The Pig Rig!

[1976gmc20]

I'm thinking the porportioning valve may have failed somehow

That seems to be the purpose of those valves

[ericjon262]

Originally Posted by 1976gmc20

That seems to be the purpose of those valves

Actually, I'm starting to think the shuttle valve inside the porportioning valve is doing exactly as designed, unfortunately for me, that means it's making my life harder too.

[1976gmc20]

Originally Posted by ericjon262

Actually, I'm starting to think the shuttle valve inside the porportioning valve is doing exactly as designed, unfortunately for me, that means it's making my life harder too.

Well, all I know is that my 1989 had no rear brakes when I got it. Now I've got it all fixed and the brakes work good but the light is still on and sometimes it flashes.

[ericjon262]

Does your 89 have ABS?

I tripped the shuttle valve, that's why wasn't getting any fluid. I just reset it, and am now going to gravity bleed the brakes before continuing.

The valve was a PITA to reset, only because of it's location on the frame, which is now under my ORD steering box brace. If it isn't flowing to the front brakes, there it a button on the valve you can push to reset it. If it isn't flowing to the rear, you have to remove the porportioning valve from the combination valve, and then push the shuttle valve towards the front circuit, it clicks into place.

[1976gmc20]

Originally Posted by ericjon262

Does your 89 have ABS?

I tripped the shuttle valve, that's why wasn't getting any fluid. I just reset it, and am now going to gravity bleed the brakes before continuing.

The valve was a PITA to reset, only because of it's location on the frame, which is now under my ORD steering box brace. If it isn't flowing to the front brakes, there it a button on the valve you can push to reset it. If it isn't flowing to the rear, you have to remove the porportioning valve from the combination valve, and then push the shuttle valve towards the front circuit, it clicks into place.

Not sure; I don't think so.

I thought the valve was the one right outside the master cylinder, with the wire running to the top? There is also some sort of module right beside all that. Both the 89 pickup and the 91 suburban seem to have the same system.

The shop that I had fix the brakes (they were completely destroyed!) didn't know how to get the light off and didn't know why I should even care. Yeah, it's just a "ranch truck' but I don't go to that shop anymore

[ericjon262]

Originally Posted by 1976gmc20

Not sure; I don't think so.

I thought the valve was the one right outside the master cylinder, with the wire running to the top? There is also some sort of module right beside all that. Both the 89 pickup and the 91 suburban seem to have the same system.

The shop that I had fix the brakes (they were completely destroyed!) didn't know how to get the light off and didn't know why I should even care. Yeah, it's just a "ranch truck' but I don't go to that shop anymore

I'm pretty sure 89+ got ABS. 4x4?

you probably need to reset the switch like I described above, or the ABS module is on the fritz. I don't know how exactly ABS worked on the later trucks, I've never needed to look into it. when I install late model brakes on this truck, I plan to move the combination valve up to the master cylinder like most applications have.

[68Timber]

I've read something here about the PV reset getting tripped, it happened to someone else here once.

[1976gmc20]

Originally Posted by ericjon262

I'm pretty sure 89+ got ABS. 4x4?

you probably need to reset the switch like I described above, or the ABS module is on the fritz. I don't know how exactly ABS worked on the later trucks, I've never needed to look into it. when I install late model brakes on this truck, I plan to move the combination valve up to the master cylinder like most applications have.

4x4, yes. I think special-K or someone on here said these trucks had RWAL.

Either one, I would just like to delete (probably isn't working anyway). I drove for decades without either one of those

Sorry to interfere in your build thread.

[ericjon262]

Originally Posted by 1976gmc20

4x4, yes. I think special-K or someone on here said these trucks had RWAL.

Either one, I would just like to delete (probably isn't working anyway). I drove for decades without either one of those

Sorry to interfere in your build thread.

I'm pretty sure that's right that they only got rear wheel. it's probably not too hard to delete, just look at the wiring diagrams and see what components ground the light.

as far as "interfering", it was on topic discussion, and we are all here to learn from one another, I have no issue with anyone posting here, as long as it's on topic.

Originally Posted by 68Timber

I've read something here about the PV reset getting tripped, it happened to someone else here once.

There is so much miss-information out there on the combination valve, the PV doesn't have any components to "trip". I did a quick write up on the components, and what they do.




on the left, you have the front brake outlets, if desired, theoretically, you could plug one of the front outlets and run a "T" off of the other to supply both brakes, it really doesn't matter which goes left or right. there is also a metering valve, which allows the rear brakes to apply slightly before the fronts(this is important in later discussion).

in the middle section, you have both inlets from the master cylinder, a warning switch, and the shuttle valve(switch piston).

on the right, you have the single rear brake outlet, and the porportioning valve. many people refer to the combination valve as a porportioning valve, but it is only part of the assembly. the porportioning valve prevents rear brake lockup on a panic stop by limiting flow to the rear, and creating a more gradual apply.

the center of the shuttle valve has a detent which operates the warning switch. in the event of a brake line failure, pressure on the side with a failure will drop, and the side without failure will be much higher, which in turn results in the valve moving to block the port of the failed section. when the valve moves, the detent activates the switch triggering a brake warning on the dash.

now, for front failure, there is a button on the side with the front brakes, which allows the valve to be reset and the brakes bled. but there is not a reset for the rear, that's because the metering valve should allow the valve to reset itself. in the case of a rear system failure, there are a few options to fix it, the more difficult and painful way, is to disconnect the rear brake line from the porportioning valve, remove the porportioning valve (***it's reverse thread!!!***)and use a pin to reset the valve. reassemble the components, and then let the rear circuit gravity bleed. there is a tool that can be installed in place of the brake warning switch to keep the shuttle valve from actuating, this will allow you to go straight to a normal bleeding procedure. the second option is more debated than the first, but should work when performed properly. with the light on on the dash, now stomp on the brake pedal, but almost as soon as your foot hits the pedal, get off of it. the metering valve will allow rear line pressure to build sharply, but not the front which should cause the valve to shift towards the front circuit and reset.

mine tripped last night while I was trying to bleed the brakes, and I decided to sleep on it. woke up this morning, did some reading, went out to reset it, and the light was out... so time might also help reset the valve, although, I wouldn't bank on it, I may have just been lucky.

[1976gmc20]

I did a quick write up on the components, and what they do.

Thanks for all the information!

It's been almost six years since I had the rear brakes restored, so I guess the light isn't going to heal itself with time.

I ran across something else about just pulling the wire off the switch terminal, but I've tried and I can get the bloody thing to come off! I'm about that || close to just cutting the wire

BTW, just what is the big flat "module" suspended just beside the MC and the valve ???

[ericjon262]

Originally Posted by 1976gmc20

Thanks for all the information!

It's been almost six years since I had the rear brakes restored, so I guess the light isn't going to heal itself with time.

I ran across something else about just pulling the wire off the switch terminal, but I've tried and I can get the bloody thing to come off! I'm about that || close to just cutting the wire

BTW, just what is the big flat "module" suspended just beside the MC and the valve ???

Cutting the wire will make the light go out, but probably not fix a problem.

try the quick stomp, I intentionally tripped it two or three times to make sure that the technique works. I made a quick video to illustrate how quick the jab is.

https://youtu.be/OJ9mrFhc5rw

The big flat module is probably the ABS Module, but I can't say for sure, I've never had an ABS equipped square.

[1976gmc20]

Originally Posted by ericjon262

Cutting the wire will make the light go out, but probably not fix a problem.

try the quick stomp, I intentionally tripped it two or three times to make sure that the technique works. I made a quick video to illustrate how quick the jab is.

https://youtu.be/OJ9mrFhc5rw

The big flat module is probably the ABS Module, but I can't say for sure, I've never had an ABS equipped square.

Thanks for the tip! I will go out and try that shortly.

The 89 pickup isn't a square, but it looks to be the same setup as my 91 suburban (which is "newer" but yet "older" ). Only difference is the 91 has steel MC reservoir while the pickup is plastic. The suburban brakes are fine; I'm not sure if I've even replaced the pads in 18 years.

[ericjon262]

Originally Posted by 1976gmc20

Thanks for the tip! I will go out and try that shortly.

The 89 pickup isn't a square, but it looks to be the same setup as my 91 suburban (which is "newer" but yet "older" ). Only difference is the 91 has steel MC reservoir while the pickup is plastic. The suburban brakes are fine; I'm not sure if I've even replaced the pads in 18 years.

10-4, the connector for the light is removed, at least on the squarebodies, by squeezing the sides, if you squeeze them, and pull, and the light stays on, disconnect the switch at the parking brake. if it's still on, the wire could be shorted to ground somewhere, or the ABS module is lighting it up somehow.

[1976gmc20]

Originally Posted by 1976gmc20

Thanks for the tip! I will go out and try that shortly.

The 89 pickup isn't a square, but it looks to be the same setup as my 91 suburban (which is "newer" but yet "older" ). Only difference is the 91 has steel MC reservoir while the pickup is plastic. The suburban brakes are fine; I'm not sure if I've even replaced the pads in 18 years.

Okay, I tried the quick stomp as per the video several times and no success.

I finally got the wire pulled off, and the light is still flashing so it's apparently something else. Otherwise brakes work fine and fluid level is staying steady. The parking brake is disconnected because the arm in the LR was destroyed and I haven't yet gotten to a junkyard to try to find another one. The part isn't available new so the shop put it back together without either one. I have the RR parking brake arm in my glovebox.

I compared these two trucks again, the 1989 GMT400 and the 1991 squarebody. The brakes are basically the same and both apparently have the RWAL as there is another device that the rear brake line runs through that upon closer inspection has wires that connect to the flat module. Only difference other than the steel MC reservoir is that the 91 has the PV and RWAL devices mounted crossways under the MC and the 89 has them fore and aft.

If the RWAL works on either truck, it is undetectable when driving. Maybe I just never tried to stop that fast?

[ericjon262]

if I had to guess, then I would say it's probably the ABS module detecting some sort of failure and lighting up to signify it.

[1976gmc20]

Originally Posted by ericjon262

if I had to guess, then I would say it's probably the ABS module detecting some sort of failure and lighting up to signify it.

I would guess that you're a good guesser

// true grit fan

[ericjon262]

I've been bleeding the hell out of my brakes, and I need to wake up and face the music that my master cylinder is the wrong size. the JB5 master I have stock, has 2 different size, pistons, one smaller, one larger. The JB7 master has 2 larger, same size pistons about 1/2 way inbetween the JB5 pistons, which partially explains my soft mushy pedal. unfortunately, the larger master, uses smaller fittings on one port, which would be more difficult to adapt compared to larger ports. I have found another master, that's slightly bigger, with one port the same size as my stock lines, and one slightly bigger that I may be able to adapt to with a bushing, but, then I have to worry about pedal response, if I use the larger master, will I be pushing a rock to stop the truck? the larger master would have approximately 10% more area compared to the "correct" master. they're both relatively inexpensive, so I think I'll try the larger master since it will require less work to fit, and see how the truck responds.

[ericjon262]

last night at work, I started working on a list of things I either need to do, or acquire for taking the Pig Rig on longer trips, like to Alaska and back

one of the major things I started with was spare parts, in this case, I looked for single point failure parts that disable the truck and can't be easily rigged up or bypassed to limp home on, and then added things that can make roadside "repairs" get you somewhere where a real repair can be completed.

Parts/materials:

IGN coil
IGN module
Belts
Fuel filter
JB weld
Zip ties
Bailing wire
Electrical wire/crimps/tape
RTV
tire plug kit

with the exception of the belts, I'm 99% sure all of that will fit into a single 7.62 ammo can, the belts might fit as well depending on how tight I can cram everything in.

but obviously, this is only half the picture, if you have parts, but no tools to install them, then you may as well not have the parts, so I'm also going to make up a tool list containing the tools necessary to install belts/coils/modules, as well as a few common wrench sizes and a small socket set, double covering common GM sizes like 3/8, 1/2, and 9/16.

on the other side of the field, I began looking at things I would like to add to make trails and trips more accommodating.

The truck has an AUX battery already, but I'm not sure what circuit triggers the solenoid to allow it to be put to use.
I need some means of adding pressure to the tires when getting off the trails
Recovery gear in in the event I get stuck, which is a whole topic by itself...
camping gear to include a means of cooking food and making coffee
a water supply
communications of some kind, I'm looking into signal boosters for cell phones.
animal control (bear spray and the like)
and a charging station for go-pros, phones, and the like.

I will elaborate more on how I plan to accomplish some of these ideas as I go.

[1976gmc20]

My understanding is that the Alcan and Cassiar highways are paved all the way now, so it's not quite the adventure that it was back in 1977/1979. I would suggest doing the Cassiar at least one direction as the scenery is breathtaking the entire 400 or so miles through northwestern BC. I did it both ways, and it was much improved coming back 2 years later.

Unless things have changed in 40 years, there isn't much real off-road adventure in Alaska. Mostly you have to hike, fly, or boat off a maintained road. Pretty much everything is either a built road or muskeg/bush/mountains. Of course there are some gravel roads where a capable vehicle is always an advantage, but there's a good chance you may never lock in your hubs. The only real "four wheeling" I ever got to do up there was gleaning firewood from power line right of ways. You probably can't do stuff like that anymore, and anyway you can get buried to the headlights if you go the wrong place and that's a little too much "fun."

It's a dang shame that you can't take a significant sidearm through Canada, at least that I know of? You might want to check into the paperwork to take a .30-30 levergun or a 12 gauge slug gun with you.

[ericjon262]

Originally Posted by 1976gmc20

My understanding is that the Alcan and Cassiar highways are paved all the way now, so it's not quite the adventure that it was back in 1977/1979. I would suggest doing the Cassiar at least one direction as the scenery is breathtaking the entire 400 or so miles through northwestern BC. I did it both ways, and it was much improved coming back 2 years later.

Unless things have changed in 40 years, there isn't much real off-road adventure in Alaska. Mostly you have to hike, fly, or boat off a maintained road. Pretty much everything is either a built road or muskeg/bush/mountains. Of course there are some gravel roads where a capable vehicle is always an advantage, but there's a good chance you may never lock in your hubs. The only real "four wheeling" I ever got to do up there was gleaning firewood from power line right of ways. You probably can't do stuff like that anymore, and anyway you can get buried to the headlights if you go the wrong place and that's a little too much "fun."

It's a dang shame that you can't take a significant sidearm through Canada, at least that I know of? You might want to check into the paperwork to take a .30-30 levergun or a 12 gauge slug gun with you.

Planning to take a ferry partway up don't really have a particular destination in mind yet, but I want to put tires on glacier at some point during the trip. the way back will be entirely over the road. it will be one hell of a shake down run, after I get back, I plan to leave for speed week in Bonneville, and then hit Arches National park. who knows what else!

[1976gmc20]

The stretch from Terrace BC up to Watson Lake YT (the 90 degree turn right on the line) is the Cassiar Highway (37, I think). Very beautiful; don't miss Boya Lake! The side trip down to Stewart past Bear Glacier is well worth it, though I guess there is a lot less ice now than 40 years ago when the toe of the glacier was clear down to the water right across from the road.

I wonder how one would handle a fuel pump failure on the road ??? I guess start with a brand new one and hope for the best

[ericjon262]

Originally Posted by 1976gmc20

The stretch from Terrace BC up to Watson Lake YT (the 90 degree turn right on the line) is the Cassiar Highway (37, I think). Very beautiful; don't miss Boya Lake! The side trip down to Stewart past Bear Glacier is well worth it, though I guess there is a lot less ice now than 40 years ago when the toe of the glacier was clear down to the water right across from the road.

I wonder how one would handle a fuel pump failure on the road ??? I guess start with a brand new one and hope for the best

I'll most likely start with a brand new one. I have a 40 gallon tank to put in it now and am debating on whether or not to install it before the trip. if I put the 40 in, It will definitely have a new pump, and I may or may not carry a spare. probably not as they don't really fail too often... (knock on wood...)

I appreciate the trip plan feedback more than you can imagine. I have never been to Alaska and I really don't have a plan. I made a goal about 6 months ago to drive to all 50 states, Alaska being the last hard one to get to. if you're wondering, I already have Hawaii checked off. I worked in the engineroom on a vessel that transited to Hawaii so I count that.

[ericjon262]

well, I don't have anything to cool to report. I picked up some steel at an auction, in the pictures, it looked like it was 1/8" wall, turns out, it's 1/4", so I'm not sure whether or not I will make bumpers out of it.



I got the driveshaft back and installed, and the new master cylinder in, but I need to bleed the brakes again. hopefully everything goes off without a hitch and on saturday I can take it for a shakedown tour around the block or something.

[ericjon262]

Originally Posted by ericjon262

I've been bleeding the hell out of my brakes, and I need to wake up and face the music that my master cylinder is the wrong size. the JB5 master I have stock, has 2 different size, pistons, one smaller, one larger. The JB7 master has 2 larger, same size pistons about 1/2 way inbetween the JB5 pistons, which partially explains my soft mushy pedal. unfortunately, the larger master, uses smaller fittings on one port, which would be more difficult to adapt compared to larger ports. I have found another master, that's slightly bigger, with one port the same size as my stock lines, and one slightly bigger that I may be able to adapt to with a bushing, but, then I have to worry about pedal response, if I use the larger master, will I be pushing a rock to stop the truck? the larger master would have approximately 10% more area compared to the "correct" master. they're both relatively inexpensive, so I think I'll try the larger master since it will require less work to fit, and see how the truck responds.

something of note here:

never trust parts store info. on the Oreilly auto parts website, they list the 1/2 and 3/4 ton trucks as having different size brake master fittings, they are swapped front to back, but are not different sizes.

[ericjon262]

did a little interior work today, I pulled the back seats out, and am making a panel that lays flat to replace them, it will have two hinges center, so that it opens gullwing style and allows for a bit more storage. I am going to remove the seatbelts too, I just don't have the right torx bit on hand to do it.







one of the seatbelts had a regular bolt in it, I removed it to find the hole torn and stretched. I'm begining to think this truck was hit HARD on tha passenger side. I think I might start looking for a 3/4 ton in better shape to do the duramax swap into.