First of all, do you have a limited slip differential in the vehicle? That will push a decision towards either wanting a fluid with FM, or adding it in afterward.
It's likely that any decent GL-5 will suffice, but SAE-J2360 fluids are "better" in that they are not ony tested for lab specs and content, but also include performance application testing in real world use. The SAE spec is an adaptation of a MIL spec for gear lubes, and is more robust than just GL-5.
Walmart claims that their semi-syn is J-2360 approved on their website, but when I contacted them, they could not provide full documentaiton, and I've not seen it on the list. Mobil 1 is not on the list, believe it or not. I will also note that there are some dino (conventional) lubes that are qualified, whereas some syns are not. So those of you who think syns are "da bom" and can never be topped are fooling yourself. Case in point; the Valvoline HD lubes are conventional, and the Mobil 1 is not even on the list ... food for thought.
(note- for some reason, the Synpower is listed under Ashland, but the others are under Valvoline, so you have to pay attention to the whole list. Valvoline Syngard is under Valvoline, but Valvoline Synpower is under Ashland ... get the point? Also, Mobil's products are under ExxonMobil; while they do have the Mobil
Delvac 1 synthetic lube qualified, and they do have their dino Mobilube lubes qualified, they do
NOT have the normal Mobil 1 qualified ... )
Here is the best source I know of for the direct J-2360 criteria approvals:
http://www.pri-network.org/other-programs/automotive-qpl/lubricant/
Open the link to the "Current QPL listing" and see for yourself.
Here's the Walmart page where they claim to meet the spec:
http://www.walmart.com/ip/Super-Tech-75W-90-Syn-Blend-Gear-Oil-1-Quart/16795248#Specifications
Here's the Valvoline link (the 75w-90 is qualified, but not the thicker grade!):
http://www.valvoline.com/pdf/synpower_gear.pdf
Here's the Lucas link; they claim to "exceed" specs, including a MIL spec, but there is no proof or license I can find:
http://lucasoil.com/images/documents/TDS_Lucas-Synthetic-SAE-75W-90.pdf
You can search the rest; it's not hard to do ...
I believe, unless something has changed, that
the ONLY fluid on your list that is SAE J-2360 approved by the PRI is the Valvoline. They do update this list often, so check before you buy.
I am not saying that any lube that's not on the list is junk; I would NEVER imply that. What I'm saying is that while GL-5 is a decent spec, the SAE J-2360 is a far more demanding spec, and has more robust criteria to meet. Any lube meeting SAE J-2360 is a GL05, but not all GL-5s are qualified to SAE J-2360. The SAE spec is a more demanding standard. If you tow or have harsh conditions, then the SAE J-2360 is what you would want to shoot for. And there are both syn and dino lubes that are and are not qualified, so don't make assumptions just because you believe that syns are the answer for everything! In fact, this is yet more proof that often times, conventional lubes are every bit as capable as a syn, despite all the marketing manure you read about.
Bottom line is this: while manufacturers can make claims (some true, some misleading), it's often advisabel to give third-party, non-biased testing credentials the most weight in a decision. Look over the SAE J-2360 list. Use facts and data, not mythology and rhetoric, as your guide!
Will any GL-5 work? Probably so.
Will any qualified J-2360 do "better"? Probably so.
