Hercules

Those of you who have switched to GM wheel cylinders, NAPA #4637337, and don't have RWAL, do you have a problem with easily locking up the rear wheels? To the best of my knowledge, my truck, listed in my sig, has front wheel anti-lock brakes only. I bought this truck used and didn't get an owners manual or list with it's options at the time. I believe it's only FWAL brakes because the lines coming from the ABS unit go directly to the front calipers only. So, this has left me wondering just how easily the 4637337 wheel cylinders will lock my rears. I don't tow anything, but, usually haul 1 ton of materials at a time, and more often than not, several times daily. The rest of the time, especially through the winter months, the truck is unloaded, which is what concerns me about using these cylinders. I'm worried that an unloaded truck in the snow, or wet pavement with these wheel cylinders may cause unwanted rear wheel lockup. Thanks for the help or info regarding your driving impressions with these cylinders!

2500

97 CTD here and would also like to know

dozer12216

My understanding of wheel cyl issues. The Dodge engineers played with sizing trying to get front/rear brakes to work correctly, and went to smaller diameter wheel cyls, trying to keep from rear lock up on unloaded unit.
Then another problem showed up. B3's(vans) and D3's(trux) would show premature front disk pad wear and little or no wear on rear. The cause was determined to be from normal loads and city driving at slow speeds with very light pedal application. The rear brake return springs held rears off under these conditions. Hence wear on front and none or rear. The larger wheel cyls helped with these drivers.
Now! if you have premature pad wear (less than 20000 miles) and rears show little wear in same time frame, you might consider replacing wheel cylinders.
All truxs have RWAL for years. Optional was Front wheel ABS system. Many RWAL's were mounted on frame near rear axle, and later relocated to near Master cylinder.
Qualifications: retired Chrysler/Dodge Service and JMHO

Hercules

dozer12216, when I bought the truck, I figured it probably had RWAL thinking that's what most trucks had too, that is until I had to replace a couple of the brake lines coming from the ABS unit under the hood. They run directly to the front calipers from the ABS unit. There's a small union attached to the frame, but, it's a direct run regardless. I've never seen a RWAL on the frame. I don't have knowledge of the functioning of the plumbing on ABS systems, so, given that the lines from the ABS under the hood go to the front calipers, and the line feeding the rear starts at/under the master cylinder(?) and goes directly to the rear, would you think this is just front wheel ABS, or is there some line routing between the ABS and the master cylinder in the plumbing that may make it four wheel ABS?

bob95065

I don't think I have ever seen front ABS with no rear ABS on a truck. My truck has rear ABS and no front ABS.

Take your VIN to the Dodge dealer. They will print out a build sheet with all the particulars for your truck. If you look at the underside of your hood you can find a lot of info there too.

Hercules

Well, regardless of whether it has front, rear, or 4-wheel ABS, I got the #37337 wheel cylinders and used them instead of replacing them with new stock units. They work great. It started raining as soon as I finished, so, I got to try them in the rain and I have not had any lockup issues. They do feel and stop much, much, much better...very positive feel to the brakes now. They cost the same as the stock units, thread pattern for the bolts and brake line are a perfect match, and it slips right into the stock location. For the first time, the pedal feels firm and consistant. The truck now stops harder when wanted and, most importantly, predictably. The thing I like is there's NO wallowing feel under hard braking as if there's a delay between applying the breaks and weight tranfer to the front where it feels like the whole truck floats momentarily. Now, the whole truck seems to instantly squat under hard braking rather than nose dive. The local Advance Auto Parts had to cross reference the # 37337 to theirs, but, I noticed on the package there is a list of other #'s that cross reference to other manufactorers. One was Raybestos #37337. If I can remember later, I'll dig the package out of the garbage and get the other #'s that cross reference to each other. They cost the same as the stock cylinders.

blackimpala

I did this mod on my 96, very happy with it if I got another truck it would be one of the first things I would do to it. I too got a better feel in the stopping and a higher peddle. I think I paid about $15 each at NAPA.
Floyd

billv45

RWAL is a Federal requirement (DOT) it's the front that is optional. I swapped the wheel cylinders on my '96 and did not have more of a problem with the rear end locking up and I almost always ran it empty. I was very pleased with the added braking response of the upgrade. Two thumbs up!

justme-

Front only ABS would be a dangerous vehicle to drive- the rear would lock and come around regularly. The NHTSA would never allow such on the roads.

Hercules

I got the print-out from my vin code. Appearantly the truck has 4-wheel anit-lock brakes. This explains the two lines exiting the ABS unit on the wheel-well...one going to each front caliper. I'm going to have to look at the system line routing better to figure out where it's controlling the rear. I know of one line that exits from under the brake fluid reservior and goes directly to the rear. My best guess for the location of the rear controller is a small, approximately 4"x1"x.75" union located next to the master cylinder. Outside of that, there's nothing else. Anyways, I'm just glad to know I have 4-wheel ABS, replaced most of the brake lines(another one blew, so I replace any that looked even remotely bad this time), and replaced the leaky wheel cylinders with better ones.

Stamey

The RWAL is controlled by a valve on the frame, just above the rear. If you do not have this it may be because someone else eliminated it before you purchased the truck.

Chris

Hercules

I haven't seen anything along the frame rail. I finally found my lost shop manual for this truck (it got boxed up while cleaning out the basement appearantly). It clearifies it all now. In a nut shell, there's a an ABS unit on the wheel well with lines going to the front calipers. The RWAL Valve is located directly under the master cylinder. The link between the master cylinder, RWAL Valve, and ABS unit on the wheel well is the Combination Valve located next to the master cylinder. My confusion over this is I thought the RWAL valve was actually part/piece of the master cylinder. I now know they are two seperate units.

xtoyz17

This isn't the same as the load sensing valve is it?

Stamey

Yeah, that's what I always thought was the rwal valve. Appears, from Hercules post above, I am wrong. Glad I don't do this for a living.
So Hercules, you don't have this valve above your rear?

Chris

Hercules

Stamey, I haven't seen a valve above the rear on my truck. I don't have the load sensing arm either. I'll try to describe what I saw when I was under there bleeding the wheel cylinders. I have hard brake lines wraped with a protective "spring" from each drum that meet at a 3-way union on top of the axle on the drivers side of the differential. A flexible line then goes from the union to the frame rail where it unions to the hard line that runs along the frame rail to the front. At the front, the line from the rear unions to another line that runs up to the RWAL valve just under the master cylinder. That's pretty much covers the plumbing from the rear brakes to the RWAL valve. If there is something hidden between the tank and the rail, I haven't seen it...even when I had to get in there to replace my fuel lines a while ago. There's the possibility that I could have missed it when I was focused on other tasks, but, I did do a quick visual run of the lines back there to determine if I should replace any since I was replacing so many other brake lines and the wheel cylinders at the time.