Changing rearend lube

[ISBPilot]

Getting ready to change the rearend lube and was making sure of a few things.



I have the LSD, so I need a friction modifier either already in the lube or bought from dodge and added myself. This is needed with synthetic or dino lubes, correct?



Most of my driving is commuting to work, however I haul some pretty good sized loads from time to time (20,000 lbs. or so).



I plan on doing a complete drain, but have read some synthetics don't mix well with regular lubes.



Any hints or tips appreciated, not wanting to start a brand war just needing a few pointers. Oo. Oo. Oo.



Todd

 

[RustyJC]

We tow heavy (21,180 GCVW versus 21,500 GCVWR), so I changed rear axle lube to Royal Purple synthetic 85W-140 a few weekends ago. Seems fine so far - it has the friction modifier built in, and no LSD chatter even though I didn't add any Mopar friction modifier. If you get a lube with the friction modifier included, I would try it first - you don't want any more than the absolute minimum amount of friction modifier required to keep the plates in the LSD from chattering. The more modifier you add, the less effective the LSD will be. Three (3) quarts of the Royal Purple brought me to within 3/8" of the bottom of the fill plug (Dana 80).



If you're going back on with the stock cover, pick up a tube of the gray (high temperature) Permatex RTV gasket maker. That's what Dana apparently uses, and it's worked fine for me.



Rusty

 

[fj40charles]

I use Amsoil 75-140 series 2000 synthetic lube. No friction modifer needed. I don't think mixing synthetic with dino oil is really a concern since I plan on keeping Amsoil.



Works well fo me. I'm sure others will chime in with their opinions.



Charles

 

[Shooter]

I use Mobile One 70-140 syn in the front diff. and LE 609 90w in the rear with no friction modifier. Real tight l/s with no chatter.

 

[chuck3]

I use Amsoil allso but had to add some friction modifier to mine this last weekend, I tryed the figure 8's several times but when turning left you could feel a kinda jerking as the tire was slipping, this got worse over time so broke down and added it, no problems since.

 

[LSMITH]

Here is the last post I did about how to get all the old oil out and to get the proper fill level in when you fill it.



Changing it on your own is as simple as taking the cover off, the fluid will drain out then. Jack up one wheel for a minute or two and then the other for a minute as well to get the old oil out of the axle tubes. Clean all of the oil you can reach out with a lint free rag or towel, the bottom of the case will be filthy inside and that is normal. Clean all of the silicone off of the cover, clean the magnet, and put about a 1/8"bead of silicone on a dry clean cover. I prefer to use the grey RTV, I have had less leaks with it. Put the cover on and snug the bolts down, do not tighten them as tight as you can get them, you will force all of the silicone out. The bolts on the bottom of the diff case (maybe 6-8 of them) will also need some silicone on the threads as the hloes they thread into go all the way through into the oil inside the diff case. You will see the through holes when you get the cover off and everything cleaned. Tighten them so you get an even amount squished out all around the cover. Let the silicone dry for an hour, and snug the bolts again, then refill with oil. When you fill it fill to the bottom of the fill hole, then put the plug in loosely and jack one wheel up as far as you can. Let it down and fill it up to the bottom of the hole for the plug. Then jack up the other side and let it down, refill again. You should be full now. Jacking it up on both sides and then refilling is important, if there is not enough oil in there the axle seals and wheel bearings will not have enough lube on them and you will develop a leak in the axle seal or have a wheel bearing go out. Tighten the fill plug and go. Find a parking lot or wide spot and drive in a figure eight as tight as possible, do 4 or 5 to mix the oil and modifier and to get the new oil into the clutch packs.

Depending on what type of oil you use you may need to add some friction modifier. The amount will vary depending on what oil you use, the synthetic lubes will typically need less or even none as some of them are pre-mixed with modifier for use in a LSD. If you do not have a LSD then you don't need to worry about it at all, just fill it up and drive. If you need the modifier add the quantity needed during the initial fill. If you get chatter from the LSD after the figure 8's then add a small quantity of modifier and do some more figure 8's, if it still chatters repeat untill it doesn''t chatter.

This sounds a heap harder than it really is, it will take you about an hour the first time being very careful to get it all right. Don't be surprised to find that the cover is stuck to the diff pretty well. Be careful to not damage the sealing surface prying it off, if you do scratch or bend it a little just flatten it out and clean up the scratch, no big deal.





I use Mobil 1 75-90 but I do very little towing, it needed friction modifier in mine. If you need friction modifier get it from the dealer, nothing else will get the chatter to stop in my LSD. The synthetics will mix fine with the same type of dino gear oil, ie GL-4 to GL-4. Hope this helps.

 

[ISBPilot]

Waited long enough.....

Thanks for the tips and ideas. I was waiting to do this when I got a new cover, but it's not in the budget and the time has come and went to service the rearend a couple of times. Just have to run by the dealer for some modifier and pick out a good lube and some RTV at the local parts store. The hard part is climbing back in my roll around chair when I'm finished on the creeper..... lol.



Todd...