18 replies to this topic

[maccamcvey]

Hi
Hear is a bit of info on the box i am working on, it came of a 1275 spi cooper, the lay gear has 15-21-26-30, i am not sure if this makes it a 's' ratio or not the primary gear has 17 teeth if this helps. and the cwp is 61-19 witch by my probably wrong maths makes the FD 3.21?

I need some help mainly deciding if my gear set is scrap or not. Most of the gears have pitting on 5 or 6 teeth. i have a decent camera so could get so picks if needed?

I have a bad feeling they will need replacing, so what to replace them with. I am building a fast road engine 1380 possibly turbo'ed.

I hear close ratio gears are advised but the lay-gear is the only part it perfect nick. So is straight cut gears the way to go? people say they are loud, unbearably loud? but is this a bit to much in a road car?

The crown wheel has similar pitting mainly from rust i think, what final drive would you recommend? i am running 12's and try to stick to the A and B roads.

I have a full rebuild kit and xpin diff ready to go also i have my name down for a baffle tray of paul on hear, but i need to make plans for the gear set and ratios, any help and advice will be much appreciated.

Thanks

[bigmotherwhale]

i have strait cut gears they make my mini friends jealous, and arent too noisy is you have perfect bearings.

however i would use the box untill it doesnt work anymore, ie jumping out of gears crunching ect pitting does not mean the box is scrap, its when the teeth become sharp you should change the gears.

i love the sound of strait cut gears, they arent too lound for me and i have no sound deadening or carpets. i bought them new and fitted new bearings throughout
you will need to change the oil more regualry tho it makes it thinner.

[maccamcvey]

i have strait cut gears they make my mini friends jealous, and arent too noisy is you have perfect bearings.

however i would use the box untill it doesnt work anymore, ie jumping out of gears crunching ect pitting does not mean the box is scrap, its when the teeth become sharp you should change the gears.

i love the sound of strait cut gears, they arent too lound for me and i have no sound deadening or carpets. i bought them new and fitted new bearings throughout
you will need to change the oil more regualry tho it makes it thinner.

Do you have s/c drop gears and cwp or just the gear set?
thanks

[Kerrin]

It would be worth posting up some pics.

I have four gearboxes in bits and none of them have pitted gears, however the small syncro teeth at the side of the gears are worn in one box more than others. The main things to look for are any damage to the casings or threads. and the double row bearing at the pinion, which are prone to collapse or damage. Syncro's should be replaced anyway while it is apart.

I may be corrected but rust pitting on the gears may not really be a concern as they will wear anyway, if you are looking at needing new gears then get another box or go for the straight cut setup. Check the casing before you decide.

Also I dont think many A+ engines were fitted with a close ratio gear kit. only some MG metro's you can check the numbers stamped on the laygear to be sure. The "s" first motion shaft gear had 18 teeth so it sound likely it is not.

[bigmotherwhale]

i only have sc laygear ect, i do not have sc drops, the good thing about this set up is in forth its direct drive and is as silent as a helical, i imagine sc drops to be very noisy but ive never been in a car with them fitted,

[maccamcvey]

yea i hear the drop gears are very loud, thanks

[maccamcvey]

It would be worth posting up some pics.

I have four gearboxes in bits and none of them have pitted gears, however the small syncro teeth at the side of the gears are worn in one box more than others. The main things to look for are any damage to the casings or threads. and the double row bearing at the pinion, which are prone to collapse or damage. Syncro's should be replaced anyway while it is apart.

I may be corrected but rust pitting on the gears may not really be a concern as they will wear anyway, if you are looking at needing new gears then get another box or go for the straight cut setup. Check the casing before you decide.

Also I dont think many A+ engines were fitted with a close ratio gear kit. only some MG metro's you can check the numbers stamped on the laygear to be sure. The "s" first motion shaft gear had 18 teeth so it sound likely it is not.

Thanks, i didn't spot you post last night, i will try and get some picks up, pay day has just bin and straight cut is calling yet i cant sea any numbers stamped on the laygear maybe i am just being blind!

the casting is tip top and i have a full new bearing and gasket/seal kit so that shouldn't be a worry.

What do people advise as a goof fd?

Thanks

[Kerrin]

FD totally depend on what you will use the car for, what size wheels you want to run etc etc.

We dont have motorways here so I have a 3.44 and 10" wheels. I have not tried it on the road yet.

My old motor was exactly the same spec as yours and the 10" wheels and the 3.21 diff made it quite a nice compromise.

[bigmotherwhale]

i would go for a 3.1 or 3.2, but it does depend on the gears you have in the box, some strait cut are different ratio. im after a 3.1 or a 3.2 so if you have one spare give me a shout!

[Ethel]

3.4 was almost universal on Minis, with 10" wheels, for ages and worked well. If you're sticking a cam in a higher diff will make better use of it. A well set up Turbo will have wodges of torque so you could afford to run something more refined in the revs/noise department.

Gear ratios should be part of planning your build. Do some research and decide what gearing will match the revs and speeds to your needs. Guessworks' site and Winsu have gear calculators.

[maccamcvey]

Thanks for all your advice guys.

i have had a play on Guessworks' site before but cant i don't relay know how to interpret the results?

like i say i like to stick to the A and B roads, and like driving quick. also would like a nice low 0-60. the engine will be pimped to the bursting point of my wallet! So 73.5 bore with omeger pistons fairly radical cam stg 2 or 3 head lightend fly, crank and rods ect ect... (also possibly a turbo but that another story)

So do i want longer gears as it should be nice and powerful with a decent amount of torque? Or do i want shorter gears as it should be nice and high reving with lots of lighted bits and bobs? I have being reading the yellow bible (Visards' Tuning the a series) and he talks about getting up to 9000 RPM. Or do i want something slap bang in the middle?

If only visard did a mini Gbox book, you mention do some research, i haven't looked particular hard (mainly on hear) but cant find much in the way of good advice in the gear choice/set up. Or am i just being blind again? yet you guys seam to be doing a good job!

Thanks

[Nightrain]

All depends on what the fairly radical cam will be, something with a narrow powerband is gonna need closer ratio gears to keep it on the boil.

[maccamcvey]

I haven't red the 83 pages on cam in the yellow bible yet so i am no expert yet lol but i thinking a kent 286

[Nightrain]

You'd be better of with a close ratio set the S/GT is what you want.

[maccamcvey]

Am i right in thinking this it the one you mean

http://www.minispare.....TION CLUBMA...

thanks