2nd Gen Non-Engine/Transmission Never-ending rear drum brake saga...

[GAmes]

It would be easy to pull the ABS fuse to troubleshoot. I disconnected my CAB some time ago after spending many hours trying to find the reason for the light staying on. Of course, when the light is on the ABS is disabled. IIRC, when the ABS did work there was no loss of braking to the front and I am sure the pedal did not go to the floor. I distinctly remember a panic stop on loose gravel while towing my boat. The pedal pulsed while the rear wheels were alternating between braking and releasing.

 

[Rogan]

Back when I was playing with an Abbott speedo adjuster box, a connection wasn't quite perfect and the signal to the CAB would 'drop out' at about 6 MPH while I was coming to a stop. The CAB would dutifully activate ABS and I'd lose braking for the last 20 feet or so.



ABS is your braking problem. And that is a whole other ball of wax to diagnose and repair.

Yeah, I've been dealing with an odd issue of the ABS light coming on if I start the truck, and let it sit still, idling, for about 15-20 secs, the ABS and brake light will come on, and stay on until the next key cycle. If I start it, and get moving, it doesn't come on. If within a few minutes of initial moving, and I stop at a stoplight for a short period of time, then the lights may, or may not, come on then. Usually, they do, but not always.

Some (here) were mentioning that issue may be caused by a faulty vac. switch on the driver's inner fenderwell, but I've yet to figure out how to TS that.

Rogan, Is your truck a 4x4? I ask because I have been told that the RWAL is disabled whenever the truck is in 4wd. If true, and if you have a 4x4, that might be one way to test if it is the RWAL system causing your problems.

It is a 4wd. I might try the 4HI on the way home this afternoon, then. It's all 40mph and under, driving the 5-6mi from work to home.

It would be easy to pull the ABS fuse to troubleshoot. I disconnected my CAB some time ago after spending many hours trying to find the reason for the light staying on. Of course, when the light is on the ABS is disabled. IIRC, when the ABS did work there was no loss of braking to the front and I am sure the pedal did not go to the floor. I distinctly remember a panic stop on loose gravel while towing my boat. The pedal pulsed while the rear wheels were alternating between braking and releasing.

Thanks (as always), Mr. Ames. I've never felt the normal pulsations of the ABS on this truck. Of course, this is the first 'real' panic-stop I've had to do (and hopefully the LAST. )



I'll try the pulling of the fuse, as well, after I try the 4wd trip home.

It does feel, though, as if only one end of the truck is actually braking. I just can't tell which. I'm assuming it's only the front, though, as the ebrake pedal goes to the floor, even with new brakes and hardware and cables for the rears.



Hmm. .

 

[Rogan]

Per my owner's manual (just thought I'd run out and grab it):

RWAL-
The anti-lock brake system provides increased vehicle stability and brake performance under most braking conditions. the system automatically controls the operation of the rear brakes to prevent rear wheel lockup.

The system remains operational in the four wheel drive mode. The level of performance is reduced when the front brakes are locked up. This may cause the rear brakes to lockup through the drivetrain and reduces the effectiveness of the A-LS.

During severe braking conditions, particularly with changing road surfaces, such as ice to concrete, a slight drop or minor pulsation may be felt in the brake pedal.
pg. 117

When you are in a severe braking condition involving use of the Anti-Lock Brake system, you will experience some pedal drop as the vehicle comes to a complete stop. This is a result of the system reverting to the base brake system.
pg. 118

Oddly, I do not see a 'normal' ABS pump anywhere on my truck. . All I see are:
Master Cylinder
a side block of something
a bottom block of something with a 4 or 5 wire plug on it.

Where is the ABS controller (ecu or whatever) located?

 

[fest3er]

... Oddly, I do not see a 'normal' ABS pump anywhere on my truck. . All I see are:

Master Cylinder

a side block of something

a bottom block of something with a 4 or 5 wire plug on it.



Where is the ABS controller (ecu or whatever) located?

That's it; whatever is plumbed into the brake lines right there behind the PDC and beside the master cylinder. The SM will have most of the info you need.



'Pedal drop or pulsation'? They used two different systems in production? I wonder which one passed the tests. Wait, never mind. I know which one would have failed to meet standards had it been tested: the one you and I have.

 

[Rogan]

LOL

i tried the 4wd, as well as the pulled fuse method at lunch today. Braking is same, and still on the vague side.
I noticed that when I come to a stop in town, like at a light or something, I get some slight nose-dive. More than would seem common, I guess. When it comes to the stop, the nose comes up and 'bobs' a little. I'm sure this is mostly due to worn out shocks (I have replacements, just haven't penciled in time to swap them. )
It feels as though one end isn't working so much. I know it's not a 50/50 balance in braking, but something just isn't kosher (obviously, huh LOL ). .

 

[SMorneau]

I fought with the brakes on my 96 for almost the entire time I have owned it. Here are some observations:



1) You can't rely on pumping the pedal on a 96, or any year with a vacuum brake booster because they do not have enough vacuum reservoir. There was a TSB that added vacuum tank but, as you found out, you can't assume you will have any assist if it is low. Add the 4wABS and you get no second pump on the pedal because the ABS uses it up.



2) The "falling pedal" that so many suffer from is due to calipers flexing as the vacuum boost comes to full assist. If somebody starts to build a better caliper I will get in line. I have never found a vacuum booster truck that did not have this falling pedal and I looked at about 10 of them over the years.



3) Converting to a hydroboost system will give you more brakes, more reliable power assist, and get rid of the crappy feel of the falling brake pedal while providing a better overall feel to the brake system.



4) You should never eliminate the combination valve because one of it's functions is to block off an open circuit should you rupture a line. Without it you won't be able to use the circuit that did not fail because you will loose all of the fluid.



5) If I had a RWABS I would keep it but the 4WABS is a dangerous piece of crap.



If you need an ABS unit for a 1996 with 4WABS let me know I will part with one cheap.

 

[fest3er]

I fought with the brakes on my 96 for almost the entire time I have owned it. Here are some observations:



2) The "falling pedal" that so many suffer from is due to calipers flexing as the vacuum boost comes to full assist. If somebody starts to build a better caliper I will get in line. I have never found a vacuum booster truck that did not have this falling pedal and I looked at about 10 of them over the years.

The falling pedal in this instance should be associated with a sudden *increase* in braking power as the vacuum becomes useful. The 'non-pulsing' RWAL system on my '98 yields a 'clunk', a falling brake pedal and a sudden and extreme *loss* of braking power when ABS kicks in. Standing on the brake (putting the pedal to the floor) while ABS is engaged makes absolutely no difference in braking effort.

5) If I had a RWABS I would keep it but the 4WABS is a dangerous piece of crap.

The style of RWAL (non-pulsing) on my '98 is just as dangerous. Maybe worse.



This is probably why Dodge P/Us commanded higher liability premiums for many years.



I'm surprised no one ever took the issues to NHTSA.

 

[Rogan]

The falling pedal in this instance should be associated with a sudden *increase* in braking power as the vacuum becomes useful. The 'non-pulsing' RWAL system on my '98 yields a 'clunk', a falling brake pedal and a sudden and extreme *loss* of braking power when ABS kicks in. Standing on the brake (putting the pedal to the floor) while ABS is engaged makes absolutely no difference in braking effort.



The style of RWAL (non-pulsing) on my '98 is just as dangerous. Maybe worse.



This is probably why Dodge P/Us commanded higher liability premiums for many years.



I'm surprised no one ever took the issues to NHTSA.

EXACTLY what mine did, on the '96.

 

[fest3er]

EXACTLY what mine did, on the '96.

Yup. You have a sludge or electrical problem. As soon as you hit the brakes hard, the connection to the rear sensor 'goes away', which is the same as the rear wheels suddenly stopping to the controller, which then engages ABS.



I will now almost guarantee that your problem is electrical, not mechanical. I'd even be willing to wager $1.



If there was property damage, contact NHTSA and complain that their testing, standards and regulations are of little value when they allow such dangerous systems to be foist on the public, endangering children and adults of all ages. Even if there wasn't property damage, write 'em a letter anyway; *you* may not be worth that much, but your wife and children are precious and priceless. Well, wait. Maybe you should say say that you are priceless to your wife and children in turn.

 

[Rogan]

it rained a little bit, last. this morning, leaving the house, the rears were really touchy/grabby. like, i go to slow down, and the rears just GRAB! 2 or 3 times, then it stopped, and went back to normal.



I'm so hating these brakes right now LOL

 

[WilsonF]

Never had a problem with my 96, am I just lucky or maybe it is not a defect with the system. I have upgraded the rear brakes w/GM cyls. and tow a T. T. never a hint of a problem.

Floyd

 

[guns101]

Touchy Rear Drum Brakes

My 97 right rear brake grabs once after sitting overnight at times that I forget to apply the brakes hard before leaving the yard. I usually leave slowly so no brake is required, then it locks and drags untill i use it a couple times and all is well?... . These trucks have so many little issues, I just never bothered to try to fix this one. I am too busy rebuilding the front end almost continually. . lol Still beats the F#rd that I used to own. It was junk at 50k. The mighty Dodge has 233k on it and keeps goin. I guess I just pick and choose my battles. :-{} Too bad Cummins did'nt build the whole truck...

 

[Rogan]

I choose to be able to stop with a 9000lb trailer behind me

 

[ABeattie]

I recently had similar problems with the rear brakes. After trying everything I was getting frustrated. Then a buddy of mine told me he had set up a liquid filled gauge to hook onto the brake lines at the wheels to check such a situation on his race car to see if there was any existing pressure with pedal released and to set up or equalize his braking for racing. We found that I had sometimes 2 to 8 P. S. I remaining on the rear brake when there should have been none. After a process of testong differant areas, we found the rubber hose traveling down to the brake "T" on rear was blocked. When I cut it open I found that movement had caused it to seperate inside and cause a partial blockage that would still hold pressure to rear brakes for quite a while after you took your foot off brake. After about 20 hours of testing, scrating out heads, and frustration, replacing the rubber brake hose has fixed the problem.

 

[CharlieFoxtrot]

+1 on brake hoses. Oh, and +1000 on friends with brake pressure gauges!!



My kid bought an old Camaro that drove fine when he bought it. By the time he got it home, it pulled hard to the right, brakes smoking, etc. Later when he jacked it up to check it out, he found nothing wrong and the wheels turned easily. I told him he had a bad hose that wasn't letting pressure release, at least not right away. Told him to pump the brakes ~20 times, then try to spin the wheels. One wouldn't turn! Told him to put a hose on that side (preferably both sides!) and that was that.