mstep3

I was just wondering what fluid you guys recommend using when changing differential fluid. I want to put some good quality fluid in it so extra cost doesn't really bother me. Is synthetic better to use or should I just go & get Mopar fluid. I believe my truck has 3.55 gears.

kthiemann

I use synthetic in mine and have had no problems.

sheriffav8r

I use Lucas Oil and have had no problems. Will probably go with Royal Purple next time since their stuff seems top notch....

Dartmouth 12V

I would recommend synthetic as well. I run 75W90 but if you tow heavy a lot you might consider something like 75w140 or so. I have amsoil fluid in there right now and it seems to be fine (it isn't like we could tell the difference).

GAmes

I use Royal Purple and change it out every 50k. Since most of my miles are towing I use 75w140 year around, and yes I do go into the great white north in the winter. No need to buy anti slip additive, it is already in there.

DIESELWRKS

in last 170k miles used either REDLINE OR ROYAL PURPLE. what ever was cheaper both seemed to work the same. both have anti slip additive in the product. if you change your fluid. scoop out as much of the old as you can with a lint free rag. some people will lift one side of axle alittle to get the most out. good time to consider a different pan cover. when you do put your fluid back in. drive and do some figure 8's this will get fluid evenly put through the system. good luck. quart bottles where I go usually run between 9-11 dollars a bottle.

Joe Diesel

I've had Amsoil in mine for awhile now, I put in 75W90 since i dont tow too much, use 75w140 for towing or more heavy useage

SIXSLUG

I've had the Royal Purple in mine for about two years now. Didn't have to add anti slip and my rear end still locks up when it is supposed too.

Kurt

mstep3

Thanks for the input guys. I think I will go with the Royal Purple. I use their power steering fluid & it works very good. I appreciate the information.

Ruralmedic

If you have the limited slip axle, it is recommended to do several tight figure of 8 patterns in a parking lot after changeout to make sure the new fluid gets worked into the clutch packs. Then, if you notice any chatter when making turns, get a bottle of the friction modifier, and only add a little at a time until the chatter stops. Too much friction modifier will render the limited slip useless, and will make it act like an open differential.

As stated, full synthetic lubes usually have a portion of Group V ester base oil formulated in them. Esters are good friction modifiers, so often times no additive is even needed.

mstep3

I'm still a bit confused on what fluid to use after reading the service manual.....Service manual only lists 75W-140 SYNTHETIC for both front & rear axles...

I've got a 2500HD with 3.55 gears. I'm not to sure what rear axle that is?

If I don't use my truck for towing & only occasinally use it to haul equipment around in the bed is it really ok to use 75W-90 SYNTHETIC? I just want to make sure because I already bought 4 bottles of 75W-90 of Royal Purple for both front & back.....

DIESELWRKS

your good to go. use what you bought. take time cleaning the cover and matting surface. before I bought my alum Mag-Hytec covers. I bought a big magnet and put in the bottom part of the pan to catch extra crap. just a cheap trick. button her up and take off. doesnt take long to do just long to get the fluid in. part of the reason I went with mag-hytec cover.

infidel

No matter which fluid you use read your service manual and only fill to the recommended level.
On some years filling to the bottom of the fill hole is guaranteed to cause leaks.

mstep3

I was really surprised to see this study on gear oils. I had always heard really good things about Royal Purple gear oil. I thought it was supposed to be good stuff and provide really good protection. According to this article there are other gear oils that provide a lot better protection. Just wondering how much truth there is to this article by Amsoil......


http://www.amsoil.com/lit/g2457.pdf

infidel

I've always found Amsoil articles to be very one sided.