What Temp should the drive axles be at?

I dunno... I need to replace the sending units on my pumpkins...

I DO use an infrared thermometer on my hubs when I do a walk around every time I stop... especially in the summer when I have on a big load. Kinda cool to see what those hubs are doing...

 

My front one runs hotter. This is sad, but to be honest, I can't remember what the actual numbers are because I normally just scan the guages to make sure no needle is out of whack, besides half the time the guages never work. I know they never go over the halfway point on the guage even running over 90k in the ozarks. The long grades out west might be different, but again I never remember my last truck going past the halfway point when I used to run out west but I do remember it's front axle ran hotter as well. I'm laid off for another week or so, but I'll check the actual numbers next time run if nobody else chimes in.

 

on a warm day my front will run around 200 and the rear around 150, if you get around 250 i would start to worry.

 

Synthetic gear oils are good to about 280F before you have to start worrying... mineral oil start to break down at 225F or so...

Years ago we used to have to hole up at a truck stop in the daytime during the summer before we could pull Baker grade headed west to California. 20 miles uphill in 110F heat wouldn't cut it before we had lube pumps in the rears and syn. oils.

The truck stop bunk houses used to be full of guys with daycabs ( and sleepers) waiting out the summer heat.

 

I believe the front pumkin runs hotter because there's a lot of torque transfer going on in there, since the power divider is splitting the torque between the driver axles. I remember my trucks always ran the front driver hotter. Never had a failure, tho. I was a company driver and the truck I was assigned to got great maintenance.

 

All of mine: Tranny, front & rear diffs all run right around 190 in cool weather but in hot 100 deegree plus desert type regions it will climb up to 220 (max)..

Just a FYI: if your guages don't work, it is a good idea to get them working.. If you have a wheel seal go bad and you loose oil, the first thing you might notice is the temp getting hotter... The rearend you save just might be your own either O/O or company driver!!

I have full synthetic in everything.. (I don't know anyone who runs old mineral based oil any more with the huge improvement synthetic offers)!

 

Most of the 379's I've either owned or driven over the years in the summer the main trans usually just under 200 unless I'm out west pulling mountains, front drive between 180-190, and rear drive a little less than the front...

 

My rear temps usually run about 100 degrees hotter than the temperature outside.If your fluid level is low,they would be higher.Any kind of mechanical issue would show higher temps as well.

 

On a hot day, loaded heavy, my temps are about the same as yours. I don't think you have much to worry about.