KJZ28/TA

iTrader: (1)

This all started when my break lines blew out on my 1986 T/A. Went to install all the new lines and stripped the threads on my proportioning valve. So I got a used one out of a 1989 Formula and some of the threads are different. Coarse vs. fine.

So now I went to buy a new one and the usual places dont sell them. Inlinetube, etc. Also I was told GM no longer sells them.

Why were the threads different?

Does anyone now where to get a 1986 proportioning valve for disc/drum?

ebmiller88

iTrader: (7)

GM changed the threads in late '89 so you have a changeover year car. I have 3 of those valves in my shop, new GM so if you'd like one please send a PM. I'm out of town for a few days but can get one to you pretty fast if you need one ASAP.

Ed

midwest

I ran into this when i did my 9 bolt and pbr rear brake swap.

If the lines for the fornt brakes are fine thread but the hole in the pv are course then do what i did. take both pvs the stock one and the new one and one of the lines that go form the master to the proportioning valve.
Go to carquest with them parts and ask them for the adapter fitting that changes the fine thread into the course thread of the line that goes from the master to the prop valve. They should be red with a 12mm hex. Now you may notice the the male end of the adapter is the same thread pitch, but a little to big. Do not try to force the adapter fitting. Take the two fittings to a machine shop. Tell them to reduce the O.D of the male end by .050" and then run a 10mmx1.50 die over it. I did this myself, i am not a machinist, but have access to one at work. The first fitting took about 10 mins to mod, the second one took about 3 mins, i would guess that the machine shop will charge about 15-20 bucks to mod these to fittings.

I believe this is the adapter fitting "DORMAN Part # 43503 { Bubble Flare Female Thread Size M10-1.0 Male Tube Size//16" Male Thread Size M11-1.50}
Category: Brake Adapter Fitting

And it needs to be changed to a 10mm x1.0 female to 10mm x 1.50(as you buy it, it is a 10mmx 1.0 female to 11m x 1.50)

KJZ28/TA

iTrader: (1)

Ed I sent you a PM.

Ozz1967

iTrader: (4)

Ed,

I'm sending you a PM...I also need a proportioning valve for my 84 T/A and I hope you might still have one.

Ozz1967

iTrader: (4)

Double Post...sorry

ebmiller88

iTrader: (7)

No offense to your efforts, but why not just get the right valve and install that one? I don't get it.

I'll get to some PMs tonight.

Ed

RexKarr

Could you explain what the "right valve" is? I have an '86 Firebird which I have just added a 4th gen rear to. I was told I needed a 91-92 prop vale for disc disc. So I purchased one off of ebay from a 91 Firebird. As far as I know this is as correct as I can get, yet the 2 lines for the front brakes are 10x1 on my car and the prop valve threads are 10x1.5 .

ebmiller88

iTrader: (7)

Sure. Your car is an '86 but you bought a '91 model valve which is the wrong valve for you. As you found out the threads are different between these years. You need the older model valve for '89-90 cars which will bolt right in to your car and will be correct for your rear discs.

Ed

CYARS92

Hey EB, will the stock PV on a 92 work at all with a disc rear upgrade until I by the correct one or an adjustable one. What are the effects?

midwest

Simple cause it was cheaper and faster
i drove my car to work on a sat, had the swap almost all done, then noticed when i went to install the pv i found that they had switched the threads. So my options where.

Run the drum brake pv. Would have made for unsafe braking.

put my old axle back in. Eff that, i had to rob the tee fitting. so the lines where cut

order a new pv and pay $50-$120?? and then wait 1-2weeks to get it.

Or spend eight bucks and 13 mins to trim and rethread.

So it was a matter of need it now.
edit .....
i got my rear end as a complete set up form a local private seller, he had the master, the booster, the pv and the axle complete with calipers and sway bar, minus rotors. And did not know they changed the threads.

ebmiller88

iTrader: (7)

I understand, you did what you have to do. I have 3-4 correct GM disc prop valves in the shop so should you need one in the future let me know.

Ed