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Reaper1
Reaper1 New Reader
2/26/20 1:40 p.m.

So, I have a '99 Ram 2500 2WD 5.9 Magnum/Auto truck. Now, I know trucks aren't sports cars, and I shouldn't expect them to stop on a dime, but this thing is ridiculous. It only has rear wheel ABS and I HATE it!! I have driven multiple Dodge trucks with this system and every single one acts the same way...if it senses the rears are going to lock, it reduces pressure on ALL of the brakes and it makes the truck feel like it's sliding on ice. No amount of pedal pressure can get it to slow down any faster once it kicks in, so you are back to old-school pumping while fighting to keep the ABS from kicking on. This has caused me to alter the front of my poor truck TWICE now.

After the first time, I decided to upgrade the pads/rotors (EBC Yellow Stuff and rotors) and suspension to supplement the tires(running Michelin LTX tires, *supposedly* some of the best light truck tires out there). Well, last night proved to me that none of that helped.

So, now my question is: has anyone "upgraded" a 2nd Gen Ram to have 4-wheel ABS (truly only 3-channel)? I know it was an option, mine just didn't get it. Also, is it even worth it? If the 4-wheel system acts the same way as the rear-wheel system, then there's no point and I'll just unplug the stupid thing. I need to be able to stop this thing in an emergency stop faster. 

mr2s2000elise
mr2s2000elise Dork
2/26/20 1:47 p.m.

 The 2 wheel ABS models have a different ABS module, and a different wiring harness. You would need to install the modulator from a 4 wheel equipped truck as well as the harness. Bad news is, you would also need to re plumb the front brake lines, since they don't flow through the abs module on a 2 wheel system.

It's not worth it, in my opinion.

 

 

Reaper1
Reaper1 New Reader
2/26/20 1:57 p.m.

In reply to mr2s2000elise :

I knew it was a different pump module. I didn't know how integrated into the harness it would be, or whether the harness would actually be that much different. It sounds as though the ABS is basically a stand-alone system that only talks to the rest of the truck through the CCD Bus. The line routing/plumbing, while not exactly "fun" doesn't scare me. Even the harness doesn't scare me.

To me, if I can make the truck stop better, it's worth it. I have too much into the dumb thing to say "screw it", it's not worth what I would need to get out of it to replace it with something "better"...so it's going to be with me for a while. Due to the horrible traffic and the absolutely crap drivers here (both of these incidents were cause by a person cutting off somebody to dip into an exit line) this is of prime interest to me.

AngryCorvair
AngryCorvair GRM+ Memberand MegaDork
2/26/20 2:48 p.m.

Step 1:  stickier tires

Step 2:  lower ride height

Step 3:  abandon false assumptions about rear wheel slip causing front brake pressure decrease on a system that doesn't monitor front wheel speeds or modulate front brake pressure.

Step 4:  listen to me. I did development work on dodge truck brake controls back then.

Robbie
Robbie GRM+ Memberand MegaDork
2/26/20 3:23 p.m.

Are you sure the fronts are working? ie no kinked lines or internally failed rubber hoses, stuck calipers, blown masters, etc?

Considering #3 above, if you are actually losing stopping power when the rears go into ABS mode, maybe most of your day to day braking is coming from the rears currently?

Brett_Murphy
Brett_Murphy GRM+ Memberand MegaDork
2/26/20 3:47 p.m.

Can we assume that the fluid in the lines is new and they are bled properly? The calipers are in good shape and there are no leaks in the system?

If yes to all of the above, I'm inclined to agree with Angry here. 

Reaper1
Reaper1 New Reader
2/26/20 4:21 p.m.
AngryCorvair said:

Step 1:  stickier tires

Step 2:  lower ride height

Step 3:  abandon false assumptions about rear wheel slip causing front brake pressure decrease on a system that doesn't monitor front wheel speeds or modulate front brake pressure.

Step 4:  listen to me. I did development work on dodge truck brake controls back then.

Step 1: I did a fair amount of research on the tires I have on the truck (Michelin LTX M+S, stock size)...they are *supposed* to be some of the best light truck tires out there

Step 2: My suspension upgrade was exactly this! I used the Belltech kit and lowered the whole truck along with poly bushings on everything

Step 3: Please explain then why the g-forces I experience reduce when the ABS kicks in and why I can't lock the front wheels with more brake pressure when ABS is working (EVERY Dodge I have driven with this system is that way). It's a seriously scary feeling when the thing stops decelerating at the expected rate and feels like it's on ice!

Step 4: Please see my response to Step 3.

Reaper1
Reaper1 New Reader
2/26/20 4:23 p.m.
Robbie said:

Are you sure the fronts are working? ie no kinked lines or internally failed rubber hoses, stuck calipers, blown masters, etc?

Considering #3 above, if you are actually losing stopping power when the rears go into ABS mode, maybe most of your day to day braking is coming from the rears currently?

Considering the amount of brake dust on my front wheels, I think it's fair to say the fronts are working. The rest of the system is in good shape. I just did a rear wheel cylinder about 6 months ago and the drum shoes are in good shape.

¯\_(ツ)_/¯
¯\_(ツ)_/¯ PowerDork
2/26/20 4:37 p.m.

In reply to Reaper1 :

Pull the ABS fuse?  If you like the results, stick a proportioning valve in place of the ABS thingy and be done with it.

AngryCorvair
AngryCorvair GRM+ Memberand MegaDork
2/26/20 7:04 p.m.

In reply to Reaper1 :

RWAL's job is to keep the back of the truck behind the front, ie it's primary goal is vehicle stability.

Like standard ABS, the RWAL system isolates the rear brakes from further pressure increase, then dumps fluid pressure from the rear brake circuit to an accumulator, when it sees wheel decelerations greater than certain thresholds, to decrease brake torque demand and allow the rear tires to "recover" ie to avoid lockup and return to vehicle speed.

During the dump and recovery cycle, the rear tires do indeed lose some of their deceleration, but that occurs independent of front braking.

After full recovery of the rear tires, the system can execute reapply pulses to increase rear brake fluid pressure and therefore increase rear brake torque, to regain some of the decel that was lost during the dump and recovery cycle.

All of the above is happening independent of what the front brakes are doing, because RWAL does not monitor front wheel speeds and does not modulate front brake fluid pressure. If you continue to increase brake pedal force *and if* your front brakes are in good working order, your front wheel deceleration will increase, which (depending on input force, brake condition, tire/road interface characteristics, etc) *may* lead to increased vehicle deceleration.

RWAL doesn't change front brake output. Period. If your fronts don't lock on dry pavement with about 100 lbs of force on the brake pedal, then it is likely that your front calipers are deflecting at higher pressures and not providing sufficient clamp force. It happens. The only answer is to replace them with new, not reman. If they've never been replaced, they're 21 years old. And if they have been replaced, the replacements were probably remans that have some amount of stretch in the bridge as they come out of the box.

wlkelley3
wlkelley3 UltraDork
2/26/20 8:37 p.m.

Had just the opposite occur with my old 95 F150 that had RWAL. If I pushed the brakes lightly to slow down, let off the brakes and push the brakes to stop the front wheels would lock up. Always considered this to be a feature of RWAL brakes. Wasn't really a hazard but was irritating when it happened. It did it the whole time I owned it, from 97-10 and 25k to 240k miles. My 16 Tacoma with full anti-lock braking will partially lock up the front on hard stops. I consider the fact that both are/were front disk with more stopping power than the rear drum brakes.

Daylan C
Daylan C PowerDork
2/26/20 9:11 p.m.

None of my RWAL Dodges had any weird braking behaviors. I've had a couple. I think your '99 2500 should have the best braking setup that was offered on the 2nd gen trucks. I've had truly awful examples of these trucks and never complained about the brakes. If you have issues that worry you under normal operation, something isn't working as designed. 

GCrites80s
GCrites80s Reader
2/26/20 10:15 p.m.

I put 100K (mostly city and Appalachian) miles on a '97 1500 with rear ABS only. The brakes could have a little been better in snow and ice, but I nor anyone else who drove the truck ever felt scared at any point in time under normal conditions. Not a Porsche for sure but nothing that raised an alarm.

Reaper1
Reaper1 New Reader
2/27/20 10:37 a.m.

In reply to AngryCorvair :

I get what RWAL is *supposed* to do. I just can't stand the *way* it does it. Yes, it prevents the rear wheels from locking. It's also prevents me from stopping in the distance I would consider acceptable.

I found a NHTSA report on this generation of truck (not just Dodge, but Ford, Chevy, and Toyota) and it found that the braking on them ALL sucked! Talking about over 300' to stop from 60mph (more accurately is was over 100m for 100kph). 

The front calipers have been replaced with remans, by myself. Unless you are implying that fatigue is to blame, I don't quite understand how the bridge of the caliper would be affected by it being a reman. It still have the stock calipers because I never returned them for cores as I wanted to rebuild them myself. Just never got around to it. I have attempted to increase the front braking capacity by using better parts and more aggressive pads. I wish there was a "big brake kit" for these trucks, but there doesn't appear to be from what I can find. 

Reaper1
Reaper1 New Reader
2/27/20 10:43 a.m.

In reply to Daylan C :

In normal driving, and even "spirited" driving (as much as you can in a 2500 truck), the brakes seem decent. It's also why it's especially unnerving when I get into these situations where they prove otherwise. If I *know* I'm going to be using the brakes hard, things seem OK, but I can't seem to count on that same performance from them in unplanned circumstances.

Robbie
Robbie GRM+ Memberand MegaDork
2/27/20 11:29 a.m.

So, the big question is:

Can you get both the front tires to lock when standing on the brakes? (Easy check is once you think they are locked, try to steer a bit, if the truck don't change direction, both are truly locked).

If yes, then they are working acceptably. If no, something is very wrong and that is your problem, not the abs.

AngryCorvair
AngryCorvair GRM+ Memberand MegaDork
2/27/20 12:10 p.m.

Reaper1 said :

Unless you are implying that fatigue is to blame, I don't quite understand how the bridge of the caliper would be affected by it being a reman.

Remans start as used parts. Used parts may have already experienced some amount of plastic deformation during the many apply cycles, heat cycles, etc, that they've seen in their lives. So yeah, a reman caliper is probably not as stiff as a new caliper.

Reaper1
Reaper1 New Reader
2/27/20 12:35 p.m.

In reply to Robbie :

I fully understand what you are saying, but if the ABS is preventing the rear tires from contributing to stopping as much as they could be, then it's certainly not helping in the way I am needing it to.

Reaper1
Reaper1 New Reader
2/27/20 12:40 p.m.

In reply to AngryCorvair :

I get that remans are used parts. What I have a hard time believing is that a cast iron, 1-piece caliper can undergo plastic deformation without SEVERE abuse. I mean totally overheated with excessive pressure applied (racing conditions...in a stock truck application the pads and fluid will give out LONG before the caliper stays hot enough where the hydraulic system could even keep that kind of pressure on it).

Basically what you've said to me is that the stock parts suck and I need to look into adapting better brakes...somehow.

Robbie
Robbie GRM+ Memberand MegaDork
2/27/20 12:46 p.m.

In reply to Reaper1 :

No I think what we're all saying to you is that we think something is wrong with your front brakes and they aren't even working as well as stock.

 

Reaper1
Reaper1 New Reader
2/27/20 1:15 p.m.

In reply to Robbie :

Well, I'll give them a look, for sure, but my truck stops better than my buddy's '98 (of course his is a diesel 4x4, so he's got a LOT more weight over the front wheels).

AngryCorvair
AngryCorvair GRM+ Memberand MegaDork
2/27/20 3:04 p.m.

In reply to Reaper1 :

Those front calipers were good enough when new. Not great.  Good enough.

Reaper1
Reaper1 New Reader
2/27/20 3:14 p.m.

In reply to AngryCorvair :

Do you know of, or can you suggest an upgrade? I know exactly what you are saying, and it's why I attempted to find an upgrade. I even thought about trying to somehow fit the Gen 3 stuff to it, but from what I can tell it's not exactly straightforward. I know it won't truly help my issue, but I have a rear disc conversion sitting waiting to be installed. One thing I was always unsure of is throwing the balance of the system off because the proportioning is done by the ABS and I didn't know what it would do if I started mucking around with stuff.

The Japanese race the full size vans and they "upgrade" to the 2500/3500 brakes. I would have figured they would have gone to something better by now, if it existed.

dps214
dps214 Reader
2/27/20 4:14 p.m.
Reaper1 said:

In reply to Robbie :

I fully understand what you are saying, but if the ABS is preventing the rear tires from contributing to stopping as much as they could be, then it's certainly not helping in the way I am needing it to.

The ABS is stopping the rears from locking up. If the ABS wasn't there, the rears would lock and contribute even less to overall braking.

AngryCorvair
AngryCorvair GRM+ Memberand MegaDork
2/28/20 9:15 a.m.

In reply to Reaper1 :

sorry, I do not. I will say that if there's a way to adapt the later TRW front calipers, they are significantly better than those old Bendix calipers you've got.

Maybe it's time for you to get a set of junkyard knuckles and figure out a better mousetrap.

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