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4th gen rear axle swap: brake problem
I am swapping a 4th gen rear into my camaro. I have a specific problem w/ the brakes. I've searched previous threads & couldn't find any help.
My vehicle: '85 Camaro Iroc factory 2 wheel disc.
Donor vehicle: '98 Camaro, rear disc with aluminum calipers.

Assume throughout this I've bled the brakes numerous times.
I swapped in the rear no problem. With the factory master cyl. & prop valve. With the car on a lift, drive engaged, & the brake pedal fully depressed the rear axle will not come to a complete stop. It will slow to a crawl but not completely stop. So I knew I needed a disc brake proportioning valve. I contacted an aftermarket 3rd & 4th gen site & they supplied me with a stock style prop valve that is for a late third gen ('90-'92) with 4 wheel disc & rear aluminum calipers. I put that in & the same problem occured. Rear wheels slow but don't completely stop. I did more research & found 3rd gens with 4 wheel disc also had a different master cyl. with a larger bore diameter. I installed that & still the same problem. I believe the rear calipers are not getting enough fluid.
Has anyone else had this problem? If not, then what prop. valve are you using & where did you get it from? Please provide a part #.
I want to keep a clean look, so I've chosen not to go with an ajustable prop. valve.

 

I have the same problem with mine. I tried everything. Ive checked all lines for kinks, leaks and even replaced them. there is a allen head screw that acts like a pad adjuster that I have tried but didnt work. Ive Replaced master, and prop valve. Heck Ive even pulled the guts out of the front of the prop valve. I did manage to fix it though..... I installed a 6 speed LOL...

 

It just happens that way. When the tire is on the ground, it won't move.

 

Well of coarse it will. The front brakes will stop the car. If I drive it the way it is I'll burn up the front brakes because the rear brakes aren't doing the amount of work they should be.

 

Go ahead and spend $$$ to try and make the rears stop while they're off the ground. It won't happen. Both of my cars do the same thing. It has to do with the car in gear on no weight on the tires. Put the car in gear then put it neutral and apply the brakes and the wheel will stop.

 

Original poster: Your stock master was the correct one for you. The disc prop valve number for your car is 14089496. This is an auto car, right?

With LS1s you should still be able to stop the rear discs. The LS1 rear calipers will have no small Allen screw like the LT1s do, they have no real adjustment other than the internal shoe mechanism.

I do believe the discs should stop assuming the gas pedal isn't pressed..unless it's a stick car.

Ed

 

Thanks for the part number. Yeah, the car is automatic. Do you know what options that part number is for? I've gotten several other part numbers & they all check out, but I don't know what options they are for. The company I'm dealing with is sending me a different prop. valve. This is what he wrote me:


I sent you the valve for rear 1LE brakes not front there is a difference the LT style brake is exact same as the REAR 1LE which actually came on NON 1LE cars.


Does that make any sense to anyone else? I don't think they made a seperate option for front 1LE & rear 1LE. When I get the new valve, I'll let you guys know if it actually stops the rear.

 

Read through this from 2001 and see if it's clear to you, it's been a while since I've seen this thread:

Master Cylinder

Part# Discription

18009364/ 4-WHL DISC(J65),(ECT 1LE)88-88

18009374/ Vac PWR BRK(J50) 82-88

18009374/ 4-WHL Disc(J65),(1LE) 88-88

HYDRAULIC BRAKE COMBO/MONITERING VALVE

Part# Discription

14089495 VAC PWR BRK (J50) 86-88

14089497 4-WHL DISC BRK (J65) 86-88

and:

82-83 M/C

W/J50...................18009127(production)
18013414(service)
W/J65,JE1(Export).......18009126(prod)
18013413(svc)

84-87 M/C

W/J50...................18014286
W/J65,JE1...............18014287

88 M/C

W/J50...................18014286
W/J65, 1LE..............18014286
W/J65(EXC 1LE)..........18014287

89-91 M/C

ALL.....................18014286

https://www.thirdgen.org/forums/brak...ght=valve+prop

Ed

 

Update:
I spoke with the tech line of the company that I recieved the 4 wheel disk prop. valve from. I thought they were going to send me a different valve that would have a better chance of solving the problem listed above. Not the case now. He assures me that I recieved the correct prop valve, the same one he's been installing on 4th gen rear swaps.

Ed- if you would please reply.
You posted the prop valve, I may need- 14089496. You also posted a list of M/C part numbers. Do you have a similar list for the prop. valves? The 14089496 is a good # , but I don't know the desription. I'm assuming it is 4 wheel disk, but with 1LE or without? Year? ...Thanks in advance.

 

Just a quick question but is the 4th gen rear a 3 channel or 4 channel rear? If it is a 4 channel did you put the hard lines from your original rear on the new rear?
I've heard the same thing that BlueThunder28 was saying that with the car in gear in the air the rear wheels won't come to a complete stop.

 

The donor rear was from a 98 camaro. 3 channel. It had ABS without traction control.

 

This is a direct quote from a post about 4th gen rears in drum rear cars.

For the drum rear to 4th gen conversion, you can use the stock 3rd gen master cylinder...some have even used the stock-proportioning valve with out problems. However it wouldn’t hurt to put in a disk rear proportioning valve or an adjustable one from summit racing or wildwood. I’d recommend it. You will need the proper brake lines from the calipers to the T-fitting at the rear. You should be able to keep everything factory from that fitting forward just like the disk brake cars above. This comes from the research on this site I have done, so the hardline fittings on the drum car must be the same as the disk cars. The rear brake lines and the parking brake are the only things you'll need to modify when swapping to a 4th gen rear.

Heres the link to that post.
https://www.thirdgen.org/forums/faq-...-gen-rear.html

 

IMO...you should be able to stop the wheels while off the ground. That just makes sense... They shouldnt stop before the fronts... But I have it set up on my car that after my fronts stop, it takes just a hair more pedal to stop the rears. So...spinning the fronts, with the car in gear and rear tires spinning, I push in the brakes. Front then rear goes. STOP.........STOP.

My set up is 4th gen master, wilwood adjustable prop valve, 1/4" line going from the master to the prop to the rear brake hose...then 3/16" line from the brake hose out to the calipers.

So far, it has performed flawlessly. Took a few drives to dial in the brake bias to where I wanted it, but now it stops better than it ever has...and better than a lot of other cars Ive driven. Then again I also have front LS1s...

But still. I think they should stop with the wheels off the ground.

J.

 

Stililng having with rear brakes. I gave up on a stock style prop. valve & went with an adjustable prop. valve.
I finally purchased an Wilwood adjustable proportioning valve. The prop. valve uses fittings for 3/16" brake line. My rear brake lines on my vehicle are metric, 6mm, bubble flared lines.
I needed too many adaptors to reach my line size. Do you make a prop. valve that I would only need one adaptor to reach my brake line size? i.e. Prop. valve -then- adaptor from prop. valve to 6mm, bubble flare, metric thread -then- my metric line & nut?
Does anyone now of a company that make a prop. valve with metric fittings?

-Chris