I've got a brand new built 3.0 l.s. rear end under my truck. Got the axles in today and it's fluid tight I hope... what is the groups concensus on the best limited slip diff fluid ??? first, organic or synthetic... then Motorcraft ?? Mobil ?? Redline ?? SuperPurple ??

it's ready to get juiced..

j

 

I use Royal Purple Max-Gear in my '56 Ford , F150, and Jeep Wrangler. The limited slip additive is already in the gear oil.

However, I do not use the "boutique" motor oils.

 

I've always just used conventional hypoid gear lube, 80W90 or equivilent. But with the limited slip, it's a must to use friction modifier. You'll have diff clutch chatter without it. And that doesn't feel good at all. ;( I did try some Sta-Lube stuff once that supposedly had the modifier built in, but it didn't work. I still had to add modifier. After that experience, I don't go for the fancy stuff. Just plain gear lube and a little bottle of modifier and I've always been happy.

 

X-2 Don't waste your money on fancy oil just to realize you need the bottle of friction modifier anyway. And, get the good stuff from your Dealer. I've never had any luck with the stuff from the local part stores.

 

follow up on diff oil..

talked to my rear end builder (no he ain't no proctologist) he builds all kinds of differentials... from hard slammed drag car stuff to UPS trucks and everything in between...

I asked him the same question I put out here... he never hesitated when he said all he ever used was Mystik JT-7

Mystik Store - Mystik®JT-7® Multi-Purpose Gear Lubricants SAE Grade 80W90 - Product Details

been doing it for lots of years and has never had one come back from a lube problem... several trashed from abuse and neglect... but it was usually trying to convert too much h.p. to wheel movement

so I finally found it in quart size and dumped 2.5 qts in tonite... it takes a long time to squeeze 2.5 qts of 85-140 oil thru a 1/4" tube into a 3/4" hole with a pinion gear right inside the hole...

now granted this is a subject very much like "what kind of paint do you use..." everyone has a favorite and a story with it... But since Dennis built this thing using my money I'll use his recommendation for lube... I asked him about synthetics... and he said they work fine... but I use Mystik only and it's never failed me. He buys it in 5 gallon buckets ...a pallet load at a time.

another tip... hose clamp the plastic tube to the spout BEFORE you squeeze so hard the tube blows off and sprays heavy thick oil everywhere.. ask me how I know... but brake cleaner will clean it all up

later
John

 

a trick to putting the gear lube in is too heat up the oil bottle in hot water first. pours a lot easier when it is warm (but still takes forever). and wear gloves before grabbing the bottle out of the water.

 

I hate the smell of gear oil in the morning! (In fact, any time of day).

I purchased this "handy" pump for about $4 at HFT. It holds about 1/2 a quart and you can load the cylinder by pulling the lever and unscrewing the top. You have complete control by positioning the tool at a comfortable angle, even below the differential hole. You then push the lever to force the gear oil into the differential using the tube connected to the tool. I also use it for manual transmission oil.