1988 4Runner Brake ?s (1 Viewer)

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Dec 29, 2008
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I have a 1988 1st gen with 4.3GM V6, a 4L60E transmission and a conversion Toyota disc brake straight front axle and a stock Toyota drum brake rear axle. Axle ratios have been changed to 5.29 axle gears and 39.5 tires. It has a stock vacuum booster system.

The stock proportioning and leveling valve have been removed. Brake performance is not the best and I am thinking of installing a manual proportioning valve in the line for the rear drum brake axle. Does this make sense? Are there any recommendations on the make and model of valve along with recommendations on the optimum line pressures for the front disc and rear drum brake systems or is this a trial/experimental personal preference type of adjustment.

I use this as a crawler but it is licensed as well. I appreciate any other comments/recommendations.

Thank you!
 
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Jun 25, 2021
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Marana, AZ
On my 88 pickup I installed T100 calipers and discs up front. Stock rear drums and just tied the proportioning valve fully up. We put a Wilwood adjustable proportioning valve on my son's 91 and it worked about the same as tying the stocker up.

The biggest improvement was installing a dual diaphragm booster from a 2nd gen 4Runner or 3rd gen pickup. Night and day difference stopping.

Bought the Wilwood valve from Summit. I think it was the one with 1/8"NPT ports and buy an adapter for the 10mm/1.0 (I think) Toyota brake lines.

Don't buy the one with the 10mm/1.0 thinking it will work. It's a bubble flare.

Take it out, test and adjust as needed.
 
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I also want to say there are bigger Taco, 4Runner and Tundra front brake upgrades. (Using IFS wheel hubs) I am looking into it for my 86 build.

The T100 (and 95 4runner I think) brakes on my 88 cleared my 15" Cragar Soft 8 steel wheels with 4" back space. This is on an 85 SFA with the typical 1.5" wheel spacers on stock SFA wheel hubs.
 
Joined
Dec 29, 2008
Messages
11
On my 88 pickup I installed T100 calipers and discs up front. Stock rear drums and just tied the proportioning valve fully up. We put a Wilwood adjustable proportioning valve on my son's 91 and it worked about the same as tying the stocker up.

The biggest improvement was installing a dual diaphragm booster from a 2nd gen 4Runner or 3rd gen pickup. Night and day difference stopping.

Bought the Wilwood valve from Summit. I think it was the one with 1/8"NPT ports and buy an adapter for the 10mm/1.0 (I think) Toyota brake lines.

Don't buy the one with the 10mm/1.0 thinking it will work. It's a bubble flare.

Take it out, test and adjust as needed.
Thank you for the information.
 
Joined
Dec 29, 2008
Messages
11
What is the actual issue /complaint?
How do you expect a prop valve to fix said issue?
It's my understanding, and it might be incorrect, that the front disc brakes need more flow/pressure than the rear drums. The way it's set up now both front and rear receive equal flow/pressure so the front disc doesn't perform as it should. The idea is to limit the flow/pressure to the rear drums with the proportioning valve.
It doesn't seem like it stops as it should?
 
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massachussets
It's my understanding, and it might be incorrect, that the front disc brakes need more flow/pressure than the rear drums. The way it's set up now both front and rear receive equal flow/pressure so the front disc doesn't perform as it should. The idea is to limit the flow/pressure to the rear drums with the proportioning valve.
It doesn't seem like it stops as it should?
so, I am not exactly sure, but what about the master cylinder brake system? what do you have now?

my plan was to upgrade to like a tacoma style setup for brakes, also better for odd angles, but may require electronics. I am eventually going to have to approach this with my 84.
 
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Aug 2, 2006
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Jefferson
Imo eliminating the lspv is the answer, especially with big rubber.
If your front axles doesn't already have the vented rotor/ifs caliper update, do it too.
I rec the v6 dual diaphragm booster and MC.
I also run the "big brake" kit. (fror or sord)
I can lock up my 37s no issues
 
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Joined
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Jefferson
You aren't receiving equal flow front/rear. The mc deals with that.
The prop valve bleeds pressure away from the rear of the vehicle when it gets light so it doesn't skid.
79-83 trucks didn't use the T fitting at the PF like the later stuff did.
If you have weak front brakes, you need to start with the mc, booster and front rotor /caliper setup.
The 4cyl stuff is just not up to the task of big tyres.
It's my understanding, and it might be incorrect, that the front disc brakes need more flow/pressure than the rear drums. The way it's set up now both front and rear receive equal flow/pressure so the front disc doesn't perform as it should. The idea is to limit the flow/pressure to the rear drums with the proportioning valve.
It doesn't seem like it stops as it should?
 
Joined
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Marana, AZ
gnob nailed it.

When I went bigger front brakes for the bigger tires it definitely helped.

The dual diaphragm booster made a BIG difference. I think I did just leave the master cylinder on it from the donor truck.

The proportioning valve will help keep the rear brakes from locking up too soon. You can adjust it to YOUR truck.

All these upgrades are a good investment if you want to safely drive with those big tires.
 
Joined
Dec 29, 2008
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Thanks gnob and aztoyman!

A couple of questions,
Do you happen to know if the dual diaphragm booster will fit in place of the stock booster without additional modifications?
Regarding the big brake kit, what is (fror or sord)?

Thanks again
 
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It's been a few years since I did it. It was pretty much bolt on. I think I had to adjust the length of the rod to the pedal linkage. Maybe bend lines a little? Nothing major.

Front Range Off Road and Sky Off Road Designs. They both sell brackets or entire kits for the larger brakes.
 
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Joined
Dec 29, 2008
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It's been a few years since I did it. It was pretty much bolt on. I think I had to adjust the length of the rod to the pedal linkage. Maybe bend lines a little? Nothing major.

Front Range Off Road and Sky Off Road Designs. They both sell brackets or entire kits for the larger brakes.
Thanks again guys, I really appreciate your help and suggestions.
 

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