anti lock brake question

[markmitchinnh]

My 1992 safari GT had anti lock brakes both on the front and rear yet the 94 I now have does not have it on the rear axle.
Anyone know anything about this? Did they stop putting it on the rear axles?

[Kidhauler]

Your 94 has abs on all 4 tires. It is possible that it might have a 3 channel system where it treats the both back tires as one and reads off the diff. But if you only have 2 channel abs then it is on the rear only. Remember back then abs was a option and I believe could be 2 or 4 wheel

[lockdoc]

Your 94 has 4WAL brakes and it is the same as the 92 version. It uses wheel sensors on the front and the vehicle speed sensor buffer. The ABS module uses those three pieces to read all four wheels. No actual sensors on the rear wheels or axle. All it really does is measure for a predetermined deceleration of the vehicle. I believe in 96 they started using a reluctor in the rear axle.

[markmitchinnh]

My 92 had a sensor attached through the backing plates - one on each side the 94 and the 2001 I am pulling the rear axle out of does not have these.

[lockdoc]

I have had multiple 92 Astros and none had a sensor in the rear. I could be wrong but my guess is that either your 92 had rear wheel antilock only (doubtful), or the axle had been swapped out at some point in it's life with an earlier year, 89 and below.

[markmitchinnh]

OK I did the rear axle swap today and everything works great- now I have a few questions. When I bought my 94 the anti lock brakes light was on in the dash and still is yet the brakes work fine. Any ideas on what I should be checking? Is there a way to get the code from the anti lock system?

[lockdoc]

Search the technical forum. I believe there is info in there to get the codes. If not I'll try to remember how. It's just like reading regular codes but a different jumper. The three times I have had the light go on, one was major mud in the front wheel sensor, another was a broken wire on a front wheel sensor and the latest was on my kids 94. I found it on accident. When I removed the battery for something I noticed a larger red wire was corroded in two from battery acid. When I searched to see what it was I found it was a power wire to the ABS. I still have mixed feelings on the ABS. It's nice when you slam the brakes on when it's raining, but in the snow I think it can cause you to hit things more than if you didn't have it. It takes too much time to stop and you wind up running through stop signs, etc.

[markmitchinnh]

Can I just unhook it somehow? I have no need for it either.

[lockdoc]

If your light is on, it is not working. No need to disconnect.

[Smiliesafari]

I agree with Bill. I'm no big fan of ABS. Pull the fuse.

[LiftedAWDAstro]

I just want to clear up some info on ABS on these vans. If your van is a 1992 or older and it has 4 wheel ABS, you will have a sensor at each rear wheel as well as the fronts. (I think this is correct. There may be some carryover into 93 or 94 as I am not 100% sure) There is a reluctor ring pressed onto the axle shaft behind the wheel flange and the sensor is wired through the backing plates. In the following pics you can see the cable, reluctor ring and sensor. These are axles from a 1992 AWD.







Once GM went to the electronic transmissions, they used the tail shaft mounted VSS for the rear wheel ABS function. This was a cost savings as the rear brakes were always controlled by a single line from the ABS pump module.

[markmitchinnh]

OK now I understand why my 92 had the sensors on the rear axle and yet my 94 does not. Thank you for clearing that up.

[lockdoc]

I just want to clear up some info on ABS on these vans. If your van is a 1992 or older and it has 4 wheel ABS, you will have a sensor at each rear wheel as well as the fronts. (I think this is correct. There may be some carryover into 93 or 94 as I am not 100% sure) There is a reluctor ring pressed onto the axle shaft behind the wheel flange and the sensor is wired through the backing plates. In the following pics you can see the cable, reluctor ring and sensor. These are axles from a 1992 AWD.







Once GM went to the electronic transmissions, they used the tail shaft mounted VSS for the rear wheel ABS function. This was a cost savings as the rear brakes were always controlled by a single line from the ABS pump module.

I have had a 91 AWD, 92 RWD, and another 92 RWD. I'll be damned if I remember the rear having sensors as I replaced the axles a couple times and don't remember any wires. But looking at a 91 manual I have, it shows rear sensors like lifted stated. Sorry.

To answer a previous question, jump terminals A and H on the ALDL and observe the antilock light for the codes.

[markmitchinnh]

Once again I wish to thank all of you for your valuable help. now if I could just remember where I left my van last night.......... LOL just joking I think its here!