WLA speedo drive

I have researched the website in regards speedo drive repair, and I have one more question with regards to the drive that pushes into the brake plate, and retained by the horeshoe clip.
My scew gear is nylon, and some of the teeth are broken off, although it still operates OK. I want to fit a new fibre gear, whilst doing other maintenance to the wheel.
The drum and brake plate are original, as is the drive spindle. The shaft in my drive spindle has about a 1/4 inch end float. There is no shims fitted.
Can I machine up a packing washer to fit up underneath the squared end of the shaft, that way I can keep the shaft in one position, and also make sure the male squared end of the speedo drive cable fits down far enough into the spindle shaft. Is there any special precautions when fitting a repop fibre gear.
I built my bike from second hand parts, and the speedo has worked for more than 2000 miles, and still does, but the needle has always started to sway about, anything over 50 MPH. Not sure why this is?
Any advise out there would be be greatly appreciated.
Thanks Keith

Lots of views, but no-one wants to offer any help.
On the brake plate, the measurment between the horseshoe bracket platform, and the "guessed" central area of the hub drive gear , is approximatley 70mm.
My nylon gear was located about 75 mm in from the horeshoe platform, and it operatedf OK. I there any comment on this???
Keith

Well this is my first view, and despite your whining I will offer the following.
The shaft is held in place by a pressed on sleeve. the end play can easily be adjusted by moving the sleeve to where you want it. The end play should be minimal. And the gear pressed on the drum needs to be fully seated as well.
Needle hop can be caused by various issues. Excessive slop in the cable, allowing it to whip. Wear in the speedo shaft bearings allowing the cup and magnet to come into contact with each other. Basic lubrication issues. Etc...

I don't know much on this subject, but I will offer what I do know...In my opinion, the needle whipping back and forth is most likely caused by the cable binding somewhere or a speedo issue. I don't think that end play at the gear would cause that. If the end play were sufficient to cause trouble, it would likely fail to engage the inner cable and would be evident at all speeds, and would be obvious by examining the end of the cable. Another thing to think about, the rotation of the wheel should always be pushing forward on the gear. While we don't like to see excessive slop in our parts, I would think that shimming behind the gear would result in a higher possibility of the drive not engaging the inner cable. When I built my 45, I got a repro speedo of unknown origen at a swap meet and purchased a speedo drive by a very well known repro source. After about 1500 miles, the nylon gear bit the dirt, and the speedo hasn't worked in 30 yrs. I'm not impressed with the nylon gear. Just my 2 cents worth.....ARC

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I wasn't really having a whine, just a bit of a tear. I'm OK now. I've come good.
Yes!! the rotation of the wheel tends to push the speedo drive forward, and the pushed on sleeve/spacer next to the driven gear, regulates the amount of endfloat in the assembly. I can see that now. My hub gear is pressed on the same as in your picture with a slight protrusion. I have another hub, that I am restoring, and its gear appears to be cast with the hub, not a separate peice. Anyway, Whilst I have the wheel out, I would like to apply some type of non drying putty or similar to the hub gear section, assemble the hub and the brake plate, then slide in the speedo drive, to determine the location on the hub gear where it drives the speedo gear. I think my speedo drive assembly sits too far in, although, as I said, it has always worked OK. (if it aint broke??)
Interesting comments regarding why speedo needle waves around over 50 miles per hour. I'll have to investigate lubrication issues, wear in the speedo bearings, cable whip ect. My cable does slop around a bit inside its casing. The cable inner, does spin quite fast. Its geared up 8:20 ratio with the wheel I think. I grease my cables with common high temp, water resitant bearing grease?????
I have my speedo's restored outside, so I have never had one apart myself. I think these stuart warner's have a crimped on outer rim, preventing people like myself accessing the internals, and playing around with what I don't understand. Unfortunately, I'll just have to pull the speedo out, and have a look. May-be sent it away again, to more knowledgable people.
On my new 45 flathead resto, the restored speedo odometer has registered 84 miles, and the trip has registered only 73 miles. Not sure whats going on there either.I definately want to know when 500 miles is up, for its due oil change ect.
Thanks for all your comments, it has been very helpful
Keith