Transmission Rebuild Help


13 replies to this topic
  • tpars121

Posted May 30, 2014 - 11:48 AM

#1

I broke the lugs of the 5th wheel gear, I ordered a new oem gear and it wont slide up and mesh with the 3rd wheel gear as well as the old one did. It seems like the inner teeth of the gear arent cut as deep. It does slide up inside 3rd some but it binds on the shaft. Is this normal???



  • grayracer513

Posted May 30, 2014 - 12:27 PM

#2

Model? Year?



  • tpars121

Posted May 30, 2014 - 12:35 PM

#3

Model? Year?

sorry, 2008 yz450.

 

Also is it possible to get the shift cam in wrong, I am concerned on which way it rotates. The manual doesnt have a clear picture.


Edited by tpars121, May 30, 2014 - 12:38 PM.


  • grayracer513

Posted May 30, 2014 - 02:10 PM

#4

Check the splines on the output shaft to see if there's a "ledge" at the end of the wear marks that the old 5th gear left.  Touch it up carefully with a Dremel if needed.  If it shifts into third and then fourth, it probably doesn't need to move as far as that anyway.

 

The shift cam rotates both directions depending on whether you're up shifting or down shifting.  It can't really be put in place incorrectly because the followers on the shift forks would not fit otherwise; the cam grooves are closed at the ends.  A mistake you can make is to mis-index the "segment" (star-shaped indexing wheel).  There is a 2-3mm pin in the end of the cam that indexes the segment, and every now and then someone will misalign the two and torque it down.  This pushes the pin down flush, after which it's difficult to remove and reinstall so that it will function again.



  • tpars121

Posted May 30, 2014 - 02:34 PM

#5

Check the splines on the output shaft to see if there's a "ledge" at the end of the wear marks that the old 5th gear left.  Touch it up carefully with a Dremel if needed.  If it shifts into third and then fourth, it probably doesn't need to move as far as that anyway.

 

The shift cam rotates both directions depending on whether you're up shifting or down shifting.  It can't really be put in place incorrectly because the followers on the shift forks would not fit otherwise; the cam grooves are closed at the ends.  A mistake you can make is to mis-index the "segment" (star-shaped indexing wheel).  There is a 2-3mm pin in the end of the cam that indexes the segment, and every now and then someone will misalign the two and torque it down.  This pushes the pin down flush, after which it's difficult to remove and reinstall so that it will function again.

Thanks Gray, I checked and it doesnt have a ledge, what is strange is I can slide the old 5th gear on the shaft and it will slide back maybe an 1/8 of an inch further than the new 5th gear. 



  • tpars121

Posted June 01, 2014 - 06:38 AM

#6

I just measure the difference between the old and new 5th gears. The old one slides 2.5mm farther in than the new one.



  • grayracer513

Posted June 02, 2014 - 07:12 AM

#7

Assemble it with a minimum of parts for a test fit and see if it shifts.  If it does, you're OK.  The gear doesn't travel the full distance that it could when in operation.  Remember the sprocket and nut should be spun on to position the output shaft correctly.



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  • tpars121

Posted June 05, 2014 - 02:38 PM

#8

Assemble it with a minimum of parts for a test fit and see if it shifts.  If it does, you're OK.  The gear doesn't travel the full distance that it could when in operation.  Remember the sprocket and nut should be spun on to position the output shaft correctly.

I assembled it partially and it wouldnt shift through 4th and 5th. It was like it would jump from 3rd gear to 5th gear. I took it back apart and the new 5th wheel gear was stuck on the shaft up inside the 3rd wheel gear. Its the issue I had noticed earlier where the new 5th gear (I ordered another one to make sure it wasnt cut wrong) wouldnt slide up inside 3rd gear far enough without binding on the shaft. I did some measuring and it is binding because it is to the point where the grooves on the shaft start to get shallower. I am baffled  :banghead:


Edited by tpars121, June 05, 2014 - 02:40 PM.


  • grayracer513

Posted June 05, 2014 - 04:05 PM

#9

I'm suspicious of the output shaft having been twisted or otherwise damaged in the incident that blew the lugs off the 5th slider.  The shaft and both gears still show as 2S2-(X)-00-00's so none of them has been revised since '06.  Assuming the gear is correctly made, which is an entirely safe assumption, there almost has to be something wrong with the shaft.



  • tpars121

Posted June 05, 2014 - 04:22 PM

#10

I'm suspicious of the output shaft having been twisted or otherwise damaged in the incident that blew the lugs off the 5th slider.  The shaft and both gears still show as 2S2-(X)-00-00's so none of them has been revised since '06.  Assuming the gear is correctly made, which is an entirely safe assumption, there almost has to be something wrong with the shaft.

I think you must be right, the old 5th gear and shaft must be twisted the same for them to still fit. I have bought two new 5th gears and neither will fit. 



  • the go-devil

Posted June 17, 2014 - 07:12 PM

#11

I have swapped full WR transmissions into 2 2012 YZ450's in the last year and had the same 5th wheel gear fitment issues both times. This is with all new gears and new main axle and drive shafts. I applied engine assembly lube to the splines and had to forcefully slide the 5th wheel back and forth quite a few times to essentialy lap the splines to allow free movement. Both bikes shift fine. I don't know what the deal is with that 5th gear, none of the others had any issues.

  • grayracer513

Posted June 18, 2014 - 06:21 AM

#12

Interesting.  I had no such difficulties when I swapped in the new 4th and 5th WR gears to my '06.



  • tpars121

Posted June 21, 2014 - 04:53 AM

#13

Interesting.  I had no such difficulties when I swapped in the new 4th and 5th WR gears to my '06.

I finally got my new shaft and 5th gear slid back and forth much better. I have put the cases back together and I'm making sure the transmission will shift thru all the gears but it doesnt shift as good as I hoped. I have to turn the output shaft quite a bit to get it to shift to the next gear. Does this sound normal?



  • grayracer513

Posted June 21, 2014 - 07:25 PM

#14

Yes.  A gear might have to rotate nearly 120 degrees relative to the one it engages before it can lock.  Since both gears are turning in the same direction at near the same speed, that can take a rotation or two.







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