what is your RPM at 70mph?

[nissanh]

I have replaced rear axles oil seals, bearings, pinion and ring gear. I know fluid cannot change the ratio.

What my point is, before I did the rear axle oil change the RPM was at 2900 and speed was 80 MPH. After the rear axle oil change with 80 -90 W, the RPM has dropped to 2500 for the same speed of 80 MPH.

Never seen this dramatic change in a 5 speed car/truck after an oil change.

 

[Insight Mike]

not to worry thing are good as long as you aren't to low and the engine picks up and goes when it should

That's an uinderstatement! I haven't dyno'ed this truck yet, but I've got to be pushing over 300hp. This thing screams at 13psi!