What weight, 75-90, or 140-90?

[Fuddrucker]

My manual says to run 75w 90 in the rear end. I have read in these fourms and others that if you tow on a regular basis to use 140-90. I tow about once a month (8500lbs) and was thinking of going to 140-90 from what I have read here. I called my dealer to ask about using 140-90 and thay said to stick with what the manual says. Also Eaton's site says to use 75-90 in the rear with the (G-80).

 

What are the advantages of going to the 140 stuff? If I do, will it hurt anything?

 

Sorry if I sound stupid, I am just concerned and don't want to screw anything up.

 

Thanks!

[points]

Theres no 140-90 oil out there. Theres 80w 140 witch is thicker than 75w 90. Stay with 75w 90.

[SilveradoWV]

I agree with "points"

[bigtruck21]

the 85w140 gear oil is much more viscous than the 75w90. This also causes it to have a higher pour point. It takes much longer to "flow" in cold weather so you lose gas mileage in the winter. The only benefit is under wear, it will give less of a scar, so it protects better. You only tow once a month and if you go through winter, i'd say the 85w140 isn't worth it.

[03Bluerado]

My manual says to run 75w 90 in the rear end. I have read in these fourms and others that if you tow on a regular basis to use 140-90. I tow about once a month (8500lbs) and was thinking of going to 140-90 from what I have read here. I called my dealer to ask about using 140-90 and thay said to stick with what the manual says. Also Eaton's site says to use 75-90 in the rear with the (G-80).

 

What are the advantages of going to the 140 stuff? If I do, will it hurt anything?

 

Sorry if I sound stupid, I am just concerned and don't want to screw anything up.

 

Thanks!

Stick with the 75-90, and use a quality *synthetic* of your choice...I like Mobil 1.