cause severe axle wrap under braking? Truck sits up way higher in the back because of the spring. EX: a one ton load just barely puts the truck back to stock height, a good 6 inches abouts.

I don’t experience hardly any axle wrap on take off unless I shift hard and fast, but it is mild compared to what happens when braking. I will have the wife drive while I follow and see if it IS axle wrap or the cause…

Looking forward to what you find out (if I don't beat you to it) MudHippy!

chukarhunt

iTrader: (1)

Quote:

there isn't any connection between the diff and the brakes.

Thanks osv, and that is very probable. I was only speaking what was on my mind, which has gotten me in trouble many times before.

The lsvp, from the looks of it, has never been tampered with. You think it seized up, causing the difference in the pedal pressure? I forgot about the lsvp…definitely could be it.

There is a lot of back lash, but I have never done anything to adjust it. Are you talking the carrier bearing that the pinion sits in?

Thanks for the replies. I obviously have a lot of troubleshooting to do….

osv

I believe that the lspv distributes braking force between the front axle vs. the rear axle, based on the load in the truck... tying it off, in effect locking the valve down, could be interesting, if it's possible... I've never actually worked on it, we need to hear from someone who knows more than I do about it.

the carrier bearing sits between the two pieces of driveshaft that you have, and it can go bad... there can be backlash in the rotation of the pinon bearing(where the driveshaft attaches to the third member)... most rwd vehicles have some degree of axle wrap, which means that the front of the axle housing rotates upwards under acceleration... you can put the rear axle up on jackstands, and with the vehicle in gear, motor running, see axle wrap in real time, although it would be fairly minor.

Dan Carey

One trick worth considering is to high light the text and copy it before taking the chance of losing it.

chukarhunt

iTrader: (1)

Thanks for the replies! Sorry for the few days delay... wife tore ligaments in her ankle before I could get to the truck, so needless to say I have been a bit occupied. BUT... I did get to look at the truck for a bit on Friday. Jacked the rear axle up and hand spun the tires, and let me tell you what... SEVERE warping of the drums. I mean it is loose for part of the spin and then extremely tight the next as if the brakes were applied. If I am not mistaken, that is warped? It is possible, though, that the rear lug nuts are over tightened, causing warping of the drum, but if that is the case then I am sure it is too late to reverse the effects. Any thoughts?

Didn't mess with the lspv yet, will do so when I am changing out the drums.

Anyway, if anyone has any other input I would appreciate it. Until then,

osv

possibly... but consider also, the drum doesn't always sit exactly centered on the axle... it fits very loosely over the lug nut holes... it has to center off of the axle flange... on my rig, the drum hole around the axle flange is too big, or, being that they are aftermarket axles, the flange could be smaller than stock... the flange actually measures out to less than 106mm diameter.

see how the drum fits, relative to the flange.

wmayota

The LSPV helps to redistribute breaking power when loaded down. If you change the ride height of the truck and do not compensate by re-positioning where the LSPV bolts to the axle I could only assume that it would lead to problems. You said your truck has a bout 6 inches of suspension travel before it returns to stock height? Most guys with that much lift remove their LSPV and put in manual proportioning valves.

You can stick a screw driver in the back of the brake drums to adjust the slack adjusters so that they are not pressing the shoes against the drums to the point where they overheat. The elements can cause the slack adjusters to rust and gum up. You can get rebuild kits from NAPA. I have pulled them apart before and got them freed up, although putting them back together was a little bit of trial and error.

Although your problems don't really sound like they are being caused by a bad wheel cylinder, they can often go overlooked. If there is any fluid weeping out from around the boots on the wheel cylinders, change them. I have had bad wheel cylinders cause the brakes to lock up and overheat.

chukarhunt

iTrader: (1)

Thanks wmayota. I definitely need to get under the truck this weekend and figure out what is going on. Been too busy lately with everything going on at home. Braking hasn't been too bad lately, but I engine brake most of the time. I have a mechanic friend who knows these trucks quite well (he is implanting a 12V cummins in his FJ80, pretty awesome build so far), maybe I will invite him over for a beer and help me figure out what's up!

chukarhunt

iTrader: (1)

Just read this, OSV, and you make an excellent point. Mine is fairly tight to the axle flange, from what I remember, but that will be something I look at closely this weekend too. Thanks!

chukarhunt

iTrader: (1)

Ok, so I was delayed again when the plastic fan blades decided to break. Been converting over to electric fan. Will see how this setup works for now, being cold and all. But a new development with the brakes....

Today driving home, I felt like I had full braking power! I hit the brakes and they responded instantly and I stopped faster than usual. Now the weather is getting colder, does anyone think that might have something to do with it? I felt very confident with the braking power I had coming home. It has been cold for the past week, so I am not sure what changed....

Thanks for the input!

chukarhunt

iTrader: (1)

Well, I hate to be one of these guys, but here I am reviving an almost 4 month old thread, but I figure I might as well finish what I started....

I took the truck out a while ago and there was some serious mudding going on with the quad in the back. Needless to say on the way home I thought I may have ripped a brake line, but after pulling everything apart, turned out the mud just coated the pads in the drums, rendering them somewhat useless.

Putting the drums back on I torqued the wheels down in a specific pattern, different from what I had done before, and now the rear brake pulsing/surging is completely gone from what I can try to recreate. For a while I just got used to the way the brakes worked, but now they seem to be doing pretty good. Only thing I am going to do now is mess with the LSPV and see if it makes a difference in the front brakes, as stated from above. I will eventually put in a manual valve.

Hope this helps someone else. Sorry for the long and somewhat old thread. Thanks for all the help and new info!