mountainmanjoe

I know you were being light-hearted, and I wasn't taking it personally or anything. I just wanted to present an example of an LSD that was used fairly hard and didn't get any chatter without FM. All I had to do was keep it dry and topped up. Pretty reasonable as far as maintenance I think. I changed the fluid once during my ownership.

I admit you're not wrong about GM ignoring complaints. Apparently my Savana wheels vibrating as I turn the steering wheel is "normal" to a tech.

We may never know the truth about what GM actually puts in their fluids.

I need to do a drain + fill on my two Savana axles pretty soon. I've got 83,000km on them now. The pinion seal is seeping so I'll get that done as well. Will I put GM fluid or plain GL-5? With or without FM? I haven't decided yet. I wonder what the difference in cost is. My tranny guy says gear oil is really expensive.

tsoleno

I have really only 2 things going through my head. 1) I could really depend on having both wheels locked and trying to get me out of a sticky situation. 2) I'm hoping that some wear on the larger governor gear won't terribly interfere with that and not cause the locker to come apart and grenade my differential in the middle of no where. If it does, I swear I'm gonna hop in the first Mercedes with a pretty woman that offers to pick me up and support me and not look back....

Garner Ames

FWIW I pondered for weeks about what to use in my G80 diff for its first change at 32,000 miles. I wanted some fresh fluid in there before departing on a 2500 mile cross country trip towing my travel trailer. GM fluid was expensive. I agonized about issues with the G80 using an after market gear oil and the FM additive debate that is endless on internet forums. I read the same above link posted by mountainmanjoe and that sealed the deal for me. I wanted Amsoil severe gear 75w90 but by the time I made that decision I was too close to departure to wait on the fluid to be shipped. I ended up buying Mobil 1 75W90 that also has FM included (blended with the fluid) for 12.99 a quart and haven't looked back. Changed the oil, cleaned both magnets and no issues what so ever. I also tested the "locking" mech on grass and everything working fine and no weird noises. I dont know why I made such a big deal about it. Probably because I have a 2014 Caprice 6.0L LSD G80 that IS very picky about the diff fluid and I only use GM fluid in it which is some kind of carbon modified fluid made by Castrol for GM but those issues are fairly well documented in the GM/Holden world for cars built on the Zeta platform such as the Caprice, SS, G8 and 5th gen Camaro. On the other hand, I have a 45 year old Pontiac with a limited slip diff that still works like a champ using all kinds of different brand fluid and the old school small bottle of GM friction modifier additive.