You know a guy can read all this and change his mind 3 or 4 times about what to use
in his transmission. I just bought a 2014 Tri Glide103 6 speed and upon looking on the shelf in my garage
I found a qt with exactly 28 ounces of Valvoline motorcycle syn 20W50
just sitting in a bottle! That convinced me what to do right there. Who knows what is best but this for damn sure won't hurt anything.
Done Deal. 20 50 Synthetic in the trannie, we'll see...

 

Last time i changed transmission oil i used amsoil 75w-140, i felt it shifts better and i can find neutral now at red light

 

Bro, ROYAL PURPLE 75/140 IS just the best. I have worked at almost every chemical plant down here & 15 yrs off shore. Every one had ROYAL PURPLE in 55 gal drums because it was used in all types of gear boxes threw out the plant. Work boats & rigs with heavy equipment use it. Yea its not 100% in all equipment, but 90% has to mean something. My 03' FAT BOY has had it in the trans sense day one & comes out after 5,000 miles. Bought the bike in OCT of 2010 w/9,500 miles, now have 80,500+. Yes it also 100% SYNTHETIC. If ROYAL PURPLE is that good with big gear boxes, what they make for motorcycles should be looked at. Retired & have nothing to do with ROYAL PURPLE.

 

This is my choice also .

 

I finally got around to trying the HD 80W140, after 15 years of nothing but Formula +. Mainly as I was bored and had some soon to expire dealership rewards $ to use. It shifts a little softer and neutral a bit easier to engage. I’ll stick with F+ in the primary as zero reason to try and improve anything there. The 80W140 is a good candidate for wife’s trike trans so will switch to it there

 

Finally, we know what is best..

 

That's what I thought with Spectro Heavy Duty Primary Chaincase Oil til I tried the B&M TrickShift(or any type F atf really) and the Spectro is a little thinner than F+ which is just too thick for cold weather especially. Clutch plates stick together(stiction). Like 50wt motor oil. I dont know how people can run 20W50 in the primary but I guess if it's all you know...
You'll notice even better shifting and finding neutral with atf in the primary and I've been a firm believer in Spectro Heavy Duty Primary Chaincase Oil. Didn't think it could be any better. Clutch discs grab better which makes for better shifting. At first I started blending the Spectro and B&M TrickShift . Then went straight B&M TrickShift when I put the 30 tooth from Evolution Industries in. Figured why not try it. Lot of people running it. I was pleasantly surprised.
Try it once. Original tho. Not the synthetic.

As for the gear box, everyone knows the Spectro 75W140/Spectro 6 Speed is better than Royal Purple 75W140.
Oh yeah, take it for what it's worth, Baker recommends Spectro with their compensator and gear boxes. E1 recommends B&M TrickShift with their clutches and no synthetic.

 

That's exactly what I use in the primary and the transmission. I'm very pleased with both products.

 

There's already a million replies and I'm sure nobody cares at this point but...

I use full synthetic 20w50 in the engine (usually Mobil 1)
I use Super Tech brand ATF Type F in the Primary since that's recommended by my clutch manufacturer (Barnett)
I user Super Tech full synthetic 75-90 in the transmission

this would be for a 2000 Dyna with a bunch of motor work and stuff done to it. Recently acquired an 07 CVO Road King and not sure what fluids I'll be using in that yet

 

I just did a 5K service and used Redline shockproof. I definitely notice a difference. Much smoother, less clunk.