Friday, December 16, 2016


One thing about having this race car is I am delving into areas I've never ventured before. Case in point, gearbox rebuild. Never really needed this on my street Spitfire, I simply swapped out the gearbox or diff for another. Not sure what compelled me to tackle it but I am very glad I did.

Early on, I broke the tailshaft on the Toledo gearbox that was in the race car when I bought it. I was given I donor 3 sync gearbox and promptly tore it down. This gave me a bit of insight into the workings of a gearbox. That and a bunch of U-TUBE videos. After the motor blew, I had the gearbox out and noticed a bit of wobble in the input shaft so I decided to tear it down. My hunch was correct, the front bearing was bad so I ordered a rebuild kit from RIMMER BROTHERS.

The problem for me is the Toledo box is not the same as a four sync Spitfire three rail gearbox. Or let me put it this way, the Toledo "DG" gearbox case I have and the gears in it are not the same. I am still trying to figure out this box. The input shaft has 19 teeth and the syncro rings are smaller that the Spitfire "FK" boxes I have. The Spitfire FK boxes have 16 teeth and the syncro rings are larger. Also, the caged needle bearing in the DG box is bigger as is the mainsheet tip. It is .62" versus .50 for the FK box.

Most of the input shafts I have, the gear is quite worn. The tip on the mainsheet of the Toledo box is damaged. One of the FK mainsheet tips is very worn and one is pitted, another has a chip out of it. I was hoping to pick the best of them bunch to rebuild one solid gearbox. All this has been a frustrating trying to find commonality among these gearboxes I have, it seems there is always one piece of the puzzle wrong.

I will say after tearing down five gearboxes, they don't seem to be the mess of spagehtti they looked like to me at first. I now recognize the parts, what they do and which order they are in.  The rebuild of one of the FK boxes when very smooth.

 A couple tips, get some 1/2" or so ALL THREAD rod and put a nut and large washer on one end, as you remove the gears and such, put them on the rod to keep them in proper order and facing the correct way. Them place another washer and nut on the other end to keep them in place till rebuild time.

Another tip is to put the syncro units in a plastic baggie when removing the springs and ball bearings. This will keep them from flying all over the workshop. Also, thick grease is you friend during the rebuild. It will keep parts like the split thrust washer in place as well as the needle bearings in the layshaft. It also held the springs and ball bearings in place when putting the syncro unit back together.

And finally, put some string in the case then, set in the laygear. This will help to lift it in place to insert the layshaft after the mainshaftand gears have been installed.

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