Is it safe to run Syn3 in the tranny? Just seems to me it is too light for the transmission? I have a 00 FLHTCUI and am thinking about replacing the tranny oil with a Mobil semi syn.

Thank you.

Mike

 

I would not run Syn3 in the tranny. Use either Mobil 1 or Amsoil 75W-90 or Redline Shockproof Heavy.

 

I would NEVER run syn 3 in the trans. It needs a gear oil like said above.Mobil 1 75/90 or redline shockproof heavy.

 

And as an FYI for others...even Harley isn't recommending Syn 3 in the '06 trannies.

 

Funny! Just had the 1000 mile done on my Low Rider and they put Synthetic everywhere.

Here is the Harley page on Synthetic oil.

http://www.rmh-d.com/parts/syn3_faq.php#a10

Lee

 

Been running SYN 3 in all 3 holes for the last 24000 miles and no problem but still have reservations about it. I figure if it hasn't done any harm yet I might as well stick w/ it.

 

Same here, Had the 1k done and they put syn3 all the way around. They told me it would be fine. I have thought about making the changeover to Amsoil at the 5k oil change. I ran Amsoil in my Yamaha and had no problems at all.

 

Without getting into the discussion too deep, gears in the tranny need gear oil because of the shear factor from the gears. Engine oil in the tranny is a mistake and as stated above HD doesn't recommend it in the 06 bikes.

Because you have significant miles on it and it hasn't seen any problems does not make it OK . It could possibly be seen in a different light that if you were to use gear oil in the trans that you would possibly get high mileage out of the trans whereas with the syn three. you may even make some decent mileage but not as much as you would with a gear oil. Why wouldn't you use straight 10 weight in the engine applying this theory???

 

Just My 2 cents. I did the 1k service on my sportster and switched out the primary oil with syn and really dont like the way it feels. sounds a bit nosier too so Ill be switching the oil back to the formula plus.

Chris

 

Redline Shockproof for the V-Twin tranny....................Sync3 is poisen.