What Gear Oil to use with Detroit TrueTrac?

[John Smith]

Hi,

I am unsure as to what oil i should use with my Detroit TrueTrac differential. When I wrote there tech support I was told I do not need any friction modifiers, and that they recommend the use of standard oil (as opposed to synthetic) Why would this be?
Also, I am unsure as to what weight oil I should use since the oil Ford recommends(75W-140) only seems to come in a synthetic formula. I did notice that Redline offers a synthetic oil of the right weight that does not include a friction modifier.

Thanks,

 

[triggz]

According to DetroitLockers website, it will not require friction modifier.

Synthetic oils provide more lubrication and are typically thinner, and throws off the torque biasing for the differential. The fluid ford recommends is based on the carrier design they use. with the Detroit dif you need to use what they recommend. If they say use what the manufacturer says, then I would try to find a close match in dino oil.

 

[xseler8]

Let us know how you like the diff.

 

[John Smith]

Alright, here is the response I got from the Detroit TrueTrac people (who, by the way, were recently purchased buy Eaton):

The warranty does not state a type of oil to use as long as the unit is
properly lubricated. I recommend the standard oil because in my
experience it does better in rear end than the synthetic oils. As far as
weight goes use a heaver oil in a warmer climate and a thinner oil in a
colder climate.

Kind of helps, but not really. I may use the Redline 75w-140, that doesnt include the friction modifier. I havent found any oil in the Dino variety that is the weight that Ford recommends. I could use 80w-90, which is what they put in the 7.5 rear ends, Im not sure about that.

I'll let you know how the diff works out, along with the other stuff Im having done to the car (10th anniversery Cobra brakes, front and rear. Oh yeah Im also having something called a Kenne Bell put on. I went ahead and ordered the 9 psi intercooled kit, so we'll see how that works out )