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My Service manager told me that i would be ok using 75 90 mobil1 snythetic and using the Transx additive.... with no problems Just for your FYI....:bigthumb:
 

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In my line of work, I get it in writing or at the very least, I record the phone call. Otherwise, if anything should happen to go wrong, it becomes a cluster f*** or "he said she said"

You should be just fine with the M1 gear oil. A Toyota TSB from late 2007 now requires the use of a fancy-schmancy Toyota 75W-85 (Not a typo, that is the viscosity) synthetic gear oil

I'm just wondering why you would need to add a LSD additive into the rear diff? The only reason to use such an additive is to prevent chatter in clutch packs, as the additive has different friction characteristics. Otherwise it does nothing to "help" the differential

Indeed, for heavy duty geartrains intended for highway tractors - Mack, Kenworth, Peterbilt, etc - LSD additive is forbidden. The only way to maintain the long warranty on such a HD unit is to use a HD lube on their vendor approval list. One such approved gear oil, Mobil Delvac 75W-90, I use in my FJ with great results

Mobil has a toll free number. I suggest you call them and ask if the LSD additive is needed or appropriate - or will help gear life - in a differential with a mechanical locking rear end, with no clutch plates
 

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What he said.. Straight-up M1 75W-90 is the safe choice IMO. I'm changing mine next month at around 3500; I'm curious to see how the factory fill looks.. Ron

In my line of work, I get it in writing or at the very least, I record the phone call. Otherwise, if anything should happen to go wrong, it becomes a cluster f*** or "he said she said"

You should be just fine with the M1 gear oil. A Toyota TSB from late 2007 now requires the use of a fancy-schmancy Toyota 75W-85 (Not a typo, that is the viscosity) synthetic gear oil

I'm just wondering why you would need to add a LSD additive into the rear diff? The only reason to use such an additive is to prevent chatter in clutch packs, as the additive has different friction characteristics. Otherwise it does nothing to "help" the differential

Indeed, for heavy duty geartrains intended for highway tractors - Mack, Kenworth, Peterbilt, etc - LSD additive is forbidden. The only way to maintain the long warranty on such a HD unit is to use a HD lube on their vendor approval list. One such approved gear oil, Mobil Delvac 75W-90, I use in my FJ with great results

Mobil has a toll free number. I suggest you call them and ask if the LSD additive is needed or appropriate - or will help gear life - in a differential with a mechanical locking rear end, with no clutch plates
 

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I heard 2008's were already changed over. This true?
The TSB does imply that the FJ Cruiser and 4Runner were getting the synthetic 75W-85 as a factory fill, effective the TSB posting of Nov 8, 2007. Any 4Runner model year 2003 and up, and all FJ Cruisers, are applicable

There are two versions of this gear oil at Toyota dealerships. Some 4Runners have a LSD clutch pack rear axle, so those need a gear oil with LSD additive to prevent chatter. Looks like the regular synthetic 75W-85 does *not* have this additive

Guess I should have added the TSB. Here it is
 

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Royal Purple 75w90 already has the Limited Slip Addative. Too much LSD additive and your FJ will go on a trip without you!
 

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Most auto gear oils already have some LSD additive blended in. AFAIK the Mobil 1 gear oils all do. Most commercial gear oils do *not* have the additive. For example, the Mobil Delvac Synthetic 75W-90 does not contain any LSD additive, and should *never* be used in any axle with a clutch pack
 
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