New Member with a Question about a leak in the 4wd

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jordanrx

Junior Member
Joined
Jan 29, 2024
Posts
1
Reaction score
0
Location
Oklahoma
First Name
Will
Truck Year
1980
Truck Model
K20
Engine Size
5.7
Hi Everyone. I'm 15 and this is my 1980 K20, standard transmission, that I bought from my uncle and look to drive when I turn 16. I noticed a leak from the 4wd and was hoping to get some help identifying what part/seal I need and maybe an idea of what it would take to replace it. I have attached a couple of pictures, one of the truck and one of the leak, that may help.

Thanks in adavance
Will


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legopnuematic

Licensed Junk Dealer
Supporting Member
Joined
Oct 27, 2016
Posts
1,736
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3,734
Location
MO
First Name
Spencer
Truck Year
1971, 1̶9̶7̶4, 1976, 1979,1̶9̶8̶5, 2002
Truck Model
Dart Swinger, Sierra 10, C10 Cheyenne, C10 Big Ten, Silverado 10, Ram 2500
Engine Size
225/6, 350 c.i., 350 c.i., 5.9l Cummins
Welcome from Missouri.

Looks to be leaking at the pinion seal, without disassembly hard to say if it only needs a seal, seal and speedi sleeve on yoke, or a new seal and yoke.

If you are lucky it could be as simple as a clogged vent/hose causing it to build pressure, pinion seals are not really made for holding against pressure, it's lot of times the path of least resistance.
 

dvdswan

Full Access Member
Joined
Mar 11, 2014
Posts
2,366
Reaction score
2,024
Location
Port Orchard, WA
First Name
Dave
Truck Year
1978
Truck Model
K10
Engine Size
350
Welcome to the site. Nice purchase from your uncle. It does look like a pinion seal, but be careful, engine oil leaks can drip down onto the front axle.

I would buy some Gunk engine degreaser and spray the engine and front axle. (be careful not to soak electrical connections or distributor with high pressure water, You'll have a real hard time starting the truck up again for a long while.) Then drive around for a bit (10-15 minutes should be more than enough) then check for leaks again.

The rear of the intake, valve covers, oil sender, oil pan, and rear main seal are key spots to look for leaks. Unless, the front hubs have been locked forever I really doubt it's the pinion seal leaking.
 

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