7 replies to this topic

[dansalter]

i'm doing up a metro 1275 engine for my 1989 Mayfair.
putting in a MG Metro camshaft
and the head is off being skimmed and re-seated atm

anyway, brought a 3.1:1 final drive ratio crown wheel and pinion from the IMM
payed £40 for and it looks unused, good price? :s

I am attempting to fit it atm and have run into a problem firstly how am i ment to take off the nut that holds the pinion in if i can't stop the gearbox from turning???
also does anyone know if this nut has to be at a specific torque setting for when i put it back on?

before i actually get it fitted does anybody feel the 3.1:1 is a bad idea for this set up as i am wondering how much it will kill the acceleration?

Thanks guys, Danny.

[Grayedout]

Yes very very tight!! Can't remember the exact figure but check Haynes.

To stop the gearbox from turning you need to remove the selector rod and then put the gearbox into two gears at the same time.

[Stevie W]

i'm doing up a metro 1275 engine for my 1989 Mayfair.
putting in a MG Metro camshaft
and the head is off being skimmed and re-seated atm

anyway, brought a 3.1:1 final drive ratio crown wheel and pinion from the IMM
payed £40 for and it looks unused, good price? :s

I am attempting to fit it atm and have run into a problem firstly how am i ment to take off the nut that holds the pinion in if i can't stop the gearbox from turning???
also does anyone know if this nut has to be at a specific torque setting for when i put it back on?

before i actually get it fitted does anybody feel the 3.1:1 is a bad idea for this set up as i am wondering how much it will kill the acceleration?

Thanks guys, Danny.

Hi Danny,

I've just changed the diff on an MPI gearbox I am using for my Mini project. Changing from a 2.76 to a 3.1 as I wanted more aceleration.
The 3.1 diff seems a good all rounder giving good acceleration and cruising speed and in my opinion is the best ratio to use.

You will need to lock the box by engaging 2nd and 4th gears together. This wil lock the 'box and allow you to undo the output pinion. Engaging these gears can be done using a long screwdriver to move the bellcrank levers to engage the gears.

You will find the nut extremely tight as it has to be torqued up to 150lb/ft!! Best to do this with the 'box on the engine sothat you have something to sit on in order to hold the 'box still whilst your heaving on a long arm wrench!

Cheers,

Steve.

[Pauly]

Be best to get the pale blue haynes manual (one before the lastest version I think) that documents the full strip down and rebuild of a gearbox.

But you will need to engage 2 gears at the same time, as already said.

Paul.

Edited by Pauly, 10 August 2009 - 07:51 PM.

[dansalter]

thanks alot steve. couldnt trying to get the nut off at that huge torque bugger up the teeth on the gears stopping it turning

also any idea of what size the nut is?

i may end up having to take it the the local mini engine bloke to get it off as i can't find a big enough spanner and even if i can will it be long enough to give me enough leverage to get the bloody thing off??

just a thought is the pinion the same on the 3.44 to the 3.1? i doubt if it is as the teeth wouldnt corrispond but just a thought.

[dansalter]

also, pauly i do have that but could not find the right part as most things are for the A series engine not the A+

[Guess-Works.com]

nut is 1.1/2", use a ball joint socket

and no the pinion is not the same.

[Pauly]

You will need to use a socket on it and a breaker bar, doubt it you will crack it off with a spanner (unless you got arms like arnie). The haynes covers both a and a+ boxes.

Paul.