55K MI Rear Diff Fluid Change

[CaptnKirk]

Guys:

I bought 4 quarts of Amsoil 75-145 Syn and a tube of limited slip treatment for the rear diff. I got under there today and the cover has never been removed and I thought better of prying it off until I checked the forum.

Question 1: Am I correct that the right way to drain the rear diff is simply to open the rear cover? I didn't think to order a gasket - should I wait until I have one in my possession or do most of these open up without drama?

Question 2: Any suggestions on a better way to fill these diff's other than trying to manhandle a funnel, etc? Given I have 3 AWD/4WD and six axles ahead of me, thought I'd ask those who have been there and done that so to speak.

Question 3: Is there more to this than popping the cover, draining and then filling it?

Thanks in advance.

[mah77]

Originally Posted by CaptnKirk

Question 1: Am I correct that the right way to drain the rear diff is simply to open the rear cover?

Yup. To avoid a huge mess, just loosen the top bolts slightly, the side bolts a little more, and the bottom bolts completely. Then just use a flat head to pop the cover.

Originally Posted by CaptnKirk

I didn't think to order a gasket - should I wait until I have one in my possession or do most of these open up without drama?

No gasket. You'll gave to get some high temp silicone gasket maker from the auto parts store. Be sure to clean the old silicone gasket junk off both the diff and cover. I use a putty knife or razor blade.

Originally Posted by CaptnKirk

Question 2: Any suggestions on a better way to fill these diff's other than trying to manhandle a funnel, etc?

The gear oil bottles are just like a funnel. Just snip the tip, insert, and squeeze away. The fill hole for the rear diff is on top, so it's an easy one. The front diff is on the side, so be prepared for a little drippage.

Originally Posted by CaptnKirk

Question 3: Is there more to this than popping the cover, draining and then filling it?

I would definitely use some cleaner for the inside, and wipe out all the oil that collects in the little potholes in the bottom of the diff.

[WildStyle]

1. Yes pull the cover, let it drain and completely clean off all the old RTV silicone from both surfaces. Make sure both are spotless clean and no oil residue left on them. Some brake cleaner works wonders here.

2. Get some Ultra Gray RTV silicone, lay a 1/4" bead of it around the diff cover staying to the inside of all the bolt holes. Reinstall cover and snug down the bolts. Some say wait for the RTV to set up before filling with oil...this just never happens in a shop environment and I have never had a leak yet just filling it right away.

3. If you want you can buy a fluid transfer pump/suction gun. Comes in handy for filling diffs and transfer cases. Usually around 20 bucks for one at most parts stores.

4. Spray it out good with some brake cleaner and give it a good wipe out and call it a day.

[smokersteve]

Nice! I also have amsoil in my diffs and transfercase. love it!

I used a funnel and a hose to fill the diff. I also had the truck at an angle on a hill so that the fill hole was higher than the diff, = more fluid in the diff.

I did not use the LS fluid, the gear oil has enough. I have been using amsoil in my drive train since my truck was at 30,000 miles.

[travisH3]

I'm thinking I need to do this. I'm at 60k. What's the best fluid to use and how much for front and rear diff

[mah77]

This is what I used:

Rear: Mobil-1 75w140
Front: Mobil-1 80w90

[89MustangGX]

Above suggestions are all right-on, one more I would add: Before you go opening up the diff, take out the fill plug to make sure it's not seized or stripped or anything.

Adam

[smokersteve]

I thought about using mobil but I wanted the cold viscosity "75" 75w-90 and there was none around when I did the work.

[CaptnKirk]

Thank you all for the great feedback and support. I love forums!

Did the work, it was a non-event. I am an avid Mobil 1 user, but the Amsoil was easy to order online and it was actually cheaper than the Mibil 1 - go figure. I recall Amsoil always being more expensive.

Again thanks all for the support.

[bfrank81]

So next month I want to do the same service. I was planning on using the Severe Gear 75W-140 Product Code: SVOQT-EA front and rear. Is 8 oz of this Slip Lock Differential Additive Product Code: ADATB-EA really necessary?