14 replies to this topic

[Wupding]

Help?!

 

I have acquired what I have been told is a genuine GT Gearbox

 

It has 22G1832 on the casing and the Lay gear states 22G1040

 

Please can someone shed some light if this is the right gearbox for the year of the car?

 

Also, what would be the best ratios to have it refurbed to?

 

I believe that if the gearbox is original it should be

 

1st; 3.330

2nd; 2.094

3rd; 1.353

4th; 1.000

 

Thanks in advance for all your help

[A-Cell]

The gearbox casing is a rod change small idler gear one, the Laygear was used on Cooper S and 1275GT and would be closer ratio. it has 15,20,25,29 teeth. The 1st motion would have 18 teeth. This box was married upto the A series engine.
However the A+ engine with the later standard gearbox was started to be fitted on production as early as 1979, so a 1980 GT would not have this gearbox as it would not marry upto the A+ engine.
The A+ engine was developed for introduction with the Metro which started life as the ADO88 slated for sale in 1979 so the tooling was ready and the A+ engine production began in 1979 and these engines went into the Mk3 Allegro and Mini. The actual Metro, the LC8, larger than the ADO88 did not launch until Oct 1980.

[A-Cell]

What engine is in the car now? If an A+ then the box you have wont marry upto it. If the engine has been changed and is an A series then it will fit.

[Vipernoir]

A+ engine doesn't neccessarily mean an A+ gearbox.

The small idler transfer housing and 'box will fit quite happily under an A+ block, and I'm sure that BL wouldn't have retooled to put a close ratio gearset into an A+ casing.
Without changing the brochures, even BL couldn't sell a GT without the correct gears.

[Wupding]

Hi

 

My block say 12H706AAH    Z 29256

 

Does that Help?

[Spider]

The Original Gearbox would have been an A+ as the other guys have said, with a DAM2886 Case, regrettably, these were probably the weakest gearbox case that BL ever made, I broke countless numbers of them, and it didn't take much to do so. As a result, they are a little hard to find.

 

Gear Sets fitted would have been same as the earlier Rod Shift on the Main Shaft, though it will have had the 18 mm nose.

 

First Motion Shaft would have been a DAM3167, this has 18 teeth and also fits over the 18 mm Nose Bearing of the Main Shaft.

 

Laygear would have been a DAM3168 (very rare!), this was 'gear-wise' same as MKII Cooper S (the 22G1040 that you currently have), however it was made such to run on the '3 Step' A+ Type Layshaft.

 

Drop Gears would have been the A+ Type, 29 tooth Primary and Input Gears with the 37 tooth Idler.

 

Many of the later A+ Gears were either known as 'Single Line' or 'Twin Line' sets, the Gears that would have been fitted would have had no lines on them.

 

Final Drive would have been 3.44 in the Pre-A+ type.

 

<Edit: These were fitted to the Pre-A+ Engines from late 78 (October I think) with the A+ Engine coming on-line mid 79>

Edited by Moke Spider, 20 May 2015 - 09:14 PM.

[welshdan]

I had a cross over a to a plus gt box. It was the a gt gearset built into an a plus casing

[Spider]

I had a cross over a to a plus gt box. It was the a gt gearset built into an a plus casing

 

That may have been a DAM4818 which is another even earlier A+ Casing.

 

The DAM3167/DAM3168 were part of last GT Gearsets.

[A-Cell]

Hi
 
My block say 12H706AAH    Z 29256
 
Does that Help?

1275GT engines in 1978/79 were 12H706. The A+ block was used from engine number 026400 about mid 1979 on production line

[A-Cell]

To add further confusion to the actual parts used in the last 1275GT builds in Longbridge, the factory was undergoing huge changes to accommodate the new Metro. CAB1 was rearranged to make room for Metro final assembly and the Mini was moved from one side of the building to the other. Added to this that run out models often suffered from parts shortages due to poorly controlled logistics the specification may not have been very well controlled!

[Wupding]

I am even more confused now......

 

Will my 12H706AAH  Block 

 

Fit onto

 

a 22G1832 casing?

 

Or do I get a later Gearbox case and transfer over the GT Gears?

[Spider]

I am even more confused now......

 

Will my 12H706AAH  Block 

 

Fit onto

 

a 22G1832 casing?

 

Or do I get a later Gearbox case and transfer over the GT Gears?

 

Yes, they'll fit together, no issues.

[Wupding]

 

I am even more confused now......

 

Will my 12H706AAH  Block 

 

Fit onto

 

a 22G1832 casing?

 

Or do I get a later Gearbox case and transfer over the GT Gears?

 

Yes, they'll fit together, no issues.

 

Hi... And thanks Moke

 

Is it wise to get a different casting if this is prone to giving out?

[Spider]

 

 

I am even more confused now......

 

Will my 12H706AAH  Block 

 

Fit onto

 

a 22G1832 casing?

 

Or do I get a later Gearbox case and transfer over the GT Gears?

 

Yes, they'll fit together, no issues.

 

Hi... And thanks Moke

 

Is it wise to get a different casting if this is prone to giving out?

 

 

Those particular casings were what I'd loosely call 'mid-range' and far as strength / reliability is concerned. The Drop Gears use the smaller bearing, the 'Nose Bearing' on the Main Shaft is the 14 mm type (smaller one of the two), the Laygear has the smaller bearing on it's little end - all these are not as good as they could be, though coming back to the casing itself, it's biggest weakness is that the Main Bearing is retained by 4 bolts, the additional hole can be a weak point in the casing itself.

 

Idler Gear Thrust Faces on the Case

 

 

 

The offending bearing

 

 

 

'Nose Bearing' journal on the Main Shafts, the 14 mm one on the right, the later 18 mm on the left

 

 

 

'2 Step' Layshaft, this has a smaller little end, the wear like crazy

 

 

Casing Failure (just one of many!)

 

 

 

By contrast the later DAM 5626 Casings only had 3 of the 4 holes drilled for the retainer and so far less prone to cracking

 

 

 

If the funds will stretch, then yes, i would recommend up-grading what you can afford to. If you can track down a DAM3168 Laygear, this would be a good starting point and there are modified Layshafts that will allow you to fit them to the earlier Case that you currently have.

 

Next in line, would be to Up-grade The Main Shaft, to the later 18 mm type, this will also mean changing the First Motion Shaft too, but again, these will fit the case you have without modification and the gear set currently fitted to your Mainshaft will go on to these later ones.

 

If originality is not an issue, then I would suggest finding a DAM5262 Case and A+ Drop Gears, by which stage you'd possibly be better off selling the Gearbox you have and starting over.

 

From my own experience, the earlier set up for the most part will only last for about 20 000 to maybe 25 000 miles before it starts getting noisy from the Idler Gear Bearing but more so from the Layshaft wearing. You may get as many as 50 000 miles before it needs a rebuild, but 35 000 - 40 000 would be closer to the mark, especially if topped with a 1275.

[Spider]

Just found a couple more photos.

 

These are of the DAM5262 Cases, be aware as even these are prone to cracking!

 

 

 

I will say though that it is quite rare to find a cracked one, though I've had two here in the past 12 months. It always pays to check.

Edited by Moke Spider, 22 May 2015 - 09:59 PM.