Have you tried to drive one? Bloody horrid especially reversing. Highway driving sure, but around town no fun. Those HX and early HZ V8 clutch setups are heavy on the pedal too.

M20 with 3.08 is a bit taller 1st and reverse gear than M21 with 3.36, and these were the standard GMH fitment for 14" wheels until the 253 was so gutless in HX they changed it to 3.55. 3.36 x 2.54 = 8.5:1. 3.08 x 3.05 = 9.4:1. 3.08 with M21 is 3.08 x 2.54 = 7.8:1. I've had standard 308 M21 with 3.01 rear axle and they are awful in stop-start driving. A fully laden HZ Premier with A/C, steer and trying to take-off up hill is a real challenge.

My first choice will always be 3:08 with a 4 speed. I absolutely hate the 3:36 in both WB utes I have had. They scream their tits off at 100 and are just not the go on the highway. I know it's horses for courses. I don't doubt around town the lower diff might be the go. Not on the highway though.
3:36 behind a turbo400 would have been a rocket off the line. I doubt that even 3:08 would have been common! They are generally in the 2,s.

So I got my HHS report proof back today.
Still a little confused as to what its actually telling me.
You see on the vehicle identification certificate I found under the seat it has the original engine number scribbled out and a different number written in with pen.

I assumed that this change would have been made when the previous owner changed it from manual to TH400.
Holden Historical services have listed it as the engine number on the certificate.

Could this mean that it was changed during production and the motor that is in it may be the original and it may be drilled for turbo pattern?
However "QT901953" wouldn't that number be a lot later than HZ???

If i could figure out how to host images on here I would show you exactly what I mean.
On the original vehicle identification certificate I found in the car, It has the engine number stamped QT and then the rest of the number is scribbled out with pen and 901953 is written above it in pen.

I assumed the correct/original engine number was the one that has been scribbled out.
Assuming that the 901953 was written in when the previous owner changed the the motor to TH400.

So QT90153 is the motor in the car now and has either been re-stamped or it has been drilled to take the TH400

What would the correct cast date need to be for QT90153 so I can check if its the original block?

Edited by user Monday, 3 July 2017 4:57:39 PM(UTC)  | Reason: Not specified

This is getting interesting. Would be great to climb over the car to try and work it out.

If a transplant was done at the dealership, you would think they would also need the pedal set up for the donor car to put the 4 speed in and they would have put in an auto brake pedal,

There's nothing way they would have left the clutch pedal in it?? They would have needed it in the other car.
I reckon that they stuffed the engine number up on the documents and that someone has swapped the transmission later on.

Edited by user Monday, 3 July 2017 6:28:23 PM(UTC)  | Reason: Not specified

Remember 1st gear in an M15 3spd was 3.07:1 (except the close ratio HT V8 box), and 1st gear in a normal M20 aussie box was 3.05:1. The 3.08 ratio rear axle was the standard rear axle for both of these boxes behind 253 until the HX 4.2L became such a dog they quickly changed the diff to 3.55. 3.08 diff is even better in an M15 3spd as reverse is 3.59:1 vs the 3.05:1 reverse with the M20. If you look at the ratios the M21 1st gear is actually closer to the M20 2nd gear than it is to M20 1st gear.
M21 on the other hand is 2.54:1 1st and reverse, and that makes a huge difference to the drivability with the 3.08 rear axle. This is why just about all 5.0L M21 cars from HK through to HZ are 3.36:1 rear axles as standard, only those rare few cars optioned with the economy 3.08 or the performance 3.55 exist.

Torana always used M21 with 2.78 rear axle as the gearing with 13" tyres was roughly equivalent to 14" tyres with 3.08 rear axle, and the car is significantly lighter than a Holden. For some reason L34 and A9X with 14" tyres didn't see this change, although both L34 and A9X both used DR70 tyres rather than the Holden's ER70 which were a bit taller meaning the ER70 with 2.6 did 45.7km/h/1000rpm versus the DR70 doing 44.8. Torana was a lot lighter too.
The 2.6 was the replacement for 2.78 in large salsbury in 1977 so A9X was treated as per L34. Lots of A9X also got 3.08 rear axle, as did L34 but with L34 the 3.08 cars also got a closer ratio box with taller 1st gear.

Edited by user Tuesday, 4 July 2017 8:14:50 PM(UTC)  | Reason: Fixed error

There was only 2 x V8 banjo ratios, so L34 had to have either 2.78 or 3.08 and it got both. The fact Torana was lots lighter than a Holden also meant it was easier to get off the line and thus 2.78 was deemed acceptable, same reason Torana got a banjo not a Salisbury for L32/3, L31 and L34 engines. Same reason manual Toranas got a smaller clutch than a Holden for the same engine.

A9X got the equivalent to what L34 got but in Salisbury rear axle, gearing really had little meaning as they homologated other ratios too like 3.36, 3.55 and even a rare 3.90:1 large Salisbury.

Wheels were simply the same rally rims as fitted standard or optional to Holden but with different offset to suit Torana. Tyres would probably be the smallest diameter H rated 14" tyre made in Australia at the time that GMH could affordably fit.

I agree the L34 wasn't for the average Joe as it was a muzzled race car in hiding but the A9X was, it was simply a road car with a few mainly stronger part tweaks to homologate stronger (more durable parts) for racing like thicker snout crank and camshaft, rear axle and the optional Super T10 box. It really had no more engine performance than any other post 6/76 LX 5.0L manual. Most A9X got HZ engines though which were a better (sorted) engine than the HX version, only the first one or two got the old HX engine. If say GMH had put the A9X's RTS under a 2-5/76 SLR5000 or SS with 5.0L/M21 and ran it side by side with an A9X the A9X wouldn't see the earlier car for dust, unless heavy braking was involved of course!