Motul Gear Competition 75W-140 for differential?
 

Is anyone using Motul Gear Competition 75W-140 in their diff?

Given the high temperatures of the diff when tracking I was wondering if the 140-grade might be more suitable for track usage than the usually recommended Motul Gear 75W-90 LS?

What diff temps are people seeing?

Are you overheating your diff?

I doubt many, if any, have temperature sensors do actual measurements. Or do you just mean IR measurements of the casing?
I had a torque wrench in a plastic case in the spare wheel well. The casing partially melted.

I know it get's very hot, but not to a point where I have any troubles. What are the symptoms of overheating?

The real question is if 75w140 is better protection for the diff?

In the mean time I did some reading in bobistheoilguy.com and came up with this:
http://www.bobistheoilguy.com/forums...pics/1788287/1

According to the posters there, the disadvantages of heavier weight are a slight loss of power and worse cooling properties because the oil is thicker. I think I will stick with Gear 300 LS 75W90.

Toyota runs 90w140 in the CS-V3 (with a diff cooler). Several guys locally run 90w140 in dedicated track cars and track/street cars and recommended me doing the same. That's why I'm asking here for a second opinion.

Isn't that area closer to the exhaust than the diff? If that's your only measurement I'd do a bit more investigation before deviating from OE spec fluid.

The silver rectangle behind the exhaust is the heat shield between the spare wheel well and the exhaust, it's pretty much dead center to the well, no way in hell is the diff the main heat contributor to the spare wheel well.

http://www.mxp-performance.com/wp-co...Chrome-Tip.jpg

Yes, you are probably right. And no I didn't investigate at all if the heat is coming from the exhaust or the diff. It's beside my question though and I shouldn't have mentioned it.

My questions are if the 75w140* oil will better prevent wear at track temperatures than 75w90? (Toyota Motorsports Group uses 75w140* in the CS-V3, albeit with a diff cooler).

And are there are any disadvantages to running 75w140* at street temperatures?

If it's true that it cause a loss of power and fuel economy cold and is worse at dissipating heat at track temperatures, I will stick with 75w90. I would be curious if anyone has any experiences.

*Edit: Wrote 90w140 in error

I have used it but thats with a clutch type LSD that generates much more heat then the stock Torsen.

Okay, thank you all. I will stick with Motul Gear 300 LS 75w90.

I'm using Motul Gear Comp 75w-140 in my 5.29 rear end with 1.5way MFactory diff. I also have the Greddy diff cover.

I personally had a very strange experience with the 75w-90. I took my car to the track with 75w-90 for a track day and was greeted with the smell of diff fluid after the day ended. And there were like little spats of oil under my muffler, so i decided to drain and refill. The oil that came out seemed really thin and I don't think 1.3l came out (some leakage/burnt off?).

So i decided to give the 75w-140 a try... And I haven't had an issue since. TBH I am not really sure what is going on since almost everyone I talk to runs fine on the 75w-90.

As I mention there are some here locally that use 75w140 too without problems.

My car has an acrid hot/burned oil smell after tracking or when being driven hard (along with a smell of brakes and melted rubber :D).
No, not the cam plate, it's a different indescribable smell, the cam plate smells like "engine" and this is different. But the diff and transmission oil was never changed on my car, so it's well overdue (18k miles total, and 400 miles track this year - 2 1/2 years old).

Well, the smell of diff oil cannot be mistaken. It's really sick inducing. The first time when I opened the drain plug I nearly threw up lol

Differentials do have a breather on the top so you could be loosing hot fluid out the breather. Would account for the smell and evidence around the exhaust.

This also happens more so if the diff is over filled. I see people over fill the diff when the lift the car up funny on jack stands. The fill it up till it pours back out method doesn't really work when the car is still at an angle.

I guess even fumes could cause the smell too then? I get like whiffs of said smell, it's not really constantly there. Fumes from a breather would explain that.

Probably, I just need to replace the oil with some fresh one.