M8 6 speed transmission.

[Durwood]

I had a customer with a 124" M8 build report that he busted 2nd gear and was curious if anyone here has had the same issue?

He said that he's heard of a half dozen with big engine builds that did the same thing but I haven't seen this anywhere myself.

[kd]

Not an M8 but my  2011 120 TC build striped 3rd gear bare and I have heard of others with the 3rd gear issue.   

[bigcraig]

I have seen a few reports of this on a FB road glide owners group. Most of them lack a lot of details other than only stating that big bore builds were done.

Even after I tried to inquire about if they monitored the bikes for possible trans fluid migration, a know possible issue with some M8s. Those questions were never answered.

So, we are left wondering, if the added HP load is too much for the factory transmission, was/is there a heat treat issue with some transmission gears or could it simply be folks had a migration problem they failed to catch and/or monitor.

As they say, the world may never know!

[PoorUB]

Waiting for the guys that drag race to post!

Seems to me there are a few guys running big cubes and racing with stock transmissions that have little issues.

[Durwood]

Waiting for the guys that drag race to post!

Seems to me there are a few guys running big cubes and racing with stock transmissions that have little issues.

That is where I am UB. I am by no means easy on my bike but I haven't had the 124 very long.

This guy's failure was a breakage and not from lack of lube.

[Durwood]

Not an M8 but my  2011 120 TC build striped 3rd gear bare and I have heard of others with the 3rd gear issue.

I have seen some 3rd gear failures with the TC 6spd. But this is the first I have heard of second gear failure in an M8.

[No Cents]

   Daren...I know exactly what bike you are talking about and I honestly think it was a case of missing a gear. 
Let's just say it showed all the signs of a missed gear...and then trying to cram it into gear.
But what do I know.   

[festus]

2017 M8  stage 4 
Now with a t man 226   
Dynod At 124 SQ  valley racing 
Tore up 2nd gear  locked up the tire lucky my
Brother in law and my sister on the back we’re only doing
25 when it locked up   

Background  he broke two belts and when I rode it
The clutch came on almost immediately of the bar??
Was this an issue? Don’t know
Harley replaced the whole gear set and primary under
Warranty   With what he was told the update 2018 version 

 

[harttoo]

Mine is in for transmission repair now.Third gear had teeth missing.Stage 2 build.

[crewchief25H]

I've seen a 18 CVO with less than 300 miles back at my local dealer last spring with missing teeth on 3rd gear.

[Billy]

 2019 CVO Road Glide with Fuel Moto 128 kit. Maybe 200 miles after the install.

Third Gear

 [ You are not allowed to view attachments ]  

[Ohio HD]

Yikes, maybe Andrews should fire up their gear hobber again.

[MakoHD]

my fathers 120 busted 3rd gear but it had like 5oz in the transmission because it had fluid transfer
my uncles cvo busted 6th gear and all it has its a cam.
mine just makes an annoying shattering noise at idle, i believe its coming from that spring loaded 5th gear, i have grudge a box on order they state it'll get rid of the noise. the noise goes away when i pull in the clutch.     

[kd]

I'm hoping my new GrudgeBox will cure my 3rd gear experience. 

[No Cents]

   I wonder if a lot of what we see is some guys choose to run a thinner motor oil in their tranny instead of a thicker gear oil that will cling to the gears keeping them lubed as they spin. Of course the transferring issue on the M8's could play a big role if the tranny was to get low enough with the thinner motor oil and it can't cut the mustard when it gets low and it doesn't bath the gears any longer and cushion the meshing action like the thicker gear oil would.    Just thinking out loud here.

[Billy]

The trans pic I posted in reply 10 had formula plus in it and was full of fluid. Waiting on a GrudgeBox to go back in this one.

I believe axial forces from the helical gears combined with high torque loads from the 128 pushes the main and lay shafts slightly apart in the center (where third gear is) causing this type of damage.

[Geezer_Glider]

I'd second that idea. Wonder if they thought that big Christmas tree gear set would help hold the shaft straight. Be interesting to hear what Baker or Andrews would say about the 6 speed.
Just saying,
R Meyer

[MakoHD]

   I wonder if a lot of what we see is some guys choose to run a thinner motor oil in their tranny instead of a thicker gear oil that will cling to the gears keeping them lubed as they spin. Of course the transferring issue on the M8's could play a big role if the tranny was to get low enough with the thinner motor oil and it can't cut the mustard when it gets low and it doesn't bath the gears any longer and cushion the meshing action like the thicker gear oil would.    Just thinking out loud here.

I use in the transmission severe gear SAE 250 by AMSOIL SYNTHETIC EXTREME PRESSURE LUBRICANT... THICKER THEN HONEY.

[cmashark]

I’m thinking a DD7 is on my Christmas list.  I loved it in the bike Chad at Wide Open Cycles put together for me.

[No Cents]

   Bert Baker told Randy last week that a T/C 6 speed gear set won't cross over into a M8 without changing a lot of stuff. Bert said right now it's cheaper to replace an M8 broken gear set with factory parts.

[MakoHD]

   Bert Baker told Randy last week that a T/C 6 speed gear set won't cross over into a M8 without changing a lot of stuff. Bert said right now it's cheaper to replace an M8 broken gear set with factory parts.

Then why not just doing a grudge box you’ll get better performance and with the over drive 6th you’ll drop 250rpms when cruising onthe high way. I also got mine with neutral all the way up everything down, also the drum has the ignition kill when you want to shift with out letting go of the gas or using the clutch. I just don’t see the purpose of 7 speed when the grudge box is available.

[No Cents]

  I don't own a M8.
It was a customers bike of Randy's in question from the OP.

[PIRSCH FIRE WAGON]

Yes, Second and Third Gear. Seen more Third than anything. About 6 Total. "They" know there's an issue.

[rbabos]

Yes, Second and Third Gear. Seen more Third than anything. About 6 Total. "They" know there's an issue.

Apparently so does Google. Do the problems ever end with this M8?
Ron

[Admiral Akbar]

All the gears in the m8 tranny are the same as later twincams except for the countershaft.  Wouldn't be surprised if it interchanges.  Mainshaft is the same. 2nd/3rd gear countershaft are the same.