Gear oil question

[Gremlinsteve]

I’m about to my 500 mile service after rehearing to the 488’s
I’d like opinions on gear oils. The rear has the factory trac lock
I’m thinking about going with a conventional oil over a synthetic. I’ve just never trusted synthetics in my axels.

What’s everyone’s opinions on that

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[MrZappo]

I think that it doesn't make a bit of difference.

Never trusted synthetics ?

Look at the spec. If it meets the spec you will be fine. Synthetic of not.

 

[ShadowsPapa]

I think that it doesn't make a bit of difference.

Never trusted synthetics ?

Look at the spec. If it meets the spec you will be fine. Synthetic of not.

I've run synthetic in everything I've had - granted most of it's been old-skool stuff, but they are limited slip.

 

[jay21mojave]

GO with the recommended / suggested by the GEAR Mfg you installed.. Personally I use Amsoil

SEVERE GEAR® 75W-90
Package Size: Quart Easy-Pack

 

[Renegade]

I don’t trust the Federal Government, but I do trust synthetic gear oil of the correct viscosity. (Here’s where everyone tells me I’m using the wrong viscosity…)

 

[DAVECS1]

I threw the BG syncromesh gear oil for a manual transmission in my diff as I was not aware I was out of gear oil. It has been whisper quiet and smooth for the last 2000 miles.

 

[Kindafearless]

I'm pretty sure 75W-140 is what we are supposed to be using. I don't remember where I found that number though....

Anyway, I've been running my truck on: https://smile.amazon.com/gp/product/B0049J5FJY

Hasn't blown up yet. I change my gear oil out more often than expected though, due to an over abundance of caution and driving through deep mud on trails.

 

[ShadowsPapa]

I'm pretty sure 75W-140 is what we are supposed to be using. I don't remember where I found that number though....

Anyway, I've been running my truck on: https://smile.amazon.com/gp/product/B0049J5FJY

Hasn't blown up yet. I change my gear oil out more often than expected though, due to an over abundance of caution and driving through deep mud on trails.

Could it be - GASP - You looked in the BOOK??

It looks like "it depends" on which axle/differential you have back there................ there's a difference.

 

[cb4017]

GO with the recommended / suggested by the GEAR Mfg you installed.. Personally I use Amsoil

SEVERE GEAR® 75W-90
Package Size: Quart Easy-Pack

I second Amsoil Severe Gear. Very highly rated stuff. I ran it in my JKU, my JLU and it will be going in my JT when I hit about 5,000 miles. I use the 75w-140 because of severe duty, trailer towing, off road, etc.

That said it probably doesn't matter much. Differentials seem to last forever with most anything in them. Makes me feel better though.

 

[ShadowsPapa]

......... (Here’s where everyone tells me I’m using the wrong viscosity…)

Not me - if it's that close it's likely fine. If it meets specs, if it's right there close in "weight"/viscosity, it's fine with me. I went through so much of that with the T5 transmissions and every book having a different spec I finally settled on Penzoil symchromesh fluid in my T5 and it made it into a new transmission - that was over 30,000 miles ago.

 

[Kindafearless]

Could it be - GASP - You looked in the BOOK??

It looks like "it depends" on which axle/differential you have back there................ there's a difference.

I have been known to read manuals occasionally. shhh… Don’t tell anyone though!

 

[ShadowsPapa]

I have been known to read manuals occasionally. shhh… Don’t tell anyone though!

Your secret is safe. I know books are forbidden here. (and no one reads my posts.)

 

[MPMB]

We've used a variety of brands throughout my racing history from Redline, Amsoil, Valvoline, and Mobil, off the top of my head. Only had 1 rear end issue in 16 years, and it wasn't oil related.

The critical point is the correct volume of fluid. Too much will actually create too much heat and be forced out of the rear end. And we all know how much JTs love getting hot and bothered.

 

[Renegade]

I'm pretty sure 75W-140 is what we are supposed to be using. I don't remember where I found that number though....

Anyway, I've been running my truck on: https://smile.amazon.com/gp/product/B0049J5FJY

Hasn't blown up yet. I change my gear oil out more often than expected though, due to an over abundance of caution and driving through deep mud on trails.

For towing, yes. The manual actually states to use this if your Jeep has the towing package.

 

[AggieJeep]

I have used synthetics in my vehicular for hundreds of thousands of miles without issue. Proper selection based on specs and using the correct amount, you will do fine. I can’t offer any real stats for comparison but have no complaints with either form of oil from a decent brand.

Do pay attention and know if you have a limited slip reqiring a friction modifier. The friction modifiers won’t hurt anything if added to a diff that doesn’t directly require it. If you put other parts in there, like an ARB locker, consult their docs. I understand the modifiers can eat at some seals in air lines that engage the system.

It all comes down to following the specs for your setup.

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