Ridiculous

ok guys, i got tired of searching for the answer i wanted. i just wanna know what gear oil i should put in my front/rear differentials? what weight, and brand? synthetic or not? why or why not? and how often should this be done?

thanks

fbx22

service manual for 2002 says
front 80w90 GL5 rated

and rear sae 90 GL 5 rated
______________--
basically means 80w90 in both. Be sure that the rear has limited slip additive in it. The synthetic reccomended is 75w90. Under the severe schedule every 11250 miles. Sythetic probably lasts longer than that. I do mine every 15,000

Ridiculous

thanks much. can you tell me what the 'GL' ratings are all about? and how often should this be done? what about that synthetic or not?

HRDROKN

I would run 75w-140 synthetic.

Ridiculous

for what reason?

lovinCTD59

I like 75W140 synthetic for the rear.. Most dealers and operators reccomend this due to the high stress from towing a load on a hot day.. (dont forget the right abount of limited slip additive if you have a limited slip rear axle...)

For the front I run 80W90,synthetic or not i doubt it matters..

As far and brands I usually run Mobil 1 or Amsoil for synthetics, and Valvoline for a regular dino oil..



My bud runs Super Tech from walmart. He changed it on his 99 3500 CTD when it had 35,000 miles on it and he now has over 180,000 miles on it with no probs at all... my point is, as long as it has the correct ratings the brand doesnt matter. But thats up to you. Good luck!

HRDROKN

For the same reasons that lovinCTD59 has stated....

CTD's can really put some strain on a rear differential, I know as I just rebuilt mine. Even our most popular ring and pinion shop has recommended 75w-140 in all the work they do!

Ridiculous

ok thanks guys. i'll try 75w-140 synthetic in the rear and 80w-90 in the front synthetic too. i've never tried synthetics so it'll be a new experinence.

another question i had was, what's the best way to change the fluid? just drop the pan and let it all drain out, then put back on with new gasket and fill?

oh and 'lovinCTD59' now you've got me worried about the limited slip additive. i have no idea what you mean, is this something seperate i gotta buy? is it already in the oil? etc. etc. please elaborate.

fbx22

might already be in the oil. what brand is it?

Ridiculous

don't know yet, haven't bought it, i was thinking mobil 1. (from what i heard)

and then i was doin some more research and the concensus seems to be this:
buy the additive but don't add it right away, put oil in and go do some figure 8s, if it chatters, then add the additive 1 oz. at a time until it stops.

lovinCTD59

I dont think the additive will already be in the oil itself. You will have to buy it seperate. Walmart or autozone is the best (cheapest) place for it. IF I remember right you will have to put in 6.5% of the total volume of fluid in the rear differental...

fbx22

mobil sells LS 75/140 synthetic
http://www.mobil.com/USA-English/Lub...LS_75W-140.asp Should be fine for normal driving. If you are going to be pulling 10,000 + pounds around then you probably need to add some to this as well

Ridiculous

thanks guys for the help. so does the 80/90 sound good for the front? and there's no additive in there right?

fbx22

no addtive needed in front. and yeah 80/90 sounds good. and is also the reccomendation in the service manual. Mine has 75/90 synethic in the front

Ridiculous

thanks a lot for everything. i'm gonna do a good tune up when summer rolls around so i'm just gettin all the info i need to do it.