Royal Purple 85w-140 in rear differential
- Thread starter PDX2500HD
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I've never used Schaeffers but it has a lot of loyal fans. So does RP. You couldn't go wrong either way and the differences would be minimal, IMO (despite what fans on either side would proclaim). If you want to choose between only those two, go with what whichever you can get the most easily and cheaply.
"Found a good price on the Schaeffer 75w90 at a local dealer for $10.95 a quart."
Wow, you're lucky! I have to get Schaeffer shipped to me. I bought a large quantity with friends years ago but I have since run out.
I'm not an RP fan ... but there are plenty of others who are. I suspect that the price will approach $20 per quart, especially if you have to get it shipped to you.
With that price difference, I don't think it's a difficult decision between brands.
Wow, you're lucky! I have to get Schaeffer shipped to me. I bought a large quantity with friends years ago but I have since run out.
I'm not an RP fan ... but there are plenty of others who are. I suspect that the price will approach $20 per quart, especially if you have to get it shipped to you.
With that price difference, I don't think it's a difficult decision between brands.
Originally Posted By: PDX2500HD
does Schaeffer 75W90 need an additive for the locking diff? or is it blended into it?
While it might have enough for some applications, in others it may need some extra LSD additive. Run it and see what happens. I needed 4oz of additive to get my 11.5AAM to stop chattering when I changed from 85w140 RP to Schaeffers 75w140...I actually may need a little more (I also have a deep aluminum cover).
And for the naysayers, I saw what I believe was an increase in MPG using 85w140 RP after changing from M1 75w90, and can definitely say it made mileage no worse (I document every mile). I also ran 85w140 over 100k in temps ranging from +115*F to -25*F without any appreciable wear particles on the magnet in that 100k. I would say it is a good choice in an HD application.
does Schaeffer 75W90 need an additive for the locking diff? or is it blended into it?
While it might have enough for some applications, in others it may need some extra LSD additive. Run it and see what happens. I needed 4oz of additive to get my 11.5AAM to stop chattering when I changed from 85w140 RP to Schaeffers 75w140...I actually may need a little more (I also have a deep aluminum cover).
And for the naysayers, I saw what I believe was an increase in MPG using 85w140 RP after changing from M1 75w90, and can definitely say it made mileage no worse (I document every mile). I also ran 85w140 over 100k in temps ranging from +115*F to -25*F without any appreciable wear particles on the magnet in that 100k. I would say it is a good choice in an HD application.
The Dodge version is a Trac-Rite, and its a cross breed...its like a helical, but it still forces pieces called "brake shoes" together to make the friction...so it still has clutches, just a different way to engage them.
They also state right in the manual that LSD additive is not needed, but they will still chatter with certain oils.
They also state right in the manual that LSD additive is not needed, but they will still chatter with certain oils.
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