35 replies to this topic

[alex-95]

Checking over the idler gear and the aluminium casing today.

Problem one. One of the idler gear shims is stuck on the idler gear. I can't turn in so my guess is that the shim is seized on to the gear. Has any body else had this problem? is there anything I can do with it or is it now just an oily paper weight?

 

The second problem was probably caused by the first. The casing is slightly damaged where the shim fits against as shown in the photos, given it a quick measure with a depth mic theres a difference of 0.02mm (just under a thou). I have access to a mill so can skim the minimum off to make the casing flat again.

 

 

 

[nicklouse]

it will pop off just put a sharp blade in the gap.

[Spider]

The Thrust Washer will usually come off the Idler Gear, but sometimes needs 'help'. Whether it can be used again or not, you won't know until you do get them apart.

 

In regards to the Transfer Housing - how does the Gearbox side also look?  Looking at the Transfer Case, a little hard to say with certainty, but it looks like the wear is deep in one part than the rest of it. Also, looking at the shaft of the Idler Gear, it seems like it's had more load on the end of it than across the whole of the bearing area of the shaft.  If that's the case, then the Housing is mis-aligned to the Gearbox and this will have been the cause of these issues. Dressing it and freeing (or replacing) the Idler Gear and Thrust Washer will only result in the same happening again.

 

Check the Out-rigger Bearing on the First Motion Shaft Nose too.

 

If the Housings are misaligned, you could of course try different ones, but there's no guarantee here that they'll be any better - could be worse!

 

I had one recent that was real bad (0.9 mm misalignment) and chewed out the bearings and thrust faces in 10 000 miles. It also chewed out the Out-rigger Bearing too.

 

There are Stepped Dowels to coff coff maintain alignment between the Housing and the Gearbox. What I did was to remove these dowels, mount the Gearbox in the Mill, fit some Dummy Shafts to both Idler Gear Bearing and First Motion Shaft Bearing Tunnels, clock up (and log) the location of the Dowel Holes in the Gearbox (they are 7/16" dia on this side), fit the Housing and nip it up on the Studs, then re-bore the Housing on the Centres for the Dowels in the Gearbox (parallel), Turned up some 7/16" Dowels (in Stainless) and fitted those to the Gearbox.

 

There's no doubt other ways to skin this cat, but that was the best way I could come up with. Carbon mentioned to me that Vizard has a method mentioned in his book 'How to Modify your Mini', which I did read up on but I wasn't crazy about.

 

It didn't quite end there for this one as the tunnel for the Idler Gear Bearing was distorted too (in both the Housing and Gearbox). The Bearings just fell out.

[alex-95]

it will pop off just put a sharp blade in the gap.

cheers. That sorted that problem  Just stuck a scraper in the join and gave it a light tap and it popped off.

Edited by alex-95, 04 February 2018 - 07:26 PM.

[alex-95]

The Thrust Washer will usually come off the Idler Gear, but sometimes needs 'help'. Whether it can be used again or not, you won't know until you do get them apart.

 

In regards to the Transfer Housing - how does the Gearbox side also look?  Looking at the Transfer Case, a little hard to say with certainty, but it looks like the wear is deep in one part than the rest of it. Also, looking at the shaft of the Idler Gear, it seems like it's had more load on the end of it than across the whole of the bearing area of the shaft.  If that's the case, then the Housing is mis-aligned to the Gearbox and this will have been the cause of these issues. Dressing it and freeing (or replacing) the Idler Gear and Thrust Washer will only result in the same happening again.

 

Check the Out-rigger Bearing on the First Motion Shaft Nose too.

 

If the Housings are misaligned, you could of course try different ones, but there's no guarantee here that they'll be any better - could be worse!

 

I had one recent that was real bad (0.9 mm misalignment) and chewed out the bearings and thrust faces in 10 000 miles. It also chewed out the Out-rigger Bearing too.

 

There are Stepped Dowels to coff coff maintain alignment between the Housing and the Gearbox. What I did was to remove these dowels, mount the Gearbox in the Mill, fit some Dummy Shafts to both Idler Gear Bearing and First Motion Shaft Bearing Tunnels, clock up (and log) the location of the Dowel Holes in the Gearbox (they are 7/16" dia on this side), fit the Housing and nip it up on the Studs, then re-bore the Housing on the Centres for the Dowels in the Gearbox (parallel), Turned up some 7/16" Dowels (in Stainless) and fitted those to the Gearbox.

 

There's no doubt other ways to skin this cat, but that was the best way I could come up with. Carbon mentioned to me that Vizard has a method mentioned in his book 'How to Modify your Mini', which I did read up on but I wasn't crazy about.

 

It didn't quite end there for this one as the tunnel for the Idler Gear Bearing was distorted too (in both the Housing and Gearbox). The Bearings just fell out.

Thanks Chris. I'm not sure about the gearbox side, although that has been rebuilt by guessworks so assume it will be good but will check it. I'll stick a DTI on it to see if it's worn unevenly, Hopefully it's not misaligned. 0.9mm!! thats quite a bit out. 

[Spider]

Thanks Chris. I'm not sure about the gearbox side, although that has been rebuilt by guessworks so assume it will be good but will check it. I'll stick a DTI on it to see if it's worn unevenly, Hopefully it's not misaligned. 0.9mm!! thats quite a bit out. 

 

 

They are never spot on, but usually with how much they are out, we can all get away with, though 0.9 mm is huge!!

 

Looking again at your Idler, I'm sure yours is well out. It's clear from that that the Shaft has been running on the Bearing ends.

[Sprocket]

Never had an issue with the A+ stuff with any misalignment, certainly not worth bothering about. I modified the idler thrusts on mine with softer bronze bearings and then feed those with pressurised oil from the main gallery. I used a random A+ gear case, and an equally random A+ Turbo transfer case. No bother. Maybe the early pre A+ stuff was pants........... I've heard it all before, Austin Rover this and Austin Rover that, bad machining this, and poor tolerance that. I'll be frank, I've done a lot of CAD and CNC stuff for the A series engine and from the cooper S blocks right up to the MPi blocks, the holes are all in the same place.

[alex-95]

So tonight I got the gearbox out to look at the face and unfortunately it's not much better . The Gearbox has worn more at the bottom and the casing more towards the top. Measuring the sides of the wear it's 0.04mm out on both sides where the bottom is 0-0.01mm and of course can't measure the top. I'm wondering whether this is due to the top of the thrust face not having any face to bear on? It could be that the dowels aren't inline 'up and down' wise or because the bores for the bearings aren't square to the face or if the bearings are just knackered and the force of the helical gear pulled it that way. I'll now have to minimum skim both and sort out new shims/thrusts. I think I'll turn up a shaft to fit in the idler gear bearing bores and a 'tube' (can't think of a proper name  )to check the alignment of the dowels, if it fit's together with the dowels in and the bit's I've turned then I'll know that the dowels are in the correct position. If not then I can machine new dowels and holes when I machine the face square.

 

 

 

 

Thanks Chris. I'm not sure about the gearbox side, although that has been rebuilt by guessworks so assume it will be good but will check it. I'll stick a DTI on it to see if it's worn unevenly, Hopefully it's not misaligned. 0.9mm!! thats quite a bit out. 

 

 

They are never spot on, but usually with how much they are out, we can all get away with, though 0.9 mm is huge!!

 

Looking again at your Idler, I'm sure yours is well out. It's clear from that that the Shaft has been running on the Bearing ends.

 

 

 

Never had an issue with the A+ stuff with any misalignment, certainly not worth bothering about. I modified the idler thrusts on mine with softer bronze bearings and then feed those with pressurised oil from the main gallery. I used a random A+ gear case, and an equally random A+ Turbo transfer case. No bother. Maybe the early pre A+ stuff was pants........... I've heard it all before, Austin Rover this and Austin Rover that, bad machining this, and poor tolerance that. I'll be frank, I've done a lot of CAD and CNC stuff for the A series engine and from the cooper S blocks right up to the MPi blocks, the holes are all in the same place.

Cheers, I Wouldn't have thought they would be far out but could just be the odd one

[Wiggy]

I had this exact problem. Turns out the gearbox housing had taken a knock (thanks couriers), and therefore moving the upper dowel ever so slightly; making the transfer housing a bit tight to locate. This then misaligned the idler bearings a touch, and then caused the wear shown in the pictures.

I'd have thought the soft aluminium taking a slight knock over the years would be more likely than the dowel locations wandering from the factory. But that's a guess.

Oh, it also made the gearbox to block bolt nearest the dowel, ever so slightly harder to engage as that had moved too.

Edited by Wiggy, 08 February 2018 - 09:23 AM.

[Spider]

Alex, it does indeed appears your is out of alignment - enough that needs to be corrected. I don't see much point in dressing it, shimming it and reassembling without correcting it - you'll end up where you are now in short time. That's been my experience.

 

Never had an issue with the A+ stuff with any misalignment, certainly not worth bothering about. I modified the idler thrusts on mine with softer bronze bearings and then feed those with pressurised oil from the main gallery. I used a random A+ gear case, and an equally random A+ Turbo transfer case. No bother. Maybe the early pre A+ stuff was pants........... I've heard it all before, Austin Rover this and Austin Rover that, bad machining this, and poor tolerance that. I'll be frank, I've done a lot of CAD and CNC stuff for the A series engine and from the cooper S blocks right up to the MPi blocks, the holes are all in the same place.

 

Not sure if you've just been lucky, or if I've been unlucky. I have had some bits that have been acceptable though.

 

In regards to the issue in this thread, even David Viazard mentioned this and one possible fix in his early book 'How to Modify your Mini'. The problem is well known and is why the likes of Jack Knight and others market roller bearing conversions.

[xrocketengineer]

Stupid question: If you find the wear condition on the gear casing and correct it (machining, shimming etc.) and you are reassembling with the same transfer case, can you simply remove the dowels and just do without them?

[Wiggy]

No, the dowels are locating the housing exactly. The bolts just hold it on.

[xrocketengineer]

No, the dowels are locating the housing exactly. The bolts just hold it on.

Yes, but since the dowel locations are off and you have the idler and its (new) bearings and the input shaft with its (new) bearing, would that not line things up better during installation? However, if the dowels are for more than the installation, if they take dynamic loads during the gear box operation then they are definitely needed.

[Wiggy]

Na, there's a certain amount of 'slop' in the bearings, so you could put the housing on and bolt it up; but it still wouldn't be in the right place without the dowels.

 

As an experiment, I took the top dowel out, then placed the transfer case on with the idler in place. It takes the tiniest amount of rotational force on the top of the transfer case from the idler being free, to locking it up. Yes you could bolt it up when you think it's in the right place, but what guarantee have you got that it won't move in use.

[Spider]

Stupid question: If you find the wear condition on the gear casing and correct it (machining, shimming etc.) and you are reassembling with the same transfer case, can you simply remove the dowels and just do without them?

 

IMO, because of the surface area and number of fasteners, yes - provided it can be located correctly.