I recently bout a 90 model. The rearend was bad so I took the rearend out of my 84. The 90 had the LSPV. When I went to bleed the brakes I could not get sufficient brake pressure to the rear. So my question is can I take the master cylinder off my 84 and eliminate the LSPV?

 

when i did my notch i got rid of the lspv, so yesu can elimintate the lspv. From what the guys say on here it just allows you rear brake to have full stopping power. so far i havent had any problems.

i dont really know about the master cylinder sorry but im sure the other guys will know. good luck

 

Were the tires on the ground or was there a jack or stands under the axle simulating ride height when you bled the brakes? Or was the rear jacked up with the axle dropped out? If it was dropped out you'll have less pressure at the rear brakes since that valve is designed to add pressure as the rear squats when the truck is loaded. Lower a truck you get more pressure lift a truck you lose pressure.

This is why it's important for lifted trucks that have these valves to raise the bracket on the axle the same amount the truck was lifted to restore lost pressure.

A lowered truck, or a truck that has had the valve removed will lock the brakes easier in a panic braking situation since there is full pressure going to the rear brakes.

I removed mine when I notched and did the same on a few of the first trucks I notched, but then realized it's quicker for me to simply pull the valve back a few inches and not mess with someone's braking system.

 

Yes the tires were on the ground. My 84 rearend doesnt have a spot to mount the hardware for the LSPV. Thata why I was wondering if I could use the brake master off the 84 so I would have properly functioning brakes.

 

did you bench bleed the master after swapping axles?

if you drain the rear all the fluid comes out cept the front reserve, still have pedal but the rear of the master is empty.

 

So you have the valve still, but where is the rod now if it isn't hooked to the axle? The loss of pressue is probably due to the fact your valve is still there, but not hooked to the axle like it was stock, so the valve is in a area creating loss of rear pressure.

You can snip the rod about 1" from the valve and use this piece I make, it'll allow you to adjust the rear pressure however you like the brakes, or like mentioned in a previous post, you can install a adjustable valve with a knob and mount it in the cab which is more work but will allow much easier fine tuning compared to having to go under the truck to adjust.

 

I bypassed the valve by plugging one of the lines on the tee up front by the passenger tire and hooking the rear rubber line straight into the line that was still connected at the tee by the passenger tire. It seemed to help but the brakes are REALLY touchy now seems biased to the front brakes a little.

 

agreed, bad idea to remove it. Especially if you drive on wet/slick surfaces. I just added a adjustable proportioning valve from Summit to my 87 4Runner and am ordering one for my 78 on pay day. Your gambling without one...

 

Well I took the master and proportioning valve off of my 84 since in 84 they didnt have the LSPV. It stops on a dime now. I really didnt feel safe with just eliminating the LSPV since it was still nose diving in the front. Luckily I had my 84 to steal the parts off of