18 replies to this topic

[ac427]

I am thinking of getting a secondhand gearbox to rebuild. I would like to know what to look out for when buying a secondhand gearbox, especially the A+ DAM5626.

 

What exactly do you have to check for on the centre web, is it just cracking and that the hole is not tapped?

 

 

 

[MaximMini]

Hi ac427,

With regards to the centre web the DAM5626 is the strongest one as there are only three threaded holes bored to keep the main bearing retainer. One damage I came by in the past you can see in this thread:
https://www.theminif...-housing-scrap/

But then you will only be able to see after dismantling and clean.

As a precaution I do grind the centre webs smooth to avoid any stress risers on my gearboxes.

[Spider]

Find an early one. I know those up to 1988 were pretty good. They maybe a few years after that too, but I haven't yet come across them to check. The late ones, from about 93 are not great to rubbish.

If you look on the diff cap, there's a date code.

[ac427]

Hi ac427,

With regards to the centre web the DAM5626 is the strongest one as there are only three threaded holes bored to keep the main bearing retainer. One damage I came by in the past you can see in this thread:
https://www.theminif...-housing-scrap/

But then you will only be able to see after dismantling and clean.

As a precaution I do grind the centre webs smooth to avoid any stress risers on my gearboxes.

 

Thanks MaximMini, Is there any other area of the case that i should inspect?

 

 

Find an early one. I know those up to 1988 were pretty good. They maybe a few years after that too, but I haven't yet come across them to check. The late ones, from about 93 are not great to rubbish.

If you look on the diff cap, there's a date code.

 

Thanks Spider, Is the date code easy to understand or does it require decoding?

 

Was production quality reduced after '93?

Edited by ac427, 03 March 2022 - 09:50 AM.

[MaximMini]

This what the date code on the diff cover looks

 

And then there is a date stamped into the bottom of the gear casing like this

 

Last but not least this is how I treat the webs on my gearboxes to reduce stress risers (I hope that is what it's called in English).

 

 

[Gilles1000]

You should also check the surfaces where the drop gears are.

A usual failure is the idler gear bearing which then allows the gear to chew the casing. This can be repaired but not a happy find.

 

Cheers

Gilles

[ac427]

This what the date code on the diff cover looks

 

 

And then there is a date stamped into the bottom of the gear casing like this

 

 

Last but not least this is how I treat the webs on my gearboxes to reduce stress risers (I hope that is what it's called in English).

 

 

Thanks for the detailed reply MaximMini.

 

Do all A+ gears have the 'double groove'?

 

On the stress risers side, do you mean you smooth off any edges to spread the mechanical stresses?

[Spider]

Do all A+ gears have the 'double groove'?

 

There was 4 different gear sets fitted to the A+ Boxes over the years.

Original standard Ratio

Close Ratio (same as the original post 68 Cooper S)

'Single Line' these had wider ratios than the original standard ratio. When they started fitting these, the previous 2 sets were dropped.

'Twin Line' these were wider again (on 1st and 2nd) than the Single Line.

There was also a few combinations of drop gear sets too.
 

[nicklouse]

And then there is a date stamped into the bottom of the gear casing like this
 

That is not any date that I know.

[ac427]

 

Do all A+ gears have the 'double groove'?

 

There was 4 different gear sets fitted to the A+ Boxes over the years.

Original standard Ratio

Close Ratio (same as the original post 68 Cooper S)

'Single Line' these had wider ratios than the original standard ratio. When they started fitting these, the previous 2 sets were dropped.

'Twin Line' these were wider again (on 1st and 2nd) than the Single Line.

There was also a few combinations of drop gear sets too.
 

 

Thanks Spider, Is there any way to tell which ratios are in a gearbox, is it just a counting gearing teeth or is there an easier way?

Edited by ac427, 05 March 2022 - 11:39 AM.

[stuart bowes]

And then there is a date stamped into the bottom of the gear casing like this
 

That is not any date that I know.

The 17th of Hexember 1990

[Spider]

Thanks Spider, Is there any way to tell which ratios are in a gearbox, is it just a counting gearing teeth or is there an easier way?

 

The later sets with the lines are fairly obvious what they are.

For the earlier sets, look carefully on the Laygear, you might see a Part Number Stamped in to it;-

 

DAM3169   Standard Ratios

DAM3168   Close Ratios 

If you can't see the number, just count the teeth on the 1st Motion Shaft (this is the first gear that drives the largest end of the Laygear) - 17 tooth is standard ratios, 18 tooth is close ratios.

I mentioned too that the drop gears came in a few ratios, the standard types have unmarked gears, there's also single line available on the Primary and Input Gears and also a twin Line Primary Gear for the 1275. These all used the same Idler Gear and give Over-drive ratios. The plain gears are 29 tooth, the single line Primary Gear is 30 and twin line Primary is 31. The plain Input Gear is 29 tooth and the single line 28 tooth. Personally, I'd suggest sticking with the 1:1 Ratios here, and changing the Final Drive ratio to get the outcome you are seeking, the geartrain losses are higher when using these overdrive gears.

 

Here's a cheat sheet I put together a few years back for the all synchro gearsets;-

 

Hopefully it makes some sense. If you look across the top, pick out which Laygear you have, then look down the column, where there's a X, that gear will fit and mesh in that set. Pretty much all the early gears go together, with the exception of 1st Motion and Laygears and in the lined sets, only lines of matching number will go together. I haven't included the drop gears as I only use the 1:1 sets.

 

[ac427]

 

Thanks Spider, Is there any way to tell which ratios are in a gearbox, is it just a counting gearing teeth or is there an easier way?

 

The later sets with the lines are fairly obvious what they are.

For the earlier sets, look carefully on the Laygear, you might see a Part Number Stamped in to it;-

 

DAM3169   Standard Ratios

DAM3168   Close Ratios 

If you can't see the number, just count the teeth on the 1st Motion Shaft (this is the first gear that drives the largest end of the Laygear) - 17 tooth is standard ratios, 18 tooth is close ratios.

I mentioned too that the drop gears came in a few ratios, the standard types have unmarked gears, there's also single line available on the Primary and Input Gears and also a twin Line Primary Gear for the 1275. These all used the same Idler Gear and give Over-drive ratios. The plain gears are 29 tooth, the single line Primary Gear is 30 and twin line Primary is 31. The plain Input Gear is 29 tooth and the single line 28 tooth. Personally, I'd suggest sticking with the 1:1 Ratios here, and changing the Final Drive ratio to get the outcome you are seeking, the geartrain losses are higher when using these overdrive gears.

 

Here's a cheat sheet I put together a few years back for the all synchro gearsets;-

 

Hopefully it makes some sense. If you look across the top, pick out which Laygear you have, then look down the column, where there's a X, that gear will fit and mesh in that set. Pretty much all the early gears go together, with the exception of 1st Motion and Laygears and in the lined sets, only lines of matching number will go together. I haven't included the drop gears as I only use the 1:1 sets.

 

Blimey thanks Mate, That's excellent info.

[MaximMini]

Nick and Stuart, you are absolutely right that this can never be an actual dated stamped in the bottom but I'm pretty sure that the last two digits do correspond to the date on the diff cover. So, it could be a four digit serial number with two digits for the year at the end, if that makes any sense. 

[stuart bowes]

I don't pretend to know anything about it or have anything constructive to add lol I was just being silly

 

I thought in passing perhaps it had something to do with the week number or something but I couldn't make anything fit logically.  1990 makes sense though at the end