Example of a worn out transmission

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nuckinfuts

Lifetime Member
Apr 11, 2012
#1
This came from a used 2006 engine I recently acquired. There were a multitude of symptoms including mis-shifts, no engagements, slipping out of gears and ultimately a broken shift drum.

The pictures represent worn dogs which cause problems with slipping out of gears and possible mis shifts from poor engagement.







Bent shift forks which usually cause metal on metal contact indicated by the heat discoloration ring in the second pic:





And someone forgot a clip when previously assembling this which cause the gear in the center of the pic to make contact with the splines on it's mainshaft. Also note the heat ring on the left fork channel:




As a result of constant transmission problems (forcing into gear breaking the drum, twice), the owner swore he'll never buy another trx again but this goes to show that it isn't necessarily the transmission itself but the way it was assembled and ridden.
 

hoser

Active Member
Apr 11, 2012
#2
Thanks for sharing the pics and info! This should help greatly with the infamous "what are dogs" question!
 

Mattonln

Active Member
Apr 10, 2012
#4
nice thread dustin. many think when their tranny is messed up that, when pulled apart, will come out in a hundred pieces or have all the teeth missing. not necessarily so. transmission diagnosis takes a skilled eye and problems can be easily overlooked by someone without much experience. thanks mr. futs!
 

Dr. Beardface

Active Member
Apr 13, 2012
#5
Innnnnnteresting, thanks for sharing! Now, is back cutting as simple as just reshaping the dogs with an angle so they pull together or is there more to it than that?
 

nuckinfuts

Lifetime Member
Apr 11, 2012
#6
Innnnnnteresting, thanks for sharing! Now, is back cutting as simple as just reshaping the dogs with an angle so they pull together or is there more to it than that?
Basically that's it but it's critical that the angles are cut the same on both meeting surfaces to mesh perfectly. Usually it's only a couple degrees cut into the 'power' side of the dogs and obviously not the deceleration side. The part that takes a good machinist is matching the internal cuts inside those specific gears.
 

Dr. Beardface

Active Member
Apr 13, 2012
#7
Basically that's it but it's critical that the angles are cut the same on both meeting surfaces to mesh perfectly. Usually it's only a couple degrees cut into the 'power' side of the dogs and obviously not the deceleration side. The part that takes a good machinist is matching the internal cuts inside those specific gears.
Are we talking able to be done with a cutoff wheel and some patience, or setting things up on a mill and getting exactly right? Also, I'm assuming there's some heat treating that the factory did to the gears?
 

nuckinfuts

Lifetime Member
Apr 11, 2012
#8
Are we talking able to be done with a cutoff wheel and some patience, or setting things up on a mill and getting exactly right? Also, I'm assuming there's some heat treating that the factory did to the gears?
There's no way you can use a cutoff wheel to cut the inside dog contacts. They need to be set up on a mill or cnc machine to be cut.
 
P

Phantom Z

#9
Thats an awesome diagnosis of a worn out tranny. I love how when you dissect really anything mechanical you can basically tell the story of the life of that piece.
 

nuckinfuts

Lifetime Member
Apr 11, 2012
#13
I've always wondered what worn out dogs look like. Is it hit and miss with 06+ tranny issues?
All of them will wear enough at one point or another. The 06+ seem to do it quicker than the earlier transmissions. As noted tho, a lot of it has to do with the way it's shifted/ridden. Like the history of that trans above, the owner was blowing through these faster than I've ever heard of! Bent shift forks are usually caused by bad or forced shifting.

Will worn dogs cause it to downshift by itself from 4th to 3rd under heavy throttle? Thats what my 06 does..
It can cause it to slip out of gear yes. Before I had mine cut and all, I have had it slip from out of third back to second before a couple times. Mostly cause I may not have fully engaged it into gear enough to hold it under power. If it consistently does this despite of careful shifting, it would be safe to say it's probably worn dogs.
 

grtrat1

Active Member
Apr 11, 2012
#14
It only does it under hard throttle.. just cruising, it will stay in gear..What is the avarage price on these parts Id need if it is the dogs? My neighbor use to be a honda tech, so he will more than likely be helping me..
 

nuckinfuts

Lifetime Member
Apr 11, 2012
#15
The replacement gears aren't all that cheap but I bought mine from an OEM parts website that used to be a sponsor on the org. The best way to figure out what needs to be replaced is to split the cases and inspect the gears (dogs and teeth) for any wear, corrosion, or casting flaws like my original trans had. Also it is highly recommended that all the spacers, washers and clips be replaced too. You only want to do this once and don't want to skimp out on anything that can cause another part to wear more quickly than it should.
 

grtrat1

Active Member
Apr 11, 2012
#16
Ok thanks.. I just orederd a new Tusk clutch.. My neighbor thinks its just the clutch... But I think its more just from reading the history of this transmission... Plus it use to be a MX practice bike so Im sure it was ridin pretty hard..
The places we ride, Ill never get to 4th gear, so maybe it will be ok till I can afford to tear it down and replace whats needed.. Im also getting it cryoed..
 

nuckinfuts

Lifetime Member
Apr 11, 2012
#18
Also look for fractures that may originate at the base of the dogs. I found my second gear had two fractures, one made it across the fork groove into the main part of the gear. Time bomb just before det!