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First of all I want to state that I'm no engineer and the observations here are from personal experience and 40+ years as a auto and bike repair shop owner/mechanic. In the last 30 years I've built well over 1000 automatics for every application from stock to all out race applications in 1000+hp race cars and monster trucks.

For those of you (including myself) that use ATF in the primary here's some facts that I have verified over the years.
There are approximately 25 types of ATF but I'll cover the 5 most common as the other twenty are either obsolete or very vehicle specific.

Type F or (Ford) fluid was developed for and used in Ford automatic transmissions back when the clutch discs were made of sintered bronze or asbestos and there were no bearings used. All parts were supported by bronze bushings and thrust washers. It is essentially 20wt hydraulic oil (pure mineral oil) with a red dye and that's it. It is commonly sold as Racing ATF under brands such as B&M Trick Shift because it provides the quickest lockup of the clutch packs (Hardest shift). It has no place in 99.9 percent of modern applications unless you're just looking for neck snapping shifts (or in the case of motorcycles used for drag racing where quick and harsh clutch engagement is the primary goal and you're gonna change it very often.

Dexron II and III are the most commonly used fluids with the only difference being additives in Dexron III to make it more compatible with the electronics used in modern transmissions.
They both have an additive package that includes friction modifiers for smoother cluch engagement, oxidation control, viscosity stabilizers, corrosion inhibitors and proper lubrication of bearings and bushings of all types. Since the advent of gerotor pumps and better friction materials such as Kevlar and Aramid, Dexron II or III has even replaced the use of Type F for racing use by most transmission builders.
Dexron III is commonly used in many automotive manual tranmissions and is probably used in more transfer cases of 4WD vehicles than any other fluid.

ATF+3 uses higher quality base oils with the highest content of friction modifiers to prevent torque converter shudder. It lubricates a bit better than Dexron III but can also cause slow clutch engagment (slipping). If you ride easy and your primary goal is smooth clutch engagment then this is the fluid to use in your primary if you're gonna run ATF.

Synthetic ATF comes in many formulations but the most common is Dexron III. It has the same properties of clutch engagement as Dexron III with some advantages.
The main advantage of synthetic fluid is it's ability to resist thermal breakdown. If you ride in extreme heat or just want to extend your primary fluid change intervals then this is probably your fluid.

You may want to think about this too. Although the primary doesn't generate much heat in and of itself that's not the only concern when choosing a fluid.
The primary on your motorcycle is not a seperate entity. It is attached to the engine and it acts as a giant heatsink for that engine. The temps seen on a long hard run are probably within 20-40 degress of the engine oil temp.
Mineral based ATF starts to break down at around 220 degrees and is almost useless as a lubricant at 250 degrees.
On most Harley's the rear exhaust is in close proximity to the primary case and that adds heat too.

I have measured the temp on my primary after a hard run and have never seen temps above 180 degrees but that doesn't mean it doesn't happen. If you ride loaded, two up, in heavy traffic, the desert, or alot of hard pulls in the mountains then you'll probably see temps over 200 degrees.

Most people notice that shifting is immediately improved when they change over to ATF in the primary. This is because ATF is designed for wet clutches. When you pull the clutch in it releases cleaner than with motor oil. You'll also notice that finding neutral is no longer a chore.

Personally I use any major brand of regular Dexron III and change it out every 5000 miles but if I did alot of the riding described above I would probably use synthetic (although I am a cheap old bastard).

I'm not promoting the use of ATF in the primary!
But!
ATF has proven itself in hundreds of millions of auto applications and tens of millions of manual tranmissions and transfer cases.
You almost never see a 4wd transfer case failure anymore and I've personally seen 4wd trucks with a quarter million miles on a manual transmission and transfer case using Dexron III and still going strong.

I feel comfortable using it in my primary and I love not hearing the rattle when I snick it into first. But what I really love is not fussing with trying to find neutral on a cold day. And the over 300,000 miles I've put on primary's with ATF without a single lube related failure doesn't hurt either.

Geno:coffee:
great geno, thanks so much gona try it
 

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we went with the Lucas synth blend. Clutch lockup was improved.. shifting, not so much. and loud from gear to gear, not just first. First sounds like someone drops a rock on the trans. CAHLUNK! but we're gonna let it stay in till the next oil change. then we are going to try the same 20w50 we used in the engine and see what it does. what came out felt like gear lube. about as thick as 20w50 but stickier. I also have some 75w90 gear lube I could try, but that can wait till round 3. I will post my opinions ( they really can't be call results...)
 

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ATF was removed. lots of shavings after 1000 miles, but those could have been leftover from previously. hard shifting and some noise. hard to tell over the pipes. going with castrol dino 20w50. not sure if the gear ol i have has firction modifiers in it so we want to be sure before usining that. but my personal opinion is that ATF+ sportster.. not so much.
 

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Hello....i'm a brand new member here.

So my first question is which ATF would you recommend that i use in the Primary chain case on my 1996 Fatboy FLSTF ? Dexron III ???

My bike is still like brand new, it only has 15,000 miles on it.

Thanks for your assistance !
 

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Hello....i'm a brand new member here.

So my first question is which ATF would you recommend that i use in the Primary chain case on my 1996 Fatboy FLSTF ? Dexron III ???

My bike is still like brand new, it only has 15,000 miles on it.

Thanks for your assistance !
I Use Amsoil Super Shift Atf In all wet clutch Harleys with great Results!
 

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Thanks for your reply, but isn't that a "racing" fluid ? I'm just a cruiser..:+)
That doesn't mean you have to race. The only reason to use an ATF in the primary is to get better clutch action and at the same time more clutch life. if you are just a cruiser then use the same oil you are using in the crankcase if it is a motorcycle specific oil.
george
 

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That doesn't mean you have to race. The only reason to use an ATF in the primary is to get better clutch action and at the same time more clutch life. if you are just a cruiser then use the same oil you are using in the crankcase if it is a motorcycle specific oil.
george
Thanks for your reply, George.....i guess i don't know what i wanna do yet. Still trying to decide.

The only lubricants that i've ever used in my bike is the stuff at the local Harley dealer.....HD 20/50 motor oil and HD Formula+ in the transmission and primary cases.

I'm just not sure about using the Synthetic stuff. And it's not the money that i'm worried about either.

My bike is a 1996 Fatboy FLSTF (Evo engine) with only 15,100 miles on it. Do i really need Synthetic ? However, though....i do like the idea of only "1" lubricant for all 3 compartments.

Please let me know if this is the correct Synthetic oil for my bike.

And other user comments are welcomed..thank you !

http://www.amsoil.com/lit/databulletins/g2090.pdf

http://www.amsoil.com/shop/by-produ...dvanced-synthetic-motorcycle-oil/?GroupID=169
 

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Would ATF+4 be a good choice for the primary in a 2012 Heritage Softail Custom since ATF+4 is considered a synthetic and withstand high temperatures.

Main reason is withstanding high temperatures and I have Dodge Cummins that uses ATF+4 so I have it on hand and can use the same oils without having multipal fluids laying around.

My Choices are
ATF+4 in the primary
Mystik 15-50 synthetic blend diesel oil in the engine
75-90 synthetic gear oil in transmission

Give me the good, bad, or ugly on my choices.
 

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Would ATF+4 be a good choice for the primary in a 2012 Heritage Softail Custom since ATF+4 is considered a synthetic and withstand high temperatures.

Main reason is withstanding high temperatures and I have Dodge Cummins that uses ATF+4 so I have it on hand and can use the same oils without having multipal fluids laying around.

My Choices are
ATF+4 in the primary
Mystik 15-50 synthetic blend diesel oil in the engine
75-90 synthetic gear oil in transmission

Give me the good, bad, or ugly on my choices.
Any ATF used for automotive will work fine in your primary. The difference between ATF+4 and other ATF's is a slight difference in viscosity and a few additives is all.
George
 

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Any ATF used for automotive will work fine in your primary. The difference between ATF+4 and other ATF's is a slight difference in viscosity and a few additives is all.
George
It's those additives that has me worried. Too much friction modifier can be a big NO NO for the clutch plates.

I don't know how much more friction modifiers there are in comparison to each type of ATF. That's the change a clutch question.

( notice how I snuck in change a clutch instead of $1,000,000 ) :D
 

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It's those additives that has me worried. Too much friction modifier can be a big NO NO for the clutch plates.

I don't know how much more friction modifiers there are in comparison to each type of ATF. That's the change a clutch question.

( notice how I snuck in change a clutch instead of $1,000,000 ) :D
Don worry about using an ATF in your primary. They have the proper friction modifiers for your wet clutch plates. What do you think is in automatic transmissions? They are full of clutch packs. Many after market motorcycle clutch manufactures highly recommend ATF with their wet clutches.
george
 

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Thanks for your reply, George.....i guess i don't know what i wanna do yet. Still trying to decide.

The only lubricants that i've ever used in my bike is the stuff at the local Harley dealer.....HD 20/50 motor oil and HD Formula+ in the transmission and primary cases.

I'm just not sure about using the Synthetic stuff. And it's not the money that i'm worried about either.

My bike is a 1996 Fatboy FLSTF (Evo engine) with only 15,100 miles on it. Do i really need Synthetic ? However, though....i do like the idea of only "1" lubricant for all 3 compartments.

Please let me know if this is the correct Synthetic oil for my bike.

And other user comments are welcomed..thank you !

http://www.amsoil.com/lit/databulletins/g2090.pdf

http://www.amsoil.com/shop/by-produ...dvanced-synthetic-motorcycle-oil/?GroupID=169
Sorry that I missed your post on this. If you decide to use Amsoil you will get dealer prices through me like all other forum members have for the last 12 years.

Now with that said concerning your question whether or not you need a synthetic in your EVO engine, in my opinion, that depends on what climate you mostly ride in and how you ride it. The EVO engines typically do not run as hot as the twin cams do so a dino oil does a good job. If you ride a lot then you might want to use Amsoil so you don't have to change oil as often and or having the comfort of knowing that if you do get stuck in traffic during hot weather that you are not going to cook the oil. The oil in your links is the proper one if you decide to use the Amsoil. Let me know if you have any more questions.
george
 

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Atf

we started using ATF in the primaries back in the Shovelhead days when we sealed the primaries from the engine oil. Have had 0 problems using it, the clutches work much smoother. I had to rebuild the motor in my TC but I'm still on the original primary chain
 
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