has anyone successfully fixed a rear wheel lock-up scenario under hard braking?

[roma042987]

Swapped the lines this evening and no joy, it actually made it worse. I think I'll probably try a factory style prop valve next.

 

[h82crash]

Look up combination valves. I think the OEM ones are true combination valves. The common proportioning valves just try to limit the pressure to one circuit. A combination valve is different.

How Does a Combination Valve Work?

A Combination Valve, commonly called a Proportioning Valve, is a valve that does a combination of things. The valves are available for both disc/drum and for disc/disc brake systems. Learn about their importance and shop our selection today!

techtalk.mpbrakes.com

 

[roma042987]

I'm not going to say it's fixed but it works better if the prop valve flow is correct. Since I started making the hard lines at the frame and was working my way toward the master I just intuitively made the bracket to position the "in" on the side i was working from.

I redrilled my bracket, made a new line, and bled at the master again. It's better, but rear still locks first as far as I can tell. I didnt get to try it on wet pavement or gravel yet.

 

[ToyotaMatt]

when i was just a youngling around 17 or 18 , on my first FJ40 1978 ,


i bought all new wheel cylinders at TOYOTA dealer where i worked part time after skool ,

on saturday morning i dove in with 2 feet , by dinner time i was done , or so i thought ?


i went for a test drive and the rear brakes locked up like you would not believe

INSTANTLY !

the truck lurched side ways and almost rolled over more then one time


after a few days of head scratching and panicing , my dad gave the family mechanic a case of natty boe beer to come over and look at the brake job i had done so perfectly i thought ?


- he said , SON your top shorty shoe is NOT forward , ?

i say huuuuuuuuh ?

it turned out i had installed all the wheel cylinders on there wrong locations and upside down ....


you can actually interpret the FSM to do just this .,...


my shoes were on upside down on both sides



easy fix , sorta ....


long time to figure this out for sure

 

[cruisermatt]

when i was just a youngling around 17 or 18 , on my first FJ40 1978 ,


i bought all new wheel cylinders at TOYOTA dealer where i worked part time after skool ,

on saturday morning i dove in with 2 feet , by dinner time i was done , or so i thought ?


i went for a test drive and the rear brakes locked up like you would not believe

INSTANTLY !

the truck lurched side ways and almost rolled over more then one time


after a few days of head scratching and panicing , my dad gave the family mechanic a case of natty boe beer to come over and look at the brake job i had done so perfectly i thought ?


- he said , SON your top shorty shoe is NOT forward , ?

i say huuuuuuuuh ?

it turned out i had installed all the wheel cylinders on there wrong locations and upside down ....


you can actually interpret the FSM to do just this .,...


my shoes were on upside down on both sides



easy fix , sorta ....


long time to figure this out for sure

Roma has the later +80 setup with the single wheel cylinder

 

[Theodore]

Yes. My 40 was like this when it was stock as well. As a matter of fact I think every 40 I've owned that had working brakes locked the rear up first.

I have a 83 BJ42. everything is stock and in excellent condition. It too will lock the rears first, on all surfaces.