Aussie 4spd XU1 there is one standard for the late LC and most of LJ and then 3 x others homologated for 1973 XU1. Early LC use an Opel box, not sure of its ratios..

Standard (XU1 M20) is the same ratios as V8 M21 except 3rd gear is 1.25:1. These are essentially the same box as a normal 3.05:1 1st gear M20 but use an input shaft with the same gear on it as the V8 M21. The cluster gear is a modified M20 cluster with the front gear different to mesh with the M21 size input shaft gear

Optional M21 is the same ratios as V8 M21.
Optional close ratio box is the same as the optional L34 box with 2.32:1 1st gear.
Also the standard GTR M20 (3.05:1 1st gear) was homologated.

It is unlikely any production XU1 had these optional boxes, they were homologated for GroupC rules.

Edited by user Wednesday, 24 February 2016 9:18:27 PM(UTC)  | Reason: Not specified

There were 3 x Aussie 4spd with M20 code (grabbed these online as I don't have my books with me so hopefully correct!):

XU1 is:

1st & reverse - 2.54:1
2nd - 1.83:1
3rd - 1.25:1
4th - 1.00:1

Regular M20:

1st & reverse - 3.05:1
2nd - 2.19:1
3rd - 1.51:1
4th - 1.00:1

HQ 6cyl commercial M20 (later became M22 (around 1974)):

1st & reverse - 3.74:1
2nd - 2.68:1
3rd - 1.68:1
4th - 1:1

That is one of the optional ratio sets I was talking about, same as the optional L34 ratio set. Very rare cluster gear.

I wouldn't use it in a HR ute, sell it to an L34 owner and buy a normal M20. In a HR ute with 13" tyres and a normal 6cyl and a normal M20 i'd run a 3.08 or 3.36 rear end, just depend upon what you are using it for.

From memory the 2813496 cluster is indicative of a 3.05 1st gear (M20) box.

Dr Terry

It's listed for HQ for 173 and 202 passenger vehicles, and for 253.

That doesn't mean it's from a HQ, just that it could be.

Edited by user Tuesday, 1 March 2016 11:05:27 AM(UTC)  | Reason: Punctuation

XU1 box is the same as what you have except the input shaft has the same size gear on it as a V8 2.54:1 M21 box, and the cluster gear has the gear at the input shaft end to match the input shaft. The XU1's 899 cluster gear is essentially the 1st, 2nd and 3rd gear portion of a normal 3.05:1 M20 cluster joined to the end gear of an M21 cluster. This is why 1st and second gear ratios of the XU1 box mimic the M21 as the physical gears themselves (input shaft, front gear of cluster, 1st and 2nd are the same (all aussie 4spd's share the same physical 1st and 2nd gears)). However as the XU1 box uses the M20's 3rd gear and matching gear on the cluster it means the actual 3rd gear ratio is 1.25 rather than 1.38.

I guess the other way to try and describe the XU1 box is (ignore the length of the input shaft) take a normal M21 box, put in an M20 3rd gear and modify the cluster gear where it meshes with 3rd gear so that it has an M20's gear on the cluster. Now taking into account the length of the input shaft, when you describe it this way you see that 4 components need to be changed to convert an M21 into an XU1 box (input shaft due to length, input shaft cover due to length, cluster gear and 3rd gear). Whereas only 2 components need to be changed to convert an M20 into an XU1 box (input shaft and cluster gear), or 3 if you are changing a V8 M20 into an XU1 box as you'd have to change the cover as well.

So using the above info if you get it clear in your head, you can convert a V8 M21 into a 6cyl M21 by using the XU1's input shaft and a 6cyl input shaft cover in a V8 M21 box. This box would have the M21's 1.38:1 3rd gear rather than the XU1 M20's 1.25:1.

Edited by user Tuesday, 1 March 2016 1:20:07 PM(UTC)  | Reason: spelling