ATF in the gearbox.

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#1
Up to now, I've always run Hondalube 20w50 or whatever was available, but was at the car parts store buying 2-stroke oil (half the price of the motorcycle shops) when I decided I could save myself a ton of money by just getting my tranny oil at the same place (truck's getting about 14mpg right now and I paid $3.61 for a gallon of gas). The trouble is, the place that has cheap 2-stroke oil doesn't sell cheap tranny oil. So, I decided to grab some Dexron IV, instead (I'm a GM guy so I'm partial to the GM oils plus they are the most compatible with the most transmissions and it was only $3.50 a quart). I'll let everybody know if I grenade anything.

It seems pretty logical that I run ATF in a motorcycle gearbox. Automatic transmissions have gears and clutches all submerged in oil, so do motorcycle transmissions. The only real difference I can see is that automatic transmissions don't have to deal with the actual gear shift with the engaging of the dogs and such. MX trans are also subject to more shock because they don't have the damping effect of the torque converter. However, ATF has an additive package that is well suited to a MX transmission (go figure). They have anti-foaming additives, friction additives, and a strong detergent package (ever see how clean the inside of an automatic transmission is?). ATF also has a seal conditioner in it which may help prolong the life of my right side crankshaft seal. As a plis, the stuff gives off a horrible smell if you overheat it so you'll know you've been riding the clutch too much and it's time to change your oil.
 

Jaybird

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#2
Do a search and you can find a couple of good threads that discuss this issue.

ATF is made with heat RPM in mind. It is also formulated for a closed system, meaning there are no combustion byproducts that can foul the fluid up. And in a closed system, there is little to no need for a detergent package(the real reason the inside of a tranny pan is so clean)...which no ATF that I know of has. Sure, you hear old school crap about the magic cleaning proerties of ATF, but it simply isn't true. The cleaning prowess of an ATF is due mostly to it's lesser viscosity than conventional motor oils, and when a quart is added to a crankcase, it tends to help the fluid flow better and perhaps remove particles faster. But, just using it alone as a cleaning agent is a worthless venture...no matter how many Harley guys swear by it. Nor is it any better for a rebuild fluid than a simple motor oil.

ATF could indeed help with some seal issues, but not a cure-all for a leaky CS.

Type F would be a preffered fluid for a bike box, as it is designed to increase friction when the revs go up, whereas a Dexron/Mercon type ATF is designed just the opposite. Although most riders will not feel any differnce between the two.

Heat is a major concern with ATFs. And they all do a good job of handling heat for prolonged periods.
Probably the best at this is Mobil1 synthetic ATF. As it is formulated using PAO. Many riders use M1 Syn ATF with great success. The downside of it is cost. M1 will run you about $6 a quart, and a conventional Type F is about $1.50 a quart.
I use typeF in all 2t bike engines because it is wet clutch compatible, can take care of the gears well, and is CHEAP, so I can change it out every ride with no concerns.
Instead of a $6 ATF, I would just use a more robust motor oil.
Even if I had to pay $3.50 a qt for ATF, I would opt for something else with a similar price, like Rotella T, Delo 400, or Mobil Delvac 1300.
But, Type F is cheap and I use it, and have for several years with no sort of mechanical issues as a result.

I would also not use any ATF in a 4 stroke bike engine, as ATF's do not contain EP (extreme pressure) additives like robust engine oils do. The OHC, plain bearings, and solid lifters simply need more protection than any ATF can provide.
 
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#3
Gm,caught you sleeping again. Do you ever do a search before these cheaper,more better ideas come to light? Do you think you are the first? There is a never ending line of guys who see dollar signs over good sense and proven theory. I understand the school thing,kind of,more focus on weazlying money from other money holes is always a better option than your bike. By the way,I prefer phillips 66 chevron racing technology's 2 stroke transmission oil for any trans separated from combustion lubrication! 15 bucks a quart,well invested! You have not changed them crank bearings yet?
 
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#4
You didn't catch me sleeping, I've seen a ton of posts about this. I just threw mine up because I made the switch yesterday. Why should I change my crank bearings? They seem fine. The right side seal was bad, I changed that.
 
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#5
Good results with Type F here..........less clutch drag.
 

Jaybird

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#7
whenfoxforks-ruled said:
15 bucks a quart,well invested!
There is absolutely NO way you can justify that price. I see it more of a losing venture, than a well made investment.

Emotionally, maybe...
Mechanically, no way!
 
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#8
AGREED!

Let's say I change my oil 10-15 times a year, that's $150-$225 a year. I could repair a blown up transmission for much less than that. I feel better paying $3.50 a quart knowing I have exactly the same chance of blowing up my transmission as the guy with $15 a quart oil AND I have the money to fix it if it happens (or a lot of extra beer money).

I did ride the bike a little today, there certainly is less clutch drag.
 

Jaybird

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#9
The high cost of some of these so called "moto specific" oils are the reason many folks...especially funds challanged kids, leave the fluid in the box for far too long.

I'd venture to say that more engines have been hosed by high-dollar oils left in too long, than any are by cheapo ATF changed out every ride or two.

Although, if I were to have to pay >$3 a qt, I would opt for 15w-40 Rotella T or Delvac 1300 for about the same price. Both of these can be used with great confidence in either a 2T or a 4T.
 
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#10
Jaybird said:
There is absolutely NO way you can justify that price. I see it more of a losing venture, than a well made investment.

Emotionally, maybe...
Mechanically, no way!
If you buy Bel-Ray Gear saver by the case you generally get a good discount; it works out to about $2.50 a quart (at least for me).
 
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#11
For what its worth, Gas Gas and Scorpa both recommend ATF in the 2 stroke trannies....... Clutch action and feel is really important on a trials bike........never had any issues with my GG Pro 280 trans.
 
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#12
ATF fluid in a pw-50,smoked clutch plates.Honda line 4t trans fluid in a CRF450,every 2 motos and practice(about an hour engine time) TRASHED oil and plates last about 6 races if I was lucky,every other time the hubs and every 10 to 15 races the basket. 15 dollar oil and it will last longer than the hubs will,about10 races and the engine temperature has dropped significantly! The first change was dirty and subsequent changes have resulted in fairly clean oil and no clutch fiber stench! I am pretty sure a pw-50 trans could be rebuilt for 350,10 year old 250 2t at least a grand,450 trans would be close to 1500! IF BEER IS THAT IMPORTANT,then atf is no big deal,FOLLOW MANUFACTURE RECOMMENDATIONS OR PAY THE PRICE! They pay people enough money that they do not have to sacrifice good sense over being a CHEAPSKATE so your bike will live long and prosper, THE SUITS are not out to screw you out of your precious beer money! I am still surprised some genius has not discovered he could put 2t engine oil in his trans and work around the blown crank seals!
 

Chili

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#13
I've run ATF Type F in a 99 KX80, 02 RM250 and 03 RM125 with no issues at all. The only reason my son's 05 RM125 hasn't seen the ATF is that I still have a bunch of Pennzoil left over from one of his previous sponsorships. ATF Type F for me costs me more than a cheap 10-40 Auto oil but It solved solved shifting issues with the 99 KX80 so we stuck with it in that, then I bought the 02 RM250 from a local Pro and that's all he'd ever run in it so it stayed as well. I change the oil every ride, there is not a hope I'd ever leave any oil regardless of it's cost in any of our bikes for 10 racedays.
 
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#14
76GMC1500 said:
It seems pretty logical that I run ATF in a motorcycle gearbox. Automatic transmissions have gears and clutches all submerged in oil, so do motorcycle transmissions. The only real difference I can see is that automatic transmissions don't have to deal with the actual gear shift with the engaging of the dogs and such.
The major difference between an automatic transmission and a conventional gearbox is the torque converter. Whatever special properties the ATF has, it will be for the transfer of power in the torque converter.

I am sure that when the engineers designed the transmission that they started with the needs of the torque converter and then designed bearings and other critical areas so that they would survive in ATF.

The amount of clutch debris from a motorcycle transmission is far, far greater than the amount of debris from the wearing of transmission bands. I really have no idea how this might effect the end result, but I would think that if the engineers of your dirt bike said to run a specific type of oil then that is the oil that you should run.

Rod
 
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#15
This one time, I was like, changing the oil in my CZ. And I like, totally forgot to put the new oil in. So then I rode it, like around the parking lot, and it worked good. It was a little noisy but it didn't hurt it. Then I put the new oil in and rode some more. Those clutches are dry so oil won't help them none anyway, no matter what kind you use.