Hot Pumkins!

[southernspeed]

I ran my rebuilt axles for their first decent run today and after 80 miles of constant 70mph the rear diff cover and housing was hot to the touch. You could touch it but not keep your hand on there for long.
How hot do they normally get? This is a 12blt with GL5 80/90 lube.

 

[dontoe]

I remember reading that 140 degrees F, can cause minor burns.........so it must be less than that.

Ya have a temp probe for cooking? Stick it in the gear oil..............

 

[mrk5]

In the steam plant we would have contests to see how much heat we could stand. 150° seemed to be the temp where we couldn't stand to hang on more than a second or two.

Four Wheeler or 4Wheel & Offroad did a big article on diff temps. Their stock Sterling 10.25 rear axle in an F-250 with dino oil ran 170° in an unloaded mixed 50-isH mile loop. Switching to synthetic fluid dropped that temp 15-25°(they tried 2 types). The Mag-Hytech cover(3 quarts add'l cap) and the cooler of the 2 synthetics got the temp down to 125° IIRC. Pretty dramatic difference if you're going to be towing.

We're talking Farenhiet by the way Mark.

 

[ntsqd]

We're talking Farenhiet by the way Mark.

What's that in Kelvins?

For the conversionally impaired:
140f = 60C
170f = 76.7C
125f = 51.7C

 

[neverendingproject]

or
333K
349.7K
324.7K
respectively

 

[blazinzuk]

I would say keep a close eye on it. I have had diffs do that on the first run (well only a couple). If it stays that temp then you should be fine but if it starts to get hotter something went wrong. You may want to pull the cover and double check your backlash and generally look things over. Some weird things can go wrong with new diffs even if you did everything right

 

[southernspeed]

OK thanks everyone. Kind of puts my mind at rest a bit. I'll pull the cover anyway.
As I have the pinion up at 6* I put a bit extra oil in but it doesn't cover the pinion bearings as such. Are they ok with a splash feed? I know there is a kind of tunnel in the casing that directs oil to the bearing. I'd read that it's not a good idea to overfill them. Opinions anyone??

 

[blazinzuk]

In some diffs I have done pointing them up to much has caused lack of lube to the pinion bearings, feel up there when you are checking your diff temp if there is alot of differential than it is probably starving them. If not then you are good. The only problem I have had with overfilling a diff is some of the oil came out the breather