Gearbox rebuild

[SilverShadow]

What's the cost of getting a M20 gearbox rebuilt?

Anyone recommend a place in London?

Is this something that can be tackled at home with a rebuild kit?

[trevski]

It would be cheaper to source a known good box on here. They can be picked up for around £50-£100

[jimbom30cab]

factor in £60 an hour plus parts for a rebuild and at least 6 hours work

That's if you can find someone brave enough to take on a Getrag Box, they are notoriously hard to work on.

For the price of a re-build and VAT you could probably buy 10 spare boxes

[Topblag]

all gears in Nottingham rebuilt my M30 dogleg box for about £1000.

[Kos]

I've used these guys before, not far from you either

http://www.exchange-gearboxes.co.uk

[SilverShadow]

Cheers Kos I gave them a call and was quoted £200 plus parts for strip and rebuild.

The main reason why I'm thinking of going down this route is that currently the gearbox has that annoying chattering noise when the clutch is not depressed.

The concern I have is the price on the parts that would need replacing. Do you know what element of the gearbox would be causing that noise?

[ross_jsy]

To be fair all getrag boxes have a bit of a rattle. It's will be the layshafts rattling.

Even my 71k sport box which has had an easy life has a rattle. (The 200k one I have is so bad I thought my bottom end had gone)

[SilverShadow]

To be fair all getrag boxes have a bit of a rattle. It's will be the layshafts rattling.

Even my 71k sport box which has had an easy life has a rattle. (The 200k one I have is so bad I thought my bottom end had gone)

I guess the layshaft would be a dealer part only costing and arm and a leg?

[ross_jsy]

Even replaced they apparently rattle slightly.

Thought about upgrading to a zf unit out of an e36 or is originality important?

[SilverShadow]

Thought about upgrading to a zf unit out of an e36 or is originality important?

Originality not really as the car started of as a 320i and I upgraded the diff to 3.91LSD and engine to H2.7 lump.

I have been running the origin box (240.) and started researching the options that available.

Im still trying to define which ratio would be best with my current setup.

Couple of people I has spoken to me have suggested to use a Sport box as its close "ratio"? But reading the zone wiki the sport box and 240 box are very similar.

Tell me more about the zf unit?

[ross_jsy]

Yeah Sport boxes aren't far off a 320's box in terms of gearing. From memory mine would hit 30 in first, 60 in second and 90 in third? But this is going back almost 5 years now.

zf unit is just the e36 box so have the advantage of being a slightly more modern box than an e30's and they don't rattle like Getrag units do. You will have to use a lower ratio diff though as they have a 1:1 5th gear as opposed to the Getrags overdrive box. You might also have to change your prop but not 100% on that.

Getrags will rattle away for ever mind, it's just the way they are. I have my low mileage quieter box to replace my rattily one I doubt it will pop any time soon. More of an annoyance than a problem

[DanThe]

You will need a different prop, diff and custom made gearbox mount and selectors to use an E36 ZF box, the box will sit rotated approx 10 degrees anticlockwise

Bearings are generally not expensive, so £200 + parts would be a lot cheaper than the ZF route IMO

[Kos]

The gearbox chatter can be resolved by using some good quality fluid

I had nasty chatter in my e36 box after fitting the m20 flywheel but it's all but disappeared after using some good fluid

[DanThe]

The gearbox chatter can be resolved by using some good quality fluid

I had nasty chatter in my e36 box after fitting the m20 flywheel but it's all but disappeared after using some good fluid

To a degree, but as yours is a decent box to start with Kos you have a head start so to speak
Redline stuff is good, worth a try before writing it off at least

[SilverShadow]

You will need a different prop, diff and custom made gearbox mount and selectors to use an E36 ZF box, the box will sit rotated approx 10 degrees anticlockwise

Bearings are generally not expensive, so £200 + parts would be a lot cheaper than the ZF route IMO

Agree! Sounds expensive and a bit of a ball ache. I don't really fancy changing the prop, diff making up custom linkages

Also reading up on the zone wiki on drivetrain what do the individual gear figures mean? Correct me if I'm wrong but I'm assuming e.g. (On a 240 box 1st gear - 3.72) is one complete rotation of the flywheel which equals 3.72 at the output end of the gearbox?

Is that correct?

[SilverShadow]

Anyone?

[ross_jsy]

Other way round. 3.72 rotations from the engine = 1 turn on the output shaft

[Brianmoooore]

20,000+ RPM on the propshaft would test the balance!