1984 GMC K2500 Sierra Classic

[haro1225]

How did ya end up getting the old studs out?

[MattStrike]

I had to resort to the BFH.

[dadofone2011]

This is looking great so far, I will be following this thread.

[MattStrike]

Found the factory wiring schematics for the dual fuel tanks with dual fuel pumps, and compared to mine. The switch on the dash has two wires that run to the selector valve. One is +12v and the other ground, when you flip the switch it reverses the polarity of the wires so that the one that was originally +12v becomes the ground. For the dual fuel pump setup GM just spliced those wires so that one goes to one fuel pump and the other goes to the other fuel pump. So whichever side is hot has power to the fuel pump on that line. Now all I have to do is make sure I get the left pump on the correct wire so that it turns on when the switch is in the left position.

Now I just need refills for my weatherpack connector kit.

[MattStrike]

So I'm now two steps back on the fuel tank valve. My switch is a momentary switch and the valve is motor driven. So those wires are not hot at all times, and can't just tap into that with the fuel pumps. But it looks like that changed in '88 if the wire schematics I found are correct. All the auto parts chains list the same generic valve across all the variations, but the AC Delco OE part is different with no mention anywhere on what the difference is other than to note that one of the aftermarket parts is a universal valve that requires a new/different switch. So I'm not sure what the difference is between the valves, if any, because of course there is much conflicting/incomplete information online.

It sounds like I need to find the valve and switch off a '88+ truck. I think that means a junkyard trip is in order.

Edit: So based on further research, looks like the original tank switch valve for the non-EFI trucks is a simple motor driven valve. When they changed to EFI the valve was updated to include circuitry that only powers the motor during switching, so the 'momentary' power needed is handled in the valve and the switch supplies constant power which is required by the fuel pump. As far as I can tell, all aftermarket valves now have that feature and are backwards compatible in addition to being rated for much higher fuel pressures. Of course, some of that is speculation, I don't have a factory original motor driven valve to verify. At some point in the past, the selector valve was replaced on this truck.

So all I need is a ammeter to test if the valve I already have has the automatic motor shutoff, if it doesn't then I need one that does, as well as the switch from the '87 that is not a momentary switch.

[MattStrike]

Managed to get brackets mounted for the rear brake hoses.


Yep, that's an H-body bracket!


Somehow I ended up with the wrong rear axle cover gasket, odd that the FF axle would have a different gasket than the SF.

[MattStrike]

I'm in the process of trying to rebuild the load sensing proportioning valve. Replacements were discontinued years ago. I've manage to de-rustify the housing and take apart the valve side, but the adjuster side is stuck on due to rust. The snap ring came off in 2 pieces, and it's on day 3 of it's soak in evaporust. I've found one seal that's leaking so far, but need to get the adjuster side off to be able to change it. And if you believe the internet, I am the first person to try to do this, so I'll be pioneering replacement parts (snap rings, seals, and anything else that's broken).

Also I think I found a set of GMC aluminum wheels for this.

[MattStrike]

I didn't get anything done today, because I found these:


From a '07 2500 HD Sierra. Came with center caps, two good Michelin 265-70R17 LT tires, absolutely no curb rash, no oxidation. Brought one of the front hubs with to check the fitment before I got them. Price was too good to pass up.

Also managed to fit all 4 in the SE, with room to spare.

[MattStrike]

I've managed to get the rear brake lines in up to the proportioning valve location, and the axle is back together and the rear end back on the ground.

[MattStrike]

Both tanks are plumbed in, need to get refills for my metri-pack kit to change the connectors on the sending units, and finish making the wire harness. I'll be running duel fuel filters, they are temporarily clamped to the frame until I can find a better/real clamp. I ran out of 5/16" line though, so the last run from the tank valve to the engine bay is not done. Also need to get more quick connect fittings from a junkyard to finish the fuel filter connections. Planning to return to the local U-pull today for the clamps/fittings if I can find them.

I ended up getting a new universal tank valve that uses the steady-on switch, rated for 65PSI. All that need to be done is to change the momentary switch in the cab out with the '87 steady on switch.

[MattStrike]

While I'm waiting for my metri-pack kit refill to get here so I can finish the tanks, I moved on to the front axle shafts. It only took 3 hours of hitting them with a sledge hammer but I finally got both of them apart. I may end up having to replace one of the outer shafts, the yoke on it looked a little thin.

Almost forgot to add, the axle universal joints were in really bad shape. Only one cap was still sealed against the elements, the rest of them were rolling around in rust, and then there's the joint that already blew the roller bearings out. I'm looking into adding some zerk fittings to the new Spicer joints.

[dadofone2011]

You are making this build in record time

[MattStrike]

Here are the details on the load sensing proportioning valve rebuild.

This is after disassembly, the rotor pulls off by pulling out the brass center after the snap ring is off. There is a very small oring still inside that seals the red plunger from the rotor section that I didn't have out yet:


And here are the seals. I did not have to replace the plunger seal. The O-rings are HNBR. McMaster-Carr 9403k55 for the rotor seal.


And this is why it was leaking, there was a gash where it's supposed to seal off to the lower O-ring:


Used JB Weld to repair it; picture taken before sanding it flush.


The rotor and housing with the new seal.


The lower O-ring in the valve side:


RTV to seal the rotor from the elements. I coated the whole rotor with a light oil.


Rotor reinstalled with a new stainless steel snap ring:


And back on the truck, with the adjustable stainless linkage to replace the rusted out worn out piece.


This is what the front axle universal joints looked like:


And for some reason the one outer shaft was horribly pitted with rust. So I'll be replacing it as it is getting thin in the yoke area:

[PRD2BDF]

I am going to have to ask, why not just replace the truck with a better shape one?

[MattStrike]

Because I can fix this one. You are coming to the MI meet to see it, right?

[MattStrike]

So I had been on the fence about replacing the motor mounts, but when I split them open today they came out of the shells in about 12 pieces. So I'm glad I decided to bite the bullet and get new Energy Suspension poly mounts. The shells are soaking in Evaporust now, should be able to put the back together tomorrow. Really hoping everything works out that I can get the truck back down on all 4 wheels this weekend and have the first test fit of the motor.

[BBamm]

I can't wait to see the finished product!! How close do you think it will be to rolling by the time the MI meet happens??

[MattStrike]

I should be able to have this done before the end of the month.

[MattStrike]

Tank wiring is done, remaining lines and fuel filter mounts are coming Monday, the passenger side tank is mounted, ready to mount the other tank, transfer case is ready to go back in, and the new Spicer axle shaft and universal joints are ready for re-assembly.

I got sidetracked with a welding project, so didn't get as much done as I anticipated this weekend.

[MattStrike]

Both tanks are in now, just need some quick disconnects and mount the filters.

Spicer joints re-assembled:


And I've got the trans valve body out to try and find out why it wouldn't upshift when cold for the first time. Had to put it in neutral then back in gear to get it to upshift and after that is was always fine. Still not finding any glaring issues, some wear on the TCC valve train but that's it. Governor was fine, no stripped teeth on the gear and the roll pin joint was in good shape, and no missing/stuck check balls.


Transfer case all cleaned up and going back in:


Still working out the adapter plate, the one I got is a little thin and the instructions call for a lot of unneccessary block and trans case mods. If the plate were just a little thicker I could use flat head socket cap screws to flush mount them in the adapter plate and bypass all of that sillyness. So I'm going to try to see if I can find a waterjet or something locally (again) that can make one for me at the thickness I want. Should be easy to create my own cad using this one as a template.

And yes, I realize I could just use the trans currently bolted to the 3800, but it needs to be stripped back down again as it lost 4th gear or something. I know the one I had worked other than that one issue.