Identify this 1990 Brake part

[ncgirl05]

Hi guys! It’s been quite a while since I have posted here but we are doing some brake work on our 1990 Driftwood Reatta, and we are trying to locate a part that we need to replace along with the rear brake lines. It is pictured in the attachment. Can you tell me what this part is? Do you have a part number?

Edited May 29, 2023 by ncgirl05
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[2seater]

That is the rear brake proportioner. I know it looks crusty on the outside, and you will likely need a vice and small pipe wrench to remove the fittings, but I would bet it looks clean and new inside. The part itself is unobtanium and has not been available new for many years. I always relocate it to the front center of the rear crossmember held in place by a steel wire bundle clamp. Route new steel lines to the original ports and it will work just fine.

[Barney Eaton]

That is called the proportioning valve.  

# 25525844

Believe it was only used 1988-1990 with ABS brakes which all Reattas have

but other GM vehicles with ABS would also use it.  

2 seater is correct,  the part has not been available for quite some time........ there are other proportioning valves used on other cars 

but I do not know if anyone has tried them.... in most cases they are not plug and play and brake lines might need to be modified to fit 

I suspect you live in the salt belt.... maybe someone down south could find one from a southern vehicle.   The ABS brakes were used on other 

GM cars.   Cadillac Eldorados and Seville had ABS standard if they had the Touring Package.  Pontiac Bonneville SSEI had ABS standard

also Buick Electra "T" type.  

Edited May 29, 2023 by Barney Eaton (see edit history)

[ncgirl05]

Thank you so much @2seater and @Barney Eaton!  I appreciate the help!!

[2seater]

From the look and the fact that the lines are clipped off, I would bet every steel line from about the drivers seat to the rear are being replaced, and I have done a few. Relocating the valve will make life much easier. Actually, doing so equalizes the length of the two brake lines at the rear. Simply connect to the original ports and the flex hose that jumps from the body to the proportioner area can be eliminated. All fittings are metric M10 x1.0  bubble flare on 3/16" tubing

Edited May 29, 2023 by 2seater (see edit history)

[Barney Eaton]

As some parts become unavailable,  we need to investigate the possibility of substitution of parts.   

Here is a sketch showing some thoughts.... 

The 1988-1990 Reatta proportioning valve does not look like both rear wheels get the same treatment but obviously they do.

In 1991 and later each rear wheel had a separate brake line going to the rear and used a different style valve (one inlet/one outlet)  which seems to be common on other newer vehicles. 

(B) is a thought using a 1991 style valve with a "T" after the valve. 

(C) is a "T" with a 1991 style valve for each rear wheel. 

(D) is a common available ADJUSTABLE valve commonly used on street rods etc that have custom brakes.   

What are your comments on these .......  in all cases, the rear brake lines would need to be modified. 

[ncgirl05]

Thank you Barney - you are always a font of information and such a valuable member of the Reatta community - I always appreciate your input!!  I have one question though (or at least Neal does) - "Proportioning Valve" - if I re-position this valve does it matter the length of the brake lines to each caliper? 

[Barney Eaton]

No...... the hydraulic pressure is not affected by the relative short distances on a vehicle. 

As 2 seater touched on,  the location of the proportioning valve is not important either.

I suspect its design and location allow GM to use fewer parts (fittings) 

[2seater]

I know it is called a proportioner, but when looking at the interior design, it pretty much looks like an asymmetrical tee. The early Reatta has 4-wheel ABS sensors, but only 3-channel control so it treats the rear brakes as one system with two calipers. I have never tried it, but it sure looks like a simple tee would suffice. It is possible the internal passages are reduced to act as limiters, but the Teves2 system uses boost pressure from the booster pump directly for the rear brakes and that is modulated at the master cylinder.