TRC's 790 Sure Universal 90W in Pete 359 rear

[Wrehch]

Here's a UOA on a forward rear (power divider) in a Peterbilt 359. The oil sampled is Texas Refinery Corp.'s 790 Sure Universal in straight 90W.

 

[benjamming]

Was it changed at sample time? What has been used in the past?

 

[Wrehch]

Oil was not changed at time of oil sample, that's what the sample was for.

The previous oil was a regular off the shelf 85W/140. It was changed to TRC's 790 when the truck was purchased used about 2 years ago.

 

[Steve S]

Synth oil? is there a filter?

 

[Wrehch]

No, it is a conventional oil and this model power divider does not have a oil filter.

 

[MolaKule]

Without a VOA or priior UOA it is difficult to make any detrermination about the used oil, except that I would cut back the OCI to 150k.

What type of gearing, chains, etc? Worm, hypoid?

 

[Wrehch]

It's a power divider, the front rear differential in a tractor trailer. They are called power dividers because they split the power between the front rear and rear rear differentials and allow you to lock the forward rear and rear rear together if you get stuck or are in low traction situations.

Why would you do the OCI at 150K? On average the OCI is around 800K.

 

[MolaKule]

Why the OCI, because the Fe is approaching 100 ppm in 192K.

I would use the Amsoil 75W110 or one of Schaeffer's industrial strength gear oil blends for diffy's.

 

[Wrehch]

That's actually not a bad Fe count for a power divider. It was also rebuilt at the time the oil was changed along with the trans being overhauled. This would account for higher levels in this analysis. I also doubt that another brand is going to make a difference. TRC makes a superior oil and is great at lowering operating temps in power dividers.