Changing Differential Fluids

[kars85]

Going to hopefully change the front and rear differential lube this weekend. My Hayne's has the rear needing about 1.5qts, but mentions nothing about the front differential.

Can anyone guess as to how much fluid is in the front? Cornburner, you used 75W-140 in both right? Any real benefit, or just the convenience factor of not needing to buy two different fluids?

Thanks,

Karson

 

[E.B. Cornburner]

I was advised to use 75w140 full-synthetic gear oil in both diffs from a person who specializes in 4x4 drivelines. He's never had a failure with any axle, front or rear, that he's filled with 140 weight syn-oil. He mentioned that the front diffs that are filled with 80w90 conventional oil from the factory show much more wear than even the rear ends that are filled with 75w140 synthetic. We concluded that it was done this way from the factory simply as a cost-saving maneuver. Save ~$5 per axle using conventional oil in the front end, times how many million units sold, and it does add up. Probably more than the small percentage of warranty claims that it might have caused.

That, and the added convienience of not having to buy two different weights of lubes I suppose makes life a little easier.

Personally, I can't see any negatives about using the same weight in both diffs. Fluid drag is still going to be better than if the front were filled with 80w90 conventional, as even a 140 weight synthetic is thinner when cold than a conventional 80w90. The difference in fluid drag between a full-synthetic 75w90 and a 75w140 is negligible.

As for capacity, I think it's a little more than a quart. Getting the front cover off is a PITA. I just sucked mine out with a MityVac suction pump, and refilled it. I might not have gotten every last drop out of it, but sometime in the future, I'm going to change them both again, and that'll ensure a complete fluid exchange, or close to it.

 

[kars85]

I see your point on the difference between the two fluids. I'm going to just pump the front differential out rather than deal with the hassle of taking the cover off.

I may have to do this to the rear diff too. What size is the square end on rear diff drain plug?

 

[E.B. Cornburner]

Geez...Now I have to think??!?

It's either 3/4" or 1". I think 1". I used a 1/2" drive to (whichever size it was) socket adaptor on my breaker bar. I just grabbed the one out of the toolbox that looked right. I never really paid attention to what size it was.

 

[High_Order1]

I never could get anyone to explain why the front needed a different lube. I used a suction gun that I clean and use for other things to replace mine.

The back one, I wound up grinding down a large bolt head to make it work.....



-Shawn

 

[kars85]

One of the guys I've gotten to know @ Advance Auto Parts said the rear 8.8 takes more on the lines of 2.5 quarts, not the 1.5 as quoted in the Haynes.

They only had 3qts of Mobil 75W-140 on hand, so I saved my $50 bucks and came back here for advice.

He also mentioned that I might have a Dana 44 front...is that true? Either way, I'm thinking I might need more on the lines of 5qts to do this all the more I talk to him. This is about as expensive as changing 12qts of transmission fluid...geez.

I've got 85k on the ticker, and he said to just leave it if there isn't problems. Why bother with leaky drain plugs, etc... if you don't have to.

 

[E.B. Cornburner]

Your guy at Advance (what's the opposite of Advance? Retard!) is trying to look smarter than he is. That's a totally new rear and front end in the Gen III...Not a 8.8 and Dana.

I bought 6 quarts just because that's the minimum I could order at one time. I still have some left...I think the rear took close to 2 quarts, and the front a little over 1.

 

[coombs]

rear end

anyone have any pic's of changeing the rear and fluid let me know or just post them for me thanks guys

 

[majorhavoc]

was size is the square hole on the front differential fill plug?

 

[gmanpaint]

Check axle code on drivers door sticker. Refer to here for codes :
http://www.explorerforum.com/forums/showthread.php?t=239360

The rear diff has a 3/4" drain plug, & a 3/8" fill plug. Holds 1.5 quarts of full synthetic only 75-140. For Limited slip, use 8 oz of gear additive. To fill, use a flexible tube adapter that fits on the fluid bottles. Shove the tube in the hole, squeeze the bottle to fill. When close to half of 2nd bottle is empty, watch for fluids draining out of fill hole. Stop filling at this point, let drain till fluid no longer drip out. plug back up. A little anti-seize on the plug threads will help future changes.

Front diff is a 3/8" fill plug. Drain by pumping out fluids, or removing the diff cover. Use same method to fill as rear. It is safe and recommended to use the higher temp (74-140) synthetic gear oil (1.5 qt) The front is open carrier, no additive needed.

 

[stuartr]

So how do you know when the front is full. The rear in understand. Or is the hole on the side like the fill hole in the rear? If so nevermind stupid ?. I have a pump but not sure if it will get into that hole I will have to look. If and when the weather ever breaks around here. I am also going to do syn fluid in the transfer case as well.

STU

 

[majorhavoc]

The 3/8 ratchet didn't work for me but the plug was sticking out far enough that a could grab it with vice grips with minimal damage to none on the threads. It would go in so far anyway.

Stu, on my wife's X there is only the fill hole on the front. I just stuck my finger in the hole and dipped it down a little and struck oil. It stinks too.

 

[rumpledoll]

I put Amsoil 75W-140 sever gear oil in the rear with 4 oz of LS friction modifier of my 2002 V6 4WD Eddie Bauer and put Vavoline SynPower 75W-90 synthetic in the from after sucking out the old, nasty 80W-90 fluid. Truck runs very well. A good synthetic 75W-90 is a nice upgrade from the dino 80W-90 the factory puts in.

Rumple

 

[Oldwolf]