SBJD trans September 27, 2010 03:55PM
Question 1:

If you change the tooth count combonation for 7th gear in a syncro trans (faster for example), does this increase the speeds for ALL OTHER GEARS?? ( I have been told this is the gear all power travels through in the "high range" regardless of selection)

Question 2:

If question 1 is true, then how do you figure out how much it has sped up the other gears in %??
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Re: SBJD trans September 27, 2010 05:17PM
you can change the tooth count on 7th gear and speed up or slow down the other gears but 7th gear will always stay the same
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Re: SBJD trans September 28, 2010 05:19AM
If you change the tooth count (ratio) on 7th gear, how could it not change the speed for 7th gear??

If it changes for the others, you would think it changes 7th itself. Please explain what you mean, I'm lost.
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Re: SBJD trans September 28, 2010 05:47AM
In a stock SBJD setup the high range gearset & the 3rd speed (4 & 7) range gearset share a common countershaft gear. Techincally it changes a little, but because of that relationship it doesn't change much unless you change the gears a bunch. If you were to put a larger gear on the top shaft, the countershaft gear has to get smaller & the bottom shaft gear has to get larger. Since the top & bottom shaft gears both get larger the ratio change is very small.

To answer your original question, speeding up 7th will speed up all the high range gears (3rd, 5th, & 8th) but would slow down 4th. For example, if you changed the tooth count for 7th gear by 2 teeth 7th would only speed up by 2.5% but 3rd, 5th, & 8th would speed up by 17%. 4th would slow down by about 12%.
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Re: SBJD trans September 28, 2010 12:30PM
These guys are feeding you b. s.

They have me so confused I dont even know where to start explaining this to you.
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Re: SBJD trans September 28, 2010 01:22PM
I wish you would, because I don't understand how changing tooth count can affect things in two entirely different ways inside the same box!!

To me it's either all or none. Please feel free to enlighten me.
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Re: SBJD trans September 28, 2010 03:12PM
on a stock setup 7th gear you have three gears on 3 different shafts. when you add 1 tooth on the input you have to take 1 tooth off the counter shaft and then you have to add 1 tooth back on the pinion shaft. the ratio will be so close to stock it wont make any difference on 7th gear. but you will speed up the counter shaft so your other gears, 3rd 5th and 8th will be faster.
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Re: SBJD trans September 29, 2010 12:10AM
Don't mess with 7th gear. Change 5th gear. You can change 5th gear to like a 7.5 or whatever you want, and it will not affect the other gears
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