2nd Gen Non-Engine/Transmission Diff. oil

[fyrescott]

New TDR member and looking for some advise. I tow a 7000 lb. 5th wheel and want to change my rear diff fluid to synthetic. Do I still need to add a limited slip additive? I tow all year under different conditions. Also will be changing transmission fluid too. What grade to run in both? Great to be on board!

 

[CrewCabDiesel]

Yes you need to still use the OEM limited slip additive, and I do believe that the Dana 80 comes from Dodge with synthetic 75W-90 gear lube, (but I could be wrong). Dodge does offer a 75W-140 full synthetic for severe duty use which almost costs more the gold . I use in my 3500 (not to cause an oil war ) 5 qts of Amsoil series 2000 75W-140 synthetic and 2 bottles of dodge friction modifier (AKA Limited slip additive). I use my truck daily, which has 395 RWHP and 870 lb feet of torque to occasionally tow a 9000lb 5th wheel and 16' boat in tandem, and I tend to push it, so I like the extra protection of the 75W-140.



Kyle

 

[jwilliams3]

You can save some money and have some great oil in your rear end.

I use the Valvoline Durablend gear oil in 85w-140.

You can also run Trans X limited slip additive it works just as well as the Mopar ripoff brand.



I also just changed my rear end fluid with this combination after 40,000 hard hard miles of drag racing and street racing at over 400hp and 800ft lbs.



No metal on the magnet, and no wear.

And to top it off the oil was clean and still had its yellow/blue tint.



--Justin

 

[TSRAM]

Originally posted by jwilliams3

You can save some money and have some great oil in your rear end.

I use the Valvoline Durablend gear oil in 85w-140.

You can also run Trans X limited slip additive it works just as well as the Mopar ripoff brand.





--Justin

I second this Justin. I have been using the exact same thing and the lube always looks just fine. I did try to get by without the friction modifier, but the chatter of the anti-slip rear prevailed within a few days. Have changed the rear twice and the front once using this same lube.

 

[kentdiesel]

After doing a search I read where some of guys said their limited slip did not work as well or at all when they changed to synthetic differential oil and used a additive or modifer with it.



With this info I changed to synthetic differential oil (dare I say which brand?) and I did not put in any additive. My thoughts were if it still worked that would be great and if it started grabbing I could always put the additive in later.



10,000 mi later the limited slip holds fine, does not grab and I never put any additives or modifers in.



I'm not suggesting anyone use or not use additives or modifers in Limited Slip Differentials, just thought I would pass this experience along as food for thought.



Kent

 

[rweis]

I think you will find that there are no "formulas" for your (or any) particular rear end and transmission. There are things that others use and work for them.



I think there are a couple of threads (grin) on diff oil and changing procedures. Generally I would change to a systhetic you are comfortable with and see if it chatters. If so add a little, like in a little, friction modifier. See how that goes.



I think the reason that they all don't act the same is the way they are driven and the condition of the clutches in YOUR unit.



You basically need to read the diff threads and decide on a brand of fluid. You also need to decide on a modifier that works with that brand of fluid. Then do the change, see how it goes. Adjust, see how it goes, etc.



The only thing I can add to the diff threads is I did not raise each rear wheel off the ground so as to drain the maximum amount of old fluid to the center. I did not pick up on that. Will next time though.



Bob Weis

 

[illflem]

It seems to have to do with the amount of clutch wear in the LSD whether or not you need to add the friction modifier. The brand or type of oil make little difference, one truck will need it and the other not even with the same brand of oil. Best bet is to start out with none, drive it then add it a quarter bottle at a time if warranted.

 

[klenger]

1st time I put in Amsoil 75W140, I didn't need any modifier. 2nd time (27K later), I needed to add 1 bottle.



I still have a 2nd bottle (Dodge brand) that I will sell for $10 shipping pre-paid.

 

[GAmes]

I recently changed out to Royal purple 85-140. The bottle said no modifier was needed so I didn't add any. In the past I had been using Mobile 1 with modifier, not Dodge's. Have put about 7500 miles on it since then. No chatter and the L/S worked in my gravel driveway 3 days ago.

 

[WadePatton]

You were exactly right in trying the synthetic without modifier. I changed to "Synpower" with no additive and have no chatter and fine LS action now for 6000 miles. It's much easier to add LSA than to remove it.