Changed both diff. fluids/ T.C. fluid now lower rpm's???

[blueoval9erlifer]

Hey all I changed my rear differential fluid about a month ago and then 2 weeks ago changed front diff fluid and transfer case fluid.
Not that this is a problem but now when i'm cruising down the highway i have noticed im running about 2 to 300 rpms lower at 70mph and about 500 rpms lower at 80. Does this really make sense?? Could my fluids been causing that much drag on the vehicle? I haven't done anything else.

 

[corkey]

it could be,
as it got easier to move the mass of the vehicle, the force on the tourque converter required to get to and maintain the same speeds can change, thus lowering the rpm's,,

easier to push in an auto means less rpm's,,

 

[pet575]

Agreed. If the fluid change made things work better, there is less resistance.

 

[IAmTodd]

Once the converter locks though you should be at a 1:1 with the engine speed and the trans input shaft speed.

 

[blueoval9erlifer]

Agree with the resistance but i'm with Todd on the ratio and going from about 2700 rpms at 80 to around 2200 (which is about where i was running before at 70) seems like a huge difference to me.

 

[wenailem1]

two points of interest for me here
1- when i let off the throttle my x seems to slow itself down instead of coasting
2-when i throttle im hearing a noise not a whine not a grind sorta like a noisy rotation noise which stops when i let off the throttle
2000 x e/b