Anybody have a 90-91 Sub/Blazer with working ABS? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Irish1941 · 05-19-2021, 01:04 PM

Pretty sure my ABS has taken a dump on my 90 V1500 Sub. I get no noise from the valves in a hard stop or pedal vibration but I don't get a brake light error code either.
The rear were locking up before the fronts but did brakes all around, properly adjusted the rear shoes and that seems fixed.
I have just plumbed out the ABS altogether in past trucks but kinda want it to work now as this one is seeing a lot of highway with my wife & 8yr old in it.
Anybody have experience with the ABS? A way to test the valves without complete tear down on the system?
Thanks in advance.

Just call me Sean · 05-19-2021, 10:13 PM

The ABS on those is mostly for decoration.

Irish1941 · 05-20-2021, 12:34 AM

Quote:

Originally Posted by Just call me Sean

The ABS on those is mostly for decoration.

A brake system that's decoration....well now that clears up EVERYTHING.

**Zoomad75** · 05-23-2021, 11:43 PM

It's one of the first ABS systems GM used. Zero parts availability to replace the pump/module assembly.

Plus the system is only functional to the rear wheels which won't help with directional stability if the front wheels still have the possibility to lock up.

Chances of getting a good used one is pretty slim since it's been 30 years since they came out. Also the GMT400 rear ABS system is different so it's not a possibility to retrofit to the earlier platform.

When attempting to bleed my '91 during the intial LS swap we ran into a major issue where we could not get fluid to flow to the rear circuit. We followed the service manual procedure with a fabricated bracket holding the plunger down on the proportioning valve, still wouldn't flow. We tried everything, the system would not push fluid to the rear.

I ended up pulling a proportioning valve and the lines between it and the master cylinder from an earlier non-abs truck. Swapped them in and rears bled just fine with the same master cylinder on it. You do have to change the tube nut on the rear line to match the fitting in the prop-valve, but there is just enough on the stock rear line to cut the line, take the nut off and re-flare with the correct fitting on the line.

I haven't been in a situation where I felt the Rear wheel abs would have helped better.

05-19-2021, 01:04 PM	#1
Irish1941 Registered User Join Date: Nov 2012 Location: Los Angeles, CA Posts: 450	Anybody have a 90-91 Sub/Blazer with working ABS? Pretty sure my ABS has taken a dump on my 90 V1500 Sub. I get no noise from the valves in a hard stop or pedal vibration but I don't get a brake light error code either. The rear were locking up before the fronts but did brakes all around, properly adjusted the rear shoes and that seems fixed. I have just plumbed out the ABS altogether in past trucks but kinda want it to work now as this one is seeing a lot of highway with my wife & 8yr old in it. Anybody have experience with the ABS? A way to test the valves without complete tear down on the system? Thanks in advance.

05-23-2021, 11:43 PM	#4
Zoomad75 K5Camper Join Date: Mar 2004 Location: Pueblo, CO Posts: 1,513	Re: Anybody have a 90-91 Sub/Blazer with working ABS? It's one of the first ABS systems GM used. Zero parts availability to replace the pump/module assembly. Plus the system is only functional to the rear wheels which won't help with directional stability if the front wheels still have the possibility to lock up. Chances of getting a good used one is pretty slim since it's been 30 years since they came out. Also the GMT400 rear ABS system is different so it's not a possibility to retrofit to the earlier platform. When attempting to bleed my '91 during the intial LS swap we ran into a major issue where we could not get fluid to flow to the rear circuit. We followed the service manual procedure with a fabricated bracket holding the plunger down on the proportioning valve, still wouldn't flow. We tried everything, the system would not push fluid to the rear. I ended up pulling a proportioning valve and the lines between it and the master cylinder from an earlier non-abs truck. Swapped them in and rears bled just fine with the same master cylinder on it. You do have to change the tube nut on the rear line to match the fitting in the prop-valve, but there is just enough on the stock rear line to cut the line, take the nut off and re-flare with the correct fitting on the line. I haven't been in a situation where I felt the Rear wheel abs would have helped better. __________________ Rob Z. 1975 K5 350/465/205/D44/12b 4" lift on 35's- RIP 1991 K5 8.1L/NV4500/241/D44/14b FWC Camper



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.