Do differentials run HOT?

[Jim Allen]

Okay, here's a little foreplay then, in the form of temp numbers for the unaltered '86 F-250HD 4x4 diesel, 4.10 gears.

34,000 # x 5 miles = 285 degrees
7,400 # x 45 miles at 50-70mp= 170
18,625 # x 25 miles at 45mph = 195

 

[Jim Allen]

I forgot to say that as much as I would like to share all the data with my friendly and helpful fellow BITOGers, I am precluded, by the need to keep my job, from doing so until after the story appears! I also now have a dyno available on which I can place an artificial load on the rear axle for hours at a time and I may line up some time and re-run some of my tests. I'd like to try some other lubes to see how they stack up. I only used three in my tests.

 

[Christian_89LSC_96XJR]

Jim,

if you rerun the tests, could you try Chevron Delo ESI 80W-90 as the 'odd one' (different anti-wear chemistry) among non-synthetic GL-5 oils.

 

[Junior]

Over filling a gearbox will cause it to run hotter too. IMHO anything under 200F is fine. Seals typically don't like much more than 250 F. Of course, cooler is better.

 

[Alan]

The rear end on my ole 280zx ran much cooler with the redline 75W90 I put in compared to the vile crap that came out.

 

[Junior]

In testing I have seen, synthetic was good for about a 20F reducion in temperature in our particular application.

 

[Cressida]

I happened to check my differential case temp's after a 100 mile highway run with my Toyota and was surprised to see 180 degrees F. Didn't think it would be that hot. Anyway it seems that isn't too bad after reading the other post here.

I'm running Shaffer's 267 fluid.

 

[Bamaro]

At the risk of stating the obvious, the more heat generated at the differential, the more horsepower loss.