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Automatic transmission fluid

Technical help for Series one, two and three Lambrettas. Models include the Li, Li Special, TV, SX, GP, Serveta and API/SIL models

Automatic transmission fluid

Postby alex_hughes » Sat Aug 07, 2021 2:00 pm

There was some chat about using this a year or two ago, I think mainly for race bikes. I am considering using the automatic transmission fluid in a road bike. I wonder if anybody has tried using this in a road bike, and what difference (if any) it made? Anything negative to report? Thanks
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Re: Automatic transmission fluid

Postby Warkton Tornado No.1 » Sat Aug 07, 2021 2:46 pm

It was probably me going on about it :roll:

I knew Bantam racers used it in the 70's with their very high first gear ratios (three speed 'boxes, close ratio) & still not burning out their clutches. Unlike Lambrettas @ that time.....

Years later, I had a Mazda Bongo & serviced it with new ATF. What came out was so squeaky clean, I thought I'd try it in a race engine. That worked well, so the next trial was to see if it would improve a road engine with a scootRS six plate clutch that dragged & would also need 'nursing' to stop it slipping with ST90. I just drained the ST90 & replaced it with the Bongo's ATF. The ATF cured that so I have been using it ever since. New stuff as well as the old :x Even in other people's engines & they are totally unaware......until I tell them later.

I imagine that there is a lot of misunderstanding about the stuff. I used to think it must be 'designed to slip' but, of course, it is designed to transmit torque but be tolerant of shock loads in absorbing them. My belief is the stuff might just help save gearbox teeth.

The last road engine rebuild is the most powerful/torquey I have ever done, even though it's not been on a dyno. Anybody that has fitted a six plate clutch based on generic Lambretta parts will probably agree that you will be lucky if all goes well from the off. That was the case & credit to CamLam plates & corks that it all fitted in standard OEM parts & function d so well. The only modification was the crown wheel had its slots extended, which is easy if it's two piece by de-riveting & re-assembling with SBHS's.

I thoroughly recomend it & only wish I had started marketing it as "my product" & get it showcased on a Facebook page. You know the one. Or is that page only for AT or MB products?
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Re: Automatic transmission fluid

Postby alex_hughes » Sat Aug 07, 2021 3:01 pm

WT1 Thanks for that reply. I wonder if you noticed any increase in drag when clutch lever pulled in? Or indeed less drag with lever pulled in?
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Re: Automatic transmission fluid

Postby martyn dwane » Sat Aug 07, 2021 10:46 pm

I was advised by an ex racer not to use it when i mentioned it on a Facebook page.
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Re: Automatic transmission fluid

Postby al pushpak » Sun Aug 08, 2021 8:00 am

I'm interested in trying this but just wondered what brand/make you guys use ? & is there a specific grade ? thanks in advance ;)
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Re: Automatic transmission fluid

Postby ULC Soulagent » Sun Aug 08, 2021 8:36 am

Millermatic ATF DM is highly recommended in them Bongo engines
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Re: Automatic transmission fluid

Postby Warkton Tornado No.1 » Sun Aug 08, 2021 11:22 am

alex_hughes wrote:WT1 Thanks for that reply. I wonder if you noticed any increase in drag when clutch lever pulled in? Or indeed less drag with lever pulled in?


In engines that comprise clutches with additional plates based upon the generic Lambretta design, drag, such as creeping forward in first gear was eliminated. I wish I'd tried the stuff years ago. There were many times that I have had to replace burnt out clutches, including those with up to nine plates.

I don't know the precise science of how come ATF can perform well, but it has for me. I'd guess that viscosity, ability to shed heat & durability/tolerance to heat would be the characteristics to compare with ST90. However, there is another thing, not scientific in any way. Cost. ATF wins that one as it's cheap as chips & lasts a long time.

martyn dwane wrote:I was advised by an ex racer not to use it when i mentioned it on a Facebook page.


You should listen to any advice freely given & make your choice. There are always those prepared to think outside the box. If there weren't, we'd all be running Dell'Orto PH's, Indian electronics & box exhausts with tailpipes too small.

Wet clutches are used extensively in other areas, predominantly motorcycles. Besides Bantam racers, many motocrossers use ATF.

al pushpak wrote:I'm interested in trying this but just wondered what brand/make you guys use ? & is there a specific grade ? thanks in advance ;)


ULC Soulagent wrote:Millermatic ATF DM is highly recommended in them Bongo engines


Dexron III is the stuff.
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Re: Automatic transmission fluid

Postby al pushpak » Sun Aug 08, 2021 12:29 pm

Cheers guys :)
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