The 30mm GM wheel cylinder swap is something I picked up from a bunch of CTD owners. They had been doing it to their trucks. And since all the 3/4 tons and 1 tons use the same type/style of wheel cylinder (with the exception of the ones with rear discs) I decided to do it on my truck, and the results were VERY noticeable and well worth the $30.
It's a simple mod to do and is very effective. You can see in the comparison below how much bigger the cylinders are.
GMC 1 ton -----------= 30mm = 1.18"
Dodge 1 ton----------= 27mm = 1.06"
Dodge pre-'97 2500-= 24mm = .94" (Though they have been found installed on POST
97 Heavy Duty Trucks)
The difference in stopping power between 30mm and 27mm is 23%! That may not seem like much, but it definitely is noticeabe out on the road! I know there are some people that think disc brakes are the answer, but for $30 you can have drum brakes that are just as capable as the disc brakes found on 01+ Trucks. And unlike the disc brakes, the drums don't have issues with mud and gravel getting in them...or slides seizing up. There's a good reason GM switched BACK to drums some on their trucks.
What you'll need for the swap is a set of 1 Ton GM wheel cylinders. Don't go to the stealership to buy them. Head down to NAPA or Bumper To Bumper...or order them from Rock Auto. Below are some part numbers. If you go into NAPA (or somewhere else to get them), DON'T
tell them what you're using them for. That will just confuse them!
They should run you anywhere from $8 to $15 a cylinder. I have heard of some costing as much as $40. DON'T get those...the cheap ones work just fine. In fact, the guy that came up with the idea specificly said to use the cheapo NAPA cylinders. I used Wagner cylinders in mine (they're probably the same) and I still noticed a huge improvement in braking. A warning though, the first time you use your brakes (after you have them properly adjusted) you will most likely lock up the rears. I know I did. That's beacuse you're used to using brakes that don't function very well. After a while you get used to using a lighter touch on the pedal.
A concern that some have had about this mod is the master cylinder. Some think that it doesn't have the capacity for the larger cylinders, but let me assure you that it has MORE than enough capacity for them!
Installing them is a simple task. Simply remove the springs at the top of the shoes. (You don't need to remove the shoes). The wheel cylinder is held on by two bolts and the brake line. Remove the brake line, and then the two bolts that hold the cylinder on. When installing the new cylinder, it's helpful to start the brake line, then install the cylinder and bolts, and then finish tightening the brake line. After that, reinstall the springs and you're done. You now have larger wheel cylinders.
Alternatively, I've been told you can install them WITHOUT
removing the springs by sliding one side of the cylinder into place at a time. Then loosely installing the bolts. After that, install the brake line and then tighten the bolts. I haven't tried this, but if it's possible it does sound like a much easier way to do it.
An optional step is to bleed the system, or at least the rears. You don't have to do this. I did though, just to get some more of the old fluid out of the system (it was really crappy when I bought the truck...sucked mosted of it out with a turkey baster). It shouldn't take more than two or three pump/release cylces to do. A few brake bleeding tips...
- If you use the pump the pedal method, try to resist pushing the pedal all the way to the floor. What happens is the master cylinder travels in an area where it doesn't normally go in normal braking operation and that area is often rusty. This CAN result in torn up seals that can cause internal leaking and a mushy pedal.
- I've always started with the furthest brake away from the master cylinder and worked my way towards it. In other words, right rear, left rear, right front and then the left front.
Some owners who have done this mod have complained that it didn't do anything for their braking, or in some cases made it worse. This is because of two things. The first is the simple fact that the adjusters on our trucks SUCK! They are NOTORIOUS for not working, especially if you live in a climate where there is a lot of road salt used in the winter. The way you are supposed to adjust them is by backing up and then jabbing the pedal, but many have found that method to be unreliable as the self-adjusters often don't work. Like many others, I've found that if you crawl under the truck every oil change...or every other oil change...and adjust them manually, you will have much better braking. The method many use (including myself) is to jack the rear end up. Then, while spinning the tire, click the brake star wheel upward until the shoes just start to rub. That's it. The first time you use the brakes, the shoes will even out and there will be no rub. There are some that claim this method is no good when working with trucks that have Limited-Slip/Anti-Spin differentials because the amount of drag will be different on each side. But you're not going by the amount of drag on the wheel. You're going by the SOUND
of the shoes.
The other problem (which I have never dealt with, only read about) occurs on some of the 96.5 and newer models. Why it doesn't occur on them all is something that seems strange to me. It involves the brake proportioning valve that was installed in the rear axles of those trucks. Basically what it does is limit the amount of pressure that the rear brakes receive based on how much weight is in the bed of the truck. The more weight, the better your braking. Well not everyone travels around with a bunch of weight in their truck. Dodge has a TSB out that applies to vehicles with LIFTS ( http://dodgeram.info/tsb/1998/05-04-98.htm
) but from the way it sounds, guys have been doing it to their non-lifted trucks as well. It's been said to make a big difference.
There is a "redneck" way to modify/test the valve, and that's to disconnect the rear axle load sensor (proportioning valve) rod from the axle and tie it up to the frame with a ziptie. Like I mentioned, sometimes the proportoning valve assumes that your rear axle is very light and won't let enough pressure get to the wheel cylinders. It's also possible that proportioning valve could be bad. It's a good idea to try it on a road that's not frequented, as the vehicle could sway or fishtail when applying brakes. There are ways to re-locate the lower joint of the rod for the valve to a higher position on the axle. I haven't read much into them though. Some have even come up with ways to make the valve adjustable with the use of various bolts and nuts.
I found the txt file I was looking for with the drum removal trick in it. Here it is...
There is a trick to getting a stubborn brake drum off. If the factory installation clips are still on the lug studs, remove them and throw them away. You should be able to pull the drums off with your hands. Many times you cannot do that and the drums are very hard to break loose even with a hammer.
Support the truck on axle stands. Remove all but one lug nut. Loosen it about a 1/4" or so. Start the engine. Put the transmission in gear and allow the drums to turn. Stomp on the brakes. Put the transmission in reverse and repeat. If you didn't leave at least one lug nut on you will probably have to chase a drum across the shop.