Aussie Four Speed

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Page created by T June 24th 2007:

Back to Gearboxes Transmissions and Differentials

Aussie Four Speed Manual Gearbox. Click to enlargen. Photo by HQ_SS.

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..

Ratios:

Yes, a bit misleading there. The M20-21-22 designations refer to the ratios, regardless of whether they fit 6s or V8s.
M20 ratios:
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

Identification:

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.

 

Aussie Four Speed Manual Gearbox Bellhousing, Engine Side. Click to enlargen. Photo by fjwb.

Aussie Four Speed Manual Gearbox Bellhousing, Gearbox Side. Click to enlargen. Photo by fjwb.

Aussie Four Speed V8 Gearbox with 205 mill input shaft. Click to enlargen. Photo by Kinswood.
     
     


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.  


Aussie Four Speed Manual Gearbox disembled. Click to enlargen. Photo by HQ_SS.

   

Aussie Four Speed Manual Gearboxes. 6 Cyl front, V8 back. Click to enlargen. Photo by HQ_SS.
The Transmission Control Switch on a Manual Gearbox from HX and later. This is the side plate of an Aussie 4 speed. The TCS is mounted on the 3rd and 4th selector shaft. Click to Enlargen. Photo by TomKelly88.
 
 
Gearbox damage. See the bent crossmember image. Click to enlargen. Photo by Dusty Dirt Roads.
 
Aussie Four Speed Clutch Cover Plate and Flywheel. Click to enlargen. Photo by HRPanelvan.
 
The Transmission Control Switch only permits Vacuum Advance in Top Gear when the Engine Temperature is above 63 degrees C. Click to Enlargen. Photo by TomKelly88.
 
Gearbox damage. See the bent crossmember image. Click to enlargen. Photo by Dusty Dirt Roads.
 
Gearbox damage. See the bent crossmember image. Click to enlargen. Photo by Dusty Dirt Roads.
  
M20 Gearbox from above showing the filler hole on the nearside . Click to enlargen. Photo by Zac.
Aussie Four Speed Reverse Light Switch. Click to Enlargen. Photo by HQ_SS.
 
Aussie Four Speed. Click to enlargen. Photo by SLR_6.
 
Aussie 4 Speed Allsynchromesh Gearbox with Reverse selected. Click to enlargen. Photo by Qute.
 
 
Reverse Light Switch. Click to enlargen. Photo by Snowdownunder.
 
Bent Crossmember associated with the failed gearbox. Click to enlargen. Photo by Dusty Dirt Roads.
 
3 Speed Crash  Box. The blue discolourisation may have been caused by Towing with the Rear Wheels on the Ground. Under this condition the Mainshaft rotates but the Layshaft doesn't. Photo by Stock EJ. Click to Enlargen.
Broken gears. Click to enlarge. Photo by Shaun.a
 
Gear identification number. Click to enlarge. Photo by Shaun.a
 

 

Towing:

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 selector shafts. These use 11/32" UNF nuts. Info by Ben Simpson. Click to Enlargen. Photo by TomKelly88.

   

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  

M22 Ratios:

These are the ratios M22 Ratios: 1st 3.74:1
2nd 2.68:1
3rd 1.68:1
4th 1:1,
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

Output Shaft:

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..

Links:

Full image set at HQ_SS' Shed

Tom Kelly's Shed

9939484 Cluster Info

Part Number Details.

Selector Nut Thread

Terms:

Terms

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