Advice on Rear Differential Leak for 1980 C10

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

AlabamaDan

Junior Member
Joined
Nov 3, 2024
Posts
10
Reaction score
16
Location
Alabama
First Name
Dan
Truck Year
1980
Truck Model
C10
Engine Size
350
Hey everyone,

I’m in the process of getting my 1980 Chevy C10 back on the road after it sat in storage for about 15 years. The truck was my grandfather’s, and I’m aiming to keep it as original as possible. While I was under it recently, I noticed what looks like a small leak around the rear differential. The fluid level isn’t dangerously low yet, but I think it might be time to check or change it and make sure everything is sealed up.

A few questions for you all:

  1. What’s the best way to confirm if it’s a small leak or something bigger? Anything I should look for specifically?
  2. What’s involved in changing or topping off the rear diff fluid on these trucks? Do I just need to pull the cover to drain it fully?
  3. Any parts or supplies you’d recommend? I’m guessing I need fresh gear oil and maybe a new gasket if I pull the cover, but let me know if there’s anything else that would help.
Thanks for any advice you can share, especially if you've been through a similar job on a C10. I appreciate the help!
 

JD Miller

Full Access Member
Joined
Sep 30, 2024
Posts
192
Reaction score
395
Location
Goober Idaho
First Name
JD
Truck Year
1981
Truck Model
K20 silverado
Engine Size
350
Wash off all the crud, dirt, oil. Check the oil level. Look for leaks after the differential is cleaned
 

AlabamaDan

Junior Member
Joined
Nov 3, 2024
Posts
10
Reaction score
16
Location
Alabama
First Name
Dan
Truck Year
1980
Truck Model
C10
Engine Size
350
Thanks JD. Would you recommend proactively cracking it open to change all the fluid?
 

DoubleDingo

Full Access Member
Joined
Jul 3, 2012
Posts
11,250
Reaction score
17,177
Location
Right where I am
First Name
Bagoomba
Truck Year
1981
Truck Model
81-C20 Silverado Camper Special-TH400-4.10s
Engine Size
Carb'ed Vortec 350
Thanks JD. Would you recommend proactively cracking it open to change all the fluid?
Yes. Don't pry on the cover to break it loose. Use a thin putty knife and tap it between the differential and cover in various spots. Clean the inside with break clean, and note any oddities or lack thereof in the gear oil.

Then fill it with fresh 80w or 80w90 gl5.
 

legopnuematic

Licensed Junk Dealer
Supporting Member
Joined
Oct 27, 2016
Posts
2,508
Reaction score
6,486
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
Leave one bolt at the top of the cover installed loose, then when you break the seal of the cover, it stays put, let’s you drain it, then remove the bolt and pull cover after drained.

Then you don’t have the cover fly off and make a big splash.

Make sure you can remove the fill plug first before pulling the cover.
 

AlabamaDan

Junior Member
Joined
Nov 3, 2024
Posts
10
Reaction score
16
Location
Alabama
First Name
Dan
Truck Year
1980
Truck Model
C10
Engine Size
350
Good advice from all. Love it!
 

Forum statistics

Threads
44,167
Posts
950,743
Members
36,282
Latest member
Doug Hampton
Top