Take off the bolts surrounding the differential cover on either axle and make sure you have a drainage pan underneath so all that old nasty muddy gear oil drains.. put the cover back on and refill. With 90 weight gear oil that's what I use it seems to be fine

 

Sorry slick
I didnnt know you post that my bad
And I forgot also the gasket glue crap u gotta put around the cover before you put it on

 

All good brother.... back me up lol... ya rtv is your friend :-)

 

On the 90w..... that should be fine.... there is however a different spec if you do a lot of towing (I think the only towing most of us do is towing our lazy asses to the store) but if by chance you do do a lot of towing I would have to look it up.... something like 75-115... something I.haven't used before so I can't remember exactly.

 

alright so 90w gear oil for the difs i also have a question as i have a few surface rust spots, Ima sand it down and buy por-15 and coat it. And then paint over it. My questions is whats that one spray i need that once i sand the area to clean it with so if theres any remaining rust it will convert it to some black stuff. I wana do that before i apply the por-15 to be sure all of the rust is gone.

never mind about it found it its called por-15 metal ready

 

That's what I figured but had to ask to be sure rather than mess it up by going about an obvious way that isn't the correct way.

 

I usually use permatex stuff... similar to por 15. Turns the rust black. Fully sandable... prime and paint. BTW I don't know how I feel about telling you to use 90w when the spec calls for 75-90... however in my experience it will be just fine (mainly don't want to get beat up by others on the forum :-) ) anyhow for difs a little Lucas works well also aw the gears need thick oil. Read the directions on Lucas if your interested and make your own decision. I like it, thats just me. I always figured hey they use it in the Lucas dragster... prob be ok in my differential.

 

Differential Fluid Specs are:

75W-90 GL-5 in the front and rear (light duty)
80W-140 GL-5 in the rear (towing/heavy duty/trail)

 

hehe thanks for the heads up il read some more about it. So far my list is

difs flush
t case flush
brake fluid
power steering fluid
coolant/heater core flush

I think those are the only fluids ima flush out and replace. Sounds good am i missing anything? I already did oil change and filter.

oh so if i would use the car as a daily driver and some trails and mudding every now and then what dif fluid should i use 80w front and back or ?

 

Always 75W-90 in the front unless it's a trail only rig.
I use 80W-140 in the rear since i sometimes tow and go offroad.

Brake fluid just needs to be topped off or bled if low. No need to change it unless you have serious braking issues.

Don't forget to grease your zerks also. You want to use a "Moly" grease

 

thanks and yeah i checked it at this program that the shop uses and it says 75w90 but when i go to the specification tab for differential fluid it says 80w90 so im not sure anymore but il go with what you said so 75w90 up front and how about the back ? Also how do i know if i have trac lok cuz it says you need to add some friction modifier if you do have it?

 

Jack it up put tcase in neutral and spin a tire. If they spin the same direction its trac lok if not its open.

 

80W-90 was for some reason specified for the factory towing package...dunno why it had a separate spec but it's not that important. Factory service manual says what i posted above

 

oh alright thanks slick il give it a try and dukie 75w90 for the front and 80w140 for the back if ima do some offroading ? I dont think ima tow much.

 

I'm thinkin with 33" or bigger tires end stock gears heavier oil then stock is good :-) shouldn't hurt anything.