1976 GMC SIERRA

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Aug 24, 2016
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70
Location
N.C.
I‘m about to take possession of a1976 GMC Sierra 1/2 ton pickup that was bought new by my wife’s grandparents. It’s in pretty much original condition aside from the 350 engine and transmission being rebuilt sometime in the past. Her grandparents passed away many years ago, and no one else in the family has any information on the trucks history.

I haven’t owned a V8 this old in a long time, and would value recommendations on the correct oil and transmission fluids to use in this classic truck. I’m looking forward to restoring this truck, and will post some pictures when I get it home.
 
The wrong grade of motor oil in that engine has an extremely remote chance of doing any damage. Those 350 engines liked to run even when all sorts of internal parts were close to being worn out. Not sure about the tranny.
 
10w30 would make this truck happy. If it is in need of an internal clean up, maybe some Shell Rotella T.
Have fun with it!
Why not run some Liqui-Moly engine flush for the clean up or is that snake "oil"?
 
Why not run some Liqui-Moly engine flush for the clean up or is that snake "oil"?
I wouldn't recommend it in an engine this old, unless OP is ready to replace seals and gaskets. The LM flush would likely clean up deposits that are functioning at the oil seals at this point, and when you clean it up the old dry/brittle gaskets aren't going to stand a chance.
 
Has it been in use all this time, or has it been sitting? It may need a good going through, before using. New rotors, rubber brake lines, rubber anything.

It sounds like you might pull it home and give it a good looking over?

This is the era of nylon timing gears, right? I wonder if contemplating swapping that out if the water pump is seeping would be good. Who knows what is in the reman.
 
I wouldn't recommend it in an engine this old, unless OP is ready to replace seals and gaskets. The LM flush would likely clean up deposits that are functioning at the oil seals at this point, and when you clean it up the old dry/brittle gaskets aren't going to stand a chance.
You know that's what I hear a lot but even in my 17 year old Scion with 180k miles, it did not develop any new leaks. I cannot see how some sludge inside an engine on top of gasket can withstand a pressurized environment and prevent a leak.

I think if the seal is going to go, it's going to go regardless if there is sludge overlapping it. Then again I'm not a tribologist or an engineer.
 
You know that's what I hear a lot but even in my 17 year old Scion with 180k miles, it did not develop any new leaks. I cannot see how some sludge inside an engine on top of gasket can withstand a pressurized environment and prevent a leak.

I think if the seal is going to go, it's going to go regardless if there is sludge overlapping it. Then again I'm not a tribologist or an engineer.
Engine isn't pressurized like that, the pressure is read from the resistance of flow that the bearing provide in the engine. You got lucky.
 
Has it been in use all this time, or has it been sitting? It may need a good going through, before using. New rotors, rubber brake lines, rubber anything.

It sounds like you might pull it home and give it a good looking over?

This is the era of nylon timing gears, right? I wonder if contemplating swapping that out if the water pump is seeping would be good. Who knows what is in the reman.
It’s seen occasional use, but hasn’t been driven regularly. I’m guessing less than 200 miles in the last couple years. I’m seriously considering trailering it home because it’s 150 miles away from me now. My mother in law has the truck right now, and has recently had it serviced, but I don’t really want to drive it that far before thoroughly checking it out.
 
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A bone stock flat tappet v8 will run fine on 10W30,40 SL,M,N,P those transmissions originally called for dex II but dex 3 or above will work fine.
Using the low viscosity dexron fluid you will notice firmer and faster shifting.
 
10W-30 HDEO would be great fit in that engine.
If it’s been driven in the last couple of years, I’d drive it home.
It’s been driven to the dump occasionally, but that’s about it. That’s far enough to get it up to operating temperature though. I have a friend there who’s a decent mechanic, and I’ll have him check the truck out and make sure it’s good for the trip. Tires are fairly new, but the brakes are my biggest concern.
 
Got it home Tuesday. Drove it four hours without any major issues. The accelerator pump in the carb is worn out, causing an off idle stumble. Kinda exciting when taking off in front of traffic, but I made it. Carburetor rebuild will be the first thing I do.
 

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The second thing you need to do is replace the timing chain assembly. I almost lost an engine in a ‘71 Impala that I once owned when the cam gear lost the plastic coating on the gear and plugged up the oil pump. The acids that build up in the engine in combination with the heat can make the plastic brittle even if it does have low miles.
 
The second thing you need to do is replace the timing chain assembly. I almost lost an engine in a ‘71 Impala that I once owned when the cam gear lost the plastic coating on the gear and plugged up the oil pump. The acids that build up in the engine in combination with the heat can make the plastic brittle even if it does have low miles.
The truck has a Goodwrench replacement 350 crate engine from around 1987 from what I can figure. Didn’t know this until I took possession this week. It holds 40 pounds oil pressure, and has no leaks.
 
Impressive to see a truck that old in that original of condition! Even the seat vinyl isn’t torn!
Good job, enjoy it!
My BIL once bought a mid-80’s GMC 2500 to restore, but it needed too much work and he didn’t have the time, so he sold it. Usually a lot of rust on those old square bodies.
 
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