How to tell a V8 M21 on the ground.

[mauser]

I was wondering the best method to determine which gearbox it is from looking at one on the ground.

I was led to believe ages ago an M21 had two rings in the input shaft over an M20. Another way is to put the box in first and count the turns??


Mauser

[adam perth]

yeah 15 years ago that was the way to tell M21 on the ground, not so much tru anymore as alot of the repo input shafts are blank.

2.5 turns 1st gear = M21
3 turns first gear = M20

[mauser]

Cool thanks Adam. Which selector is it to put it in first gear? One closest to the input shaft.

Mauser

[thatotherguy]

apart from ratios is there any difference between an M20 and M21?

[V8VAN]

Pretty sure they're the basically the same box, apart from the ratios.

[HK1837]

apart from ratios is there any difference between an M20 and M21?

Input shaft (4th gear), cluster gear and 3rd gear. Rest is the same (V8 and 6cyl differences aside).

--- Updated ---

I was wondering the best method to determine which gearbox it is from looking at one on the ground.

I was led to believe ages ago an M21 had two rings in the input shaft over an M20. Another way is to put the box in first and count the turns??


Mauser

Also, you won't find a 6cyl M21 unless someone has made one. Only a very few cars ever had them (possibly only Repco Rally Commodores).

[mauser]

Thanks Adam and HK for that. Picked up a M21 local so saved me the shipping costs and risk of buying one elsewhere. The parts just to fix another one had easily tipped into $800 bucks with associated cluster and bits.

The box was supplied as a spare with an AusCar years ago and the guy never used it and is moving so was cleaning out his shed. It has bolts with some type of wire seal inter-twined around them. Looks clean as though it hasnt been in a car since a re-build. Right ratio in first from your advice, it has the two rings ground on the input shaft and feels good. Hopefully nothing major wrong inside but thats the way it goes.

The shifter I got with it is slightly more laid-back than the one I have. Is the Commodore M21 shift slightly different from the HX-Z one with the rubber joint in it? (I realise the HQ had a solid chrome shifter but oh well..lol)

These gearboxes are getting harder to come by now unless they come in a bucket. Wont be walking past any $50 ones at a swapmeet anymore. Just need a bellhousing for the rat trap now as this one came with a cable setup and fork.

Mauser

[HK1837]

The side covr will probably also have a switch on it to show 4th gear, so you might want to use your old side cover.

I used to buy them for $50 at swapmeets but invariably all I'd get was a case, input shaft cover, extension housing and side cover. Rest was normally r00ted.

[Sandaro]

I've bought exchange M21 boxes and referred mates to a guy in Blacktown who specialises in mainly the Holden Aussie boxes, never had any problems, well rebuilt. Just take a complete box in for exchange.

Called him now, currently $495 exchange, on the shelf. No relation to me, but don't mind plugging someone who has given me good service, J & VR Transmissions 1/6 Chigaco Ave Blacktown (02) 96717904

He is way cheaper than anyone else I ever got a quote off (up to $1,500)

[mauser]

I've bought exchange M21 boxes and referred mates to a guy in Blacktown who specialises in mainly the Holden Aussie boxes, never had any problems, well rebuilt. Just take a complete box in for exchange.

Called him now, currently $495 exchange, on the shelf. No relation to me, but don't mind plugging someone who has given me good service, J & VR Transmissions 1/6 Chigaco Ave Blacktown (02) 96717904

He is way cheaper than anyone else I ever got a quote off (up to $1,500)

cool, wonder how long he will be able to do those. Most of the time I think the cluster is pg13'ed in them. At the below price that doesnt leave much in fat to cover labour and other incidentals.

http://www.ebay.com.au/itm/Holden-Au...item519cae64db
AU $275.00


Mauser