Recommended Diff Oils - 100 Series

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Hey guys,

All this talk of better gas mileage has me thinking, I need to switch all my diff oils to synthetic. What is the groups recommendation on diff oil for the 100 series? I used mobil 1 in the 80 series some years ago. Is that still the way to go and what are the oil weights and amounts for each diff?

Thank you in advance,

uzj100
 
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The weights should be in your owner's manual, and I'd bet it's still 80w90 as one of the choices. I use M1 75w-90 which simply means when the oil is cold it's slightly thinner than spec'd, but at operating temp it is dead on. IMHO, this is a good choice and I've used it since new. As a data point, my axles/TC are notably quieter than other 80s I've been in with fewer miles than mine.

IdahoDoug
 
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I personally like Redline Gear oils the best (their gear oils are what built there reputation) and then Mobil 1. That said, any of the synthetic gear oils should be good.

Cary
 
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I just changed mine about a month ago and went with Motul gear 300 75w90. I used it on my Subaru before I got my LX 470 and I did see an improvement in mileage by 1-2 miles per gallon. I recently drove my LX to the coast over some coast range here in Oregon and averaged 18.8 mpg for 160 miles.
 
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I replaced my front diff, rear diff and transfer case fluids six weeks ago with M1 75W-90. I decided to check them and top off if necessary last weekend. The front was full (seeped when I removed fill bolt), the rear needed just a little bit before fluid started coming out, but the transfer case took about 1/4 quart more fluid. Is this normal? Did I just not get enough in initially? With 1.4 qt capacity in the TC, having it .25 qt low seems a bit worrisome. Or, is it possible to put too much oil in?? I have not noticed any leaks at all.
 
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I replaced my front diff, rear diff and transfer case fluids six weeks ago with M1 75W-90. I decided to check them and top off if necessary last weekend. The front was full (seeped when I removed fill bolt), the rear needed just a little bit before fluid started coming out, but the transfer case took about 1/4 quart more fluid. Is this normal? Did I just not get enough in initially? With 1.4 qt capacity in the TC, having it .25 qt low seems a bit worrisome. Or, is it possible to put too much oil in?? I have not noticed any leaks at all.

I pump oil in there until it is really flowing out nicely before capping. I had a similar experience as you, front and rear were clean, TC was a bit low and really dirty. I wouldn't be worried about much, sounds like you are getting it topped off and maintaining it properly.
 
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I just changed mine about a month ago and went with Motul gear 300 75w90. I used it on my Subaru before I got my LX 470 and I did see an improvement in mileage by 1-2 miles per gallon. I recently drove my LX to the coast over some coast range here in Oregon and averaged 18.8 mpg for 160 miles.

Not sure if it matters a lot, but I believe front and rear diff calls for 80w90 (I use Motul HD in those), and transfer case calls for 75w90 (I also use Motul Gear 300 in that)
 
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I pump oil in there until it is really flowing out nicely before capping. I had a similar experience as you, front and rear were clean, TC was a bit low and really dirty. I wouldn't be worried about much, sounds like you are getting it topped off and maintaining it properly.
Yes, originally I pumped in til all three were flowing out and then plugged. Figured I’d top off just to be certain they were at appropriate levels.
 
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I used 75w-90 in all three. My front diff was a milkshake because my front oil seal failed and let water in during a crossing. The transfer case was pretty dirty at around 30k miles since the last change. The rear looked brand new when I changed it a few days ago.
 
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Is everyone replacing the crush washer in each fill? If not I’m guessing your not seeing any leaking.

I'm in the minority that hasn't. No leak on the diff, but I did get a tiny drip from the oil pan, it went away though. I dont think its critical personally, but if you can just order some
 

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