2001 wr426 transmission

G'day fellas I just bought a 2001 model wr426 and it doesn't have 3rd or 5th gear, I have pulled the transmission out and it all looks good, no missing teeth or anything, I do have a second hand transmission and will put that in the WR, but the original shift cam and then second hand one are a tad different, I'm not sure if I should go with the original or second hand one, thoughts? The original shift cam is on the left ImageUploadedByThumper Talk1390477248.901571.jpgImageUploadedByThumper Talk1390477335.271880.jpgImageUploadedByThumper Talk1390477158.759462.jpg

As long as it is from any 400F/426, it's OK.  The "skeletonized" one is a newer version.  If you're concerned about it, though, there should be no problem with the original, as the cam is a low wear part.  Check along the insides of the grooves for anything obviously dented, worn, etc.

Why would 3rd an 5th be slipping? The trans I pulled out looks fine, no missing teeth or anything so I have no Idea why it would be doing it

If you had a condition in which the affected gear would fail to hold in under a significant load, but would stay engaged as long as you didn't put more than a certain amount of power to it, the fault is with the lugs on the sides of the gears, not the gear teeth. 


All 5 gear pairs stay in mesh with each other at all times, thus the term, "constant mesh".  In each pair, only one is splined to the shaft, so they cannot transmit power.  This is how things are in neutral.  To engage a gear, first, for example, a shift fork moves the 5th gear on the output shaft, which is splined in place, over against the side of the free spinning 1st speed output shaft gear, whereupon the lugs on the 5th gear lock to slots in the 1st gear, preventing it from turning, and causing the 1st gear pair to drive the output shaft.  The various gears are shuffled around in sequence by the shift cam and forks as you shift each one.


As built, the lugs have a very slight undercut so the load placed on them actually holds them engaged.  As the lugs wear, the round over, and eventually they get to the point that they actually push away from each other.  Since the fork can't be driven on the shift cam by the gear as it can in most car gearboxes, instead of popping out into neutral cleanly, they force the fork out of the way by flexing it until they slip out of engagement, which breaks the coupling, so the load force on the gear goes away, and the fork pushes back.  When the gear aligns with the next gap in the lugs, it drops back into engagement, and the whole thing repeats.


So if you've lost 3rd and 5th, the problematic gears would be the 3rd and 5th gears on both shafts, as they engage each other.  The two forks involved will also be bent, perhaps not visibly, but unusable, nonetheless.

I can't put any load on those gears, it's like they don't engage at all, I have a whole nother transmission, which does look in a bit better nick, so I will just replace it

Are you interested in getting rid of the old transmission?

Well I'm not sure? Whys that?

I can't find a transmission for my w426 sense it's obsolete now, but I came across a 1999 wr400 tranny on eBay will it fit my 2001 wr426??

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