My first winter w/ 75w140 in the diffs

I’ve spent this last fall & winter in the mountains of ID and have seen low temps well below 0 for about a week or so in length. Currently we’re having a heat wave with temps dipping into the 20’s at night.

I switched to a heavier weight gear oil due to running the truck right at GVWR and sometimes a bit beyond that when hauling my slide in camper as payload.

Last trip I scaled at 6k *gasp*

I haven’t had any issues thus far running the heavier stuff and I don’t lose sleep at night as to whether or not it’s going to do any damage at these low temps.

What have been your experiences with heavier gear oils at cold temps?

 

Well the weight of all variable weight oils changes and is only a certain weight at a certain temp.
So 75w90 and 75w140 are both 75 at whatever temp that oil was designed as.
So on the 140 end it will only get to 140 weight if your diff reaches that temp.

Hope that makes sence. Been doing alot of oil research lately.

 

I haven’t seen any problems with

$30 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 in the rear diff and transfer case and 85W-140 in the front. It gets pretty cold here.

 

If you're happy shifting that 6 MT at -20 using 75W140 seems like you're good.

 

I’m a BIG fan of RedLine. I run MT-90

$30 75w-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75w-90 GL-4 in the MT.
T-case gets the recommended 75w-85.
Just put the heavier stuff in the boxes.

 

I was running 75-140 all summer, pulling my travel trailer. Aside from the fluid friction effect (noticeably less power) it was fine.

My rear diff was hot enough that it was ticking and pinging after 4-5 hours of straight towing, I'm glad I had the thicker stuff. It was probably water thin at those temps.