gearbox circlips

in my 08 the 2 circlips and stop discs in the middle of the output shaft (the ones that get hammered if you change into 3rd or 4th) got badly distorted and the circlips were ripped out of their grooves, result was brocken gear dogs.

looking at my old circlips they are much beefier and stiffer than the ones on this 06 550 box and they are much beefier than the new ones I got from BOSS.

ok so has anyone noticed this before? im wondering when they changed them and if the new ones are actually better given that mine had a meltdown. they are larger in OD which might not help. the beefier clips are thicker too so maybe there is too much side load on the stop discs when in gear. more side load and more leverage from the bigger OD might mean the stronger clips are worse than the little ones..

It looks like the gear destroyed the stop disc by grabbing it instead of sliping on it and then smashing off the 2 tangs and then both the stop disc and the gear mated together and ganged up on the circlip both pressing it into the splines on the shaft and twisting it off.

Will post some pics and dimensions soon when I get this camera working.

regards
Bushie

RE: Re: gearbox circlips

stop disc failure on rotating gears

its the 2 rotating gears in the middle of the output shaft inner bushings fine, I guess worn dogs and nasty shifts could have caused the stop discs to fail but also vice versa. if the circlips jump off cause the stop disc is spinning with the gear then the dogs will fail soon after.

all the other stop discs and circlips are fine I guess the side loads are better distributed outward into the gearbox housing and bearings on all the others, just these two in the middle I think its 3rd and 4th, bugger me the two gears we use the most are the weakest....

pics soon

RE: Re: gearbox circlips

that'd be awesome Craigy I had planned to make new stop discs with a lip that locks over the clips to hold them on better and lock onto the shaft better with a full spline rather than 2 tangs.

I can get kwaka stuff pretty quick and cheap.

cheers
Bushie

ok im making some locking discs but just had a thought to take the idea to the full the circlips could be round in secton and say 2.5mm thick and the stop disc could be super strong and lock over the round circlip as it took the thrust. shouldn't come off then.

only needs to be done on the 2 that broke in the middle of the shaft, rest of the box is strong as.

old circlips 1.15mm thick, new 1.20mm thick, installed OD of old clips 27.1 and new clips installed OD is 28.4

so old ones are about 1.7 by 1.15 in section and the new ones 2.35 by 1.20

ausberg those stop discs are flimsy affair indeed ha and yes I got brand new gears for the output shaft, and from the 550 wreak I stole the shift drum, a fork and the input shaft gears. dogs all in better condition than mine, i guess its a pluss not many people can get more than 20 hours out of a 550 rebuild.. still you'd wonder when reliability goes down a notch after each attempt..

regards
Bushie

ok im taking a guess as to which circlips hang on better with repeated side impacts, the small ones..

the small circlip OD is such that the rotating gear can pass over them if the stop disc is removed. you can see the wear mark in pic



that sharp groove in the stock disc is from the OD of a small clip. so I reckon the stop disc is bending over the circlip in side loads and helping hold it on. just a tad.

the larger circlips OD means that the gear can push on the OD of the clip through the stop disc without the stop disc bending so every side impact acting on their OD is bending the clip and doesn't help hold the clip on at all , with enough impacts it becomes dammaged and falls off. the bigger clips are stronger and perhaps put up a better fight. don't know really.. just a guess.

worth noting that this guesome pic is after 50-60 000 shifts in total and mostly between 3rd and 4th, the 2 weakest gears for side loads.



dunno if thats really what happens or if its by design or accident with the small clips but changing the gears to have inner bushings so the gear doesn't push directly on the OD of the clip may have been a great thing. maybe not anyway have made these stop discs to try and improve things,



will know if its better in 170 hrs. Ausberg probably nailed it, the dogs were worn and either circlip would have failed.

If it happens again I'm making proper locking rings though, worn dogs are inevitable so its going to happen sooner or later, if better round section clips and lock collars get another 100 hours out of a box its worth doing IMHO.

only bummer is of the 2 in question only 1 can be locked unless its a 2 piece and welded on after assembly.

regards
Bushie

what would be real nice is if the thrust load could be taken by a something proper like whacking great big 2 peice collar (like for the clutch) that sits in a big groove in the shaft between 3rd and 4th idlers and is clamped firmly on with a big outer collar with 2 bolts. there is plenty of room in there. say a 3mm thick one meaning taking 1.5mm off each gear and making a groove in the shaft.

or just gear down and use 5th/6th or gear up and use 1st/2cnd or even remove 3rd and 4th from the box altogether ha!


and yes taffy your bum allways looked big in that chair time for a new one

regards
Bushie