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Author Topic: WTB: 3rd & 6th Gears Countershaft  (Read 204 times)

Offline havinnoj

WTB: 3rd & 6th Gears Countershaft
« on: March 14, 2020, 05:43:14 PM »
Looking for great condition only 3rd & 6th countershaft gears 88-89.  Anybody got em?

Offline jwraymond6

Re: WTB: 3rd & 6th Gears Countershaft
« Reply #1 on: March 15, 2020, 04:21:52 PM »
I have complete tranny that seem to be nice not sure of the year though
87 363 sphynx built by Pete @ hybrid engineering

Offline havinnoj

Re: WTB: 3rd & 6th Gears Countershaft
« Reply #2 on: March 15, 2020, 06:03:16 PM »
I have complete tranny that seem to be nice not sure of the year though

Thanks Jeremy, I'll message you.  In the meantime, anyone have just those gears?

Offline atvcrazy

Re: WTB: 3rd & 6th Gears Countershaft
« Reply #3 on: March 16, 2020, 09:16:08 AM »
What year of transmission?  Third should be the same in al of them but 6th I'm not sure of.  I have a ton of gears I can look and see what I have

Offline havinnoj

Re: WTB: 3rd & 6th Gears Countershaft
« Reply #4 on: March 16, 2020, 01:57:33 PM »
What year of transmission?  Third should be the same in al of them but 6th I'm not sure of.  I have a ton of gears I can look and see what I have

I'd like later years with the design change.  Note that the # of countershaft teeth are the same for 3rd & 6th across the years.  But the mainshaft # of teeth went from 26 teeth to 25 teeth starting in 1987 and stayed 26 after that.

Offline Jerry Hall

Re: WTB: 3rd & 6th Gears Countershaft
« Reply #5 on: March 16, 2020, 08:40:58 PM »
When a gear ratio change is made on two meshing gears the pitch diameter is changed.  This requires both meshing gears to be changed even though one gear may have the same tooth count. 

The pitch diameter of the 23 tooth gears  should be different on the countershaft gears when the tooth count of the mating gear on the main shaft is changed for a properly designed set of gears.

I think you will find the following if you measure the outside diameter of all of the 6th gears:


The 26 tooth gear from the 1985/1986 6th gear on the main shaft will have a slightly larger diameter than the 25 tooth 6th gear on the 1987/1989 mainshaft gear.

The 23 tooth gear from the 1985/1986 6th gear on the countershaft shaft will have a slightly smaller diameter than the 25 tooth 6th gear on the 1987/1989 countershaft gear.

The transmission would probably go into the cases if you used the 1085/1986 23 tooth on the countershaft and the 1987/1989 25 tooth gear on the main shaft, but would have excessive backlash.

The transmission might not go into the cases if you used the 1085/1986 26 tooth on the mainshaft and the 1987/1989 23 tooth gear on the countershaft, because the combination of the pitch diameters will push the two shafts too far apart to fit into the case bearings.



« Last Edit: March 16, 2020, 08:43:36 PM by Jerry Hall »

Offline Jerry Hall

Re: WTB: 3rd & 6th Gears Countershaft
« Reply #6 on: March 16, 2020, 08:48:17 PM »
What year of transmission?  Third should be the same in al of them but 6th I'm not sure of.  I have a ton of gears I can look and see what I have

I'd like later years with the design change.  Note that the # of countershaft teeth are the same for 3rd & 6th across the years.  But the mainshaft # of teeth went from 26 teeth to 25 teeth starting in 1987 and stayed 26 after that.

If I remember correctly 1st through 4th gear ratios were the same in all years, but the ratios for 5th and 6th were different on the later model transmissions. 

Offline havinnoj

Re: WTB: 3rd & 6th Gears Countershaft
« Reply #7 on: March 17, 2020, 01:41:53 AM »
Thanks Jerry. That's great info to have!

If I remember correctly 1st through 4th gear ratios were the same in all years, but the ratios for 5th and 6th were different on the later model transmissions. 

The gear ratio calculator is here: http://trx250r.org/GearRatioCalculator.html and yes ratios change on 5th & 6th from 86 to 87-89 however 6th countershaft is SAME # teeth for all years even though the design is different.


Offline atvcrazy

Re: WTB: 3rd & 6th Gears Countershaft
« Reply #8 on: March 17, 2020, 09:13:52 AM »
Okay give me a day or two and I will look through everything i have i know i have something for you. I have some stuff I am getting ready to sell as well 86 and 89 complete bikes and a few parts

Offline havinnoj

Re: WTB: 3rd & 6th Gears Countershaft
« Reply #9 on: March 17, 2020, 01:28:15 PM »
Okay give me a day or two and I will look through everything i have i know i have something for you. I have some stuff I am getting ready to sell as well 86 and 89 complete bikes and a few parts

Awesome thank you!

Offline Jerry Hall

Re: WTB: 3rd & 6th Gears Countershaft
« Reply #10 on: March 17, 2020, 02:31:21 PM »
Thanks Jerry. That's great info to have!

If I remember correctly 1st through 4th gear ratios were the same in all years, but the ratios for 5th and 6th were different on the later model transmissions. 

The gear ratio calculator is here: http://trx250r.org/GearRatioCalculator.html and yes ratios change on 5th & 6th from 86 to 87-89 however 6th countershaft is SAME # teeth for all years even though the design is different.



I did not know if you were aware that there was more than a part number change between the different years of the 23 tooth gear but an actual dimension change.

I wanted you to avoid incompatible gear meshes if you were only changing the main shaft gear.

 

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