HS400/550 Dexron 3 ATF in front differential...

[cliffyk]

In a recent thread fellow forum member mcraigchr asked about Hisun's recommendation to use Dexron 3 ATF in the front differential--I had noted that in the latest SM I received for my HS400 (a "UT400"as labeled by  Coleman) that was also the recommendation. AS it was in conflict with other information in the manual I contacted both Coleman and Hisun who both verified the recommendation.

from the HS400 SM¹:

from the HS550/750 SM¹ (same table obviously):

I did not find this at all odd, as ATF is used in many high torque gearboxes and manual transmissions--it is VERY heat and wear resistant with additives intended to protect the sliding contact of helical gear sets as well as excellent protection for ball bearings, and bushings. 

I had replaced the front diff juice on my 2020 HS400 to 75W-90 SAE GL-5 gear oil at 20 hours (per OM "break-in" recommendations) and decided I would use Dex 3 at the "next change".  Today in a bout of ambition I did just that--then took off for a 5 mile ride to see "what was what?"

My first impression was that the differential was noticeably quieter and smoother, after riding a couple miles I stopped and engaged 4WD--as I had suspected 4WD engagement with the ATF was much improved, no need to blip the throttle (or drive a few feet) to get it in or out of 4WD as had been the case with the gear oil. The front differential lock also engaged much more positively and smoothly.

FWIW I used Valvoline DEx/Merc Full Synthetic MaxLife ATF (fully Dexron 3 compatible)--it took about 19 ounces to fill it to the botom of the filler opening (the OM says 9.6 oz.; on my first change I drained out 18 oz. or so).

So, bottom line; highly recommended!

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¹ - "Dextron"  with a "t" is a very common misspelling/mispronunciation of "Dexron"--I guess because so much contemporary stuff is named "somethingtron" I have even seen it on many sites that should REALLY know better.

[cliffyk]

Put  15 miles on it today mostly on the beach in 4WD--the front diiferential is definitely smoother and quieter, and engaging/disengaging  4WD and front lock more positively with the ATF...

[KentC]

I suppose this would also be applicable to the Massimo Buck 400?

[cliffyk]

34 minutes ago, KentC said:

I suppose this would also be applicable to the Massimo Buck 400?

The MSU400 (which is a re-branded Hisun HS400) probably--the Buck 400 maybe not. After Hisun (Chongqing Huansong Industries (Group) &nbsp;Co., Ltd.) cut Massimo loose for poor customer service in 2018 they scrambled to find other suppliers--according to the EPA emissions certification database the 2018 through 2020 Buck 400 was made by the Taizhou Nebula Power Co., Ltd.  (<-- this is a link to their Alibaba presence, probably where Massimo found them).

The EPA certification sticker on your Buck should tell you who made it:

You need to check with Massimo...