75W-85 Vs 75W-140 for Jeep Rear diff and the confusion HELP

[kfxnando]

Morning
The differential service on my jeep 2012 Grand cherokee Overland 5.7 Hemi Quadra Drive II Right Hand Drive is due
This is not my 1st jeep, also a 2001 WJ 4.7 limited Quadra Drive, so have done these services before
However
When looking online and talking to different Jeep dealers Locally, was left with more questions then Answers
On line it says I need 75W-85
The one jeep dealer says 75W-85
Another Jeep dealer says 75W-140 with the friction modifier(the dealer says in South Africa we use 75W-140 on all our jeeps)
Admittedly I have not yet looked in my owners manual
A 3rd jeep dealer also told me 75W-140 with the friction modifier


As I only know one place that can help me with such info, here I am
Thanx in advance for the help

 

[SnowDrifter]

Originally Posted By: kfxnando

Admittedly I have not yet looked in my owners manual


That really ought to be the first place you look

 

[Johnny2Bad]

Last time I was in the US I couldn't find those high viscosity differential oils for sale anywhere (and we're talking MN here). The vehicle spent half it's time in the US and half in Canada, where the higher viscosity diff lubricants are the OEM fill and recommended in the manuals. US spec vehicles are as far as I know factory filled and manual spec'ed for the lower viscosity types (the chart in post2 is a USDM chart).

Obviously it won't harm anything to go 75W-140; that's as wide a range as any vehicle will encounter in North America, hot or cold, and South Africa isn't much different as far as temperature extremes go. Differential lubricants quickly come up to operating temperature after only a few miles driving.

More viscosity improvers usually means a faster additive depletion but then again I've never heard additive depletion to be an issue with differential lubricants and there is no evidence of unusual warranty issues or reliability here with those types, and every OEM specs them. That's about all I can think of for downsides besides availability and cost issues, maybe.

If the dealer recommends it as an experienced adoption for local conditions I don't see any harm and possibly a benefit.

The friction modifier is used in specific types of differentials. Use it if recommended and don't if not.

 

[dlundblad]

Originally Posted By: SnowDrifter
Originally Posted By: kfxnando

Admittedly I have not yet looked in my owners manual


That really ought to be the first place you look

Assuming this is a US manual, it'd be interesting to see this compared with OP's.

 

[totegoat]

If local dealers recommend 75w-140, why not use it, especially if towing anything.

 

[zeng]

75W140, never mind what the manual says.

 

[Kira]

75W-110 ( if you must go rouge? ).

 

[Johnny2Bad]

SA Manual says:

" ...
226 RBI
For trailer towing, use Mopar Synthetic Gear & Axle Lubricant (SAE 75W-140). Models equipped with Trac-Lok require an additive.
..."

Note: same as what is listed in the Canada Domestic Market (CDM) manual.

Looks like the 75W140 is full synthetic and the 80W90 is conventional.

 

[CT8]

75W-140 FM as needed.

 

[Gimpy1]

It interesting to see that the manual doesn't spec what type of FM to add type "F" or type "G". Also remember that the majority of synthetic diff fluid has some FM in it already. If you have to add some get good FM from Torco or Redline. The no name stuff at parts stores isn't that great.

 

[kfxnando]

Thank you Thank you Thank you to every one on here for Shari g your knowledge on oils

Yesterday afternoon on the way home, I went past another jeep dealer(Think I am out of jeep dealers) to go past

Asked them what oil I should use in the diffs, as it's a bit confusing
They pulled out a bottle of 75W-140(Mopar branded offcourse) and said this is what we use in South Africa, with the friction modifier

Looked up oil specifications, found that there are different standards for engine oils and other oils, to explain what the number mean
When I got home(the jeep is our weekend vehicle) looked in the owners manual(eventually) and that says 75W-85

From what people who know better on here and from what the majority of the dealers have told me, am going with 75W-140

Once again THANX

 

[kfxnando]

Had a look in a Liqui Moly catalogue and the also recommend 75W-140

 

[zeng]

Sticking to an xW140 in the Jeep would free you of worries on potential gear whining noise several hundreds of thousands of miles down the road, in relation to a CAFE/fuel efficiency xW85.