7 replies to this topic

[jase12377]

I need a MPI gearbox rebuilding as 2nd Synchro is worn.

What is a x pin diff?

If going to turbo or supercharge my engine in the future what do you recommend I do the gearbox to strengthen it if at all possible?

Any help or guidance would be helpful thanks

[Steve220]

Hi Jase,

 

First off, if you want your gearbox rebuilt, I'd send it to Guessworks (he's a member on here also). A X pin (cross pin) diff has an extra set of satellite gears within the diff itself to add strength and give better power delivery, it's usually a common upgrade when people are increasing the engine's power.

 

The best thing you can do to your gearbox if increasing power is X pin diff and a fresh rebuild on the MPi box. If you don't mind the noise, then straight cut gears are your next bet.

 

The MPi is a bugger to turbo with the standard manifold due to the injector firing sequence. However, the Specialist component inlet system, coupled with a load of other supporting mods (low compression pistons, oil feed/drain, manifolds, GT17 turbo, intercooler, ECU etc), you should have an effective turbo set up.

[jase12377]

Ahhh didn't really want straight cut gears due to noise on long journeys think my ears will.bleed

[cian]

I build quite a few gearboxes and straight cuts are not any stronger but what they do do is transfer more power through the gearbox, the other benefit is the close ratio and longer first gear it's up to your own spec and preference if you want this, as Steve mentioned a x pin diff is a must! If your going to be putting big power through the gearbox I would be changing both the double roller and the single roller bearing certainly, I would also change your silly 2.7 diff ratio to a 3.1 or 3.4 depending on what driving characteristics you want

[jase12377]

What would you change the double roller and single roller to?

What's the difference between 3.1 and 3.4 ratio?

I just would like the gearbox to be quick through the gears, handle the power output and be reliable

[cian]

I would replace them for new items, the 3.1 would have more acceleration than your 2.7 and have good motorway manners, meaning it would have sensible rpm at motorways speeds, the 3.4 is much more of a B road diff it's great at accelerating but it's not great on motorways, it sounds to me like straight cut is the way to go for you with a x pin diff and built by someone who knows what they are doing! Check out my fb page cc minis my details are there if you want to call for advice! Oh and don't forget a straight cut gearset won't produce much of a whine it's the drop gears that give you that distinct noise

Edited by cian, 19 March 2017 - 03:03 PM.

[jase12377]

Cheers m8

[ukcooper]

drop stright cut gear are louder than gearbox s/c as the gears soak some of the nosie up i think.