Aussie Four Speed
Page created by T June 24th 2007:
Aussie Four Speed Gearbox:
Officially called the M20 or M22 gearbox in a 6 cylinder car or the M21 when fitted to a V8. M21's were also made for 6 Cylinder cars. (LJ XU-1's only) End of submission by 383HGBrougham: Thread1
The LJ XU-1 Gearbox, is NOT an M-21, it's an XU-1 M20.
It has all the same ratios as the M21, except third gear, third gear ratio is 1.25:1, where the M21 is 1.38:1.... The GTR XU-1 box, is unique.
There simply is NO SUCH THING, as an M21 6 cylinder box, however, there are now Chinese gear sets available to turn any box into an M21.
I will look out and list the ratios and cluster gear part numbers for all 5 different ratios in the Holden 4 speed box..
Yes, a bit misleading there. The M20-21-22 designations refer to the ratios, regardless of whether they fit 6s or V8s.
1st & reverse - 3.05:1
2nd - 2.19:1
3rd - 1.51:1
4th - 1.00:1 M21 ratios:
1st & reverse - 2.54:1
2nd - 1.83:1
3rd - 1.38:1
4th - 1.00:1 End of submission by GraemeG
Submission by Ben Simpson. Front selector is 3/4 rear is 1/2, first gear is the tell all with these. From memory an m22 is 3.74:1 first, an m20 same as a 3 speed at 3.05:1 and m21 is 2.54:1 all from memory but 99% sure I'm not far off these numbers. End of submission by Ben Simpson.
I've you get a copy of my book '60 Years of Holden' you will find every gearbox & rear axle listed for every model series, including the super low HK 12-bolt rear ends. They were:3.73, 4.10, 4.56 & 4.88 BTW. Trust me, there was no M23 or M24 gearbox in any Holden. This book will put an end to the guesswork & errors that you often see on the internet. see: http://www.topgear.c... End of submission by Dr Terry.
===Draining the Gearbox:=== To drain the oil remove the rearmost and lowest cover bolt from the offside of the gearbox and catch the oil in a tin.
===Filling the Gearbox:=== When filling the gearbox make sure the drain bolt has been fitted and tightened down. Remove the large filler bolt in the nearside of the gearbox and place a tin under the hole. Pour in oil using an external funnel and a length of hose until the oil begins to run back out the filler hole and into the tin. When the oil stops draining out, install the filler plug and tighten it down.
Improper Towing can burn up the Mainshaft because the Layshaft gears are stopped. When the Layshaft Gears are stopped, no Oil is circulated through the Gearset and damage will result. Towing the Vehicle with the Rear of the Car raised avoids this problem.
Coasting in Neutral:
When Coasting in Neutral there is a big difference in Speed between the Mainshaft and Layshaft Gears. This does not occur when the Gearbox is in Gear. Coasting in Neutral results in a lack of Lubrication to the Mainshaft and damage will result.
Aussie 4 Speed Gearbox With Cover TCS:
Submission by TomKelly88 note that the rubber seal is located in the side cover not on the selector shaft itself unlike the other selector in this gear box and the selectors in earlier gearboxes. End of submission by TomKelly88
These are the ratios
rev 3.74:1 They where used in one tonners for pulling a lot of load, but for everyday if you dont need it dont get one cause the would give good acceleration bu otherwise be a nightmare. Cheers
ALL TRIMATICS , AUSSIE 4 SPEED AND 3 SPEED all syncro have the same number and type of splines on the out put shaft only the early part syncro boxes had a course spline output shaft... v8 have a different size uni to sixes.. wombat..
Full image set at HQ_SS' Shed