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I'm replacing my oil seals but I know I'm gonna get shafted if I go and buy "Motorcycle Fork Oil" and I am on the tightest budget imaginable right now.

I heard somewhere that you could use automatic transmission fluid as fork oil, specifically Dexron II. I was wondering if anyone has tried anything like this. My brother has a 5 gallon bucket of this stuff just laying around with nothing to do with it so as far as I'm concerned... as long as it will work, it's free fork oil.

I did some research myself on viscosity and whatnot, but it's quite confusing, especially since fork oil isn't really going to get hot.

I hear Dexron II simulates about a 7.5 weight oil when used in forks, and the repair manual says the front forks should take SAE 10W-20. So I figure I could put it in there and just put a little air pressure in the front forks to stiffen it up, since 7.5 weight would be a tad soft, correct?

Let me know if I'm about to do something stupid.

Thanks!
 

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I been using ATF (Dexron) for years, in my Harleys too...thing about ATF thats good, is that its non corosive, and anti-foaming, which can be a prob in forks. Try the ATF...if ya dont like it, easy enough to drain it out again and change. In the 70s, I used straight non-detergent 10 weight.
 

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All right, thanks! That's very reassuring. I'm sure it will be a fine substitution, at least for now.

Once I come into some money I'll probably get around to swapping it out with "fork oil".
 

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We went through this whole subject awhile back.

The short story is... Yes you can use it.

The main issue is there is no standard testing to determine viscosity... Even 10w fork oil from one maker may not be exactly the same as 10w from another. ATF can be anywhere from 5w to 15w really, but the point here is that does not matter to you NOW, go ahead and use it.

The oil you use does not really make the forks "soft"...it's the springs that do that. Fork oil effects the dampening ... the rebound + compression speed.

Not knowing anything about how much you weigh or how you got your bike outfitted, I couldn't make a recommendation as to what would be best for you to use oil weight wise, but ATF will work fine in a pinch if you can't get any regular fork oil.....
 

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there is no standard testing
May not be a standard test, but I been "testing" it since 1975...rough roads, bish on the back, no air assist...never a problem....however, Id still prefer straight 10 weight if I could find it. Mebbe 20 with these japanese forks. My last forks before these were almost double the diameter.

 

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Not knowing anything about how much you weigh or how you got your bike outfitted, I couldn't make a recommendation as to what would be best for you to use oil weight wise, but ATF will work fine in a pinch if you can't get any regular fork oil.....
Well I can say that I am a regular rider ~150 pounds, and I have no accessories on the bike really. It's mostly stock. I occasionally ride a passenger as well.

While I've got the forks apart I'm refinishing the aluminum base, stripping the clear coat and painting them a black semi-gloss. Should look sharp when it's done.
 

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I'm using Shield AW 32 Hydraulic Jack Oil, from Advanced Auto @ $5.99 a quart. ISO 32 oil is Equivalent SAE Grade of 10W.

AW – Stand for Anti-Wear; also protects against Rust & Oxidation, and contains AntiFoam additives.
AW32 is approximately a 10 weight oil with the additives
AW46 is approximately a 15 weight oil with the additives
AW68 is approximately a 20 weight oil with the additives

AW –provides many of the advantages of premium hydraulic oil at a moderate price. Suitable for use in applications where a Premium AW product is not required. All are blended with highly refined naphthenic/paraffinic base oils.

Q) What is the difference between AW32, AW46, and AW68 Hydraulic Oils?
A) The weights (10, 15 & 20) Sometimes called (ISO32, ISO46, ISO68)

Q) What is the difference between Premium AW32 and Quality AW32?
A) Quality AW32 is approximately a 1500-hour oil, whereas, Premium AW32
has increased oxidation stabilizers making it approximately a 5000-hour oil.

Source -> http://hollonoil.com/PDF/Getting%20to%20know%20Hydraulic%20Fluids.pdf


Ma Kaw says change your fork oil every 24,000 miles. I'm doing mine at 20K just because that's a easy number to remember. :) So the AW 32 is good for 1500 hours or so and say you average 45 miles an hour, then that works out to be 67,500 miles, if you are only averaging 30 mph, then you should be good for 45,000. Plus I like the way it rides with the jack oil better than when I first put in some Yamaha 10 fork oil.
 

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Im same weight as you, but 6'1" (skinny cuss)...try the ATF, unless by you you can find straight 10 weight...then go the 10, or if an older bike with tired springs, go 20...but use NON detergent...VERY important...the detergent oils (like reg 10-W30) will eat away at your seals slowly...
Check yer local Harley custom shop and ask about fork oil for Showas on an Evo (SAME FORKS ! lol)...bet they can sell ya some low buck stuff...dont go to a Harley dealer, go to a custom shop...
 

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Discussion Starter #10
I think I'll go with the Dexron for now, since it would be free. This is all way more helpful than I could have imagined, thanks guys.
 

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I would be scared to run ATF in my forks since ATF is generally used as an engine flush agent in high millage and diesel engines. which means that there is some kind of detergent or abrasives in it. also.. when introduced with air Dextron III foams really badly, which could also give adverse handling to the suspension
 

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Dex 2 never foamed on me...and the cleaning qualities are because its a super refined petro oil (as is kerosene and #2 fuel oil)...ever use Marvel Mystery ?...its basically ATF...but he should be good until he finds some straight 10 or 20 (which I prefer, btw)...heck, the summer is almost half over...
 

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Just as a reference point.....

When I did the progressive spring install on my bike, I used Bel-Ray 15w Fork Oil. Many have done the same. I had a Plexistar 2 fairing one the front. The front end was ALOT better than the stock set up.

Personally.... I'll spend the extra few bucks and buy real "fork oil". After 40 years, I only use Bel-Ray fork oil. Biggest reason here is I know exactly how it's going to behave. ATF is just hit and miss. Granted, a cruisers front suspension is not as critical as a sport or race bike....but in my mind... Why compromise? If you can't tell the diffrence, I guess it does not matter. But if you know what your trying to fix in your front end, real fork oil from a company you have some experience in what they offer makes a diffrence.

The front end on my Vulcan when I was done was perfect for me. No jolts over road seams, no wallowing through fast turns, no excessive diving when braking.


You can use anything you want ... But if you really can't tell the diffrence between a properly set up suspension over one that isn't...it won't matter anyway.
 

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I used Bel-Ray 15w Fork Oil.
:smiley_th

Just a note, but I always used Bel-Ray (30w) in my motocross racing bikes... wasnt too costly back then...how much now ?...I might try it again...
 

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:smiley_th

Just a note, but I always used Bel-Ray (30w) in my motocross racing bikes... wasnt too costly back then...how much now ?...I might try it again...
It's around $13.00 a liter. Guess you might find it cheaper if you search online awhile.

I got some "on sale" for about $11.95 back when I did my Vulcan forks.(

(One liter is enough to do three Vukcan forks...:))
 

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Sparky!!!
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Dex 2 never foamed on me...and the cleaning qualities are because its a super refined petro oil (as is kerosene and #2 fuel oil)...ever use Marvel Mystery ?...its basically ATF...but he should be good until he finds some straight 10 or 20 (which I prefer, btw)...heck, the summer is almost half over...
Dextron II and Dextron III are different.. I know Dextron III Foams because we use it on the HMMWV as power steering fluid, and to bleed the air out of the system, you turn the wheels hard clock right to hard clock left repeatedly with the engine running untill the pink froth is gone. Dextron II however does not, and when we have to substitue the latter for the first it is a little harder to bleed the air out because all you can see is an air bubble or two. However.. finding Dextron II is coming harder and harder to find as the auto manufacturers are starting to use Dextron VI and VII. Type FA ATF is even more rare to find.
 

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Let's Ride!!
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So what would the difference in feel be between 10W or 20W (equivalent) oils?
 

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finding Dextron II is coming harder and harder to find
The local cornvenience stores here still have it...my "Dothead" Mart has plenny...

10w AND 20w...A higher viscosity is used for 1) heavier bikes...2) constant fork travelling (like an MX course)....also, as Im sure you know, in colder weather to swith to lighter if meeded, and in brutal heat a heavier...
So with straight 10W, normal road riding w/o a load, would be fine...
 
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