Hercules

Now that I finally got the other brake problems sorted out, it's on to the one that's been a problem since I installed the GM 1 ton wheel cylinders earlier this year. Simply put, if the truck isn't loaded, the rears will lockup on anything that isn't dry pavement and are "grabby" in slow traffic and parking lots. Heaven forbid there are ripples in the pavement when slowing to a stop light, too. My truck does not have a proportioning valve like I've read in some of the forums here...ie. the lever controlled valve. So, I was wondering if anyone has tried installing a manually controlled proportioning valve with the **** adjustment to combat the rear lockup and, if so, what's you impressions? Since winter's several months away, and I don't normally move heavy loads then, I'm planning on putting back in a set of new original wheel cylinders to combat the rear lockup that I am 99% sure is going to be a problem on icy and snow covered roads. I like the idea of being able to control the pressure to the rear for loaded and unloaded situations. I love the GM 1ton cylinders when loaded, but, hate them when the beds empty, which is about 60% of my driving until winter hits...then, it's empty until spring.

bob95065

What is the source for this valve? I am in the same boat as you are. I love my GM wheel cyliders when laoded but hate them when empty.

Bob

infidel

I've seen the valves for a good price but have never used them.
Check here http://store.summitracing.com/egnsea...115+4294918718

Long shot here, I've had the larger 30mm cylinders on both my rigs for over 7 years, no problem at all until I got new tires. The tire monkeys didn't follow my instructions to inflate the rears to 55, instead ran them up to 80.
Thought I was going to lose it the first time I stopped with the brakes locking and tires hopping. After lowering the tire pressure all was fine.

I've had the 30mm cylinders for a long time and have installed them on dozens of rigs with no problems. In fact I was the one who introduced the idea here four years ago after first making sure there were no problems involved.
So far I haven't heard of even one person who has reverted back the the small stock cylinders although I'm sure some have. My bet is that hundreds of people have made the switch. This leads me to the conclusion that the larger cylinders aren't the problem, something else is wrong.

a77ssii

I put them on my trail rig Scout II, they take ALOT of tweaking until they are right and under heavy 4 wheeling (lots of vibration) they would readjust themselves a bit. I used an engraver and put a scribe mark on the body and the **** so I could move them back to where they needed to be. Adjustment consisted of finding a dirt road (the environment where the Scout always was) running up to about 30MPH and putting the brakes to the floor then adjusting the front or rear accordingly until they stopped the way I wanted.

Hercules

I thought about adjusting the tire pressure. Currently, I run LT265/75/16 tires with the rears at 65 psi. Come to think of it, I run the fronts there, too. I found 65 psi gives me a great balance between tire wear, handling, mpg and constant hauling of 1 to 1-1/2 ton during spring to summer (more often 1 ton than anything else). I have a set of new oem wheel cylinders, so, I can wait until winter and swap them out at any time if needed. Besides, I still have a lot of jobs lined up until then and would like to continue to use the GM cylinders through all the block, stone, and top soil I'll be carrying. As for something else being wrong, there's not much of the original brake system left. All but the abs controllers and 4 short lines near the master cylinder have been replaced due to either blow outs, siezed calipers, or just plain starting to throw parts at it to solve the intermitant hyperactive vibration I would get when stopping. Which, by the way, started shortly after installing the GM cylinders. That appears to be nothing more than a coincidence, since the resent replacement of front calipers and brake hoses seems to have cured that problem. I am wondering if the rear abs sensor may be a source of concern, or, possibly the rear brake hose deteriorating inside. I have no codes of any kind, but, have heard the sensor does not always trigger a code. Can the rear sensor be cleaned like the fronts? I've never had it out, so, I don't know what it's like inside there. I do know the wire and connector are in great shape. I do hear the controller under the dash from time to time when I hit ripples that cause lockup, but, I'm moving a little faster than I would in a parking lot. I guess until the snow hits, it's all speculation. I just don't want to be caught in a bad situation trying to get home with a truck that wants to lockup the rears when it doesn't have enough traction in the snow/ice.

bob95065

I had a 1994 Toyota truck before I bought my 97 CTD (BIG step up BTW). One of the things I really liked about the Toyota is it had a proportioning valve bolted to the frame under the bed that had a rod that went down to the rear axle. As you loaded the truck and the frame went down to the axle the proportioning valve opened allowing more pressure to the rear brakes. I want to set up a system like that for my Ram. Maybe I'll start combing the local junkyards for a early 90's Toyota truck.

infidel

Have you crawled under and taken a look?
Your '97 should have exactly what you're talking about.

Hercules

If bob95065's '97 is anything like mine, it does not have the rod. I've looked before by tracing the lines and inspecting along the frame and suspension. The only reason I can think of for not having the load sensing valve is the 4-wheel abs. Outside of that, I don't know why mine doesn't have it.

uglyscout

I have used an adjustable proportioning valve on 2 trucks I have owned. Worked great in both cases. Neither were dodges and neither retained the rear drums so your mileage may vary....

I did need to add a residual valve to one set up as the factory prop. valve is actually a 'combination valve' with proportioning and residual valving all in one (and a place for the saftey idiot light switch).

I used the Wilwood valves that everyone sells for around $50.

Palmetto_kid

Mine will lock up so bad that if you arent paying attention when it happens, you might hit youir head on the steering wheel! My wife hates riding in my truck. It only happens after the truck has been sitting awhile, and hit the brakes a few times at low speeds.

Sometimes, i do it just for fun on the pavement. It will really lock'em down. But if you arent expecting it, get ready for a red spot on your forehead.

ne_plus_ultra_1

It sounds like you are referring to ABS system activation.

An actual pulsation (symptom of warped or poorly machined steel) would likely not be intermittent and it's unlikely that changing hoses would stop ABS from pulsing.

Too much braking force and your rear wheels are locking up and your ABS begins to pulse is the theory that I have settled on.

Larger wheel cylinders are sometimes helpful, I put handi-van cylinders in the back of my wife's van with some success. She never had enough braking force back there from the start.

Years back there actually was a service bulletin that made it all the way to the brake shops about Dodge trucks of approximately this vintage needing different wheel cylinders in back as they were under-designed by the engineers.

Why not just use the updated cylinders instead of Chevy ones?


-ultra

infidel

The updated cylinders only applied to pre '97 2500s.
The updated cylinders are 27mm and were stock on both 2500 and 3500 trucks starting in '97. Pre '97 3500s also had the 27mm cylinders, 2500s had 24mm.

The "Chevy" cylinders are 30mm this results in a 24% increase in rear braking power than the "improved" 27mm cylinders.

Fueling around

Bill;
This is something from my collected notes, but never verified.
Dodge revised 3500 wheel cylinders to a 1-1/8" (approx 28.5 mm)

infidel

You could be right John, I've never measured but have seen the 27mm number tossed around quite a bit.
Nevertheless 30mm is still bigger than 28.5

Hercules

I swapped in a set of new oem wheel cylinders today. I had enough of the lockup after two days wet weather here...actually, one day wet and the second was drying up slowly. Anyways, I had enough. I figure going back to a stock set up will accomplish one of 2 things. It will either cure the lockup, in which case I know the 30mm cylinders were the source of the problem, or, the lockup will continue and I know to look elsewhere in the brake system. Either way, it's a step forward. If the lockup stops now, then I can start to concider how to incorporate the 30mm cylinders with some type of proportioning valve. As I have mentioned in previous posts, I can't help but think the lack of a proportioning valve on my '97 Ram is related to it having 4-wheel abs. That's the only reason I can come up with. So, I wonder if the use any type of proportioning valve will cause problems with the 4-wheel abs and is why it's absent from my truck. If that's the case, the only other option I see is to give the 3500 Rams' wheel cylinders a try. I just got finished saying to my wife before logging on here that the oem cylinders don't have enough brake power and the 30mm have too much...I need something in between. If the 3500's are 28.5mm bore size, then that might be the balance that I'm looking for. Of course, I still have to put some miles on to see if the lockup in unloaded conditions is gone or still continues. If nothing has changed after doing this, I'm not sure where to start looking for the source of the problem. I can see this is becoming one of those issues that I'll view as a challange and won't rest until I conquer it.