2nd Gen Non-Engine/Transmission Axel swap abs light on

[robertleo]

I swapped Axels from 3.55 to a 4.10 recently.I have read everything on the web on ABS lights.But my situation is different,it does not come on until I get up to 55 or 60 miles an hour.i changed the sensor on top of the Axel,problem still exist.I did a complete brake job on the new axel before I installed it.Bleed the brakes and adjusted them.The brakes work great with the Chevy cylinders that I also installed.The master cylinder is full.The ABS and red brake light come on at the same time.The ABS wiring is in good shape.Truck is a 1998 3500- nv 4500 -4x4,pretty much stock with a Gear Vendors.....Thanks for any suggestions...Robert

 

[NIsaacs]

With the engine running and truck stopped, step on your brake really hard about twice. That might reset your ABS module, it can do goofy things.

Nick

 

[Bob4x4]

Why would a speed sensor issue be affected by brake application?

 

[NIsaacs]

Why would a speed sensor issue be affected by brake application?

Because it is only 1/2 speed sensor, the other half is ABS. When air has been introduced into the system it's hard to get out and can give the ABS module a false signal.

Nick

 

[HHhuntitall]

ALso, check and make sure all your fuses are intact and your brake lights are working.....

 

[Bob4x4]

Air in the hydraulics will not affect speed signal. I don't think hitting the brakes at rest will do any bleeding. There must be wheel speed signals to initiate abs activation. Getting air in front of the abs unit would take quite a screw up when only changing out the rears-but I guess it could if the system were allowed to drain

 

[NIsaacs]

Air in the hydraulics will not affect speed signal. I don't think hitting the brakes at rest will do any bleeding. There must be wheel speed signals to initiate abs activation. Getting air in front of the abs unit would take quite a screw up when only changing out the rears-but I guess it could if the system were allowed to drain

I don't have all the answers, however, as a long time mechanic, I am sure you have fixed things that don't make sense, that sometimes are not rational. ABS/CAB is one of these areas. We also don't have enough info. The OP said he replaced axles (plural) so if the truck has 4 wheel ABS, it might not be the speed sensor at all. I have found that a real hard brake application can sometimes reset the pressure differential switch, if it is not quite centered. This procedure is free and only takes a few seconds. Are there any codes? Was a code reader used?

Nick

 

[robertleo]

Thanks for the responses. I only changed the rear axle. There is only rear wheel abs no front.I forgot to mention that I did have it scanned and the scanner pointed to the rear abs sensor. I don't have the numbers.I changed the sensor. No change.I did stand on the brakes real hard.I will drive the truck later.The light won't come on till I get up to 60....robert

 

[Bob4x4]

Check the connectors and wiring

 

[B.G. Smith]

Is there a tone ring on the new installed ring gear? If so, it might be different diameter than the original? bg

 

[CharlieFoxtrot]

So you say the truck is 4wd.

And you changed only the rear.

And you changed the rear from 3.54 to 4.10.

So now you have a 4.10 in the rear and a 3.54 in the front?

That's unconventional....

Remember to not engage 4wd...

I know the wheel speed shouldn't have anything to do with gear ratio, and you only have RWAL, so I guess this isn't related, I just had to comment. Hey, how does RWAL know the difference between locked brakes and a stopped truck?? Does it have sensors in front, but just doesn't have ABS mechanism up there? I've only ever had 4w ABS...

I think the ABS system in our trucks is crap anyway. I used to get random ABS & brake lights. They'd come on maybe once a month or so and they'd go off after a few days without any apparent reason. That stopped when I changed the rear sensor. But I also had a problem for a long time of the ABS totally overreacting and rendering the brakes nearly non-functional under hard braking - talk about a panic stop! I never got an ABS light when that happened and the new sensor didn't help that at all. Pulling the ABS fuse gives me working brakes and an ABS light, but no brake light. So the light comes on for a glitchy sensor, but not a major system malfunction?

 

[CharlieFoxtrot]

BTW, I thought 4w ABS became standard on 98s. No?

 

[B.G. Smith]

BTW, I thought 4w ABS became standard on 98s. No?

99, also maybe the 98 1/2s. bg

 

[HHhuntitall]

Hmm, what I'm not seeing is what year the donor axle was.... There is a different tooth count on the ABS sensor for pre-98 truck rears.... that could be causing a check-sum error in the PCM when trying to calculate wheel speed.

Also, have you checked to make sure the brake sensors are plugged in on the master cylinder? Should be a single pole plug directly under it.

 

[robertleo]

Axle swap abs light coming on

The donor axel is a 96.that may very well be the problem. I have went through all the suggestions with no success. Light still comes on at 55 mph.I will check the master cylinder plug in today. Wonder if I could change the abs module in the engine compartment to a 96 instead of pulling the guts in the pumpkin to change the tone ring?I did use a 96 speed sensor in the rear end when I changed it ...thanks Robert

 

[robertleo]

According to the quad 4x4 website all dana 80s from 94 through 2002 use the same tone ring. ....robert

 

[DavidC]

This may not have anything to do with your problem but I will throw it out there. My ABS light would come on at 45mph,the light would reset by shutting down the truck then re starting. When I would get to 45 the sequence started all over again, speedo worked just fine. I unplugged the hitch, went for a drive and no more light. I cleaned the plug and packed it with die electric grease, problem solved.

Dave

 

[HHhuntitall]

According to the quad 4x4 website all dana 80s from 94 through 2002 use the same tone ring. ....robert

Hmm, I remember there is a difference there somewhere... maybe it's the sending unit... I had the problem on a truck I bought and changed axles for the gear ratio... I think I finally found it to be the wires, but I thought I found a difference there somewhere....

 

[robertleo]

It could be something quirky. I may try a 98 speed sensor.I put in a 96 to match the axle.ll keep yall posted...Robert

 

[Berrigan]

So you say the truck is 4wd.

And you changed only the rear.

And you changed the rear from 3.54 to 4.10.

So now you have a 4.10 in the rear and a 3.54 in the front?

That's unconventional....

Remember to not engage 4wd...

I know the wheel speed shouldn't have anything to do with gear ratio, and you only have RWAL, so I guess this isn't related, I just had to comment. Hey, how does RWAL know the difference between locked brakes and a stopped truck?? Does it have sensors in front, but just doesn't have ABS mechanism up there? I've only ever had 4w ABS...

I think the ABS system in our trucks is crap anyway. I used to get random ABS & brake lights. They'd come on maybe once a month or so and they'd go off after a few days without any apparent reason. That stopped when I changed the rear sensor. But I also had a problem for a long time of the ABS totally overreacting and rendering the brakes nearly non-functional under hard braking - talk about a panic stop! I never got an ABS light when that happened and the new sensor didn't help that at all. Pulling the ABS fuse gives me working brakes and an ABS light, but no brake light. So the light comes on for a glitchy sensor, but not a major system malfunction?

I remember reading in the 98 fsm that the rwabs uses the pulses from the ring gear exciter ring and then determines a panic deceleration rate. if the rate is slowing down too quickly, that means impending lockup. That's when the computer allows some brake fluid to escape into the temporary reservoir (or whatever its called) to release some pressure to stop lockup.