Locker Fluid Reccomendation

[Delta]

Time has come to replace the rotted differential cover on the S10, as with it I need gear oil. Previous owner replaced the stock internals to a Detroit style locker, not sure what brand it is. Pretty sure they didn't spring for the Eaton brand. I've heard not to use synthetic and no friction modifier. Also have read that a 75w140 will help quiet down all the popping, banging, and clicking. Not worried about economy as it might get 15-20mpg on a good day. It will also be daily driven in the winters around here. What do you guys think, stick with a 75w90 or try the 75w140?

 

[StevieC]

This would be my choice.

I'm using a thinner version of it in my Diff/Transfer case currently. It's amazing stuff offering cooler temps, great protection and performance. It's a big hit with the off-roading community.

https://www.amsoil.com/shop/by-product/gear-lube/severe-gear-75w-140/

They also have Slip-Lock you can add to this for your type of Diff.

https://www.amsoil.com/shop/by-product/gear-lube/slip-lock/?code=ADATB-EA

 

[FlyNavyP3]

Slip-Lock won't matter in a ratcheting differential, nor does the differential require it. Very little will quiet or smooth out the locker, I know I had one for 75,000 miles in my 4Runner, I ran everything from 80w90/75w140/Redline Heavy Shockproof. They were all noisy, popping ratcheting due to the action of the differential. I'd recommend using whatever you can find cheap or suits you. Walmart Super Tech 75w90 Synthetic or 80w90 Conventional will suit you just fine.

 

[SargeBB]

The following produce GL-5, mineral oil, 75W-90, or 75W-140 without LS (friction modifier): Mobil, Chevron, Conoco/Phillips, and Traveller (Tractor Supply house brand)...I'm sure there are many others that meet the recommended specs. All are good and meet specs., including not having LS additive. The instruction booklet with my (Torsen) Detroit True-Trac says mineral oil in grade GL-5 with no friction modifier is best. True-Trac is a clutchless limited slip. Detroit Locker is a true locker. Look in the instruction manual, available on-line, for their recommendations for the locker. The Traveller, and I'm not 'pushing' for any brand, is easily available and is inexpensive.

 

[Delta]

Thanks for the insight fellas. Went up to the local Carquest and picked up their house brand 85w140 regular mineral. We'll see how it goes. I would really like the quiet down the popping, banging, and clunking, but I'l probably just have to live with it. It is a little embarrassing trying to make tight turns in a parking lot full of people

Stevie:

You did post some nice recommendations, but those are a little out of price range for this truck. Not that I'm on a tight budget. I think the cost would be greater than what my truck is worth, lol. Although I'll probably get something for the Jeep as it will see some hard use this winter in the snow.

 

[StevieC]

No worries.

 

[code5coupe]

Sounds like the OP has a Lock-Right in his rear axle. I have them in the front and rear of my K10. They do not require any special lubricant, so I run Full Synthetic Valvoline Gear Lube.
The Detroit TrueTrac is not a Torsen, even though it uses helical gears like the Torsen. Even though Eaton recommends mineral-based gear lube for the TrueTrac, I run the same Valvoline Full Synthetic in mine and it has worked just fine so far (2000 miles).

 

[Delta]

Not sure what brand it is, but it is indeed a Detroit style (was able to look in the top part). Maybe someone can identify it from this quick picture:

Has F D F written on the pin, Google has proven me nothing. Also it seems the 85W140 has reduced some noise, not all.

 

[zeng]

Originally Posted by Delta
Also it seems the 85W140 has reduced some noise, not all.

Does it run relatively cooler under harsh condition ?