differential oil

[ishbo03]

i have a 77 blazer 4x4 and was wondering how often i should change the oil in the differentials. what is the best oil to use? also, what is the easiest way to do this? do u have to take the whole cover off or is there a plug or something. thanx

[TXsizeK5]

You have to pull atleast the bottom bolts off the cover to drain it, but its better to take whole cover off and inspect for damage or wear.
I usually only change if i've gone through alot of mud or water crossings. There is a plug on the frontside of the housing, passenger side that you can unscrew to fill it up with.
Usually takes a little more than 2 quarts in a 10bolt.
80w90 synthetic is good.

[ishbo03]

aight thanx, any other general maintenance i should do on the truck, i bought it used and im not sure how well it was kept up. i bought it strictly for off road use, no daily driver.

[uglyota]

Originally posted by ishbo03
i bought it used and im not sure how well it was kept up.

Change every fluid and filter it has (fuel, tranny, tcase, engine oil, diffs, radiator) right now, then drive a few hundred miles and change them all again while it's all still hot (well, maybe not coolant). Take note of any glittery stuff or chunks that come out with any of the fluids.

If I had a diff that didn't have drain/fill plugs, I'd replace the cover with one that does...one of the easiest ways to prevent big $$$ repairs is to change your gear oil early and often. I wouldn't waste money on synthetic though.

ummm...squirt grease into every zerk fitting you can find, suck all the brake fluid out of the reservoir, fill it up with fresh and bleed master cyl, proportioners, and all 4 wheels (in that order) until everything comes out clear (this will keep your cylinders from blowing too soon). Same for the clutch hydraulics. Look in the owner's manual and do everything to the vehicle that it recommends up to and including 100,000 if you have no history of the vehicle's maintenance.

If you do all this and find something funny, sell it to someone you don't know and buy a yota

[Chadnutz]

If you want good gear oil you can use Mobil 1 Synthetic 75w90 but expect to pay $6 or $7 per quart. It can be used in both diffs, t case, and manual tranny.

[uglyota]

Originally posted by ishbo03
what is the best oil to use?

Oh yeah, forgot this
whatever weight of Castrol GTX/Fram Tough Guard in the engine (good stuff, and if it hasn't had synthetic in 26 years, why start now?) and, whatever weight the manual says everywhere else. Don't have the manual? Try this: vehicle specs
$6/quart??!! Tractor Supply's el cheapo 85w90 is maybe $6/gallon! How hot do you think your diffs get?

[stx4wheeler]

i wouldnt change the tranny fluid if automatic, that aint to cheap to change it out then do it again, just run it a while and check the dipstick and see if it has any white frothy looking stuff on it that usually means water in the tranny or if it is not the red color it should be, then a change is in order.
also i would check and make sure the bearings have been packed recently i didnt do that on my 78 when i bought it and it costed me a crap load or cash and time to fix all the damage it did when they blew.

[JB]

I have got about $900 inside each of my diffs. You guys think that the cheap non synthetic stuff is ok? I was planning on running the Mobil One synthetic stuff.

[TXsizeK5]

Synthetic keeps it cooler, that's what I'd use.

Don't use synthetic if you're breaking in your new gears.

[JB]

Originally posted by TXsizeK5
Synthetic keeps it cooler, that's what I'd use.

Don't use synthetic if you're breaking in your new gears.

Why?

[redcagepatrol]

TRAIL ONLY RIG. (strictly off-road use)

he doesn't need synthetic if the truck doesn't see lots and lots of long highway trips.

water will get into diffs on a TRAIL RIG (what he bought it for). It is WAY too expensive to put synthetic in a trail rig just to change it after your first trip out.

[JB]

I get that.

My Bronco will drive to the trail, through the trail and back home again. That is my goal. It will also see around town and highway miles.

Does anyone know the difference between the synthetic v. non besides the obvious?

[TXsizeK5]

Well from what I know and what i've been told, bassically, when you're breaking in your gears, you want them to get hot and let the metal cool to make them stronger. If you're running synthetic your diff won't run as hot as if you used normal gear oil. And you only really need to run your gears for about 15-20min at a decent speed then let it cool for a while and you really only need to do it once. After that change it out to synthetic, and yea scott's rght, if you see highway driving synthetic is better if its mainly trail rig and ur changing out your fluids alot keep wiht the cheap.

[TXsizeK5]

I known someone who shattered his ring gear.... in a 10bolt though.

[eight]

Yes I said wore out. My little brother broke a d30 gear set and I hear busa's broka number of toy gear sets. Plenty of people do that. But to have one wear out cause of cheap oil is completely different.