So can we use 85W140 in the rear diff or do we have to use 75W140?

And does anyone have the same problem I do, that none of my auto parts stores carries the gear oil I need! It's freaking driving me nuts.

I guess my other option would be to order online and pay out the wazoo on shipping!! Any suggestions??

 

try IH or a place where they sell big truck parts..

 

i've been out all day today. been to 5 differant part stores and no luck on the 75w, just 85 and 75w-90.
its funny u posted this, i was coming on here to look for some feedback on this subject.
i really want to stix to the specified 75w-140 and not have to think about it. gonna keep lookin..

 

I found this off of the diesel truck resource site:

Can't get Royal Purple 75W-140 for my 2002 3/4 ton at the moment. Mark from Royal Purple informed last Fri RP will phase out the 85W and keep the 75W.

My local NAPA dealer says this is no difference in performance (all they have is the 85W at the moment), Mark agreed but said NAPA could order the 75W for me if they used the part number he gave me.

What do you long term owners use? BTW the local Dodge dealer says their synthetic blend costs 20 bucks a quart - wow.

Need advice...towing season is right around the corner again.

and another:

We tow a 13,500 lb 5th wheel that puts us on the road at 10,380 lbs GVW (10,500 lbs GVWR) and 21,180 lbs GCW (21,500 lbs GCWR). I switched over to Royal Purple synthetic 85W-140 and have had excellent results. The differential runs quieter and cooler, and no supplemental friction modifier was required for the limited slip.

The 75W and 85W parts of the rating are viscosity ratings at the cold end of the operating spectrum - the 140 indicates the viscosity rating at the hot (i.e., closer to operating temperature) end of the spectrum. Therefore, the only practical difference between the 75W-140 and 85W-140 would be flow at cold conditions. Living in Texas, it makes no difference whatsoever. If I lived in northern Minnesota or Maine, I might be somewhat more concerned.

What do you guys think? I may just get some 85W140 since I live in So Cal.

 

Wow, I just scored on some Royal Purple for my rear diff. Got it off of e-bay. 4quarts for $20. What a steal!!! Now I'm looking for more for the front.

 

while your at it go ahead and swap out the rear diff cover for the new style finned cover. it was around $65 or so online. i forgot were i got mine at.

-mike

 

Here's a good place to find one,aluminum diff cover


I"m in the same boat, can't find 75w/140, or for that matter, 85w/140 anwhere locally. Probably have to order somewhere online.

 

I got my oil from the dealer.

 

Do you have to run 75w-140? Looks like my pinion seal will never quit weeping and at $20 a quart, I need a cheaper alternitive.

 

Well, after talking with the Royal Purple guys I'm going to use the 85W140. They said it's not going to harm anything and it will work just fine. Now, if you live in a colder climate you may have some issues. I live in So Cal so it's hotter than heck here especially in the summer.

 

Yeah I really want to get a Mag-Hytec pan. But I'm looking for one on e-bay. It's amazing the stuff you can find on there along with craigslist.

 

I bought RP 75W140 at my local NAPA when I did the front diff. Still waiting to do the rear. With the Mag-Hytec rear cover it takes about 8 quarts!