10 replies to this topic

[zomerzet]

Reet, building my first performance engine and am wondering if anyone has any particular tips on making sure the gearbox won't fall to bits when I put a bit more power through it.

I have heard about changing the diff pin, but is it neccessary with this spec? What else is a definate GOT TO upgrade and NICE TO upgrade?

I will also be fitting a central oil pick up pipe...

Cheers in advance...

[Jordie]

uprated diff pin and central oil pick up will be fine. Ive only put a central oil pickup in my box and thats running a higher spec 1330cc engine.

[mininutter]

uprated diff pin and central oil pick up will be fine. Ive only put a central oil pickup in my box and thats running a higher spec 1330cc engine.

A professionally rebuilt gearbox would be a good idea. Depends how you treat it though, spin your wheels you'll break the diff pin, rev the nuts off it around rounderbouts when its cold, you'll need the central oil pick up.

[Retro_10s]

uprated diff pin and central oil pick up will be fine. Ive only put a central oil pickup in my box and thats running a higher spec 1330cc engine.

Yeah, as Jordie says really,... uprated Diff pin would be a good choice of modification and a central oil pick up is one of those items that if you've split the engine and box, you might as well fit.

I believe in standard form the mini gearbox will take around 100ponies, but of course, even though it takes it, doesn't mean it wont wear that fast...

As with anything mini. Maintenance is the key, and I'd have good check over the gearbox (or send it to someone who knows how) and check all the tolerances, baulk rings etc and all gears for wear, before you offer it back up to the block.

The old yellow Haynes Workshop manual (not the usual book of lies) is a fantastic book, detailed pictures etc.

However, IIRC I also believe if you delve into the FAQ, our resident gearbox pro 'GW' actually built a 'How to strip and rebuild' on gearboxes,.. with pictures and diagrams and wotnot.

[Ethel]

If you have it stripped anyway think about replacing the baulk rings and fitting an upgraded layshaft.

As said, defo replace the diff pin and oil pick up worth it for peace of mind.

[Retro_10s]

outta interest, from the spec of the actual engine and not the gearbox,.. are you gonna be fitting a centre main strap?

[zomerzet]

Cheers for all the replies. A rebuilt gearbox would be a nice idea, but I'm doing everything myself and they aren't cheap. The one I'm going to use is a low miler off a 40,000ish mile metro so should be in pretty good nick.

Fair points on the pin and pipe. I do drive quite hard but never until the engine's up to temp though. Sounds like a good idea for these items to be sorted just for peice of mind really. I don't think I'm gonna hit the magic 100 with this spec somehow so should be pretty safe!

Centre main strap? Is that really neccessary with my spec d'ya think? I though it'd only be required on mental high revvers?

I had a read through the gearbox build stuff but mine is in one peice and is staying (Mostly) that way. Is a diff pin difficult to change? I've never played with a diff so should be an education!

[Sprocket]

Standard helical boxes have been proven good to 140bhp plus, in theory you could put more through it, its not the power that kills it, its the torque, high reving normaly aspirated engines may give big BHP figures, but the torque is reasonably smaller. A turbo engine puts out far more torque

I know that Specialist Components Twin Cam 8valve Demo car runs a standard helical gearbox at 128bhp and IIRC about 87lbft torque, the Standard Metro turbo putting out similar torque.

Ultimately if you put more torque through it than Rover did on the Metro turbo, its going to need a rebuild much sooner than 40k

Most important is that ALL the clearancies are within limits, and not just within, but rather nearer bottom limit.

As said, a competition diff pin is thoroughly recomended, though an X pin diff is insurance.

Other than that, I dont think you will have a problem.

Edited by Mini Sprocket, 28 August 2007 - 10:21 PM.

[Guess-Works.com]

As MS says, Upgrade the diff pin at a minimum, X-pins negate that weakness completely... the next thing I would look at is replacing the drop gears for straight cut, basically to remove the issue of idler gear sideload on the transfer case.

Rather than strengthening the case you are removing the high wear/failure issues.

[alexcrosse]

stop concentrating on performance and think more about reliability. Centre main strap is a good idea incase you want to keep the cam and do a load of head and carb work. Taking the engine out of the car just to put a strap on its effort!

Get john to do your gearbox, think it would have been more expensive to do it yourself! you would never get it as clean without certain equipment too.

Centre oil pick up is a neccesity in performance mini's. Dont think about keeping that standard. Just be careful, and keep in mind how annoyed you will be if you start it up, put it in 1st, let out the clutch and nothing happens. lol.

[Sprocket]

Why do you need a center main strap if the engine wont rev contiously past 7k????

I take my 1400 regularly to 7k with 104lbft and 95bhp