Question Regarding Diff Fluid Change..

[jasper10101010]

So...I used 3.5-4 qts, give or take, so I will check it when I get home. I didn't read anywhere about the 1/2" or so below the plug! Hopefully it will not cause any issues if it were slightly overfilled?!?!? I was on a slight incline, so maybe if I leveled it off it wouldn't have held as much...I'll keep an eye on it, but figure more lube the better...unless it starts leaking everywhere!

On a side not, unless I missed it, and I did look, I didn't see a gasket on mine. Maybe I just overlooked it...but it doesn't leak a drop!, so I guess it's fine!

I'll post an update if things start leaking from overfilling...damn it...now I'm concerned!

 

[YNOT]

i was under the impression that 99+ had synthetic fluid in the diffs, as well, can anyone else confirm/deny this impression?

Pat

chiltons said regular in front diff and synthetic in rear.

---------- Post added at 10:45 AM ---------- Previous post was at 10:44 AM ----------

So...I used 3.5-4 qts, give or take, so I will check it when I get home. I didn't read anywhere about the 1/2" or so below the plug! Hopefully it will not cause any issues if it were slightly overfilled?!?!? I was on a slight incline, so maybe if I leveled it off it wouldn't have held as much...I'll keep an eye on it, but figure more lube the better...unless it starts leaking everywhere!

On a side not, unless I missed it, and I did look, I didn't see a gasket on mine. Maybe I just overlooked it...but it doesn't leak a drop!, so I guess it's fine!

I'll post an update if things start leaking from overfilling...damn it...now I'm concerned!

if it's regular fluid go to the bottom of the hole and go 1/2 inch below the hole if its synthetic.

 

[OKLAGMCRUISER]

chiltons said regular in front diff and synthetic in rear.

---------- Post added at 10:45 AM ---------- Previous post was at 10:44 AM ----------



if it's regular fluid go to the bottom of the whole 1/2 inch below if its synthetic.

thanks for the clarification!

 

[odie301]

I work at a fast lube and from what we do going off of our spec books... they call for 75-140 synthetic in most of the rears, and the front depends on if you have auto 4x4 or not. A side note to that is it wont hurt to put the synthetic in (other than you wallet) but still better than putting in regular and recking something. Transfer cases are either ATF or AutotrakII (that cool blue stuff that ONLY GM has!!) Found out the special stuff in AutotrakII is some kind of additive that is found in 80-90 gear oil. Someone should make a small bottle of that additive so we can just add it to atf and save some money.

 

[YNOT]

I work at a fast lube and from what we do going off of our spec books... they call for 75-140 synthetic in most of the rears, and the front depends on if you have auto 4x4 or not. A side note to that is it wont hurt to put the synthetic in (other than you wallet) but still better than putting in regular and recking something. Transfer cases are either ATF or AutotrakII (that cool blue stuff that ONLY GM has!!) Found out the special stuff in AutotrakII is some kind of additive that is found in 80-90 gear oil. Someone should make a small bottle of that additive so we can just add it to atf and save some money.

I just did AutoTracII in my transfer case from GM, it was the same price as ATF Dexron VI. Someone on here said Amsoil is the only one that makes a AutoTracII replacement.

 

[jmildoc]

changing the rear fluid is really easy. you just use a half inch ratchet and pull out the plug and drain then put it back in then take out the top fill plug the same way and fill it until it reaches the hole.. I used about 2 1/2 quarts Lucas 75W 90 Full Synthetic in mine.

I have not done the front but when I do... probably next week or so... I will take pics and post them..... I will be putting Lucas in there too as I gained a little over 1mpg when i changed the rear..

 

[Max]

Royal purple is a synthetic so no you won't need a friction modifier. I gained some mileage when I switched to purple, was gonna go schaeffers but we carry the purple stuff at work and couldn't reason the cost difference. Smoother engagement of the limited slip, less whine from the front axle. I may try the other stuff next time but the royal purple and auto trak II fluid is too much to drop every 15k. I'll try to get pics once I rebuild my front diff and toss a trutrac in the back, these things are pretty easy to setup once you've torn one apart, fluids are mad easy especially if you have a drain plug in the rear axle.

 

[hapyspaz]

FYI, 99 models are the only ones that HAVE to use a gasket on the rear diff, and that is only on the Silverado/Sierra. All Tahoe's can use black RTV to re-"gasket" the diff cover.

The weight of fluid and amount of fluid is going to be dependant on the axle under your truck. As most have stated, do not fill it to the fill plug. GM recommends .6" to 1.6" below fill plug. Basically, most of them should be filled to the level of the fin that is on the axle housing uderneath the fill plug.

If you do overfill your diff, I highly recommend reducing the level of fluid. It will not ruin your diff, but I have seen axle seals leak a lot due to diffs being overfilled. Pinion seals also start to leak due to overfilling. Neither of which are fun to change out.

 

[jmildoc]

so since i filled mine to about half a pinky tip length from the fill hole is that too full???

 

[Max]

No you should fill to the very top before spillage.