98.5 Ram 2500 2WD with RWAL ABS system. The brake light and the ABS light both came on. Mechanic replaced the sensor at the differential and now says my proportioning valve is bad. p/n 5003309AA. The part is no longer available. What's my best move? There are several for sale on eBay, but that could be a long saga of swapping old valves in and out until one works properly. Thoughts? Thanks in advance.

 

I have several used ones as well, along with about anything for a 1st or 2nd gen Cummins truck.

 

I don't know about the 24-valves, but on a 94-96 (possibly up to the 98.5 12-/24-valve engine cutover) - those two lights together can be a warning of low vacuum. I don't know if that applies to vehicles with Hydroboost brakes, which I believe yours has (correct me if I'm wrong). Why does the mechanic say the proportioning valve is bad? Are both lights on all the time when the engine is running, or only under certain conditions? if so, do those conditions involve cruise-control or AC/heat?

 

The mechanic pulled codes off the ABS system.

 

I'm still working on a solution for this problem. I spoke with the mechanic and in addition to the codes from the ABS system, he verified that he can get normal brake fluid pressure to the front brakes but gets little or no pressure to the rear brakes. Therefore, he believes the proportioning valve has failed due to age/corrosion. He further says he sees this problem on older vehicles about 1-2X per year, so this is not his first rodeo troubleshooting this particular failure. Nonetheless, I'm going to get a second opinion.

On a related note, I'm trying to understand which ABS system I have. Recall this is a 98.5 2WD truck with discs in front and drums in the rear. The ABS HCU is only on one of the lines exiting the combination/proportioning valve. Assuming I didn't trace my brake lines incorrectly (always possible), the ABS HCU controls just the rear brake line pressure. This would lead me to assume that I have an RWAL system. However, I see a lot of RWAL discussions that talk about a load-sensing proportioning valve installed on the rear axle. I have no such part on my truck. Is it possible that I have a 4-wheel ABS system and I just can't see the ABS HCU for the front brakes ?? Or do I have a RWAL system that is just different from other model years and lacks the load senor? Thanks for your help!

 

I have/had several dodges from 89-95 with RWABS. None with the rear load-adjusting valve. Does that help?

 

I think you're talking about the load sensing valve maybe?
If so, replace it with a bypass. don't think those valves ever worked right anyway.

lmk if you have trouble finding it and I'll see if I can find a part #

 

Here’s the TSB for bypassing the rear height sensing proportioning valve
http://dodgeram.info/tsb/1998/05-04-98.htm
But if you don’t have the height sensing valve then I’d think you’ll need a new or used valve like the one you currently have

 

My '96 doesn't have that load-sensing proportioning valve and there's no sign it ever had it.

I believe your truck has Hydroboost brakes, and I believe from illustrations I've seen that the plumbing is different from my vacuum-assisted brakes - but I think you'd be able to find the ABS unit in the engine bay if it were there. In the 4WAL vehicles I've seen, the brake lines to all wheels come from the control unit.

If you still have any doubts - check for wiring in the front fenderwells running from the steering knuckles and near the brake lines. Those would be for the front wheel ABS sensors. If present, you have 4WAL. If not, and you can't find a control unit connected to the front brake lines, I think you can conclude you have RWAL

 

Out of curiousity, did the mechanic tell you what trouble code(s) he pulled for the ABS system?

 

I'd bypass the ABS junk and use whatever prop valve I could find from a 80s/90s 3/4-ton gm or dodge with disc/drum brakes. Preferably a brass or aluminum one. Keep it simple.