Am about the change my tranny/diff gear oil but I can not find a API GL4 spec tranny oil within a 40 mile radius of where I live (I've been to several Autozones, Oreilly and even walmart the only auto stores around Conroe, Texas).

Question
Can I use API GL5 spec oil for the tranny?
Is using 75W-90 okay versus the recommend 75W-85?
What brands do you recommend am looking for a full sync oil but only brands around here is penezoil,mobil, and exxon.

Some searching tells me GL5 shouldnt be used on a GL4 tranny, but no real answers
I hate to make a 1.5hour drive into houston to get to the bigger auto chains just for some damn oil.

 

I just went through the same thing the people at royal purple and amsoil were super helpful in describing the differences. I ended up buying the royal purple max gear 75/90 full synthetic. The friction modifiers in gl5 will destroy the synchros apparently.

 

i just switched all of my oil to royal purple. $100 later and whola buttery smooth. i went with 10w30 for the oil change, 75w90 for the tranny and can't remember what i used for the diff. stuff is crazy.

 

i've spoken with a tech rep from exxon-mobil and was told not to use GL5 lube where GL4 is recommended.

i used the redline MT90 (75W-90) in the tranny. i used the GL5 Mobil 1 75W-90 in the diff. i got the mobil 1 from autozone and redline stuff from a local race track (summit point)

get it online, it's a bit cheaper.

 

My last diff oil change, I got lucky at the speed shop and they only charged me 1.75 for two bottles of Redline. Is that even right? That's really cheap.

 

lol das not right. that's really cheap yo! :-D i dont even remember what i paid but i know it wasnt that.