1990 GMC K1500 restoration

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idlook2

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Picked up a 1990 GMC K1500 back in October 2020 down in Georgia. I’ve been wanting one of these trucks for a while, my dad had a 1988 when I was a kid and I have lots of good memories riding around in that truck.

I’ll document the restoration in this thread, enjoy!

The day it arrived at my house:

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idlook2

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First attempt at trying to address the soft brake pedal: replacing the master cylinder. The pedal is a little better, but something else in the brake system is still not right.

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YouTube video for anyone interested:
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idlook2

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Second attempt at trying to address the soft brake pedal. I started out just wanting to adjust the rear brakes but after seeing the cracked rear shoes, I went ahead and did a brake job on the rear (drums, shoes, wheel cylinders, hardware, and rear brake hose). Pedal is better but still not where I think it should be.

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idlook2

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Third attempt at trying to address the soft brake pedal. After lots of reading, I’m starting to think the rear wheel abs unit is the issue, specifically a leaky dump valve allowing fluid to leak into the accumulator rather than apply pressure to the rear brakes. This is a great article describing the operation of the rear wheel abs system:

https://www.aa1car.com/library/abs_kelseyhayes_rwal.htm

I also noticed that my combination valve was leaking a little bit of fluid out of the metering valve so I decided to replace it along with the rear wheel abs unit. Unfortunately, the “AC Delco inspired” combination valve that I purchased is leaking out of the electrical connector on top and the brakes are now probably worse than where I started. Currently sourcing a used combination valve to replace this crappy knockoff valve. The brakes will have to wait until the new valve arrives.

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idlook2

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One of the first things I noticed when I test drove the truck was that the steering column was a mess. Turn signals would only latch in one direction, gear shifter return spring was broken, and the horn did not work. Dug into the column and ended up replacing quite a few parts to get everything working right again:

- Turn signal cancel cam
- Turn signal switch
- Wiper switch
- Turn signal lever
- Gear shifter return spring

As a bonus I found someone selling new old stock GMC horn pads on eBay so I picked up one of those as well. It’s nice to have all of the stuff right in front of you fixed!

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idlook2

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Time to start addressing some of the oil leaks on this truck. The front differential was leaking really bad and looked like a good place to start. I pulled the differential and took it over to a local shop for new axle seals, pinion seal, and a re-seal on the case itself. Went ahead and added a new 4wd actuator and vent plug as well.


Nice and clean differential ready to go back in the truck:

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YouTube video on how to remove the differential:
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idlook2

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Next up, engine oil leaks! Decided to start at the top and work my way down. Pulled the intake manifold to replace the gaskets. Went ahead and added a new EGR valve, throttle body gasket, heater hose quick connect, and temperature sending unit.

I have to admit, pulling the manifold was a much bigger job than I imagined.

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