15 replies to this topic

[kkonstantinopoulos]

Hi all, 

I think I have a bit of a gearbox mystery on my 1970 Mini 850, and I'm hoping someone here might have some insight.

 

The gearbox is a 22G1128 remote-change unit. From everything I've been able to find, I was under the impression that these gearboxes were fitted with a 4-synchro helical gearset. However, mine appears to have a 3-synchro straight-cut gearset in it.

 

I'm fairly confident about this for two reasons:

• It has the characteristic straight-cut gearbox whine.
• First gear definitely has no synchromesh (I discovered that the hard way many years ago).

Unfortunately I can't strip the gearbox to inspect the gears and count teeth because the car is my daily driver, but I'm trying to understand what I have before I eventually rebuild it.

 

What puzzles me is that, to the best of my knowledge, this gearbox has never been changed, rebuilt, or replaced during the car's life. If that's correct, it would appear to have left the factory like this.

 

Any thoughts or insight would be greatly appreciated.

[nzmember]

You probably have a 22A1228 gearbox. Check the numbers again.

[Spider]

1st Gear Synchro could simply be knackered.

Off hand, you can't fit a 3 Synchro Gearset in to a 4 Synchro Case.

[kkonstantinopoulos]

You probably have a 22A1228 gearbox. Check the numbers again.

 

The case is clearly stamped 22G1128. 

 

 

1st Gear Synchro could simply be knackered.

Off hand, you can't fit a 3 Synchro Gearset in to a 4 Synchro Case.

 

I'm fairly certain 1st gear doesn't have a synchro. The synchros on 2nd, 3rd, and 4th are all quite worn, but 1st behaves as though there isn't one there at all.

 

Even if it turned out to be a 4-synchro gearbox with a completely worn-out 1st gear synchro, that still wouldn't explain the straight-cut gears. In that case it would have to be a straight-cut 4-synchro gearset, which as far as I'm aware was never a factory option. The only straight-cut 4-synchro setups I know of are the modern aftermarket SCCR kits, and I can't see how one of those could have ended up in this gearbox given that the car has never had a gearbox rebuild or overhaul.

[stuart bowes]

it hasn't had SC drop gears fitted or anything, has it 

 

is the whine in all gears or just 1st and reverse

[viz139]

The Mini is 56 years old ,are you sure you know its history from new?

Where was it manufactured , I know mini 850 assembled in Ireland (CKD) still had magic wand  gearbox?

What is the mileage , if it has never been apart the whine could be the idler bearings on the way out or the main bearing going which will effect the synchro on first ?

[kkonstantinopoulos]

it hasn't had SC drop gears fitted or anything, has it 

 

is the whine in all gears or just 1st and reverse

 

I'm pretty sure it still has the standard helical drop gears. I don't see any reason why they would have been changed on a standard 850. Furthermore, if it only had straight-cut drop gears, I'd expect the whine to be present regardless of which gear was selected. What I hear in the car is much more consistent with a straight-cut gearset, as the whine in 4th is quieter than the lower gears.

 

The whine is present (and quite loud) in all forward gears though, not just 1st and reverse, which is why I'm convinced there's a straight-cut gearset in the gearbox.

[kkonstantinopoulos]

The Mini is 56 years old ,are you sure you know its history from new?

Where was it manufactured , I know mini 850 assembled in Ireland (CKD) still had magic wand  gearbox?

What is the mileage , if it has never been apart the whine could be the idler bearings on the way out or the main bearing going which will effect the synchro on first ?

 

This Mini has been in my family since new, so I’m fairly confident about its history. It was manufactured at Longbridge, and I still have the original import paperwork from 1970 somewhere in the archives.

 

It’s currently on around 76,000 km. The idler bearings are already fairly worn, but I don’t think that would produce this particular noise. What I’m hearing is a very distinct and loud straight-cut whine, which is why I’m leaning strongly toward a straight-cut gearset rather than bearing noise.

[Spider]

. In that case it would have to be a straight-cut 4-synchro gearset, which as far as I'm aware was never a factory option. The only straight-cut 4-synchro setups I know of are the modern aftermarket SCCR kits, and I can't see how one of those could have ended up in this gearbox given that the car has never had a gearbox rebuild or overhaul.

 

Absolutely the Factory did do 4 Sychro Gear Sets, there were a few different types, here's a couple;-

 ST Gear Sets.jpg   19.25K   1 downloads

 

The whine you can hear can also come from worn bearings, given the age of the car, this is quite likely.

 

 

[stuart bowes]

 

it hasn't had SC drop gears fitted or anything, has it 

 

is the whine in all gears or just 1st and reverse

 

I'm pretty sure it still has the standard helical drop gears. I don't see any reason why they would have been changed on a standard 850. Furthermore, if it only had straight-cut drop gears, I'd expect the whine to be present regardless of which gear was selected. What I hear in the car is much more consistent with a straight-cut gearset, as the whine in 4th is quieter than the lower gears.

 

The whine is present (and quite loud) in all forward gears though, not just 1st and reverse, which is why I'm convinced there's a straight-cut gearset in the gearbox.

 

 

fair do's, just ruling a couple of things out.  sometimes people change the drop gears literally just for the noise don't they, who knows

 

and as you probably know already 1st and reverse are straight cut anyway

Edited by stuart bowes, Yesterday, 10:36 AM.

[kkonstantinopoulos]

I filmed a short video to provide a bit more context, as the sound may help determine whether this is actually a straight-cut gearset or simply noise from the idler bearings.

 

I didn't attempt a downshift into 1st while moving, as that would almost certainly result in a crunch without rev-matching, but you can clearly hear the whine through the gears. To my ears it sounds very similar to the straight-cut gear whine I've heard from other Minis.

 

Here is the video: https://drive.google...iew?usp=sharing

[Spider]

Just going off revs and speeds, they do seem to be standard ratio gears to me.

[kkonstantinopoulos]

Just going off revs and speeds, they do seem to be standard ratio gears to me.

 

So is the most reasonable conclusion just that the gearbox and bearings are heavily worn? I didn’t think wear alone could make it sound this close to straight-cut gears.

 

I’m also still not fully convinced it’s a 4-synchro box. If the synchro on 1st was there but just very worn, I would expect to feel some friction/resistance in the shifter as it tries to match speeds. On the other synchros (which are also quite worn), I can feel that resistance through the lever when shifting slowly as they work to match the gear speeds. With 1st, I don’t feel any of that frictional resistance at all, it just goes straight into a crunch.

 

At the next oil change I think I’ll stick a borescope up the drain hole and see if I can get a better idea of what’s going on inside.

[stuart bowes]

Im not sure how much you'd see with a borescope to be honest, I've never tried it but on mine (newer 'box but same layout) as you go through the drain hole you'll have the oil pickup basket right in front of you, you'lve got to get up and over that but the layshaft is in the way, them back down again into where the reverse gear is, if you turn directly left and look up, that ring there which engages with reverse, that's your 1st-2nd syncro ring, you won't be able to see much if anything of the baulk rings, but possibly if you put it in 2nd you'll get a look at the 1st syncro teeth and vice versa

 

it's a gearbox off inspection job really isn't it, if you're genuinely concerned

[Spider]

You just won't get where you need to look with a borescope through the oil drain hole. Pretty much as soon as you go in to the box there, you'll hit up against the oil strainer for the pick-up pipe.