Have an '04 Dak QC with the 4.7, pretty sure without LSD.

I was gonna change the rear diff oil since the truck has just under 100K on it and I'm not sure if it's ever been done, looks like the factory orange RTV still on the diff cover, but not 100% sure, there is some RTV squeezed through one of the bolt heads, not sure if the factory is that messy.

I popped the plug out just to stick my finger in and see how dirty the oil was and it is surprisingly clean (maybe a little dark), doesn't smell burnt at all and the level is perfect.

I know sometimes Chrysler says the factory fill is good for the life of the vehicle but I never really trusted it, but this stuff looks clean. Never seen gear oil this clean in an older diff, usually when I get older vehicles the diff oil comes out like mud or milkshake.

Is the diff factory fill on these Dakota's usually good for the life of the vehicle? Also is it ok to use LSD oil in an non-LSD diff? Seems like everything I see has the additive in it for LSD already.

Thanks.

 

Yes you can use LSD gear oil in a non-LSD differential, it will work fine, you just can't do it the other way around and add non LSD fluid to an LSD differential without also adding LSD additive. The factory does use orange RTV on the differential cover, so yours could still be original, or maybe someone did change it in the past and they used an aftermarket RTV that was colored orange.

I have no idea on a 2004, it may be the same as my 2001 but I always change my differential gear oil every 12,000 miles. I go by the severe service maintenance schedule, mostly because I do a lot of short trips. I use plain Valvoline 75W90 conventional gear oil and it always looks pretty clean when I change it too, but I still change it out anyway. Maybe Dodge used a synthetic gear oil in yours so it is still clean too. I have no faith in "lifetime lubrication".

Jimmy

 

01SilverCC is correct on everything just do it so you see what it looks like and get a feel of its wear how gritty it looks its smell so on. If you 4X4 then you should change it as much as he says. A 2wd should be ok every 50K miles a change.

 

Yeah the color of this stuff looks almost brand new, but again I have no idea how long it's been in there but it's definitely not burned and doesn't have any water in it. Will gear oil break down anyway even if it looks good and clean, are there other additives that would break down?

All I could find was 80W-90 or 85W-140, unless I bought Mobil 1 and then I could get a 75W-90, but I'm not gonna pay for Mobil 1. I'm sure the 80W-90 will work fine.

Got the Permatex Ultra Black Hi Temp RTV to re-seal the cover. Do most people put the RTV on the cover and then put it back up or put the RTV on the diff and then put the cover on it?

Thanks.

 

I would only use 75W90 if it were me, that is what Dodge calls for in it. I don't use Mobil 1 products either, Exxon Mobil makes plenty of money already, and they don't need any of mine. Autozone and Napa both sell the Valvoline 75W90, and Napa sells a Permatex gear oil specific RTV sealant that is made for gear oil and use in differentials, that is what I use to seal the diff cover. It sets up fast too but I like to let it cure for a few hours before adding in the gear oil.

It just occurred to me that it is a possibility that someone probably has changed out the gear oil in OP's truck, but maybe they used a suction pump to get the old gear oil out of the diff instead of removing the cover. So maybe that is why the gear oil looks new but the diff has the original RTV. I guess that is one way to do it, but I like to remove the cover and get a good look at the gears and inspect for any damage or problems. Plus I like to use shop rags and completely soak up and remove all of the residue and leftover oil from the bottom of the diff as best I can. Just be prepared to do some scraping, if yours is like mine was, that orange RTV is tough to remove. It took a lot of scraping the first time I did mine.

Jimmy

 

Part of me thinks it was done and just re-sealed with an orange RTV. I tried to crack the bolts just to see if it would be a fight and they are not very tight at all, took barely any torque to pop them loose, so I'm thinking this was done at some point by somebody.

I have in the past used a pneumatic "wizz wheel" (I have compressed air in my garage) and cleaned all of the old RTV off using that. Just have to be careful and use it lightly so as not to actually take off any metal, but it's a lot faster and easier.

I've also done the suck it out the fill hole technique in the past, you never get as much out but it's easy.

 

I would never suck it out the hole. I like to pop open the cover and see what the gears look like and get all the crap out. My uncle tried to save time by doing it this way and he ended up getting the hose stuck in the gears so he had to pull the cover anyway.

 

Having a bench grinder with a steel wire wheel on it helps remove the old sealer with ease off the cover. When I did my rear I used some cheap oil for about one month and didn’t use any sealer just a gasket then re did it and was surprised how much gritty muck was in the bottom in that short a time it helped clear out the muck you can’t get to probably only need to do that if it has never been done before.

 

So that will work better than the Hi-Temp black RTV I got? The stuff says Maximum Oil Resistance, but then again only shows a pic of a valve cover and oil pan. Engine oil has to be more corrosive to RTV than gear oil, right or no?

 

The friction modifier additives and other chemicals in gear oil make it more harsh than plain motor oil. I don't know if it is really all that much more corrosive but gear oil can break down regular RTV a lot faster than motor oil can. That is why I like the Permatex gear oil sealant, it is made specifically to use with gear oil, diiferentials and transfer cases. One tube will usually do my rear diff 3 times. You can also buy the Mopar differential sealant at the Dodge dealer, it is the same stuff as Permatex gear oil sealant but it is more expensive there.

Here is a link if you want to read up on it:

http://www.permatex.com/products/Aut...sket_maker.htm

Jimmy