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#4225380 - 10/14/16 01:21 PM Trying ATF in Harley primary
MoreCowbellAz Offline


Registered: 02/05/15
Posts: 322
Loc: Phoenix, Az
As I do maintenance on my '00 RK I like to experiment to see what works or doesn't work, and maybe other folks can benefit. Although I definitely follow the mfr recommendations as a starting point, I do admit I'm more willing than most to experiment a little, and with all the wildly varying opinions of the internet I like to see for myself. I'm not trying to outsmart the engineers, but I do recognize that the mfr's interests are not always aligned with the user's interests (to put it kindly).

Anyhow, I was due for a primary oil change, I had Valvoline Premium Blue 15w40 in there and it felt fine for the most part but after researching ATF in the primary I decided to give it a whirl. Lots of folks say ATF was like a night and day improvement in shifting and finding neutral, I was skeptical about that mainly because my bike already does that great, not sure how much better it could get but what the heck, let's see.

I installed Valvoline Dex/Merc ATF, and although I don't have a lot of miles on it yet it feels about the same as before with shifting and finding neutral, which is to say pretty darn good. I was happy before, I'm happy now. Where I did notice an improvement was in the clutch action, with both Rotella and Valv Prem Blue I'd feel some minor coarseness right in the engagement zone, and with the ATF it was smooth all the way through. I don't know if it's the additives or the lower viscosity, but it's definitely smooth as silk (not that it was a problem before).

I didn't notice any increase in primary chain noise, or any other problems. I have no way of knowing if it runs hotter or not. I'm going to run it 4-5k and see what the fluid and magnetic drain plug looks like. With the HDEO in there my drain plug had very little debris and the oil was pretty clean looking, so that's a decent baseline I think. At this point I think I could go either way with the ATF vs something like an HDEO oil from a feel perspective although the ATF for sure is a bit better.

Anyway, maybe this helps some of you experimenters. One thing I'll say is if your bike is banging into gear or you can't ever find neutral you have a clutch adjustment problem more than a primary oil problem. But I do love me some Redline SPH in the tranny.
_________________________
07 Toyota RAV4 2.4L
07 Toyota Prius Touring
00 Harley Road King Classic
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#4225428 - 10/14/16 02:36 PM Re: Trying ATF in Harley primary [Re: MoreCowbellAz]
MotoTribologist Online   confused


Registered: 02/03/16
Posts: 562
Loc: NJ, USA
Any thinner oil should be an improvement over the Primary+ or whatever 20W-50 HD puts in there nowadays. Those primaries excel with an SAE 30 or equivalent trans oil. I'm not surprised ATF feels good in comparison. Report back on the drain plug and fluid results at the end of your 5K. I'd be interested to hear if the ATF protects as well as some other fluids.

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#4225505 - 10/14/16 04:33 PM Re: Trying ATF in Harley primary [Re: MoreCowbellAz]
Blkstanger Offline


Registered: 08/13/11
Posts: 1945
Loc: Lakeside, CA
I did the same thing some years ago. It ended up working out great for me. Gone are the days of starting a cold bike and having it clunk into gear. I will never use anything else in a Harley primary. Much better clutch feel too. I think it was about 2006 when I started doing this. I must have 85-90k miles on two different bikes using ATF.
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99 Jeep WJ 4.7 185,000 Maxlife 10w30, Fram Ultra.

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#4225567 - 10/14/16 05:52 PM Re: Trying ATF in Harley primary [Re: MoreCowbellAz]
GMBoy Offline


Registered: 11/22/04
Posts: 7702
Loc: Texas
You'll notice more improvements with the transmission fluid change than the primary fluid. The primary fluid doesn't lubricate your gears and you can almost run anything in the primary and not know the difference.

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#4225606 - 10/14/16 06:48 PM Re: Trying ATF in Harley primary [Re: MoreCowbellAz]
MoreCowbellAz Offline


Registered: 02/05/15
Posts: 322
Loc: Phoenix, Az
I'll definitely report back at 5k. Short of there bunch of debris on the plug magnet or loads of clutch material in the drain I'm not sure I see the downside from using ATF, given the noticeably smoother clutch action. I'm sure I would be happy continuing with the HDEO, but more smoother is more better right?

As I said before, I don't see nor did I expect to see any improvement in shifting since my bike already shifted great, so I agree that the tranny fluid has more bearing there. But I'm loving the extra smoothness the ATF provides as you feather out the clutch when in gear.

Also, I'm no engineer but logic would make me guess there's nothing going on in a Harley primary in the way of plates, bearings, gears, etc. that you don't see in cars/trucks that use ATF for many times the OCI a Harley would see. I could be wrong there, but it seems the fluid would be up to the task in Harley primary if it can go 50k in an offroad 4x4 or street rod.

I will gladly eat my words if I get stranded with a toasted compensator or exploded clutch plates. But I'm betting not.
_________________________
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00 Harley Road King Classic
11 Kia Soul 2.0L (mine to maintain)

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#4225725 - 10/14/16 10:01 PM Re: Trying ATF in Harley primary [Re: MoreCowbellAz]
Blkstanger Offline


Registered: 08/13/11
Posts: 1945
Loc: Lakeside, CA
You won't have any problems. I have torn apart my primary many times. Everything looked great.
_________________________
99 Jeep WJ 4.7 185,000 Maxlife 10w30, Fram Ultra.

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#4225787 - 10/15/16 12:35 AM Re: Trying ATF in Harley primary [Re: MoreCowbellAz]
userfriendly Offline


Registered: 06/03/03
Posts: 2629
Loc: LaFinDuMonde
I'm switching my light truck transfer case fluids from ATF to THF. These fluids may work in your application.

www.chevronlubricants.com >>products>>industrial and off-road transmission fluids>> 1000 thf & synthetic all-weather thf

1000 THF
40C 58.4
100C 9.5
VI 145
flash 235C
pour -42C

SYN THF
40C 44.7
100C 9.5
VI 204
flash 242C
pour -45C


Edited by userfriendly (10/15/16 12:37 AM)

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#4225952 - 10/15/16 09:07 AM Re: Trying ATF in Harley primary [Re: MoreCowbellAz]
MoreCowbellAz Offline


Registered: 02/05/15
Posts: 322
Loc: Phoenix, Az
I don't know the chemistry, but viscosity wise it looks like a slightly heavier version of ATF, like a 30. I know the Valvoline Dex/Merc I put in is a 20. First time I've heard someone mention THF, interesting.
_________________________
07 Toyota RAV4 2.4L
07 Toyota Prius Touring
00 Harley Road King Classic
11 Kia Soul 2.0L (mine to maintain)

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#4226138 - 10/15/16 03:11 PM Re: Trying ATF in Harley primary [Re: MoreCowbellAz]
Robenstein Offline


Registered: 12/23/09
Posts: 5653
Loc: Central IA
Originally Posted By: MoreCowbellAz
I don't know the chemistry, but viscosity wise it looks like a slightly heavier version of ATF, like a 30. I know the Valvoline Dex/Merc I put in is a 20. First time I've heard someone mention THF, interesting.


You could pop in Type F, which tends to be a bit thicker than the Dex/Merc ATF's if I recall.


Edited by Robenstein (10/15/16 03:13 PM)
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#4226161 - 10/15/16 04:07 PM Re: Trying ATF in Harley primary [Re: MoreCowbellAz]
userfriendly Offline


Registered: 06/03/03
Posts: 2629
Loc: LaFinDuMonde
THF can also be used as a hydraulic fluid and therefore compatible with fork and shock seals, if the ISO grade is close to your needs.

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#4226442 - 10/15/16 11:20 PM Re: Trying ATF in Harley primary [Re: Robenstein]
Blkstanger Offline


Registered: 08/13/11
Posts: 1945
Loc: Lakeside, CA
Originally Posted By: Robenstein
Originally Posted By: MoreCowbellAz
I don't know the chemistry, but viscosity wise it looks like a slightly heavier version of ATF, like a 30. I know the Valvoline Dex/Merc I put in is a 20. First time I've heard someone mention THF, interesting.


You could pop in Type F, which tends to be a bit thicker than the Dex/Merc ATF's if I recall.
I have tried the type F and it made the clutch grab a little quicker. I liked it.
_________________________
99 Jeep WJ 4.7 185,000 Maxlife 10w30, Fram Ultra.

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#4226995 - 10/16/16 06:07 PM Re: Trying ATF in Harley primary [Re: Blkstanger]
Robenstein Offline


Registered: 12/23/09
Posts: 5653
Loc: Central IA
Originally Posted By: Blkstanger
Originally Posted By: Robenstein
Originally Posted By: MoreCowbellAz
I don't know the chemistry, but viscosity wise it looks like a slightly heavier version of ATF, like a 30. I know the Valvoline Dex/Merc I put in is a 20. First time I've heard someone mention THF, interesting.


You could pop in Type F, which tends to be a bit thicker than the Dex/Merc ATF's if I recall.
I have tried the type F and it made the clutch grab a little quicker. I liked it.


Old timer drag racers noticed this too and you would see them putting type F in GM autos for firmer shifts at the drag track.
_________________________
2011 Triumph Speedmaster
1986 Chevy Monte Carlo SS
1970 Chevy Nova
2006 Scion TC

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#4227034 - 10/16/16 06:48 PM Re: Trying ATF in Harley primary [Re: GMBoy]
Gillsy Offline


Registered: 12/09/07
Posts: 338
Loc: Owego, New York
Originally Posted By: GMBoy
You'll notice more improvements with the transmission fluid change than the primary fluid. The primary fluid doesn't lubricate your gears and you can almost run anything in the primary and not know the difference.
My experience showed me the opposite. I tried 20w50 Mobil 1, Spectro Platinum 6 speed, and Mobil 1 gear lube in the transmission. There was no difference perceived between the three. I used Rotella T, Mobil 1 20w50, and type F transmission fluid in the primary. I didn't like any of them. I put Spectro Platinum Primary Chaincase fluid in and winner, winner, winner. Smooth shifts, and super easy into neutral every time.
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Many are the afflictions of a righteous man

2018 F150 Supercab 2.7 Ecoboost 4x4
400 lbs/ft of grin at 2750 RPM
2016 Kawasaki 650 Versys LT

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#4228181 - 10/18/16 08:18 AM Re: Trying ATF in Harley primary [Re: Robenstein]
JetStar Offline


Registered: 10/02/08
Posts: 1541
Loc: Flatlands of Indiana
Originally Posted By: Robenstein
Originally Posted By: Blkstanger
Originally Posted By: Robenstein
Originally Posted By: MoreCowbellAz
I don't know the chemistry, but viscosity wise it looks like a slightly heavier version of ATF, like a 30. I know the Valvoline Dex/Merc I put in is a 20. First time I've heard someone mention THF, interesting.


You could pop in Type F, which tends to be a bit thicker than the Dex/Merc ATF's if I recall.
I have tried the type F and it made the clutch grab a little quicker. I liked it.


Old timer drag racers noticed this too and you would see them putting type F in GM autos for firmer shifts at the drag track.


I remember those days, I used to bowl with the transmission shop guys next to where I worked at the time. They told me B&M trick shift was just blue dyed, type F. I tried the type F and it did make a difference in my TH350.
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My weakness is I love all motorcycles regardless of brand
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2016 Suzuki DR650
2015 Road Glide
2007 Yamaha FZ1
1978 Suzuki GS1000 (now 1085)

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#4228280 - 10/18/16 10:25 AM Re: Trying ATF in Harley primary [Re: MoreCowbellAz]
Silverado12 Offline


Registered: 02/26/13
Posts: 3111
Loc: Central Virginia
FYIFWIW I read somewhere that on the newer 2007 up Harleys you're supposed to run 40 oz. in the primary to properly lube the weak compensator.
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