75W-90 to 75W-140 in Frontier C200K?

[Digital2k2]

I am considering switching to 75W-140 GL-5 synthetic gear oil in my Frontier's rear differential. It has the C200K that the manual calls for 75W-90 GL-5 synthetic in, but I have read on forums that some use the heavier gear oil, and someone even claimed that a warranty replacement had 75W-140 added from the dealer.

The reason I want to try 75W-140 is noticeable gear whine maintaining speed at one speed range, and whine only under acceleration at a higher speed range. I replaced the gear oil a few thousand miles back with 75W-90, and there were no large particles in the oil, but enough fine shavings stuck to the magnet. I would have expected to see that amount of shavings at maybe twice the mileage. They almost felt like grease, but had a slight roughness to them.

Anyone know if the tolerances in the C200K are enough for 75W-140 to properly lubricate everything?

 

[Oildudeny]

Is your differential a limited slip?

If so did you add a friction modifier when you changed out your fluid last?

Stick with the recommend OE viscosity.

I believe OE is 85w-90 why did you go to 75w?

 

[zeng]

There is no such thing as tolerances or clearances being associated or related to 'correct' oil viscosity grade in use.
Whining noise in differentials or gear trains is an indication of increased play/backlash between contacting pairs of pinion and ring gear teeth , which is a result of loss of parent materials from the gear tooth due to sliding motions or rubbing unprotected by adequate film thickness.

Hence all gear train systems permit an upgrade of viscosity grade or two to increase film thickness for enhanced components protection .

Your worn gear systems is a good candidate for upgrading so with 75W140 or a synthetic 80W140 or a mineral 85W140.

 

[Shannow]

They called for 140 in Oz.

edit...that was for the LSD, in the same differential.

per Zeng, the pinion/ring gear loads and speeds (pitch line speed) are the determining factor in viscosity selection, not whethere there's an LSD or not.

 

[zeng]

Yes Shannow , pitch-line-velocity is my preferred parameter/method in gear oil viscosity grades selection.

https://www.machinerylubrication.com/Read/707/enclosed-gear-drives

 

[aquariuscsm]

Try Amsoil Severe Gear 75W110.

 

[WyrTwister]

I would think this partially would depend on your location / climate ?

 

[dave1251]

Go ahead and user a thicker grade it should do your differential.

 

[Digital2k2]

It is an open differential, no limited slip, the truck just has antilock brake limited slip.

Per that link, it looks like the main question is gear speed when going to a heavier weight. Guess the C200K gear speed isn't too fast for 75W-140?
The temp here, at extremes, ranges from teens in Winter to 100F in Summer.

I was considering 1 quart 75W-140 and 3/4 quart of 75W-90, but not sure if that would make much difference, and probably will just try all 75W-140. Within the different brands of GL-5 synthetic gear oil, does the brand matter much? Thinking about carquest brand synthetic that I heard is sourced from Valvoline.

 

[Y_K]

Find a local Chevron distributor and buy a case of Delo ESI 85W-140 gear oil or a pail of Syn-Gear XDM 80W-140. It may seem like too much oil for that small differential, but you will benefit from several consecutive short changes to wash out as much of the debris as possible. Ideally, pull the axles and replace the bearings with seals when you perform the change and clean the housing as much as you can. Using broomstick handle with a towel, like you clean a shotgun barrel. All the metallic debris will kill the bearings sooner or later. The sump size in Nissans is notoriously small, and somebody mentioned 85W-90 above - that would be an ideal compromise, provided it was used from the beginning. Benzes put [Liqui Moly] 85W-90 in a lot of their miniature differentials with success - that is a super shear stable gear oil on a thicker end of the wide SAE 90 band. If your district is serviced by Shell or Mobil better, use their oil - it doesn't matter - but it seems like most of continental US is covered by Chevron more consistently. It may come down to the point that swapping the whole rear assembly is necessary. In some designs the debris are everywhere and practically impossible to wash out, the damage progresses with exponential speed while you waste your money on materials and labor.