Ok...been doing a ton of reading/research...now I need help.

Problem:
In 4low when I brake to stop....my front brakes will bring me to a stop and hold the tires locked...but my rear drums slow me down, but continue digging and pushing...not fun on down hill crawls.

Question:
How do I get my rear drums to lock up and quit trying to push through my brakes in 4low

My setup:
88YJ 4.0L/TF999/231. 35's on d30/d44 geared to 4.88 detriot in rear, stock 231. New pads/shoes/brakes fluid new and bled and bled and bled...no air in the system.

The thing is on the street....it stops really well! Just when I shift into 4low on anything other than the pavement...my rear tires just dig in and keep turning.

I have brand new shoes adjusted them and check the "automatic adjuster" to make sure everything is install right and working right. (I haven't changed my wheel cylinders, but they aren't leaking and appear to be working find) I can jack up the rear end w/ the tires in the air. Put into reverse...go through stomping procedure for the adjuster and it does help...but only temporary before the rear tires continue to spind in 4low.

So this brings me to needing help. I've read about the granada MC change over...I've read about the ZJ disc swap/proportional valve...
....I actually did the ZJ disc/proportioning swap on my old XJ running the same setup....4.88/35's, 30/44 but w/ the AW4 tranny versus my current tf999 (don't know if my 1st gear makes a difference) I know I never had my rear tires push through my brakes with that setup....but I definetely remember my braking on the road was no where near as good as my current disc/drum setup believe it or not....

Soooo... all this said, does anyone experience this problem w/ drums and deep gears....and what would be a good place to start....

Well,

You have come to the junction in the road that most of us reach at some point.

When you lowered the gears and then increased the tire size you basically reduced the usefulness of the rear drums.

Keep in mind that the rears are not suppose to lockup first. The priority is for the fronts to do most fo the work. Chances are that if your rears aren't doing you much good you are probably at the limits for the front or very close to it.

It is all about clamping pressure. There is a great guide (billavista I think, there is a post in hard core about Master Cylinders which has some good points and the obvious mistake a lot of people make by going to a larger bore MC.) that a lot of guys here refer you to on brakes and everything you ever wanted to know. But it all comes down to math. Your brakes were not designed to stop the leverage increase that the 35's give you nor the additional strength of the lowered gears.

The length of the pedal, mechanical advantage of the pushrod from the pedal to the booster, how much the booster assists in this endeavor, and then the amount of pressure generated by the Master Cylinder to the proportioning valve and actual brakes all have to be taken into consideration.

Modifying brakes can be a very bad thing unless you konw exactly what you are doing. Nothing like hearing that someone changed something on thier braking system and the next thing you know they have an accident becuase they couldn't stop.

I would start looking for a way to increase the size of the brakes. This is the best solution for safety and best stopping.

Next you might want to look into getting rid of that static proportioning valve and purchase an adjustable one. The proportining valve separates the pressure between the front and rear. Drums require less pressure than discs do. So the proportioning valve allows full pressure to the front while it reduces the pressure the rear.

By changing this to an adjustable one you can allow more pressure to the rear to your liking.

Also the Master Cylinder is setup for disc fronts and drum rear. Which is why you see two separage compartments on the MC as one requires more volume than the other to work.

I know this is not a direct answer and might not be a viable solution for you but you might want to look for a Ford 8.8 rear out of a Explorer. They come with disc brakes and you can remove the proportioning valve altogether so the brakes are more even.

Or maybe do the disc brake conversion that would come with all the parts that you need for a simple solution. They are just a bit pricey is all. But so is swapping in another rear diff and then having to regear.

I just urge you to seriously research any brake change. I had the same problem that you did but with my CJ7. I ended up with rear discs, corvette MC and a hydroboost, then just modified the proportioning valve to allow even pressure for all four corners.

My motivation was when I was towing my jetski and someone cut off a truck in front of me. No way in hell could I stop in time. Thanks god there was no real damage. Now i can lock all 4 tires up with little effort. And thats pushing 37" Good Years.

I am sure many others will have thoughts on this as well and might know exactly what you can use from a junk yard that might make all this cheaper too.

Good luck

Ok...been doing a ton of reading/research...now I need help.

Problem:
In 4low when I brake to stop....my front brakes will bring me to a stop and hold the tires locked...but my rear drums slow me down, but continue digging and pushing...not fun on down hill crawls.

Question:
How do I get my rear drums to lock up and quit trying to push through my brakes in 4low

My setup:
88YJ 4.0L/TF999/231. 35's on d30/d44 geared to 4.88 detriot in rear, stock 231. New pads/shoes/brakes fluid new and bled and bled and bled...no air in the system.

The thing is on the street....it stops really well! Just when I shift into 4low on anything other than the pavement...my rear tires just dig in and keep turning.

I have brand new shoes adjusted them and check the "automatic adjuster" to make sure everything is install right and working right. (I haven't changed my wheel cylinders, but they aren't leaking and appear to be working find) I can jack up the rear end w/ the tires in the air. Put into reverse...go through stomping procedure for the adjuster and it does help...but only temporary before the rear tires continue to spind in 4low.

So this brings me to needing help. I've read about the granada MC change over...I've read about the ZJ disc swap/proportional valve...
....I actually did the ZJ disc/proportioning swap on my old XJ running the same setup....4.88/35's, 30/44 but w/ the AW4 tranny versus my current tf999 (don't know if my 1st gear makes a difference) I know I never had my rear tires push through my brakes with that setup....but I definetely remember my braking on the road was no where near as good as my current disc/drum setup believe it or not....

Soooo... all this said, does anyone experience this problem w/ drums and deep gears....and what would be a good place to start....



Seriously are you for real?

JSmith: thanks for that...gives me some options to think about.

Seriously are you for real?

seriously!:flipoff2:

If you are in 4lo and the fronts aren't turning, the rears shouldn't be turning either no matter what brakes you have back there. With an automatic, I would think the secret to not driving through the brakes would be in the torque converter.
Travis..