synthetic trany fluid and gear lube

[rcicu]

I just rolled 30k on my 2005 V8 Limited. I am trying to get better fuel economy and was wondering what anyone has been successful with when it comes to using synthetic fluids in the trany, front and rear diffs, and transfer case. Do any of you recommend a specific brand or weight?

Thanks,

 

[jrford]

At 30k re-placed the diff fluid Mobil1 80w90 for the front 75-140w rears. although i was told the only reason why 80w90 is used instead of the 75-140w is for cost savings and you can use the expensive stuff front and rear. Rears may need LSD additive if you have a LSD rear.
Tranny blew at 52k, changed the fluids then, although i had been debating on doing it too before it blew. Wouldn't have made a difference new fluid or not for the transmission.

 

[daveleeander]

I replaced all of my fluids at 30k with Amsoil fluids. Both diffs, transmission, engine. I now have 190k, with no problems. I have extended the engine change to 15k miles. I have gone 20 with oil samples saying it was OK, but I still change at 15.
The tranny I go to 60k before flushing and changing filter.
Tranny runs cooler (I had a working temp guage at one time )

D