A great many of you are using gear oil in your transmissions. I would like to present somthing to think about. Most all metric bikes share the same oil with the engine and transmission. That means that the oil must be able to withstand both type of environments such as shear, high temps and contamaination from normal combustion of the engine. Looking in stores at gear oil and reading the lables I haven't seen where the gear oil says it is recommended for motorcycles. Now I have not looked at all brands and maybe I am wrong but I have looked at Mobile 1 gear oils of all types and none say they are for motorcycles. Amsoil gear oil also do not say they are for motorcycles as a matter of fact they recommend MCV 20-50 motorcycle with the following and I quote"Amsoil performs like a gear oil without the negitive effects of extream pressure additives". I will contact them soon and ask what they mean by that. Anyway something to think about.

 

To start with, Only some models of Harley have the engine and transmission share the same oil supply. Any application, where the Engine oil and transmission oil are seperate, You may use a Gear oil in the transmission. It is an over kill but you may use it. Never use an oil with an EP additive in the engine. AMSOIL'S primary recommendation is MCV in all three holes. Their secondary recommendation is mcv in the engine and primary and SVG in the transmission. 75W 140 will cure the 5 speed gear whine in the 07's.

Bear
AMSOIL Direct Jobber

 

Specifically, Sportsters share the oil and Big Twins (which is all other current HDsexcluding VRod) have separate tranny and engine oil.

 

Sportsters don't share the engine and tranny oil.

 

Could you tell us which harley models share engine and transmission oils? To my knowlege, none of them do, maybe engine and primary oils ? Also gear oil in the transmission is not overkill even if the white papers suggest that.

Your statement 75W 140 will cure the 5 speed gear whine in the 07's couldn't be more wrong if you try. You should get out more and get the real facts.

 

Pre Evo Sportsters, aka Ironheads, share engine and tranny/primary oil. First, on a Sporty the tranny & primary share the oil. The engine has its own supply, but there is a valve between the crankcases and primary on the Ironheads that allows oil to flow from the engine into the primary. It's not the same type of "sharing" as on a metric dump-the-oil-in-the-hole, but there is some interchange. Therefore, on an Ironhead Sporty you must use motor oil in both the engine and the tranny/primary.

 

Never heard this.....Is is true for all Ironheads? If so, they why would they recommend putting Sport-Trans fluid in 1971 and up bikes and not all of them? It has a warning on the back of the bottle telling you not to mix it with other lubricants. I wouldn't think if the bike was supposed to let the fluid go back and forth that that warning label would be on the bottle.

 

Didn't know they were reccomending that. I know my '72 CH had the valve. Maybe it only allowed motor oil to "vent" into the primary and not vice-versa? Sounds like a question for the Sporty forum. I'll see if I can dig anything up, too.

 

Looked at a coupla old HD manuals. None of 'em specifically mention the valve, but it can be clearly seen in pictures of the primary, locatedabout 4 o'clock relative to the engine sprocket.

 

My brother knows a good deal about cars, and I asked him what's the differencebetween using gear oil versus motor oil in the transmission.

He said the gear oil gives better protection and the trans will last longerbut gear oil has higherresistance than motor oil.This meansgear oil will rob a little bit of horsepower, torque andslightly lower the gas mileage.

Racing cars use the lightest oil they can get away with in the transmission/differential because going fast as possibledemands eliminating as much resistance as possible.Racing car engines, trannies & diffs are rebuilt every couple racesso longevity isnot the highest concern.

Sounds to me likebikes put motor oil in the trans to wring out the last bit of horsepower, torgue and gas mileage they can. (Wonder what hand EPA regs had in HD deciding to use SYN3 in the trannies?) Butgear oil means better protection/enhanced longevity. I noteothers on this forum writeswitching to gear oil made theirtrannies running a lot quieter and smoother.

I have a question though after reading more suff on this site.

Anybody know? True or False:Harley recommends 20w50 motor oil only in the primary on big bikes and in the tranny on Sportsters. I've wondered why and what I've read on this site suggests the fluid in the primaries/big bikesandtrannies/Sportsters lubestheclutchandadditives ingear oil will mess up the clutch.

Since the fluids in the bigbike tranniesdon't touch the clutch one can run gear oil there...but there only.

Anybody know if that'strue or not?

And anybody know if"transmission oils/fluids" are different from "gear oils" and safe to use in primaries/Sporty trannies?

I'm wondering what to put in my Sportster transmission.

Added note: Forum members recommend 25w90 Gear Oil in the Sportietrans.

CHECK IT OUT: Been reading manual on 2008 XL 1200 -to check oil, engine must be hot,no one sitting on bike,bike leaning on kick stand. My 1994 XL saysto check oil, engine hot, bike must beheld UPRIGHT off kick stand.

Wonder how many people areunder filled their 2008's oil tanks...