Overdrive 5th (MikesXS) on 1975 Transmission w/ newer insides

[dubhaus]

MikeXS clearly states that his 5th gear overdrive "XS650's 1978 - 1984 Only! Note: Yamaha changed the shape of transmission gear teeth from 78 on and this is indicated by lines cut into the crest of each
tooth."

My question is: can I swap out the transmission from a later model and get the OD 5th in my '75?

 

[Punkskalar]

Yep, I do it all the time...

 

[AceofSpades]

Yep, I do it all the time...

details? I have a CLYMER, an 80 parts bike and a 75 that I ride... needs longer legs

 

[Punkskalar]

Split the cases, remove old transmission, drop in later transmission with the 5th gear swapped over. Simple as cake...

 

[DLD1]

Split the cases, remove old transmission, drop in later transmission with the 5th gear swapped over. Simple as cake...

Sorry to hijack the thread, but Punkskalar seems to have experience on this subject.

I have a question for you. How is it that a single gear can be changed in this gearbox, without a matching gear? If the pitch matches, and there are a different number of teeth, the diameter should be different. Are the teeth a different thickness than the original?

DLD1

 

[Punkskalar]

Sorry to hijack the thread, but Punkskalar seems to have experience on this subject.

I have a question for you. How is it that a single gear can be changed in this gearbox, without a matching gear? If the pitch matches, and there are a different number of teeth, the diameter should be different. Are the teeth a different thickness than the original?

DLD1

Joe Dirt Voice - "How does a limited slip differential work, no one knows, it just does"

Seriously, I haven't even looked at it that close. I would assume that one has thicker teeth than the other, as the diameter does not change. Lots of room for error with straight cut gears when cutting teeth, I know that from machining them.

 

[XSLeo]

I think the teeth are cut shorter than the stock teeth. The shorter teeth allow room for one more.
From what research I have done on the gear change on the later tranny's, the teeth didn't change.
What changed was the way the gear rides on the splines of the shaft.
In the older the splines of the gear rode in the bottom of the grooves on the shaft. On the later models the splines on the shaft rode in the bottom of the grooves of the gear.
Yamaha says the parts will not interchange. That maybe true when the parts are new. I have heard of people mixing the parts without a problem.
Mike's new gear may work on and older model. As easy as it is to get trannies, I would just get the 78 up tranny to put the new gear on and install that in the older cases.

 

[tadd442]

Joe Dirt Voice - "How does a limited slip differential work, no one knows, it just does"

So, your into dudes, that's cool...

 

[C-Los SD]

My bike is a 77, but the engine is a 79 based on the 2F0-157753 stamp. Can some one verify that this is a 78 and later tranny from the picture below? I would like to do the 5th gear overdrive. Thanks

 

[tadd442]

My bike is a 77, but the engine is a 79 based on the 2F0-157753 stamp. Can some one verify that this is a 78 and later tranny from the picture below? I would like to do the 5th gear overdrive. Thanks

I am interested as well....this visual helps alot. Hopefully I'll have a better idea of whats up when I tear into it.

 

[XSLeo]

Yes your transmission is a 78 and up. If you look at the gears the top shaft in the pic starting from the left the gears are 1st, 4th, 3rd, 5th, 2nd. The lower shaft from the left are The first small gear is part of the main shaft, the rest are 4th, 3rd, 5th, 2nd.
If you look at the 4th, 3rd, and 5th gears you will see two lines on the teeth. These are the lines mentioned by Mike's when he tells about how to identify the trannys.
Yes, Mike's 5th gear should fit your tranny.

 

[rdvance]

I just replace the 5th gear in my tranny, Just to be positive i should replace the second gear from the right on the lower stack in the pic?