Does anyone here use 75w-90 synthetic gear oil AND tow regularly? Any problems so far?

 

75-140 syn here....it's stupid hot most of the time here.

 

no problems here with 75/90 but it only gets to the low 80s rarely in the summer. Its usually 70 to 75 degrees on a hot summer day. Hot as it is in CA I would use 75/140

 

75w/90 here...up to 38K gross, 326K miles on the truck, no problems. It can get to be 95-100* hrer for a few days, but mostly in the 80-85 range!

Chris

 

You may already know this, but the manual says 75-140 synthetic for towing.

 

I tow very heavy with 75w90.
Tried 75w140 once, it was very obvious that it was too thick in the Montana winter, truck would barely coast.
But since you're in Calif I'd use the 75w140.

 

I use 75w90 year around because of the winters here. If it was hot all the time i would probley run 75w140. I tow alot and never had any problems yet.

 

I am torn between running 75/90 synthetic or 75/140 synthetic in my part of Oregon it gets hot like 112s for weeks but get 20s n down for months in the winter. So its a toss up I could run the 140 synthetic and have it be too thick in the winter or 90 and use it year round.

 

I use 75-140 synthetic in the Canadian winters (-40*), can't see you having a problem if I don't.

 

being in bakersfield, I suggest the larger cap. diff. cover. buy it from these guys:

http://yourcovers.com/

I tow everyday in so.cal. driving to your neck of the woods(or end of the desert) once a week, from ventura. but pull the 14 to lancaster the other 4 days, and the cover lowered my diff fluid temp 30*. I think it holds two more quarts

 

anything wrong with 85/140?

 

I got my truck last April and last month I changed the rear diff. oil. I assume it was standard 75/90 oil and it was NASTY! It smelled burned and had a dark brown tint to it. I think the guy who had the truck before me used it to tow a horse trailer. I put in some Red Line full synthetic 75/90 and a Mag-Hytec cover, but I think the damage may be done. The limited slip does not seem to work as well as it should. I should have added the cover and synthetic oil earlier since I tow my car trailer often and we have had some snow this year, which raises the oil temp due to the limited slip. Oh, well I guess I will just have to look for a Detroit Locker. When the weather warms up and I start towing my car trailer on a regular basis again (when race season starts) I will switch to Red Line 80/140. Being able to change the diff oil without removing the cover is going to be really nice!

 

Strange- wouldn't they both be a 75 weight oil when cold??

 

According to this...

http://auto.howstuffworks.com/question164.htm

You are correct if I read that right. Both lubes should be viscosity "75" when cold.