Rear Differential Fluid Change

[jwhjr]

A few weeks back I posted a question on which RTV to use for my rear differential cover. I finally got around to changing it out and took a few pictures of the process. I did the change on my 04 Silverado at 93K miles. I previously siphoned the fluid out and replaced at 30K and 50K, but for this change I wanted to clean the magnet and see the condition of the differential in general. I used Amsoil Severe Gear 75W-90.

Pic before I started

The cover bolts are 13mm and I removed the bottom 3 bolts and loosened the rest in order to let the fluid drain before removing the cover.

Picture of the inside of the cover/magnet once removed

Inside of the differential after removal. From what I could tell, everything looks good. No chipped teeth or anything like that.

The bulk of my time was spent cleaning off the old gasket material in order to make sure I had a good surface to apply the RTV too. I used a rag soaked in Brake Cleaner to clean out the inside of the cover and magnet. I used a utility blade to scrape the remaining gasket material. (I also had to clean the surface on the differential as well, but I didn't get a picture of the cleaned surface) Here is the cover once cleaned:

I then applied the RTV Sealant on the cover. I used Permatex Ultra Grey.

I then replaced the cover and put all of the bolts back in and tightened in a crosswise pattern. I was also changing the front differential fluid and transfer case fluid, so I did that while the RTV was setting up. About 45 minutes later, I filled the rear differential with the proper amount of fluid. I have an allen wrench marked with a line so that I know when it's at the proper level.

Once I had it filled to the proper level I checked for leaks. I then took it up the block to an empty parking lot to do some slow figure 8's to make sure the fluid got out to the axle as suggested by theoilman. When I returned I pulled the plug out to double check the fluid level.

All in all it's not a difficult job. It took me about 2 hours to complete, but most of that time was spent cleaning the old gasket material off of the cover. I'll be keeping an eye on it to see if I have any leaks in the coming days as this is my first experience using the RTV material.

[S.D. Ice Angular]

Good Stuff, jwhjr

I wish more people would post these type of simple procedures.

I have been thinking of doing this to my 96 Explorer with 215,000 on it. I did it at 110,00 and it is due again.

Thanx Again

SD

[jeffreyd]

it is pretty easy job, smelly but not too much work required. i would have used a tad more rtv but that is just me. did you buy hi temp rtv? my dodge dealer has some orange stuff they use on them. when the warranty is up i will convert to amsoil as now they require diff service at 15k due to some special lube. i think it is a joke but dont want to screw with warranty.

[gunmunky]

Great post! I really appreciate the detailed photos. I have an 03 GMC with 77000 miles and I've been debating on doing this myself or taking it to the shop. Thanks again!!

[theoilman]

Gunmunky - Your 03 GMC may be one of the easiest. Check the bottom center of the differential housing - many GMs have a drain plug now, and the magnet is built into the drain plug. I recommend pull the fill plug first, then the drain plug.

[jwhjr]

it is pretty easy job, smelly but not too much work required. i would have used a tad more rtv but that is just me. did you buy hi temp rtv? my dodge dealer has some orange stuff they use on them. when the warranty is up i will convert to amsoil as now they require diff service at 15k due to some special lube. i think it is a joke but dont want to screw with warranty.

I'm a little paranoid that I didn't use enough of the RTV, but so far so good as nothing has been weeping out yet. I've been out there every hour or so checking... As I said, I'll just keep an eye on it and see. I used the grey based on airjer's recommendation. I figured since he does this for a living, if he said it works I'll take his word for it. I did look up the temp rating for it, and it's 450 °F continuous and 500 °F intermittent at the high end and -65 °F at the low end.

[gunmunky]

Thanks for the tip oilman!

[Jeremy airjer W]

I'm a little paranoid that I didn't use enough of the RTV, but so far so good as nothing has been weeping out yet.

I wouldn't have been afraid to put a little more on.

[jwhjr]

So far so good as far as no leaks

[Jeremy airjer W]

That's all that counts!

[WingDing2]

I did the same exact job not to long ago on my 03 Silverado 100K with the same results, the gasket clean up is the worst part of the job. I did find some wear on my Ring gear, nothing to panic about but I will be monitoring it in another 30K

[morefishplease]

I have an 04 GMC Sierra 1500 4x4 with 78,000 on it but have not had the rear differential changed yet. I have not towed or hauled anything with this truck in the entire 78k. I do check the fluid every 6 months and maintain the the proper level. I'm just wondering what is the easiest way to siphon the fluid out if I don't want to remove the cover? The front differential on this model is a lot easier as it has a drain/fill with the drain plug having a magnet attached to it.

[jeffreyd]

with that many miles on it i would change it. if there is any trash in it that way you can get it out. replace with lube and good to go for another 100k. the auto parts stores will sell a device that looks like a grease gun less the handle that has a hose on it. draw it out with that but if it were me i would pull the cover and dump it. good luck

[Jeremy airjer W]

Pulling the cover is very easy. You will get a much better fluid exchange as well vs. siphoning.

[deadeye]

All this talk about changing the diff fluid got me motivated I guess. I was throwing a set of those load adjuster shocks on my dad's durango the other night and hit my head on the diff. :grr: Figured it was a sign to change the fluid.

Anyway, I was suprised to see that after 100k the fluid almost looked new. Gotta love synthetics. The magnet had a little "dust" on it but it really looked a lot better than some I have done. Dodge used red rtv on it factory, but I had a tube of gray sitting there and it worked perfect.

One less thing to worry about now!

[morefishplease]

Thanks for the info guys!! I think im going to change it out today. One more question, is the RTV sealant the way to go or is using a paper gasket fine also??

[Jeremy airjer W]

Either way is fine. If the pan or diff mating surfaces are rusty than a Silicone smile (a small bead of RTV) won't hurt along with the paper gasket won't hurt. I have used a paper gasket maybe a couple times over the years.

[morefishplease]

I got the project done, thank you everyone for the info, and thanks jwhjr for posting your pics. The oil was not to bad with having 78,000 on it, probably being since I have not towed or hauled anything with it, and that it uses 75w90 synthetic gear oil. The front differential was more blacker when I changed that a few months ago but that does not use a synthetic oil. Once again thanks everyone!

[jwhjr]

Glad to hear it went well, and that the pics helped. Did you end up using RTV only, or the paper gasket as well? Also, for the front differential, even though they come with regular 80W-90 from the factory, I replaced mine with synthetic 75W-90 since the first change with good luck.

[morefishplease]

I used the ultra grey RTV and yes the pics did help, thanks again!

[jwhjr]

I was concerned that I didn't use enough RTV and my concern was valid. I had some weeping from the bottom, so I just pulled the cover back off and cleaned everything up. This time I used a generous amount of RTV and I'm just waiting about an hour to fill it back up. We'll see if it stays leak free this time. One thing I will say is it's much easier to clean the RTV material off than the original gasket.

[Sutty]

Thanks for the post