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gear box probs
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Author:  -=MiniMafia=- [ Mon May 10, 2004 8:04 pm ]
Post subject:  gear box probs
hey hey

ill be using my metro gear box on my 1275 turbo im building, and was wounding, what diff i should use? its geared for 12 " wheels. also the guy i bought it off said it needs a new bearing ( makes horrid noise when going along... so he said) how do i find the bust one?

many thanks guys, josh
Author:  Christoph [ Mon May 10, 2004 8:57 pm ]
Post subject: 
theres no quick and easy way, just check the end float/movement in the 1st, 2nd and 3rd motion shafts by hand. Also check the idler gear bearings (gear inbetween the primary gear on the crank and the input gear on the first motion shaft) it is held by little needle roller bearings, one in the side of the gearbox and one on the clutch housing. Anto's mini had a idler gear bearing self destruct which left needles from the bearing in the sump and 5 teeth broken off the idler gear from memory. This caused a very loud grinding noise in 4th gear especially.
It could also be caused by one of the big ball bearings for the differential but i would say more likely a bearing in the gearbox.
Author:  drmini in aust [ Mon May 10, 2004 10:45 pm ]
Post subject: 
I just finished fixing Baracade's Mk2 S box. Busted 2nd gear. The PO had built it without the needle bearing on the nose of the mainshaft... it stuffed the cluster (4 teeth) 2nd gear (2 teeth), mainshaft nose, and 3rd gear wasn't to be trusted either. Also there was NO synchro on 4th gear 'coz the 3 bits of it were acting as a pretend bearing. :shock:

Moral of this srory- always strip the box to check it! Some things like this you can't tell by feel.

I would run a 3.44 diff. 8)
Author:  Christoph [ Mon May 10, 2004 11:48 pm ]
Post subject: 
Yeah i agree, 3.44 ratio would be the best all round. 4000rpm at 100km/h roughly. any lower and its no good for drivabiliy, and if you go higher acceleration isnt as good
Author:  -=MiniMafia=- [ Tue May 11, 2004 9:29 am ]
Post subject: 
heya guys

Thanks for that! im going to check the box tonight and ill let you know what bearing is crook. and ill try and track down a new diff. do any places do exchange on them?

Cheers
Author:  Christoph [ Tue May 11, 2004 11:55 am ]
Post subject: 
First find out what ratio diff is in the box by counting the number of teeth on the crownwheel and dividing it by the number of teeth on the pinion. If it isnt 3.44 you can simply buy a new crownwheel and pinion with the 3.44 ratio. The crownwheel is bolted onto the diff cage with 6 bolts so its easy enough to replace. Remember to change the pinion in the gearbox aswell as they are a matched set.
Author:  drmini in aust [ Tue May 11, 2004 11:05 pm ]
Post subject: 
A 3.44 diff has 18T pinion & 62T crown wheel. :wink:
Author:  9YaTaH [ Wed May 26, 2004 12:15 pm ]
Post subject:  Diff Lapping??
Christoph wrote:
First find out what ratio diff is in the box by counting the number of teeth on the crownwheel and dividing it by the number of teeth on the pinion. If it isnt 3.44 you can simply buy a new crownwheel and pinion with the 3.44 ratio. The crownwheel is bolted onto the diff cage with 6 bolts so its easy enough to replace. Remember to change the pinion in the gearbox aswell as they are a matched set.


Whilst ideal to get a "matched set" I thought you could probably get away with interchanging pinions as they are both straight cut gears. With a helical diff ala holden and ford, lapping in would be required, but, in this case, often where beggars can't be choosers, could you get away with meshing gears from different boxes so long as they were both in good condition?

T :? hey probably have "standard" pinions (same teeth number across all gearboxes?) and just vary the crown wheel teeth number to give different ratios????
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