differential lubricant
Thread Starter
Pro
Joined: Apr 2006
Posts: 647
Likes: 22
From: Norwalk CT and Boynton Beach FL
differential lubricant
I want to change the differential lubricant on my 75, but I don't see any drain plug and taking the rear end cover off looks like a real bear. What's the easiest way to suck all that fluid and gunk out of the rear end. 
Pro
Joined: Mar 2001
Posts: 633
Likes: 1
From: Hamilton, ON, Canada
Get a suction tool. It looks sort of like a grease gun with a plunger and a hose on one end. When you pull the handle, it sucks in the fluid. Someone sells a drain plug kit, if you want to go to the trouble of drilling & tapping a hole. I think it may be Ecklers.
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
I think the best way is to drill, tap and use a drain plug as 75 Hot One suggests. This makes it a breeze for your next change. I did it to my '76 years ago and I glad I did. Besides, you'll never get all the crap out using the suction method. I also suggest using a synthetic such as Mobil 1 and, of course, don't forget the posi additive.
Last edited by Jud Chapin; Oct 27, 2006 at 08:08 AM.
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
If you're running an Eaton Posi, which most our Vettes have, Eaton "strongly recommends" the use of conventional/mineral lubes, 80-90w, with their posi's. Apparently the failure rate is higher with syns.
http://www.traction.eaton.com/prod6.htm
http://www.traction.eaton.com/prod6.htm
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
Originally Posted by 73, Dark Blue 454
If you're running an Eaton Posi, which most our Vettes have, Eaton "strongly recommends" the use of conventional/mineral lubes, 80-90w, with their posi's. Apparently the failure rate is higher with syns.
http://www.traction.eaton.com/prod6.htm
http://www.traction.eaton.com/prod6.htm
Last edited by Jud Chapin; Oct 27, 2006 at 12:34 PM.
Melting Slicks
Joined: Nov 2001
Posts: 2,668
Likes: 43
From: Eastern US XX
Originally Posted by 73, Dark Blue 454
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
Originally Posted by 75 Hot One
Get a suction tool. It looks sort of like a grease gun with a plunger and a hose on one end. When you pull the handle, it sucks in the fluid. Someone sells a drain plug kit, if you want to go to the trouble of drilling & tapping a hole. I think it may be Ecklers.
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
Originally Posted by Jud Chapin
I think the best way is to drill, tap and use a drain plug as 75 Hot One suggests. This makes it a breeze for your next change. I did it to my '76 years ago and I glad I did. Besides, you'll never get all the crap out using the suction method. I also suggest using a synthetic such as Mobil 1 and, of course, don't forget the posi additive.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
Originally Posted by pws69
It doesn't say that and quite frankly, I don't believe it.
Tech Contributor
Joined: Aug 1999
Posts: 15,175
Likes: 3,987
From: Connecticut, USA
I use Lucas 85-140 now but have used the 90 wt for years.
Also when I checked into using syn oil years ago I called Tom Watt and an engineer at US gear, I don't recall his name. They both advised against syn oil in the differentials, why I honestly don't recall. I figured they were either building drag race diff's or designing gears so they'll know what works in use.
Also when I checked into using syn oil years ago I called Tom Watt and an engineer at US gear, I don't recall his name. They both advised against syn oil in the differentials, why I honestly don't recall. I figured they were either building drag race diff's or designing gears so they'll know what works in use.
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
Originally Posted by gtr1999
I use Lucas 85-140 now but have used the 90 wt for years.
Also when I checked into using syn oil years ago I called Tom Watt and an engineer at US gear, I don't recall his name. They both advised against syn oil in the differentials, why I honestly don't recall. I figured they were either building drag race diff's or designing gears so they'll know what works in use.
Also when I checked into using syn oil years ago I called Tom Watt and an engineer at US gear, I don't recall his name. They both advised against syn oil in the differentials, why I honestly don't recall. I figured they were either building drag race diff's or designing gears so they'll know what works in use.
Pro
Joined: Nov 1999
Posts: 520
Likes: 5
From: Front Range
I don't know anything concrete about differential lubes, but I always thought the synthetic versus conventional argument was based on the presence of Molybdenum in the conventional lubricants. (The source was my father, so I take it with a grain of salt, as his experience was in Formula-V's in the mid to late 1970's)
I'd be interested in an assay / analysis of a conventional versus synthetic differential gear lube, as well as an assay of the GM additive... my uneducated guess is that the additive is heavy on Molybdenum and Zinc.
Anyone seen that sort of info?
I'd be interested in an assay / analysis of a conventional versus synthetic differential gear lube, as well as an assay of the GM additive... my uneducated guess is that the additive is heavy on Molybdenum and Zinc.
Anyone seen that sort of info?
Burning Brakes
Joined: Dec 2005
Posts: 1,179
Likes: 100
From: cranford nj
Go to your local gm dealer buy the lube an additive, then go in the kitchen and get your wifes turkey baster, suck out all of the fluid. Next put the additive in first then the lube find a parking lot and do figure 8's for about 10 min. Good as new.been there done that.
Melting Slicks
Joined: Nov 2001
Posts: 2,668
Likes: 43
From: Eastern US XX
Originally Posted by blue by you
Go to your local gm dealer buy the lube an additive, then go in the kitchen and get your wifes turkey baster, suck out all of the fluid. Next put the additive in first then the lube find a parking lot and do figure 8's for about 10 min. Good as new.been there done that.
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
From the link I posted:
"What type of lubricant and limited slip additive should I use with my newly purchased Eaton Limited Slip Differential?
Eaton strongly recommends utilizing an API-GL5 approved Mineral-Based 80W-90 Axle Lubricant and one 4-oz bottle of Limited Slip Additive (GM or Ford)."
But you're right,..those engineers at Eaton are probably a bunch idiots. And the failed posi units that were returned for warranty reasons or otherwise, were simply tossed into the big Eaton trash can out back. I'm sure the failures weren't studied as a part of Eaton's R&D program. And I doubt it ever occured to the engineers at Eaton to test the use of synthetic lubes with their product.
After all, why would a company spend all that time and money on R&D, since we know more about Eaton products than the mush-headed engineers at Eaton.
And those millions of Eaton posi units installed on GM cars through the years that ran a trillion trouble-free miles using conventional gear lube,..well, we know how to make it better.
Eaton,..it's a crummy company anyway. And engineers,..what do they know.
"What type of lubricant and limited slip additive should I use with my newly purchased Eaton Limited Slip Differential?
Eaton strongly recommends utilizing an API-GL5 approved Mineral-Based 80W-90 Axle Lubricant and one 4-oz bottle of Limited Slip Additive (GM or Ford)."
But you're right,..those engineers at Eaton are probably a bunch idiots. And the failed posi units that were returned for warranty reasons or otherwise, were simply tossed into the big Eaton trash can out back. I'm sure the failures weren't studied as a part of Eaton's R&D program. And I doubt it ever occured to the engineers at Eaton to test the use of synthetic lubes with their product.
After all, why would a company spend all that time and money on R&D, since we know more about Eaton products than the mush-headed engineers at Eaton.
And those millions of Eaton posi units installed on GM cars through the years that ran a trillion trouble-free miles using conventional gear lube,..well, we know how to make it better.
Eaton,..it's a crummy company anyway. And engineers,..what do they know.
Last edited by 73, Dark Blue 454; Oct 30, 2006 at 09:53 AM.
