M8 trans fluid leaking in primary

[hdrider]

Does anyone have a photo of the inside of the stock M8 hydraulic cover to see exactly what Baker is referring to and whether it's something a machinist could readily modify?

yes, way back toward the start of this thread 

https://harleytechtalk.com/htt/index.php?topic=96613.msg1152643#msg1152643

https://harleytechtalk.com/htt/index.php?topic=96613.msg1159595#msg1159595

https://harleytechtalk.com/htt/index.php?topic=96613.msg1192581#msg1192581

https://harleytechtalk.com/htt/index.php?topic=96613.msg1191493#msg1191493

https://harleytechtalk.com/htt/index.php?topic=96613.msg1186213#msg1186213

Thanks for posting this info.  The referenced photos and diagrams confirm what the Baker Technician was describing in that the M8 Hydraulic Side Cover traps tranny oil around the pushrod area that then gets pumped into the primary during every clutch actuation.  It looks like Bakers claim that their new Hydraulic Side cover design that un-shrouds the pushrod area (preventing tranny oil from getting trapped) and solves the fluid transfer problem is believable. It also looks like some judicious machining of the existing M8 side cover (as suggested in earlier posts) could accomplish the same thing.  Since I don't plan to buy an M8 until the 2019 models are out, I have time to wait to see if H-D did any meaningful changes or if I just need to buy the Baker Hydraulic Side Cover (which should be available to purchase in about a month).

[$tonecold]

So I have been reading the last few pages of this thread with some chagrin. I solved the transfer problem a few months ago. It doesn't really matter what causes it as long as the solution keeps it from happening. "The Fix" as it is called keeps the oil in the transmission and doesn't allow it to transfer to the primary!

[$tonecold]

Here is a picture to show what "The Fix" is:

[Ohio HD]

Great R&D work.         I know you've worked on this a bit. It'll be interesting to see if the 2019 bikes have a seal there.

[$tonecold]

Great R&D work.         I know you've worked on this a bit. It'll be interesting to see if the 2019 bikes have a seal there.

I sent it to the MOCO about a month ago, I haven't heard anything back from them. Not that they would have to tell me anything.

[Ohio HD]

Great R&D work.         I know you've worked on this a bit. It'll be interesting to see if the 2019 bikes have a seal there.

I sent it to the MOCO about a month ago, I haven't heard anything back from them. Not that they would have to tell me anything.

Yeah your right, and doubtful that they would say anything.

[FSG]

It doesn't really matter what causes it as long as the solution keeps it from happening.

IMO Prevention is always better than a cure/fix.

[$tonecold]

It doesn't really matter what causes it as long as the solution keeps it from happening.

IMO Prevention is always better than a cure/fix.

That's all well and fine, but so far nobody has a conclusive cause for why the transfer of fluids happen on M8's. It doesn't happen to all M8's, so why does it happen to some? What changed between the '16 models and the '17 models? The complete engine, the transmission case, the clutch actuator, the first gear, the mainshaft bearing, the engine breathers, the engine main seal. So is it any one thing, a specific combination of things? Really perplexing. You can look at "The Fix" as a cure or you could look at it as a prevention. The definition of prevention is effectual hindrance. In other words something that keeps a thing from happening.

[hdrider]

So I have been reading the last few pages of this thread with some chagrin. I solved the transfer problem a few months ago. It doesn't really matter what causes it as long as the solution keeps it from happening. "The Fix" as it is called keeps the oil in the transmission and doesn't allow it to transfer to the primary!

OK, so I read with interest your pdf on installing the "Fix".  It refers to a machined nut, a seal and a new side cover.

So where does one obtain these parts -- are you selling them online, on this forum, elsewhere, or was this a one off grand experiment for your personal use?  If selling them where do I shop and what are they selling for?

Also, what's the function of the vent hole in the slave cylinder?

[98fxstc]

So I have been reading the last few pages of this thread with some chagrin. I solved the transfer problem a few months ago. It doesn't really matter what causes it as long as the solution keeps it from happening. "The Fix" as it is called keeps the oil in the transmission and doesn't allow it to transfer to the primary!

Quite a few jump in on the tail end of the thread and don't bother reading the early stuff.
Frequent happening in this thread

[PoorUB]

Also, what's the function of the vent hole in the slave cylinder?

To vent the primary.

The seal separates the tranny from the primary, but the primary still vents through the mainshaft to the slave cylinder.

[happyman]

It doesn't really matter what causes it as long as the solution keeps it from happening.

IMO Prevention is always better than a cure/fix.

That's all well and fine, but so far nobody has a conclusive cause for why the transfer of fluids happen on M8's. It doesn't happen to all M8's, so why does it happen to some? What changed between the '16 models and the '17 models? The complete engine, the transmission case, the clutch actuator, the first gear, the mainshaft bearing, the engine breathers, the engine main seal. So is it any one thing, a specific combination of things? Really perplexing. You can look at "The Fix" as a cure or you could look at it as a prevention. The definition of prevention is effectual hindrance. In other words something that keeps a thing from happening.

would some bikes have a lot more heat generated than other due to climate  or including some ride there bikes  faster   longer than tothers therefore more heard causing the buildup of pressure?

[1FSTRK]

It doesn't really matter what causes it as long as the solution keeps it from happening.

IMO Prevention is always better than a cure/fix.

That's all well and fine, but so far nobody has a conclusive cause for why the transfer of fluids happen on M8's. It doesn't happen to all M8's, so why does it happen to some? What changed between the '16 models and the '17 models? The complete engine, the transmission case, the clutch actuator, the first gear, the mainshaft bearing, the engine breathers, the engine main seal. So is it any one thing, a specific combination of things? Really perplexing. You can look at "The Fix" as a cure or you could look at it as a prevention. The definition of prevention is effectual hindrance. In other words something that keeps a thing from happening.

would some bikes have a lot more heat generated than other due to climate  or including some ride there bikes  faster   longer than tothers therefore more heard causing the buildup of pressure?

It is not a pressure problem, it is the liquid trans fluid force and trapped above the hole in the main shaft.

[happyman]

What is the difference between force and pressure?

[1FSTRK]

What is the difference between force and pressure?

The liquid is pushed into the right rear corner of the trans case faster than it can drain back to the center of the case. This makes the oil level in the area of the main shaft abnormally high so the oil just runs down the center of the main shaft into the primary. There is no higher pressure in the trans case pushing oil or air to the primary, the trans case is vented to the atmosphere. Any pressure build up in the primary case would cause it to vent through the main shaft into the trans as designed and that would not move oil from trans to primary.  Maybe it would be better to say it is an oil level problem not a case pressure problem.


The cable clutch set-ups do not have this problem so all the engine, trans, primary changes are not the cause. The difference is the trans end cover that houses the clutch actuator, the hydraulic cover design creates a more confined area that causes the high fluid level at the end of the main shaft . One option is to take the already confined area and add parts to seal it off totally so the oil can not get in to accumulate. The other option is to the open the area up so it can match the better draining capabilities of the cable set-up. One way adds additional parts and maintenance the other requires a modification to the current parts to better match a design that has worked for 30 years.

[$tonecold]

What is the difference between force and pressure?

The liquid is pushed into the right rear corner of the trans case faster than it can drain back to the center of the case. This makes the oil level in the area of the main shaft abnormally high so the oil just runs down the center of the main shaft into the primary. There is no higher pressure in the trans case pushing oil or air to the primary, the trans case is vented to the atmosphere. Any pressure build up in the primary case would cause it to vent through the main shaft into the trans as designed and that would not move oil from trans to primary.  Maybe it would be better to say it is an oil level problem not a case pressure problem.


The cable clutch set-ups do not have this problem so all the engine, trans, primary changes are not the cause. The difference is the trans end cover that houses the clutch actuator, the hydraulic cover design creates a more confined area that causes the high fluid level at the end of the main shaft . One option is to take the already confined area and add parts to seal it off totally so the oil can not get in to accumulate. The other option is to the open the area up so it can match the better draining capabilities of the cable set-up. One way adds additional parts and maintenance the other requires a modification to the current parts to better match a design that has worked for 30 years.

I think your assumption of what is taking place in the transmission has some merit, but the same inner side cover has been used since 2013. There were reported cases of transfer on earlier models, but they seem to have been rare. The MOCO's cure for the problem was to replace the engine seal, which is why they are still doing that, but without positive results.

I had a couple people that used my fix try venting the primary by drilling a 1/16" hole in the seal near the top. The transfer continued through that tiny hole. That shows that what you are saying about the oil being forced is likely correct. There is at least enough force to push the oil to the top of the seal and probably enough to push it through the 1/16" hole. Now one thing is for sure in this situation with the seal in place. Once the oil is in the actuator cavity it only has one place to go because it is not going back into the transmission.

I am going to try opening up the inner cover as you have suggested on my 2015 Road Glide. It transferred when I had it dynoed. I have installed a DD7 in it and because of the wider bearings my fix with the seal will not work without some additional machining. One thing I have considered in this transmission is installing a shielded bearing on the mainshaft. Because of the extra width that should be an option.

One thing that has not been tried to my knowledge is installing the side cover / actuator from a 2012 hydraulic clutch. It is wide open like the cable actuated side cover. It uses a different master cylinder than the later models, but if the fluid volume is close to the 13-16 models or the 17-18 models, one of those should work.

[Bigtwin]

Could the installation of a reverse gear solve the problem?
This might give room for oil to go elsewhere?

[rigidthumper]

Looking at the 2019 parts book, they have changed the secondary actuator (37200131B) , and added the oil deflector (36300026), to all models with hydraulic clutches - so I guess that is their "fix".

[Pete_Vit]

I wonder if that part combo has been tested on any 17's or 18's - or is the MoCo just gonna 'see' if it works 

[CarlosGGodfrog]

Seeing what the fix is, It is too bad a 1/16 -> 1/8 shim + gasket sandwiched in the side plate with a corresponding longer push rod would not work. Basically just shim out the side cover so the slave piston housing is not close to the end bell of the transmission.

[98fxstc]

Seeing what the fix is, It is too bad a 1/16 -> 1/8 shim + gasket sandwiched in the side plate with a corresponding longer push rod would not work. Basically just shim out the side cover so the slave piston housing is not close to the end bell of the transmission.

You are confusing the 'fix' with a possible remedy from the MoCo

[CarlosGGodfrog]

call it what you will, maybe instead of 'Seeing what the fix is' I should have said 'a fix could be ->'

[Bigtwin]

Seeing what the fix is, It is too bad a 1/16 -> 1/8 shim + gasket sandwiched in the side plate with a corresponding longer push rod would not work. Basically just shim out the side cover so the slave piston housing is not close to the end bell of the transmission.

a reverse gear can do that no?

[Rockout Rocker Products]

As I recall the reason for the slave cylinder change from TC to M8 was for longer throw... less KLANK into first.

Wonder if they're back to making klankers?

I tried to buy a M8 cylinder for my '15 Limited when the M8 first came out, no one would sell me one.... "dealer item only". I'm guessing the new cylinders will be the same.

[$tonecold]

I have bought an M8 actuator, no problem. I have another one on its way. I don't know why they wouldn't sell you one unless you told them what you were going to do with it. The '15 master cylinder and the M8 actuator don't work well together. I actually put it on my '15 RGS and the pull was pretty tough. I had to switch to the M8 master cylinder and hydraulic line. The '15 hydraulic line has a different fitting on the actuator end. Had to change it when I changed the actuator. It was a pretty expensive swap, not sure it was worth it.