Posted 8/20/2013 09:21 (#3277719 - in reply to #3277620) Subject: Re: What oil should i use for tranny and rear diff on 1977 GMC 6500?
Hagen Brothers farms,Goodrich ND
Super 65 - 8/21/2013 07:36
50w for trans and 80w90 for diff. you will be good to go.
And make sure the trans oil has a API GL 4 or lower rating and the rear ends MUST have an oil with an API GL 5 rating.
The trans does not like the EP additives of a GL5 oil, especially if it has brass or aluminum parts inside, but the rear end gears absolutly need the Exterme pressure additive package of a GL5 oil.
What oil should i use for tranny and rear diff on 1977 GMC 6500?
