Here's a BMW Technical Service Bulletin:
Service Information - Bulletin Number 23 01 99
SUBJECT: Manual Transmission Difficult to Shift - Diagnostic Tips
MODEL: All with Manual Transmission
SITUATION: Transmission may be difficult to shift especially first gear
engagement and/or gear shift linkage is binding. Note: Field observations
have indicated that a transmission which is difficult to shift (especially
into first gear) is primarily a clutch related problem and only in isolated
cases a failure in the transmission itself.
PROCEDURE:
Verify the customer complaint:
Note: Engage the parking brake and assure that no people or objects are in
the vehicle's path.
- - Run the engine at idle speed
- - Press the clutch pedal to the floor
- - From the neutral stick shift position engage first gear
If first gear is difficult to engage, hold the stick shift at the
resistance point (approximately half of the total stick shift travel) with
constant force.
Then switch the ignition off with the other hand.
DIAGNOSIS 1:
If first gear now engages completely, i.e. the stick shift moves to the end
position without any additional pressure applied, there is a problem in the
clutch system.
Explanation:
Because the clutch does not uncouple completely, a residual torque is
transmitted to the transmission input shaft when the engine is running.
This inhibits the release and meshing of the sliding sleeve, in the
transmission, at the end of the synchronization process. Turning the
engine off relieves the input shaft of this torque thus simulating a
completely uncoupled clutch.
DIAGNOSIS 2:
If the stick shift remains at the resistance point, there is a problem in
the external gear shift linkage or in the transmission.
CAUSE:
DIAGNOSIS 1:
Possible causes for a clutch problem as per Diagnosis 1 above are:
- - Input shaft taper splines not lubricated properly/grease dried out.
- - Clutch disc difficult to move on transmission input shaft.
- - Clutch disc wobble.
- - Air in the hydraulic system of clutch mechanism.
- - Release bearing defective or difficult to move on the guide sleeve.
- - Clutch disc or pressure plate broken/worn out.
DIAGNOSIS 2:
Possible causes for gear shift linkage binding and/or internal transmission
problems as per Diagnosis 2 above:
- - External gearshift linkage binding (shift rod joints stiff).
- - Stick shift bellows boot incorrectly installed (positioned too high or
too low on the stick shift lever).
- - Sound deadening between the outer gear shift linkage and the body
incorrectly installed and/or distorted.
Possible causes inside of the transmission:
- - Faulty synchronization.
- - Internal gear shift linkage binding.
- - Water in the transmission fluid. (rare) |