Posted 09 February 2010 - 10:42 AM
Yes, old grease will make a big difference. As will old wiper blades and worn motor brushes. Do you have a fishing scale? With the blades off the screen and the motor disconnected from the rack try to pull the rack gently out of the housing with the scale. It's meant to be under 7lbs of pull, that's what the motor can cope with.
You are supposed to use something called Ragosine Listate Grease, but nobody in the entire world knows what that is. (seriously, if you Google it you will mainly get responses from this very forum and from Land Rover forums with people asking what on Earth it is). Ragosine oil don't exist any more AFAIK. You can use LM grease, I wouldn't use Vaseline. Use a little light oil on the gear shaft bushes too (not the motor shaft).
Other things that make a difference are the pre-load on the motor spindle and the cone washer under the drive gear. The pre-load can be adjusted, it will change over time so bringing it back to what it should be is a good thing. When you have it apart, inspect the cone washer. Often they are rusted and crumbling at one edge. This cone is a spring that supports the gear, if it's in bad condition it adds drag to the gear and also allows the gear to slop around. New ones are available, make sure it's fitted with the narrow end down towards the housing and is lightly greased. Once you've got the gearbox clean and regreased but the motor still out of the car, slacken off the screw on the end of the gearbox casing that faces the motor spindle. Hold the motor upright with the gearbox at the top and turn the screw in until you can just feel resistance, then slacken it off 1/4 of a turn. That sets the pre-load to what it should be, if there is too large a gap here then a lot of the motor action becomes lost motion with the motor shaft jumping in and out of the motor as the gear turns and the load on it changes.
They don't have to be slow, the same motor and system was used on many cars but people think that because it's a Mini it's different. When they were new they worked just fine, the problem is most Minis are poorly maintained.
