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View Full Version : Main shaft thrust washers - placement



AdminGuy
06-09-2006, 04:57 AM
I learned this evening that the main shaft on a sport scout 640 trans. Does need a thrust washer on each side of the slider portion. Military manu ref; 47-3, 2(f), and 47-4, 6(a). If thrust washers are used only on the right side this will not allow the main shaft to stand proud of the threaded portion of the driver gear. Which would cause the kicker to ratchet (ie. drag). *nasty noise.... and your end float inside of 0.010 and the cluster gear also. All happy and nicety-nice now. A modern lip seal on right side should hopefully thwart oil company profits. Avail from 48 up? Wish I had known. Custom made one. Darn.... sealed bearing installed now. Poped inner seal off and am using a magnetic drain plug.

Should be a sweet treat to ride with new trans gears. I'm getting gitty. Going to try a 20T front sprocket for hwy work. Stock is 18T. Will loosen up that foot clutch pedal drag for more accurate feel. Thanks Tom.

My SKF double race hemispherical bearing (left side) seems to be holding up well. This bearing allows for inner primary cover misalignment. ahhh... of my little 85mph tractor. I'm certain factory would've spec'd one if it were around.

Blah, blah, blah... So this leaves me wondering is a chief set up with thrust washers only on the right hand side? Anyone know off-hand. I'm being lazy here.

gerry
06-09-2006, 09:33 AM
Yes, that's my understanding. The thrust washer is on the right side of the main shaft.

AdminGuy
06-09-2006, 11:23 AM
Thanks Gerry.

AdminGuy
06-11-2006, 11:45 PM
Obviously I'm confused. Got it straight now. The main shaft needs a thrust washer on each end of the slider splines. This stops things from coming in contact with the splines. The total thickness of the thrust washers determines the end float. Chief and Scout and what ever else probably.

The triple cluster gear needs to be shimed on the right side only. Well the one I'm using from Kiwi does as it utilises the modern thick heavy caged needle bearings. The gear is custom made to accept these internal rollers. The old triple had bronze bushings. Which wear on the big end (1st gear) over time. Not a big deal -but I'm up to trying anything new on this old girl. Internal magnets are a must for this crash box. The small end or right side bushing is inserted and purposely left sticking out to adjust for end float of the gear. inside of 0.010

My modern Kiwi triple gear:
I was able to shim the sport scout triple cluster (right side) *read closed box with no access to right side. I can just get my hand in the thing. I pity guys with fat hands doing this job. Using Kiwi heavy needle roller triple. Oh well, I used a piece of card board the thickness of the shim washers. Washers pressed into a hole in it. Then cut to sit in postion against the back wall of box. Could just move it around a bit with a long drift. Pulling the gear towards me, trap against left bushing, to allow a little space behind it to slide around shim. A small pre-cut allowed me to remove cardboard easily after everything was together with long needle nose plyers. Took about a half-hour. Not that difficult. Slow and methodical wins every time. Well, that's just one phase. Give yourself a full weekend to do this job properly.

Anyone else got a trick for doing this? or anything else?

I must have put that box together 6 or 7 times. Could do it in my sleep now.
It doesn't take alot of pressure to shear teeth on these gears. So in the future I'll be certain to take it easy on missed shifts, and gentil dropping it into 1st gear with low rpm. I think I'm going to check that my linkage rods are correct length and are in fact getting full engagement with the detent indicator while the box is open. I think scouts can get hung up. Just the nature of the design. The y-yoke was hitting the underside of gas tank or something. I gotta check all that. Maybe I'll make a jockey shifter?

I may have just written an article for Steve Blancards "Blood, Sweat and Gears" column. Should I send it to him? hummm...This is really basic stuff......