I used Spectro platinum 6 speed trans oil 75W-140 in my 2012 FatBoy with good results.
I now own a 2018 Softail and I was thinking about using the same Spectro trans oil in it. I was doing some reading and I did see some info. that indicates that 75W-140 may be too heavy for our 6 speed trannys as the higher viscosity doesn't flow as it should to the bearings in the trans, resulting in premature bearing failure. Also can anybody tell me what the viscosity of HD Formula+ is?

 

Harley Formula + is being phased out for Syn3 20W-50. From what I have read both Mobile One V-Twin 20W-50 and Castrol Power1 V-Twin 20W-50 is designed for the engine, transmission, and primary as well.

Spectro does publish a chart showing their recommended oil by use http://www.spectro-oils.com/wp-conte...Conv-Chart.pdf
Spectro also claims their recommendations will not void your warranty, however, I would want to know more about that claim?

 

 

Stopped off at local dealer to purchase some and was told may want to stock up as supposed to be replaced by Syn3? Perhaps I misunderstood?

 

If not mistaken, Baker recommends Spectro in his transmissions. I've been using the GL-5 in my bike since 1st service, 40k later and all is well.....

 

Been using it 75W140 for a lot of Years with Great Results especially in FL Heat and Traffic ..

 

Also using Spectro 6-speed for close to 50K in 2 different bike, one 6 speed tranny and one 5 speed tranny (yep a 5 speed for 25K miles) no issues in either transmission.

Ken

 

I use the pink stuff.

 

No it is not to heavy. Here is why. They use a different system to rate gear lube than Engine oil. So your 75/140 is not much different than 20/50 engine oil. Socking yes but just they way it is. Spectro is in my 2017 RGU right now.