Want to elaborate on this with a link? Please define mess up with specifics. I see no difference in the lube other than the weight. Been running the 75/140 royal purple for a couple of months ( about 7k miles) and have not seen any problems. In fact, I have noticed that the drive line seems quiter. I was told that when towing heavy the extra weight in the lube would keep the heat and wear down. When not towing the weight of the lube was about the same as the 75/90. I have heard of others (some on this fourm) that have used the 75/140 with no issue. Your also correct about the friction modifier. Not needed in the AAM.

I might see a problem if running in colder climates with the lube not getting thin enough to flow properly. In Texas that's not a problem.

No flame intented just want specific info.

goat

 

silver_goat, per the 03 Dodge Ram Maintenace manual it states that one of the causes of overheating the rearend can be impropper grade of lubricant. I have also beeen told by DC that it can cause problems in the rearend.
I just got the info from the mechanics and their books. Sorry if the info is not correct

 

That's just the opposite of what the guys at my dealership told me. I think he said that "they" are now recommending the 75-140 for people that tow, particularly in hot climates, and that it gives an extra margin of protection.

I presumed by "they" he meant Diamler/Chrysler or American Axel... but I suppose he could have meant just the mechanics at that dealership.

SuperGewl is correct, though, that the owners manual and the factory service manual both say 75-90.

My service guy recommended the 75-140, and said it would not be a warranty issue, but if I were using a dealership that told me that 75-140 would cause problems, then I wouldn't run it.

Afterall, these are the folks who will decide if it is a warranty issue should you have a failure, so may as well do what the dealer you use recommends...

P.S. SuperGewl, that is one nice looking truck and 5th wheel!

 

Anyone use the Valvoline synthetic 75/90? It's API GL-5 and about $6/qt.

 

That's what I used the first change. Second change the store only had one bottle of Valvoline so I went with Mobil-1. I like Valvoline but it wasn't available...

 

joel,

I used the valvoline 75/90 at 15000 mile service. I now have 28000 miles and haven't noticed anything amiss. Have towed the 5er about 2000 of those 13000 miles.

 

I thought the Valvoline was a blend of synthetic and dino? Not a true synthetic.

 

Just had my rear diff serviced today. Being ignorant on the subject I didn't argue with the service manager. They put in 75/140 with a lubricant additive called AB 4318060. any thoughts on this. BTW it cost me $186 . I think my own personal rear differential hurts now.

Jamie

 

Nope. Valvoline full synthetic and Mobil-1 are the real stuff. There are some that use dino base stock that's highly refined to give the properties of synthetic but not those two.

 

Jamie, It sounds like you might have a rear end full of dino oil.

 

Hannibal, what should I do. The biggest thing I'm worried about is messing something up. The service guy said the additive had "detergents and cleaners" in it and was normal to add to the diff. I've no reason not to trust the guy, and the service was very good, they fixed a driver door rattle and replaced the weather stripping TSB23-008-04 on both sides without any hassle at all!!

Jamie

 

The reason I think I even had the idea for the 75/140 was the fact that I tried to get it at the dealership and when he told me that'll be $130.00 sir, I told him I would have to go get a second on the house and he would need to wait for me to come back with the money....

I hope he's not still sittin there waiting for me...

 

SuperGewl,

Thanks for the info. I suspect that this is DC's way of putting things in black and white for warranty sake if there is ever a question or a problem. It covers them. My guess is that it's the same as the motor oil specs as well. They recommend a weight (15/40) with the API (CI4 I believe) standand for your oil. You must meet the minimum requirements to keep your warranty in tact. Does this mean you can't use 5/40 weight? Probably not. But you should use a CI4 rated oil with a minimum max weight of at least 40.

I understand it's probably not a good comparison but you see my point. The standard for the diff. lube is GL-5 and the minimum weight is 75/90. The clause of "improper grade of lubricant" can be deceptive. What defines grade? An improper grade should mean one that does not meet the minimum requirement. (GL-5 / 75/90) In this case the 75/140 Royal Purple not only meets the requirement but exceeds it.

I also realize that you need to match your lube to your application. Your probably are not going to need 75/140 if your not towing or are living in a very cold climate.

With all that said does this mean the 75/140 is it going to hurt your diff? Probably not. There is no evidence to make the blanket statment that this lube will harm your diff. If there is I would like to see it because I will change mine out today if there a risk of damaging my diffs.

Could the 75/140 void your warranty? Well if your dealer is real **** yes it could but not likely. It's all about what your needs/preferences are and what your willing to risk if you need warranty work from your dealer. In most cases the dealer is not going to know or care what weight your using unless they see something to cause them to ask questions. If you have proof that your following the maintenance guidelines and used lube that meets at least the minimum requirement your probably ok. In most cases the dealer tech not going to know the difference between 90 and 140 just by looking at it.

To each his own I guess. That's what make this board so great. You get input from a numer of sources to make informed choices.

Just my opnion and worth less than .02.

Goat

 

Jamie, Since the dealership is a good one, I'd confirm with them that they put synthetic in even if it is 75-140. The AAM calls for synthetic only and I wouldn't be happy with dino. If it's synthetic, I'd be happy with it.

 

FWIW for dallas members, Keith motorsports in plano texas (4 wheel parts old bldg) sells redline fluids.