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Popping Out Of Fourth And Now Crunching Into 2Nd.


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#1 alex-95

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Posted 10 April 2019 - 08:08 PM

I've rebuilt my gearbox with new bearings, baulk rings, gear sector forks, springs and balls for the synchro hub  (photos of it in my build thread page 45 and 46 ---> http://www.theminifo...rebuild/page-45).

 

I drove it for the first time over the weekend every gear selects well with no crunching but when revving over 3000 rpm it will pop out of 4th gear, It hasn't popped out of 2nd gear and don't think it will, but don't think I've used it at over 3000rpm so may well do it . The engine steady rubbers and gear-selector bobbins are good and have been on the car for about 3000 miles, The rubber in the diff cover seems pretty solid. I had a different engine and gearbox in previously and it never popped out of gear then. 

 

When I'm in fourth gear I can move the gearstick back quite a bit from where it sits in as in the below video.

http://i.imgur.com/0UamjNf.gifv

 

 

I can only think it's something to do with the synchro hub?

 

Any other ideas?

 

Cheers 


Edited by alex-95, 14 April 2019 - 12:40 PM.


#2 Wiggy

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Posted 10 April 2019 - 08:23 PM

My freshly rebuilt gearbox occasionally used to pop out of 4th. After a couple of thousand miles it stopped doing it.

Scares the utter poop out of you when it happens, eh?

#3 alex-95

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Posted 11 April 2019 - 04:41 PM

My freshly rebuilt gearbox occasionally used to pop out of 4th. After a couple of thousand miles it stopped doing it.

Scares the utter poop out of you when it happens, eh?

 

Oh right, maybe it's the baulk rings wearing in?

 

Yeah did the first time :lol:



#4 Moke Spider

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Posted 11 April 2019 - 08:27 PM

I've had a look at your build thread, some nice clean and considered work going on there :proud:

 

Nothing from that poked me in the eye but I couldn't see everything.

 

I can't get your video up, but that could well be my PC too.

 

Some causes for this can be there's something not allowing the shifter itself to move all the way in to gear, those rubber bellows are a prime candidate for this but can be other things. It could be worth while selecting 4th, looking & measuring how far the shift input shaft (in the gearbox) has moved, then disconnecting it (knock out a roll pin), from Neutral, select it again directly on the shaft itself and see if it goes in further.

 

While nothing stood out in your pics and yes I see all new parts there, just to not discount it, the most common cause for this if internal in the gearbox is a worn Mainshaft Bearing, allowing the Mainshaft to float. Next to that would be the 1st Motion Shaft Bearing and doing the same. It's also possible that the Circlip for the Bearing has popped out - they do have a right and a wrong way about of being fitted.

 

Excessive clearance in the Fork to the Hub (0.015" is the max allowable, though, for me on this one, any more than 0.008" and I change them).

While on the bench and before fitting to the engine, you need to select each gear in turn and check when selecting that you are getting some over-shoot on the outer track of the hub. The Minimum Overshoot must be 0.012" and the Maximum you want is 0.020", any more than that and you'll be looking for synchro hub balls and springs :D  This is 'set' by the bosses on the selector forks, these bosses are the ones that the common shift rod goes through.

 

Something (?) in the bottom of the transfer housing. This will foul the common shift rod  and stop it going all the way in to 4th gear.

Excessive play in the Nose Bearing between the Mainshaft and 1st Motion Shaft.

 

Excessive end float or missing thrust washer from the small end of the Laygear.

 

The Bell Cranks not assembled in the right order.

 

That's all that springs to mind. If I think of anything else, I'll post them up.



#5 alex-95

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Posted 11 April 2019 - 08:57 PM

Thanks for looking over my pictures :thumbsup:. I left the little boot off as it was too tight to get on, Some of your other options I'm pretty sure are all OK, I'll try and have a look at measuring it connected and disconnected over the weekend. 



#6 Moke Spider

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Posted 11 April 2019 - 09:28 PM

Two more items to add to my list of Internal stuff (just what you wanted to hear!)

 

Coming back to my comment on a worm Main Shaft Bearing and in line with that (Yes, I see you have a new bearing here), if when mounted and the retainer plate is tightened up the Bearing Floats (as it will do if over shimmed or the 'C' Clip is too narrow) it will have the same effect.

 

Going back a fair way now, I seem to have a recollection that you had burnt out the Baulk Ring on 4th Gear ?

 

If so, with these Gearbox Cases, this is usually from the Register in the Centre Web of the Gearbox Case for the Main Shaft Bearing being Machined too deep. From measurements I've made over loads and load of these cases, often they are in the region of 0.020" too deep. The pushes the Mainshaft too far forward, in to the 1st Motion Shaft and is what causes the Baulk Ring on 3rd or 4th gear to burn out. I'm not sure you had this issue (can't recall!) and if you did, what you did to correct it.

The other effect it will have is to remove all over-shoot from the Synchro Hub when selecting top gear and this will also be a cause for it to jump out.

 

One other cause is if the Baulk Ring on 3rd Gear is sitting too tall when fitted up. This will push the Inner Hub closer to the 1st Motion Shaft and not allow the Detent Balls to proper find their track, thus not full engaging and also leading to jumping out.

 

 

These Gearboxes have load and loads and LOADS of very small detailed items in them, all critical. Around 80% of the time, we can just replace the normal consumables within them - Bearings, Baulk Rings, Forks, Layshaft - without paying too much attention to them and happy days. But now more and more non-genuine parts are appearing on the market for them, we need to pay a little more attention to them - not to say Alex, that you've been at all careless, far from it.

 

A few years back, I did start writing a manual to cover the overhaul of these gearboxes, it is very much a work in progress, so far it's around 120 pages - and that only stripping and some inspection,,,,,  I don't think I'll ever get there with it but I don't class myself as an expert with them, I'm only learning like the next guy and despite what I have seen and found over the years, there's still 'new' stuff that turns up,,,, oh the joy!



#7 alex-95

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Posted 14 April 2019 - 12:47 PM

I haven't had to time check anything properly yet, but after driving the car a bit more it now crunches into 2nd gear when dropping down from 3rd. Could this be linked to the popping out of 4th gear? Being new baulk rings I wouldn't have thought it would be them but the rubbish quality of parts means it could be a possibility. 

 

Is it Time to pull the engine back out again?



#8 cal844

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Posted 14 April 2019 - 01:30 PM

I'd pull the motor and send it to Guessworks for a check and adjustment as required

#9 imack

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Posted 14 April 2019 - 02:51 PM

Yeah, time to take it out and strip it for investigation I'm afraid.

#10 alex-95

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Posted 15 April 2019 - 05:38 PM

I'd pull the motor and send it to Guessworks for a check and adjustment as required

 

Yeah, time to take it out and strip it for investigation I'm afraid.

 

Cheers guys, better pull my finger out



#11 Moke Spider

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Posted 15 April 2019 - 06:41 PM

I haven't had to time check anything properly yet, but after driving the car a bit more it now crunches into 2nd gear when dropping down from 3rd. Could this be linked to the popping out of 4th gear? Being new baulk rings I wouldn't have thought it would be them but the rubbish quality of parts means it could be a possibility. 

 

Is it Time to pull the engine back out again?

 

Does it do this every time or only when cold ?



#12 mk1leg

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Posted 15 April 2019 - 07:03 PM

did you put new selector seals and boot if so you might need to snip 1 ring off the rubber boot as I had the same trouble once I cut 1 rib off no more trouble



#13 alex-95

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Posted 15 April 2019 - 09:04 PM

 

I haven't had to time check anything properly yet, but after driving the car a bit more it now crunches into 2nd gear when dropping down from 3rd. Could this be linked to the popping out of 4th gear? Being new baulk rings I wouldn't have thought it would be them but the rubbish quality of parts means it could be a possibility. 

 

Is it Time to pull the engine back out again?

 

Does it do this every time or only when cold ?

 

Every time unfortunately, Got the engine out this evening and should have it apart tomorrow evening. I've read it could be clutch drag? maybe the clutch plate not sliding on the primary gear or the primary gear seized on.



#14 alex-95

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Posted 15 April 2019 - 09:05 PM

did you put new selector seals and boot if so you might need to snip 1 ring off the rubber boot as I had the same trouble once I cut 1 rib off no more trouble

Didn't bother with the boot, I've put them on before and disintegrated within a couple of months. Cheers



#15 Moke Spider

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Posted 15 April 2019 - 09:48 PM

 

 

I haven't had to time check anything properly yet, but after driving the car a bit more it now crunches into 2nd gear when dropping down from 3rd. Could this be linked to the popping out of 4th gear? Being new baulk rings I wouldn't have thought it would be them but the rubbish quality of parts means it could be a possibility. 

 

Is it Time to pull the engine back out again?

 

Does it do this every time or only when cold ?

 

Every time unfortunately, Got the engine out this evening and should have it apart tomorrow evening. I've read it could be clutch drag? maybe the clutch plate not sliding on the primary gear or the primary gear seized on.

 

 

OK, that does sound like a Synchro issue here.

 

If it was clutch drag, you'd notice it in every gear up and down and big time in when selecting reverse.






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