jc67

Hi guys! I put a 04 IRS into a '67 cpe. Part of the build is installing a True-Trac lsd in the diff. Gears are 3.55. What is the correct and best brand of diff. fluid?

jimjeffords

Im pretty new here but I posted something similiar recently and every bit of feedback i got was go with the Royal Purple.

Timspony

Royal Purple...75w140 according to the book!

Blackvenom01

+1 royal purple cost alot but its the best

Timspony

+ the friction modifier is already in the fluid!

jc67

Thank you for the information, sounds like Royal Purple will be the fluid.
Hey timspony how do you like the x-pipe sound? Have you always had the x-pipe? I know the mod motor will sound different than the 302 I will be using but I wonder if I am going to like the sound. Of course the 4-5 hp increase will be great too.

Timspony

Modular engines sound much better with X pipes IMO....Push Rod engines H pipe all the way...

pkwest

from Eaton:
"We recommend that you use any good mineral based multi-weight gear oil. Synthetics are not recommended. While many people have used synthetics in Truetracs without issue, there have been times that synthetics have caused the unit to be very noisy. Additionally, many of our resellers do not recommend synthetics for high performance applications. In fact, most will void their warranty if synthetics are used.
Friction modifier should not be used in a Truetrac as it has no benefit. As for Moly additives, these products are similar to synthetic gear oils and should be avoided with the Truetrac."

jc67

PK, I read this on the Eaton website too. I didn't know how many were using the Truetrac or if they know that this is a gear operated lsd (no friction plates) ie., no modifiers needed. Sooooo...probably should do the manufactures recommendation. Any other thoughts?

pkwest

I have read posts from many truetrac users that complain of noise with synthetics. I personally use royal purple and love it. For a trutrac though I would use mineral based oil as suggested.