Gearbox..something's not right..
Turbo Mini Forums

I've just stripped my SC gearbox, literally, and found this:





The car drove perfectly well, this is from the last outing:

http://www.youtube.com/watch?v=m34IS15X09U

Obviously, there's something wrong with third gear here. I'm wondering if this happened while opening the two big nuts while dismantling. Could it be? The third gear has also got a mark on one tooth.

Edited by Vegard on 24th Dec, 2011.

Ouch
Looks too clean to have broken during use to me, either way if theyre not old i'd return it or drop the company an email and see what they have to say about it.

JB weld?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

oh dear V that head set looks as if its done no milage at all

Do you lock 2nd and 3rd then when dismantling?

I usually lock 1st and 4th for no other reason then it places the load nearer the large bearings. If my thinkings flawed I have no idea but hey ho!

Is that a minispares gear set?

The correct way to lock the box is to lock first and fourth, The ratios are much further appart. The first motion shaft is also locked to the main shaft meaning the whole gear train is locked.

Locking second and third, the ratios are very close together and the torque applied to the first motion shaft nut is multiplied by the ratio of the head gears. the result is greater force on the locked gears, and with the ratio so close together, second and third will try and climb there mating gears.

Also, using a rattle gun or impact wrench is bad as the shock loading on the gears is considerable.

Not say thats what you've done Vegard, but I've seen people lock second and third before and others recomend using an impact wrench, myself included (until I learned the error of my ways )

Obviously, I didn't lock 1st and fouth, but I didn't use an impact gun, only a long lever. I never had this happen before, but it might have to do with that this was the forst box I built back in 2004 without lock washers, only Loc-tite. Harder to open as I didn't heat anything.

I know it's my own fault, but take it as a lesson.

Ive seen a Minispares set break exactly the same from locking 2nd n 3rd without loctite

I seriously doubt it!

This is a Minispares ST set, but I guess it's not the quality of the gears that's the problem but the spannering monkey

I broke 3rd on a Tran-X gearset like that. And it wasnt from locking to dismantle.

just happened under power. Makes a light ticking noise afterwards.

Also did the same on a R-154 Supra Turbo box in 3rd gear when I had a RV8 TT. Although it was helical.

Weird that in both cases, it never really did any further damage.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I have done that to a std box once when locking in 2nd and 3rd...

When trying to untighten my helical box with two gears locked, teeth from the laygear and one of the other gears sheared off and came at me like bullets. I think eye protection needed for this job.

Edited by dazibee on 11th Feb, 2012.

how did you lock this gearbox and what tools were you using to loosen the mainshaft nuts?

I've stripped many a gearbox, not as many as others, but I have never experienced breaking or chipping of any teeth, mine or the gearboxes.

We were using a socket and long bar to untighten the mainshaft nuts. It was a remote box with two gears locked (can't remember which gears) When we stripped the box we found the nose bearing on the mainshaft to have disintegrated, which I think is why the teeth snapped off when I tried to undo the nuts