Differential fluid weight when towing

What diff. fluid weight do you prefer to use to tow with? (75w90, 90w or 75w140)

Do you prefer synthetic like Redline MT90 (GL4 75w90/140) over O.E.M. (GL4 90w)?

 

I run 85W-140 conventional myself. I buy Torco RGO. In my old Nissans with basically Dana 44 rear axles, it did not leak past the axle seal in the exact same environment where 75W-140 full synthetic did leak. I think it treats the seals better or something. After 20K or so miles in my Toyota, it looked brand new when drained for regear.

Just my 2c. No axle is that picky, I just use what I know. Many here run any viscosity in conventional or synthetic and have 0 issues, towing or not.

 

What does the owners manual suggest?

Usually a good guide.......

 

I'm trying redline syn 75w140. I am rethinking that for 75w90. So does the syn. have a reputation for leaking past seals?

 

I doubt it in a Toyota diff, Toyotas have a much better axle seal design than the type of design my Nissan D44’s used. I just used that example as a reason why I like to run what I run.

For towing I would stick to a 140 myself.

 

Ain’t going to make any difference whether you use synthetic or not or what brand you use. Just use the weight specified in the owners manual.

 

Stock is fine. No need to overthink it

 

O.k. went to RedLine 75w140 synthetic in differential, RedLine Mt 90 synthetic in transmission, Costco 5w30 synthetic engine oil.engie was flushed with Liqi Moly pre oil change. All fluids had 10% Lucas added.

This XRunner has 145k on the odometer and was a tow behind a motor home vehicle a large part of its life. Its a vrty tight vehicle, like new in many ways. It did have the somewhat typical hard shift into 5th gear. Its a whole different shifting vehicle now!

This is a new to me truck and rhe one and only fill up showed 14 mpg. I know that seems on par but we'll see

 

X runner is a 5 lug V6?

 

Yes