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The Spitfire that just needed a tidy up...


Josef

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8 hours ago, Paul H said:

Hi Pete , pretty sure it’s the same issue you identified on my Vitesse gearbox ref 156911 . 

Paul

I’ve just found your thread Paul. I think you were describing the whole hub unit moving relative to the mainshaft? My inner fits nicely on the mainshaft, but the outer can move in more directions than just up and down the direction of the mainshaft. If that make sense?

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Right, that’s what I expected would be the case. I wasn’t thinking something wobbling about in a gearbox could possibly be normal! I’m guessing the sliding sleeve is correct, and the hub is from an earlier box based on the fit of the synchro ring teeth. 
Going to be time to find another donor gearbox I think. You can get a replacement part for this shift mechanism, but at £125 I’ll gamble on getting something useful out of a second donor first, if I can find one.

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yes paul has a problem with the fit of the hub  . when i saw this i was under the impression of 3 rail single rail mixed up parts but the 1/2nd  hub part number is common to both   apart from reverse tooth count . have to say ive come across a good few gearboxes with very unmatched parts used by a previous meddler

Pete

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aha    3 rails   as a 13/60 does it have crash on 1st   ie  3 sync    not  4 sync ????

the 1/2 hub does shift on the back forth on  mainshaft there  is a ball that locks it up as y

ou make it slide during a change 

3rd 4th hubs are same but 1/2nd all very different as is the mainshafts  incl  OD 

pete

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The number on this box is for a 72 US Spitfire. It has 4 synchro rings in it so I assume most of the correct gearset. The 1/2 hub inner part does not have anything to lock against the mainshaft (I’m pretty sure it doesn’t at least, will have to double check later).

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Thanks Pete, but it's the 1st/2nd hub thats problematic. I've been playing around, the inner from the 3rd/4th hub is a good fit on the outer of the 1st/2nd. Which makes me more sure it's only the inner of the 1st/2nd hub that's wrong. I also can't get the ball bearings out of the 1st/2nd inner but that's probably unimportant for me right now!

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thats the same as we found in Pauls box  there is a explaination , but i dont have it (thought i did but wrong )

i have found this on others it makes no gearbox sense  the hub is used on a good  few variations/models 

i was sure it was single rail hubs in a 3 rail but thats not it .unless the part numbers have been pickled 

on canleys  156911 is superseded to 515377  but thats no lead either 

Pete

 

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I’ve just been playing around with the bits of gearbox again and have come to a conclusion. I think the centre of the 1/2 shift hub is just really heavily worn. Comparing with the 3/4 centre the diameters are the same, but the teeth on the 1/2 are a lot thinner, and some have almost step like forms on the inner faces. In the photos, right is 1/2 and left is 3/4.

Feels logical that the 1/2 will suffer the most punishment. Given the state of the input shaft tip too I’d guess at some of these parts at least came from a pretty high mileage box. 

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43 minutes ago, Mathew said:

That does look worn! I would of thought the outer part worn as well! Did it have sand in the box to keep it quiet!

The outer does not look or feel all that worn (this is the first gearbox I’ve opened though so this opinion may be revised in the future!). Based on the state of the synchro rings though I’d say this box has been “rebuilt” (opened, had a few new parts fitted, put back together) and then done very little, or even no, mileage. So the outer and inner parts of the hub could well be a mismatched set as it were.

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Yeah the 3/4 outer will go on the 1/2 centre, and it’s a similarly loose fit. Difficult to see in the photos but I’ve just noticed there are visible lips of worn metal on the ends of the teeth. I feel like the smaller tooth profile is just cause of how knackered it is!

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Just received a small but very rare thrust washer for the mainshaft from Mick Dolphin. The one in the box was actually cracked! So should be able to do a bit of measuring and see what other bits I might need. My possible spare gearbox lead is not panning out very fast, so I’m more and more tempted to just buy the offending 1/2 hub. Expensive, but it also means I wouldn’t be scrapping another gearbox just for one part… I’m pretty sure the rest of the important bits here are actually fairly decent. 

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So except for some rust on third gear the internals look alright. There’s no play in the 1/2 shift hub like in box number one so I’m pretty confident in my diagnosis of extreme wear on that one. Will be starting on taking the whole lot to bits tomorrow afternoon and will have a proper inspection then. 

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Well gearbox number two is in pieces. I’d say this is another one that was “rebuilt” not too many miles ago. The mainshaft tip is worn out, but it’s got pretty new looking synchro rings, new looking lay shaft, bearings feel smooth and so on. So I guess a rebuild kit was fitted without necessarily a good check for wear and tolerances on the rest of it. Anyway, the shift hubs feel more like I was expecting and definitely don’t wobble about all over the place!

I’ll take some comparison photos when I’ve cleaned up the parts of gearbox two. 

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The photos here mostly just show quite how knackered the shift hub in gearbox number one is. I think the edge of the tooth profiles of the outer gear on the shift hubs are slightly different, and the outer from gearbox one will not fit on the inner of gearbox two. Though given the state of the inner from gearbox one it’s reasonable to suppose that has resulted in some damage to the corresponding outer so that might be why. 
 

Anyway, I definitely now have enough parts to build a whole gearbox. So have ordered the replacement bits I’m going to need, and will get on with rebuilding it when they turn up.

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  • 3 weeks later...

Progress is going in tiny steps as I’m mostly waiting for back order parts to put the gearbox together again. The overdrive is sitting waiting for strip down and inspection, but I really don’t want to start that till I have a whole gearbox. However, I have just put the welch plugs back in the top cover, so that’s now complete, ready and waiting. I had to replace one of the detent springs, otherwise everything was serviceable after a good clean.

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  • 3 weeks later...

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