how hard would it be to add ABS

I'm curious about the difficulty in adding ABS to my '91 beater. I mostly use it on the street for a winter and foul weather vehicle and only use it on the trails infrequently, so ABS would be beneficial to me as long as I retain the ability to turn it off.

Being '91 I don't think it's the Bendix wiring but I don't know. It has sockets in the PDC for ABS relays and fuses. It does not have the cabin ABS harness. I am planning to get JK axles at some point and those will have ABS tone rings and all of that stuff.

From what I gather, I would need to add a cabin harness and computer, which does not seem that difficult. What else would be needed? I'm guessing that the braking system also has to be modified somehow but I don't know how hard that would be.

Any thoughts?

ehall said:

I'm curious about the difficulty in adding ABS to my '91 beater. I mostly use it on the street for a winter and foul weather vehicle and only use it on the trails infrequently, so ABS would be beneficial to me as long as I retain the ability to turn it off.

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For the amount of work involved, you're probably better off doing a rear disc conversion and cadence braking if necessary.

Being '91 I don't think it's the Bendix wiring but I don't know. It has sockets in the PDC for ABS relays and fuses. It does not have the cabin ABS harness. I am planning to get JK axles at some point and those will have ABS tone rings and all of that stuff.

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I don't know if non-ABS XJs came pre-wired for ABS (my gut feeling is that it's doubtful that they did), but I'm guessing that at a minimum you'd need an ABS booster, pump, sensors, and tone rings. Then there are a million little things like backing plates for the brakes (can't remember if they were different or not), the wiring from the PCM to the sensors, etc.

Also bear in mind that your tone rings will need to be the same diameter, tooth count, and tooth spacing as the ABS system you're installing expects - so JK tone rings may not be compatible with an XJ ABS system.

From what I gather, I would need to add a cabin harness and computer, which does not seem that difficult. What else would be needed? I'm guessing that the braking system also has to be modified somehow but I don't know how hard that would be.

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Assuming the same lines were used for ABS and non-ABS systems, you can probably scratch those off the list, though the hard lines are likely not the same where they enter the pump. Other than that, it seems as though the amount of effort required may not be worth the end result.

Don't get me wrong; I'm a fan of ABS, and (along with a couple of other folks here) eventually intend to add it in to my D44. But it really seems like an area where you may be better off investing in other things for your XJ rather than trying to retrofit it.

yea...that seems like way more work then its worth.

I hate abs in snow, ice, gravel, and pretty much anywhere else. Disconnected it when I lived up in WA.

besthaticouldo said:

yea...that seems like way more work then its worth.

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that's true of everything XJ though... if stupidly wasteful amounts of time and energy are required then I'm just the man to do it

to bad your not closer I have a 90 that I want to remove ABS from

It would be a LOT of work and I don't think it would possible, much less safe to rig it in such a way that you could turn it off. On top of that you would need to add speed sensors to each wheel so the ABS computer would know if they were locking up or not. Not sure how possible that would be. Also, getting mud/dirt on ABS sensors makes you ABS go crazy... so even if you WERE able to turn it off, you'd have to go around an clean all the sensors every time you were done mudding.

The only way I could think of to turn it off would be in the computer itself. So, you'd have to start with a system that was designed with an off switch in the first place or Perhaps the ABS system's fault mode is... if it fails, bakes works as normal? In which case you could just cut power to the ABS computer to disable it?

I'd do a rear disc conversion... would be a lot easier.

CharlieMopps said:

It would be a LOT of work and I don't think it would possible, much less safe to rig it in such a way that you could turn it off.

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Perfectly safe to turn it off, depending on which ABS system you've got. If it's the Bendix 9 system used from '87 to '91-ish, disconnecting the system (or a failure in it) results in no brakes at all as the pump also functioned as the booster. Don't attempt to disable that system unless you like stopping when gravity and inertia decide that you will.

On my 2000 (Chrysler ABS), I pulled the ABS solenoid and motor fuses in addition to the ABS relay from the PDC when the D44 went in. Been driving it like that for 18 months and no problems.

On top of that you would need to add speed sensors to each wheel so the ABS computer would know if they were locking up or not. Not sure how possible that would be.

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Did the early Chrysler ABS run a separate controller? My understanding was that (on the later systems, at least), ABS was controlled from the PCM.

Also, getting mud/dirt on ABS sensors makes you ABS go crazy... so even if you WERE able to turn it off, you'd have to go around an clean all the sensors every time you were done mudding.

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Believe it or not, that actually wasn't an issue with the ABS on mine; the sensors seemed to read well even after running through mud, snow, etc. What was a problem, however, was the lack of stopping ability on anything other than pavement.

The only way I could think of to turn it off would be in the computer itself. So, you'd have to start with a system that was designed with an off switch in the first place or Perhaps the ABS system's fault mode is... if it fails, bakes works as normal? In which case you could just cut power to the ABS computer to disable it?

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Conceivably, you could run a switch that just kills power to the ABS relay - at least on the later models, anyway. This is actually something I was thinking of doing, but by the time I got around to caring enough the D44 was in and the fuses and relays pulled.

I'd do a rear disc conversion... would be a lot easier.

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Seconded. It may not have the assistive effects of ABS, but for what you gain in stopping power it's arguably more useful.

The ABS system in XJ's was terrible anyway from what I've heard in terms of the ABS pump going out and then you lose brakes, etc...

Unless they revised it for late model XJ's?

And then don't forget no XJ came from the factory with ABS and an 8.25 rear axle, only D35's. Not sure if the parts would swap to an 8.25 or not, I really do not know. But depending on what rear axle you have, say an 8.25, you'd most likely have to downgrade to a D35 in order to get everything to work properly.

It would be easier to do the 2wd --> 4wd swap. You're looking at a ton of work for minor gains. The above recommendations for disk swap and modulated braking would be much better in the long run.

Jim www.yuccaman.com

when we swapped my buddys '91 from ABS to non-ABS we had to remove then replace

booster
master cylinder
compressor(thats the reason for the swap it failed, he had it replaced at a high cost when he tracked one down and then it failed again 2 months later)
proprtioning valve
all the brake lines
and the brake pedal

thats the major stuff

but if i remember correctly from the different pages i read ABS jeeps have different backing plates,hubs,CV joint axles or slightly larger U-joints depends on year and it free'd up unreal amounts of room

and yes it stopped just fine wasnt the prettiest job but it stopped better then it did when it had ABS and i still see it driving around out there

IMO you'd be better off going with rear disc conversion as it would be much easier and more effective, jeep brakes/ABS are crap at best plus with anything lager then stock tires it goes haywire

thanks for the detailed answer

always nice to scratch something off the list without having to do any work

I agree that the Jeep ABS isn't that great. Certainly not the old Bendix setup that was prone to failure. Not sure why you want it as ABS definitely increases your stopping distance in snow, wet leaves, or really anything but dry pavement. You are much better off in my opinion to learn how to properly brake. It was implemented for all the drivers who simply mash the brakes when something goes wrong and can't figure out why they can't steer with the wheels locked up.

I can't figure why anyone would want ABS on anything.

I drive a Colorado at work, 32K miles and already the ABS is acting up.
Last Winter it almost caused me an accident. This Summer it got upset if a grain truck dumped a bit of seed before a stop sign.

If I have a choice, I will never have it on a vehicle I own. It is not a safety feature, it is a hinderance to those of us who know how to drive.