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Anybody know off the top of their head what the tranny gear ratio is on an Ultima Pro?

Isn't it the same as the other Ultimas? 3.03?

I believe they are all the same, thanks Rich.

Not sure about that: my ultima pro came with the 0.5 (or is it 0.6?) module spur. I don't know if it's the original one I still have but it i is slightly larger in diameter than the 32 pitch ones and another 0.5 module one I have in my spares case.
A larger diameter indicates a different ratio...

I'm more concerned with the gearbox ratio. (stealth is 2.25:1 for example) I am using a non stock spur gear, the 42p thorp, so I will have to do my own calculating when it comes to choosing a pinion.

Wow, 42 teeth? The stock one is 44. So, you'll have to use a tiny pinion to get a usable ratio. BTW, 3.03 is the ratio of the topshaft/diff including the two smaller gears that are not adjustable.

He won't have to use a tiny pinion if he's running 17.5BL. I had to pick up 28-32 tooth pinions for my Rad2 when I ran it last year with a 17.5. A 27t motor and I would have been running 10 teeth less. The rpm difference is massive, but the torque on those 17.5 motors is awesome.

RichieRich wrote:Wow, 42 teeth? The stock one is 44. So, you'll have to use a tiny pinion to get a usable ratio. BTW, 3.03 is the ratio of the topshaft/diff including the two smaller gears that are not adjustable.

No, 42 pitch. I can't remember the spur tooth count off the top of my head, I'm thinking it was like a 70???

Like Civil said, the 17.5's love to be overgeared, so I think it won't be too much of a headache to get it right.

42 pitch?!?! Whatchu talkin' 'bout Willis? Never heard of 42 pitch before. Who? Where? What?........Why?

0.6mod is 42.3333 pitch. That's probably what it is... Thorp was a USA company so they probably called it 42pitch. Just my guess.

Thanks Jeff.

Yeah, try running a 48 pitch pinion on the older fine tooth Kyoshos and see what happens....

Ok, it all makes sense now.

Did Thorp make 0.6 module spurs for the ultima? Their diff and top gear are 48 pitch thopugh... not?

wasn't the "BK pitch" like a 42 or something like that? or was it in between 48 and 64? i don't remember......

I'm pretty sure BK pitch was between 48 and 64. Good info on the "42" pitch gears, thanks