gearbox limits??
Turbo Mini Forums

hi

iv been looking at prices etc for a gearboxbuild.

im going to be hoping for my turbo lump to be producing about 140BHP.
i no a x-pin diff is essential, and at least a gearbox rebild but would i benifit in spending the extra money for a fully blown c/r s/c set up?
at what point would you say that a s/c set up is needed?

i will be using the car as my everyday drive and i like the sound of s/c gears, but its a bit expensive if thats all il be buying them for if you know what i mean.


cheers
josh

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

If you're gentle with the transmission - and don't use full boost in 1st (which will be difficult anyway as it's so short) and second, and try accelerating IN the gears, rather than crashing 'through' themm you should find the trans will stand up to quite a lot of abuse - following an 'every bearing' rebuild.
4-pin diff must be on the shopping list though.

For me the course of upgrades should be 4 pin diff as a must really.

Then the next weak point IMO is the drop gears, so these would be the next thing to upgrade to s/c.

Then only after those mods are the s/c gearset needed.

For your spec I'd personally fit the 4 pin diff, s/c drops if you can afford them, and then just rebuild the rest of it.

Similar query as this.
Can sc drops be used with helical gears? And who makes the best value for money sc drop kit? And is this all I need to fit sc drops to my standard box plus 4pin?
Also will the standard clutch be up to the 140-150bhp mark?

sc drops are not necessary , i run up to 250 bhp with no problems on helical drops ,its 3rd gear that breaks on the helical gearbox at about 135lb/ft of torque,if you drag race the box and use it fairly enthusiastically.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

i disagree Robert. s/c drops with a helpical box for much more than standard metro turbo power and either with a s/c gearset.

we've all seen helical idlers missing their teeth with high power engines on standard boxes.

I'd tend to agree with Robert.

How many times can you really say people have suffered drop gear failure, and then compare that to how many times people have suffered gearset failure, including straight cuts. I think I have only ever seen one drop gear failure, and that was on a normally aspirated engine, which led me to believe there were other factors involved, rather than it just being the gear.

Robert & sprocket

So ive taken into account apbellamy's sugestions for next step.

If you disagree that the next week point after the diff is the drop gears where would you suggest I should go for my next stage of box upgrade baring in my I have a tight budget?

Oh and probably worth mentioning it's only going to be used for road use with my 2.76 final drive. Never dragged or raced

For example Wintersurfer is putting around 160nanas through and old Clubby GT helical box with X pin and SC drops.

No problems to date. This has been on the strip plenty of times and he generally drives like a hooligan.

In the 13's at last!.. Just

Haha I have also posted another Thread about my exact query and has made up what is starting to be quite an argument between theory's.
This last post is straight to the point and made more sense than all others together.

Thanks theoneeyedlizard

this is all the personal data and experience i have on the subject.

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=381228

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=168594

Edited by robert on 26th Jan, 2012.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

My personal THOUGHTS/OPINIONS on the matter:- (I make no scientifically backed claims or guarantees)

1. x-pin is essential on anything warmer than a mild 1275 or if you behave like a pillock who wheel spins everywhere.

2. sub 120nana/curly should be fine with helical box & helical drops if you have some sympathy.

3. sc drops will buy you a little more life from your helical box (say 140nana/curly) at the expense of your car sounding like a supersonic banshee (some of this benefit however is probably due to having a new bush in the primary gear and actually shimming up the idler properly when installing new drops).

4. sc box and helical drops are a great combo for a fast road car very little noise increase over a helical/helical setup (I run this in my road car) and as robert has shown can take some serious abuse. (periodic inspection of drops essential IMHO)

5. sc box and drops if you aren't bothered about it being quiet and you want to the strongest setup available.

If something is worth doing, it's worth doing half of.

Ill bet that when using heli gears and drops that when the drops have been stripped its being down to the 4th gear/input bearing collapsing or failing causing the input gear to try and climb the idler. Now wether that failure has been caused by twisting effects/side loads assosiated with helicle drops s debatable.

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

This is all great advice cheers.
So if I wanted low noise and better reliability would my standard helical drop work with say the med clubman gear kit?

If your helical drops are in good condition, you get the primary gear endfloat right and shim up the idler correctly, yes.

If something is worth doing, it's worth doing half of.

justa note, im on a 2.7, with Full S/C setup, and its not actually that bad, i use it everyday......

I battered my ears with loud music when I was a kid, so my full SC is easy to live with.

If it was an everyday car, I would give helical drops a go.

In the 13's at last!.. Just

Robert thanks for that. Octet reading those mind is made up. New gear set it is.

I will double check this with my Mechanic. I'm popping in to see how he's getting on with it tomorrow.

just out of interest, when using a helical box, to make it slightly stronger you put in sc drops.. but if you have a sc box you can use helical drops to reduce noise but surely your putting a weak link in the transmission and taking a step back? can someone clear this up as i dont understand the logic

i got nothing but time..

From the comments, it seems that a SC box is not a great deal noisier than a helical box
So why are sc drops so much noisier than helical ones

Is it down to the fact that they are not continually submerged in oil like the box is

Edited by ntm1275 on 1st Feb, 2012.