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Discussion Starter · #1 ·
Yeah, so I've got a 1970 T100R that I am rebuilding the transmission - as of right now. I've got an entire list of all the parts I need, but a friend suggested I look for a full transmission. I found one on eBay and it seemed like it might work. The description was vague:

TRIUMPH 500 T1500 UNIT TRANSMISSION ASSEMBLY GOOD GEARS AND SHAFTS. THE KICK START SPLINES ARE GOOD. JUST THE NORMAL WEAR. OFF A 1963 T100. 12G

I did ask the guy if "T1500" was a typo and he said it was. He meant T100.

I was sort of under the impression that not much had changed in the unit 500 transmissions around this time, but now reading my book, it seems much has changed. I'm just wondering if I can use this transmission - and yes, I "won" the auction and just received it.

For instance, the mainshaft high gear that came off my bike has 22 teeth whereas the transmission I received has 26 teeth. Looking at the Gearbox internal ratios for the various years, I noticed this entry which I don't really understand:



It seems I have the #7 transmission, but I don't really understand what the various columns mean. Obviously I know that Mainshaft 4 must be the high gear cause there's 26 teeth on one and 22 on the other. I just don't know what the other stuff means.

Thanks for any help. I'm still pretty new to all this.
 

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I know that there were changes made to the 500 tranny over the years. I don't know off the top of my head if one that early will work in your engine or not. If you decide to buy all the individual parts, or an NOS gear set (they're available) expect to spend a LOT ... complete gear set, I think is in the $800 range ...

A decent used gear transmission will be a better route. Just remember that most of the T100C models had the 'wide ratio' tranny ( I do miss my wide ratio 1st gear!) and most 'R' models had the 'standard ratio'.

When you do it, go ahead and do all the bearings / bushings / springs in the inner and outer gearbox ...
 

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Somewhere along the line I think they improved the hardening on the gears too. Don't have the info right in front of me, but if no one comes along with the specifics on that I will try to do a little research on that issue.
 

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one thing that won't fit is the high gear in the trapdoor in the primary . you'll need to replace it with an earlier one pre '68? . the earlier seals on the high gear bush protruding from the gear , the later on the much larger diam of the gear itself .
 

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Somewhere along the line I think they improved the hardening on the gears too. Don't have the info right in front of me, but if no one comes along with the specifics on that I will try to do a little research on that issue.
Right ... and they started cutting the gear teeth deeper and at a slightly 'better' angle ...

And I had totally forgotten about the 'small hole' vs 'big hole' sprocket door issue with the early gear sets.

I'd say find a '68 or later gear box ... with the 500 parts, the later they are, the better ... as a rule.
 

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Hmm... I wonder which one is in my 63 T100SS. The transmission in there needs attention and I have a 65 bottom end with one that shifts perfectly though all gears. I was hoping i could just swap them out
 

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Discussion Starter · #7 ·
Well thanks for all the help on this. I guess I will just try to re-ebay it and get the exact parts I know I need, which was my original plan. Thanks all.
 
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