rear brakes lock up

[Blue88Comanche]

the past couple times ive driven the jeep the rear brakes will lock up when i barely apply the brakes.  usually it will stop acting up within a mile or so of driving. but once i was towing the boat while it was raining and the rears locked while coming to a stop at a red light (i kept the jeep and boat straight, and didn't hit anyone on ether side of me thankfully).  the ive played with the prop valve to attempt to remedy the issue but I've been unsuccessful thus far.  Any advise would be welcome.  I'm not against removing the load valve if it would improve overall safety and performance. 

[fiatslug87]

This has some good info and a link to making an adjustable one.

http://comancheclub.com/topic/45839-mj-height-sensing-brake-proportioning-valve-adjustment-procedure/?hl=adjustable&do=findComment&comment=490357

[Eagle]

You mentioned rain.

 

After over half a million miles in XJs and MJs, I've learned that when the air is moist, the rear brakes typically lock up for the first stop or two. Doesn't seem to matter what brand or grade of brake shoes I use, although I wouldn't expect it with full metallic brakes.

 

Either adapt to it, or train yourself to lightly ride the brakes for the first quarter or half mile when it's wet or humid or misty.

[HOrnbrod]

Either adapt to it, or train yourself to lightly ride the brakes for the first quarter or half mile when it's wet or humid or misty.

 

And while you're adapting and/or training yourself just pray you never have a panic stop when someone's beside you while towing.    :shake:

 

It's not the load valve causing this. Solution? Junk the drums and convert to disk brakes.

[Blue88Comanche]

When it's wet I've already ride the brakes a bit when I leave the driveway to help deal with it. But when it happened with the boat I had traveled 50 ish miles in the interstate and another 30ish on the highway. That's what has me concerned. But it looks like disc brakes are coming sooner than later.

 

 

Jeff

[Blue88Comanche]

Question, does this affect D44 drums more than other axles? My old D35 never did that.

 

 

Jeff

[cruiser54]

Question, does this affect D44 drums more than other axles? My old D35 never did that.

 

 

Jeff

I believe so. 

[Eagle]

Question, does this affect D44 drums more than other axles? My old D35 never did that.

 

 

Jeff

 

All my Dana 35s do this. Also the 2000 XJs with the Mopar 8.25 axle and 9" drums.

[Marine1Texas]

I adjusted the valve pushed down also slightly and I don't get the issue since, on my newer 88 MJ. It has the smaller drums and was doing this very often.

[Eagle]

You mentioned rain.

 

After over half a million miles in XJs and MJs, I've learned that when the air is moist, the rear brakes typically lock up for the first stop or two. Doesn't seem to matter what brand or grade of brake shoes I use, although I wouldn't expect it with full metallic brakes.

 

Either adapt to it, or train yourself to lightly ride the brakes for the first quarter or half mile when it's wet or humid or misty.

 

I'm going to revise my advice on this. Since with disc fronts and drum rears the front brakes are applied before the rears, driving with very light peddle pressure will probably NOT result in enough drag to help dry out the rear shoes. I think the better solution is to make a few normal stops as soon as possible after starting out in the morning. I find this problem generally appears only in the morning, and sometimes after being parked all day at work on rainy days. The issue usually disappears after two or maybe three stops. It's definitely a function of moisture causing the brake shoe linings to swell. Semi-metalic or full-metallic brake shoes would probably eliminate it, but I haven't tried that.