Will 75w90 mix with 75w140 with out any problems, I have a extra liter of 75w140 and was gonna mix it with my 75w90 in the front end of my truck. Both are synthetic.

 

You can mix--it's better if their both the same brand, but not necessary. But, depending upon the ratio, you'll have a thicker viscosity in the front than spec'ed. I doubt you'll notice anything--though maybe an ever so slight drop in MPG since the front spins all the time.

Roger...

 

mixing fluids? sounds like a truck on truck conjigal visit. hahahahahahaha.

 

I wouldn't do it...............

 

There is no problem at all mixing the fluids. reiderr was right about the viscosity changing a bit, but thats the only thing. GO for it!!!

 

Listen, in no way would i proclaim myself to be an expert. From what i have heard, these transmissions are very sensitive, and putting anything other than what is specified will, and can, cause you some grief. Now if the service manual, or the dealership says it's o.k. then go ahead. Or, if you are one of those fortunate individuals, who have access to UNLIMITED FUNDS, then hey, it won't be a problem.
Just my two cents, and your truck.

 

He's talkin' about the front differential, not the transmission.
Mixing not a problem. I wouldn't bother though. I would keep 75w-90 in the front and use the 140 in the rear.

 

You could mix it and be ok, just don't post about poor fuel economy, haha. Also, I'd have a different opinion if you were talking about the rear, since the limited slip can be sensitive to different fluids.