8 replies to this topic

[floormanager]

Hello,

Wanted to pick your collective brains.  Recently removed my old gearbox.  It was working well synchromeshes strong etc.  The only issue was it was noisy in 1st so I bought a new laygear to swap out with new shaft bearings etc.  Here's a pic of the laygear

 Laygear.JPG   42.02K   6 downloads

As you can see, there's pitting on the gear teeth.   What causes this?  What does it mean to the first gear, does this look like it needs replacing also?

 1st gear.JPG   44.52K   4 downloads

 

I'm still deciding how much to strip out and replace (or find someone who can do it for me) however, I've noticed a bit of play in the first motion shaft bearing, if you grab the transfer gear you can see and feel movement in the bearing.   That surely must be and indication of wear?

 

Your help and advice would be much appreciated.

Paul

 

[growlerbearnz]

I'd say that laygear should be replaced, but the 1st gear looks fine. The laygear suffers more wear and damage because it has fewer teeth: the same amount of wear is spread out over the many teeth of the first gear. 

You said "new layger", do you mean "brand new"? If it's used, check the internal bearing race(s) for pitting. 

Since there's that much wear on 1st (and you have the gearbox out), personally I'd replace all the bearings, but at least wash them all out and check for roughness. Check any needle roller bearing races/shafts for pitting, especially the laygear. 

The first motion shaft will always have some movement without the transfer gear case in place: the roller bearing on the outer end of the shaft takes most of the drop gear load and stabilises the shaft. (Handy hint: don't forget to install that roller bearing. I've seen a gearbox where that was left out and it was *not* pretty.) 

 

[floormanager]

Brilliant thank you growlerbearnz for your sage advice.  I do have a new 'still in the box' laygear to fit.  Pleased to hear 1st is okay as they are quite scarce at the moment, Minispares et. al all out of stock.

 

Like I said other than 1st gear being noisy the rest of the box was strong.  I've rebuilt 4 synchro boxes before but not done a 3 synchro box.

 

Paul

 

[dyshipfakta]

All the minis I have driven 1st is very noisy almost sounds like reverse.

[floormanager]

Yes they are straight cut but mine was very noisy

[Spider]

As the other guys have said, the Laygear is karput, but as you have a new one, that's not an issue.

 

The break through on the case deep in the root between teeth like you have can be from badly worn bearings / layshaft but could also be from a mis-match in tooth form. Given that 1st gear is usually such short term use, there is a lot of wear here on yours. There may also have been an inconsistency in the case hardness on the teeth, but it's usually the tips that end up softer than the root when that type of defect occurs. These Gearboxes can be quite a mine field getting all the right combination of parts and perhaps, if it is from a mis-match in tooth profiles, this maybe how that came about ?

The First Gear Outer Track you have, ideally should also be replaced. Apart from the chipping of the teeth, I can see wear in others. Also, given the wear on the Lay Gear, these teeth would have likely worn too for that. Looking at the tooth profile here, it does actually appear to me that the teeth do have the wrong profile and I can see how the wear in the Laygear likely came about. The tooth profile, as it appears here, while having some involute shape, they are too 'flat' to be right, I feel they should have more meat in the middle of the tooth face as it's would likely be because of that, the tips of these teeth were doing far more of the 'driving' that they should have.

[floormanager]

Thank you Spider for your analysis. It's amazing what a photo taken on a phone the other side of the World can assist with.  Technology eh?

 

Ideally, I'd like the 'box overhauled but not sure I'll find someone who will do it so might have to have a go myself.  As I said, first was always noisy hence the reason to remove it from the car and give it a rest.  Guess I'll be on the look out for some 3 Synchro spares.

Paul

[Spider]

Cheers Paul !

 

The actual Part Number on that outer Track is 22G440 (go figure) and is for the A type gear set, ie, very early type. The Laygear that goes with this is the 22A381 or 22A350 for the CR set.

The 22G231 Laygear is of B type form.

[floormanager]

Oh really? So I have a A type gear in a B type box?  Guess that explains the wear and noise.

 

I saw this on the minispares website so I thought it was the correct?

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