Synthetic Differential Oil
 

Synthetic differential oil


What the heck is it with all this cold weather stuff Well its fixin to get cold so lets get those trucks in good working order for winter eh!

The Oil in the rearend of our trucks is a dino oil (Mineral Based Oil) and in my oppinion leaves alot to be desired for differential use, first off I totally dont understand this but D/C actuaaly recommends that if you are going to tow with your Dodge/Cummins that you change the rearend oil over to a full synthetic 75/90 wt. OK i have to agree with them BUT What the heck to they mean Tow with your Dodge/Cummins truck??? Do they actually think that people wont tow with this truck Heck that is what they were born to do in this world hehehehehehe, Anyway I have yet another gauge to monitor rearend temps and when I had the dino oil in the rearend and was in tow I could reach 190*F this temp is still within a tollerable range but when I put the full Synthetic 75/90 in there I havent had it past 170*F since..............so what does that tell us? It tells me there is a whole lot less friction goin on in there eh. Here is a little experiment for ya, this winter when it is as cold as it gets in yer parts take some dino 75/90 and some syn 75/90 and pour about an ounce of each on a small plate and let them set outside till morning, then go out there and pour the oil off the plate..........what you say the dino wont come off, yep its true and the syn will pour righ toff there, now think about that and what yer gears are trying to do with that thick stuff in there. Thin about how much HP it takes every single cold morning to chern thru that thick stuff, that translates to extra fuel usage inturn means less beans for the dinner table. So do yer truck a favor and switck the differential oil over to a full synthetic and change that oil every 30k miles............go ahead and do the front diff while yer at it, only change that oil with respect to how much you use it though. One tip one the rearend is you have to drain the oil from the punkin and then jack up one side of the truck at a time to tilt the axle tubes so the will drain completly. If you dont have a drain plug the diff cover will need to be removed, the torque spec on the cover bolts is 47 ft. lbs. tq. I scrape the cover surfaces clean and buff with light emery cloth then add a coat of permatex red silicone and bolt er up using a star or criss cross pattern, I like to go to 35 ft. lbs first then step up to the 47 ft. lbs. required, also if you have a limited slip rearend the use of friction modifier may be needed, usually a couple ounces but I would tru the full synthetic and see how it works first, if it chatters on a corner then add the modifier.

Cheers, Kevin

You've been a busy guy. Appreciate all the good info you've provided. Here's a link to the thread I posted last Friday for continued reading on the gear lubes:
https://www.dieselbombers.com/amsoil/5105-gear-lube-comparative-study-its-finally-here.html

Are torque values for the front diff the same as the rear diff?
I am changing my front to 75-110.
Oh yeah....how much doe the Dana 60 in the front hold?
Thanks!

Differential, with Dana 60 Front..........8.4 pints[4] amsoil website has the capacities on the site and all oils that your truck takes.

If your going to run syn Diff additives i suggest the amsoil slip lock additive , as my diffs chattered w/o it

Do you have a link? I looked on the Amsoil site and I saw the product lookup guide but only saw the oils. Are the capacities lower down?
Thanks.

DM- I don't have LS, but would use the add. if I had LS.

I am doing the front this time.

AMSOIL Products - Auto and Light Trucks Lookup - amsoiloaf.3080482

enter your truck info and scroll down and it gives the capacites and all fluids and possiblilities your truck could use

It is listed below the oil types.
Thanks!

Been running synthetics in my diffs, engine trans and t-case since the truck had 20,000 miles on it. Don't know how much it helps, but it sure don't hurt anything!:U:

As far as the torque values on the diff cover bolts, be careful trying to get them that tight. I've had several Dana axles in the Rams where the diff cover bolts twisted off well before the torque spec was reached. Soft bolts or something. Just my .02

I've always done them snug, then about another 1/2 -3/4 turn.

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I torqued them to 40#.