Primary Vent Pics
#81
06-19-2019, 08:29 PM
Outstanding HDF Member
In order to "suck" oil from the transmission to the primary, there must be air flow created by a vacuum.
This primary vent fix is a Band-Aid that stops the transmission fluid transfer into the primary, but does not address the root cause issue. There are only two areas in the motor that can create a vacuum. The intake tract between the intake valves and throttle body is under a vacuum, and the crankcase develops a vacuum when the pistons move upward on either the compression stroke or exhaust stroke. The 45 degree offset crank increases this vacuum in the crankcase because of 2 large pistons moving upward at the same time.
The primary has NO connection to the intake tract, so that is not causing a vacuum in the primary.
The crankcase is connected to the primary. There is a seal between the crankshaft (crankcase) and the primary. If you go back and review the first Technical Service Bulletin on this issue, the 2014 - 2016 bikes that had this issue were being fixed by replacing the crank seal. Some seals were installed incorrectly from the factory or were "bad". The "vacuum" in the primary is being caused by a leak in the seal between the crankcase and primary, which then generates an air flow path that sucks the transmission fluid across the hollow transmission shaft and into the primary. Replacing the crankcase seal on the 2017 and 2018's did not stop the transfer issue, so there is a design issue with that seal.
The heating and cooling of the primary and transmission cavities have nothing to do with the transfer. There cannot be enough air flow during a cooling cycle to "suck" fluid across, plus there are cases where bikes were on the dynamometer and emptied the transmission in 5 dyno runs, no heating or cooling.
There is nothing in the primary that can cause a vacuum by itself. There must be air flow in order to cause a fluid transfer, which means there has to be an air intake path (transmission vent) and an air outlet path (through the crank seal and into the crankcase) in the primary.
By adding the vent tube to the primary, the air flow into the primary now goes through the vent tube and not through the hollow transmission shaft, thereby eliminating "sucking" the transmission fluid across and into the primary. Air flow follows the path of least resistance, so it flows through the new primary vent tube.
If this crankcase to primary seal is leaking and allowing air flow right now, at what point will it leak bad enough that you will start to transfer primary fluid into the crankcase?
Harley Davidson is betting it will be past your warranty time, and you will have to fix that one on your own dollars.
This primary vent fix is a Band-Aid that stops the transmission fluid transfer into the primary, but does not address the root cause issue. There are only two areas in the motor that can create a vacuum. The intake tract between the intake valves and throttle body is under a vacuum, and the crankcase develops a vacuum when the pistons move upward on either the compression stroke or exhaust stroke. The 45 degree offset crank increases this vacuum in the crankcase because of 2 large pistons moving upward at the same time.
The primary has NO connection to the intake tract, so that is not causing a vacuum in the primary.
The crankcase is connected to the primary. There is a seal between the crankshaft (crankcase) and the primary. If you go back and review the first Technical Service Bulletin on this issue, the 2014 - 2016 bikes that had this issue were being fixed by replacing the crank seal. Some seals were installed incorrectly from the factory or were "bad". The "vacuum" in the primary is being caused by a leak in the seal between the crankcase and primary, which then generates an air flow path that sucks the transmission fluid across the hollow transmission shaft and into the primary. Replacing the crankcase seal on the 2017 and 2018's did not stop the transfer issue, so there is a design issue with that seal.
The heating and cooling of the primary and transmission cavities have nothing to do with the transfer. There cannot be enough air flow during a cooling cycle to "suck" fluid across, plus there are cases where bikes were on the dynamometer and emptied the transmission in 5 dyno runs, no heating or cooling.
There is nothing in the primary that can cause a vacuum by itself. There must be air flow in order to cause a fluid transfer, which means there has to be an air intake path (transmission vent) and an air outlet path (through the crank seal and into the crankcase) in the primary.
By adding the vent tube to the primary, the air flow into the primary now goes through the vent tube and not through the hollow transmission shaft, thereby eliminating "sucking" the transmission fluid across and into the primary. Air flow follows the path of least resistance, so it flows through the new primary vent tube.
If this crankcase to primary seal is leaking and allowing air flow right now, at what point will it leak bad enough that you will start to transfer primary fluid into the crankcase?
Harley Davidson is betting it will be past your warranty time, and you will have to fix that one on your own dollars.
#82
06-20-2019, 08:27 AM
Grand HDF Member
In order to "suck" oil from the transmission to the primary, there must be air flow created by a vacuum.
This primary vent fix is a Band-Aid that stops the transmission fluid transfer into the primary, but does not address the root cause issue. There are only two areas in the motor that can create a vacuum. The intake tract between the intake valves and throttle body is under a vacuum, and the crankcase develops a vacuum when the pistons move upward on either the compression stroke or exhaust stroke. The 45 degree offset crank increases this vacuum in the crankcase because of 2 large pistons moving upward at the same time.
The primary has NO connection to the intake tract, so that is not causing a vacuum in the primary.
The crankcase is connected to the primary. There is a seal between the crankshaft (crankcase) and the primary. If you go back and review the first Technical Service Bulletin on this issue, the 2014 - 2016 bikes that had this issue were being fixed by replacing the crank seal. Some seals were installed incorrectly from the factory or were "bad". The "vacuum" in the primary is being caused by a leak in the seal between the crankcase and primary, which then generates an air flow path that sucks the transmission fluid across the hollow transmission shaft and into the primary. Replacing the crankcase seal on the 2017 and 2018's did not stop the transfer issue, so there is a design issue with that seal.
The heating and cooling of the primary and transmission cavities have nothing to do with the transfer. There cannot be enough air flow during a cooling cycle to "suck" fluid across, plus there are cases where bikes were on the dynamometer and emptied the transmission in 5 dyno runs, no heating or cooling.
There is nothing in the primary that can cause a vacuum by itself. There must be air flow in order to cause a fluid transfer, which means there has to be an air intake path (transmission vent) and an air outlet path (through the crank seal and into the crankcase) in the primary.
By adding the vent tube to the primary, the air flow into the primary now goes through the vent tube and not through the hollow transmission shaft, thereby eliminating "sucking" the transmission fluid across and into the primary. Air flow follows the path of least resistance, so it flows through the new primary vent tube.
If this crankcase to primary seal is leaking and allowing air flow right now, at what point will it leak bad enough that you will start to transfer primary fluid into the crankcase?
Harley Davidson is betting it will be past your warranty time, and you will have to fix that one on your own dollars.
This primary vent fix is a Band-Aid that stops the transmission fluid transfer into the primary, but does not address the root cause issue. There are only two areas in the motor that can create a vacuum. The intake tract between the intake valves and throttle body is under a vacuum, and the crankcase develops a vacuum when the pistons move upward on either the compression stroke or exhaust stroke. The 45 degree offset crank increases this vacuum in the crankcase because of 2 large pistons moving upward at the same time.
The primary has NO connection to the intake tract, so that is not causing a vacuum in the primary.
The crankcase is connected to the primary. There is a seal between the crankshaft (crankcase) and the primary. If you go back and review the first Technical Service Bulletin on this issue, the 2014 - 2016 bikes that had this issue were being fixed by replacing the crank seal. Some seals were installed incorrectly from the factory or were "bad". The "vacuum" in the primary is being caused by a leak in the seal between the crankcase and primary, which then generates an air flow path that sucks the transmission fluid across the hollow transmission shaft and into the primary. Replacing the crankcase seal on the 2017 and 2018's did not stop the transfer issue, so there is a design issue with that seal.
The heating and cooling of the primary and transmission cavities have nothing to do with the transfer. There cannot be enough air flow during a cooling cycle to "suck" fluid across, plus there are cases where bikes were on the dynamometer and emptied the transmission in 5 dyno runs, no heating or cooling.
There is nothing in the primary that can cause a vacuum by itself. There must be air flow in order to cause a fluid transfer, which means there has to be an air intake path (transmission vent) and an air outlet path (through the crank seal and into the crankcase) in the primary.
By adding the vent tube to the primary, the air flow into the primary now goes through the vent tube and not through the hollow transmission shaft, thereby eliminating "sucking" the transmission fluid across and into the primary. Air flow follows the path of least resistance, so it flows through the new primary vent tube.
If this crankcase to primary seal is leaking and allowing air flow right now, at what point will it leak bad enough that you will start to transfer primary fluid into the crankcase?
Harley Davidson is betting it will be past your warranty time, and you will have to fix that one on your own dollars.
Last edited by sixguns; 06-20-2019 at 10:15 AM.
The following users liked this post:
saddlebag (11-28-2019)
#83
06-20-2019, 01:24 PM
tbob, I do not understand this comment; "start mixing fluids and you have a perfect storm. Your owners manual states you can use the same fluid in all three holes... Look at the "part" number, same stuff all the way through. CSM-H
#84
06-20-2019, 04:24 PM
Outstanding HDF Member
If you run a gear oil in the tranny and have a issue of a bad seal with transfer you may have a issue. I run HD's new gear oil in the tranny ,they say it's primary safe. A Red Line or Belray wouldn't go well in the primary or motor.
#85
06-20-2019, 04:46 PM
Seasoned HDF Member
Everything automotive such as differentials, transmissions and transfer cases are vented, because they heat up building pressure and When the drivetrain assembly cools down the air inside contracts and creates a vacuum.The Harley is no different. The air path is thru the trans main shaft and Trans vent, and trans oil is being pulled with it as the chain case goes thru its heating and cooling cycles. The question is, why the chain case is not properly venting thru the hollow mainshaft and transmission vent?
Once the system is fully heated up it stays there trying to shed heat the entire time it's being used and only cools after being turned off.
There isn't enough cooling in the primary either while its running or after being shutdown to pull a 1/2 a quart of fluid to the primary by vacuum which some report can happen in as little as 50-500 miles (for me it was 6000-10000).
The vacuum has to be from something else (prob engine).
The real question is after all these years of the primary being vented this way (through the trans) is there now suddenly this much of a problem?
Along that note, the primary is now smaller which would require less venting. The only really "new" thing is the engine which leads many to believe...well you know. Engine seal problem.
Last edited by lp; 06-20-2019 at 04:49 PM.
The following users liked this post:
saddlebag (11-28-2019)
#88
06-26-2019, 11:30 AM
Tourer
#89
07-02-2019, 06:01 AM
#90
07-29-2019, 12:24 PM
