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I've got this Track Master Excalibur direct drive transmission that I want to install in my goldpan sprint car but I'm having some trouble figuring out the proper bearing size. I have the original manual, but it doesn't list bearing size---just referrs to them as part #8106. They are obviously a flange bearing, and after measuring as best I could, I guessed them at 5mm x 9mm x 3mm. I took a trip down to my LHS and started going through all the bearings. Nothing fits! 5mm is pretty close for the i.d. Not as tight as I would like it, but workable. The o.d. is a mystery. Nothing in standard sizes fit and the only thing I can figure at the moment is to use 5mm x 10mm and drill the transmission side plates to accomodate the larger bearing. This would not be difficult at all, but the idea of drilling on a vintage transmission is sort of leaving a bad taste in my mouth. I'm hoping one of you guys has an idea what bearing is the correct one to use here.

If 5mm is too loose on the shaft, and the 9mm is also too loose, it's very likely a 3/8" x 3/16" flanged bearing.

I agree that's what would have made the most sense, especially since the trans is made in the USA in the '90s, but I tried that size and it was definitely the wrong size. 3/16 will not fit on shaft. I couldn't come up with a size between 3/16 and 5mm. 5mm isn't overly sloppy, just not as snug as it could be. At this point I'm looking for someone who has some knowledge/experience with these trans who might know the correct bearings, otherwise I guess I'll have to modify it to work.

I think your problem is that isn't a Trackmaster X-Calibur diff.

I don't remember the OD of the bearings but the ID should be 1/4".

Wow Phin, I think you're right. I have a big baggy of parts that came in a collection I picked up that included a couple trackmaster excaliburs, a couple diffs, and a bunch of spare parts along with a rather large pile of csc telescopic axles for using the TM trans in an RC10. The first TM was installed in a circle track car that I sold and I just started to assemble the second one when this bearing problem arose. After reading your post, I dumped out the baggy and separated all the diff parts and it appears that there is another type of diff in here. Both could easily match the blurry pics on the black and white copy of the excalibur manual, but the other one I found, I believe takes a 1/4" bearing. I've got a fresh cup of coffee here and I'm going to get this sorted out.

Phin---you are THE MAN! I never would have noticed the difference if you did not point this out. The difference between the two diffs is very slight but the main one being the size of the outdrive shafts. Once I assembled the correct diff, I was able to use a standard 1/4" x 3/8" flanged bearing. Success! Now I'm left guessing what the other diff goes to, but the main problem is fixed and now my sprint car can have the trans I wanted for it, Thanks!