Help with Proportioning Valve

[Rust Buster]

Hi guys, first post! I spend most of my time over on the 67-72 forum, but recently bought an old 88 Chevy 1 Ton 4x4 Dump truck to plow with. I'm slowly going through the entire truck replacing every system.

I can't locate a new proportioning valve. The truck has hydroboost and the valve is located inside the front cross member. I was told by one vendor that a typical proportioning valve (universal) will not work with a hydroboost. I believe the GM part number I am looking for is 15538213 but I can't find one anywhere.
What are my options?

Thanks in advance,
-Tim

 

[chengny]

Those are JB8 brakes:

5Z3 - LOCKING DIFFERENTIAL, RR AXLE; C5B - 15000 LB GVW RATING; C5Z - 7200 LB GVW RATING; C6P - 8600 LB GVW RATING; F44 - HEAVY DUTY CHASSIS; IDENTIFY 1ST DESIGN PARTS BY BOOSTER LABELED "AB", 2ND DESIGN BOOSTER IS LABELED "HR".; J50 - POWER BRAKES; J55 - POWER BRAKES (HEAVY DUTY); JB8 - BRAKE, POWER DISC, DRUM, 10,000 LB; JL6 - MANUAL BRAKES; R05 - DUAL REAR WHEELS; SEE BRAKE BOOSTER/VACUUM ILLUSTRATION IN GROUP 4.000 FOR DETAILS.; SEE BRAKE CYLINDER/MASTER ILLUSTRATION IN GROUP 4.000 FOR DETAILS.;
BKS: BRAKE SYSTEM,HEAVY DUTY POWER HVY DUTY PWR BRK(J55)
BRK: BRAKE SYSTEM,HYDRAULIC POWER DISC,DRUM HYD PWR DISC/DRUM BRK(JB8)CHP: CHASSIS EQUIPMENT,HEAVY DUTY HVY DUTY CHAS(F44)
GVW: GVW RATING 8, 600 LBS/3, 900 KG 8600 LB/3900 KG GVWR(C6P); GVW RATING(15000 LBS) 15000 LB GVWR(C5B); GVW RATING(7200 LBS) 7200 LB GVWR(C5Z)
OTHER: 5Z3 - LOCKING DIFFERENTIAL, RR AXLE; BRAKE SYSTEM,MANUAL DISC,DRUM(CAST IRON) MANUAL BRK SYSTEM(JL6); BRAKE SYSTEM,VACUUM OR HYDRAULIC POWER(WITHOUT DUAL REAR WHEELS) VAC PWR BRK(J50); BRAKE SYSTEM,VACUUM POWER VAC PWR BRK(J50); CONTROL, ACTIVE BRAKE VER. 2 ACTIVE BRK CONTROL VERSION 2(JL6); IDENTIFY 1ST DESIGN PARTS BY BOOSTER LABELED "AB", 2ND DESIGN BOOSTER IS LABELED "HR".; SEE BRAKE BOOSTER/VACUUM ILLUSTRATION IN GROUP 4.000 FOR DETAILS.; SEE BRAKE CYLINDER/MASTER ILLUSTRATION IN GROUP 4.000 FOR DETAILS.; WHEELS,DUAL REAR DUAL RR WHL(R05)






JB8 76 88 BRAKE SYSTEM,HYD PWR DISC/DRUM

The proportioning valve part number is: 15557344

VALVE. Hydraulic Brake Combo/Monitoring Valve.

1988 GMC K3500. Stock Code 15557344 ; 172-2184; 1722184
Manufacturer GM


At Nalley for $104:

http://parts.nalleygmc.com/products...e-ComboMonitoring-Valve/2746459/15557344.html


Or at Gm Parts Direct for $90:

15557344 - VALVE
GM PART # 15557344
CATEGORY: All
PACK QTY: 1
CORE CHARGE: $0.00


List Price: $170.56
Price: $90.40
You Save: $80.16 (47%)

http://www.gmpartsdirect.com/result...ber=15557344&singlepart=1&partnumber=15557344

 

[Rust Buster]

Thank you, but when I run that part number I get a response that it is not compatible with an 88 V30. Also, I don't have any of those electronic connection they show in that diagram.

 

[chengny]

Yeah sorry, that one mounts on the booster anyway. How about this:

You must be registered for see images attach

Does it look and mount like that?

That is one an 1986 K3500 with hydroboost brakes. Disks in front and drums in back.

 

[Rust Buster]

Yes, that is what mine looks like.

 

[Rust Buster]

Yeah sorry, that one mounts on the booster anyway. How about this:

You must be registered for see images attach

Does it look and mount like that?

That is one an 1986 K3500 with hydroboost brakes. Disks in front and drums in back.

Do you know the part number for that?

 

[chengny]

I took a personal interest in the availability of this part. I am currently replacing my brake lines and had the P/C valve out and in my hand the other day - I was considering replacing it. Decided it was still good, cleaned it up and re-installed it

As it turns out, it wouldn't have mattered if I had decided to replace it anyway- they are NLA everywhere. I searched - a lot - and the OEM part is not easy to find.

That's the bad news.

The good news is there are tons of aftermarket replacements that look fine. Here is one for example:

You must be registered for see images attach

http://www.carolinaclassictrucks.com/81-87-GM-FS-Truck-Prop-Valve.html

I don't know why you have a 81-87 style in your brake system but that should fit.


Or, if you don't want to go with an aftermarket version, you could just got to the junkyard. They are everywhere and easy to pull - and probably sell for <$10.

 

[chengny]

Do you know the part number for that?


Now I do. Here it is - item 26 in the dwg - P/N 1257087:

You must be registered for see images attach

You must be registered for see images attach

Using that P/N, I found one - at Hummer Parts Online:

http://www.hummerpartsonline.com/index.php?mod=parts&cmd=f&partnum=1257087

I couldn't order one because I am not a customer and I didn't feel like registering. So I don't know for sure if it's in stock, but at least they don't say it's NLA or Out Of Stock.

 

[Rust Buster]

It's funny you posted a link to the Carolina Classic Trucks page. I was actually very close to ordering that exact part from them and they told me that it wouldn't be able to handle the pressure of a hydroboost. Not sure I really believe that, but it scared me away...

 

[1low4x4]

Well, don't know about your hydroboost but I just installed that exact prop valve from carolinaclassiccarolinaclassica like 3 weeks ago. Veey happy with fitment and performance. Good luck in your search

 

[GreaseDog]

Don't see why it wouldn't work with hydroboost, never heard of anyone having to change the prop valve when doing a hydro boost conversion on a vacuum boost truck.

 

[1low4x4]

Don't see why it wouldn't work with hydroboost, never heard of anyone having to change the prop valve when doing a hydro boost conversion on a vacuum boost truck.

Good point. My dad put hydroboost on his 86 and never touched the prop valve