15 replies to this topic

[jonlad]

Hi folks

I'm in the middle of rebuilding my 'a+' gearbox, following the amazing guide that guesswork put together in the FAQ section. For the record its invaluable, thanks. I wanted to check a couple of things

 

I have replaced baulk rings, both mainshaft bearings in the case and refitted.

 

1) the gear selector will not move when in 1st/2nd or 3rd/4th positions. I can't remember if i could select gears by hand before, but the only position that it will move fwd/back in is reverse. Is this normal?

 

2) when i put the layshaft in, it locks everything up solid. It feels like when i put the shaft in, that the shafts are too close together and i have to tap the layshaft in with a mallet. Is this right?

 

Thanks in advance

Jon

Edited by jonlad, 12 October 2017 - 08:46 PM.

[Spider]

Selecting Gears requires the selector and spool to be in the right place, or the spool will prevent the gear selection. Be aware too, that the Synchro Hubs are on a detent, so they need a bit to start them moving. I'm saying this on the assumption the the Mainshaft and Synchro Hubs are properly seated in the forks.

 

In regards to the Laygear, is it the same laygear that came out of the set, or has then been replaced or made up from loose parts?

 

The Laygear should just about fall in to place, certainly not need tapping in.

 

Some possibilities for this could be;-

     not enough end-float (best checked before the Mainshaft is fitted). 0.0035 to 0.0065" end-float is needed.

     Bad Gearbox Case (poorly machined).

     Mis-match of one or several of the gears to the Laygear. Basically and I'll say straight up, this isn't quite complete, but you'll have either all

           plain gears, single line or twin line. The 'lines' refer to a 'line' that is ground across the tips of the teeth. They have to be used as same

           type sets. The laygear though only has this ID on the largest Gear of it.

[Rorf]

Did you assemble the inners of the synchro hubs the right way around. The minimania videos are another good source to assembling gearboxes.

[jonlad]

Thanks for the replies gents.

All the parts are what came out of the original box (save for two bearings and baulk rings). Though I've never seen it running, nothing seemed difficult to get out.

 

Regarding the laygear... End float could be a possibility. I replaced the big thrust on the laygear, I might resort to the old one and see how it fits. It was getting late last night so gave up instead of whacking something and bending or breaking it!

 

It was the shaft that needed tapping in (though gently) almost like the hole in the side of the case was *just* too tight for the larger diameter on the shaft.  That said, I tapped it back out and the shaft isn't marked at all - though the box may be?!

 

Re-reading the guide from guessworks, there is a comment:

 

"Don’t be worried is some of the gears (especially 3rd will not spin) this is due to the fact that the gearbox has not been torque’d up which will pull the 1st and 3rd motion shafts apart a little and free up the gears."

 

I wonder if this has something to do with it?

 

regarding gear selection - Moke spider, I know what you mean, the spool and selector are in the right place. Reverse works like a dream but when I raise the selector pin into either of the top two linkages it wont move forward/back. everything is lined up in the selector forks too.

 

I do understand about the detent, perhaps I'll try with a little more gusto and see if that's all it is.

 

Thanks again for the replies, its all helpful!

[Spider]

Ah, OK, that puts a bit of a different slant on some things.

 

The Layshaft (as opposed to the Laygear) can appear 'tight' to go in, sometimes needing a wee bit more than hand pressure to slide them in, it's not actually from them being 'tight' but from them being pulled out of straight alignment as it goes in, until it picks up the small end.

 

If you haven't fitted the Input and Pinion Gears then tightened it, it can be tight to turn over as it will drag on 3rd or 4th baulk rings - sometimes both. If you find it tight after tightening these nuts, then it can be from warped or out of round baulk ring(s) or if a late gearbox case, from poor machining of the case.

 

The Hubs need a fairly good wack to select gears, I use a copper dolly and a soft face hammer to get them to do so. In fact, if you need less than this, the synchro hubs will most likely need some re-work. You should also spin the gears slowly while doing this (and everyone has 3 hands of course).

[Rorf]

You have mentioned new layshaft thrust washers - definitely could be causing the laygears to be tightening up.

[InnoCooperExport]

If you replaced the bearings in the case as well be sure to make sure they're not tapped in too far. When I rebuilt mine earlier this year I found that the bearings can sometimes go a bit further into the case than you'd like them to which can cause a bit of pinching on the mainshaft. That coupled with new baulkrings that caused a fair bit of seizing with everything together. I ended up taking it apart a few times before I worked out the issue. Torqueing up the box also helps because it pulls everything slightly apart. 

 

Be patient and don't force anything! It just takes a bit of fettle and careful examination. Checking the float is also certainly worth doing as it can make a world of difference. 

[Spider]

If you replaced the bearings in the case as well be sure to make sure they're not tapped in too far. When I rebuilt mine earlier this year I found that the bearings can sometimes go a bit further into the case than you'd like them to which can cause a bit of pinching on the mainshaft.

 

That is one area of the poor machining I've found with many of the later cases. The bearings need to be driven home, in the case of the first motion shaft bearing, so the circlip can be fitted and in the case of the Mainshaft Bearing, you can shim the retaining plate off so on assembly, the bearing won't fully seat, but in use, from the side thrust of the gears, the bearing floats, it will 'bounce' between the retaining plate and the seat in the case. From the measurements I've taken, it appears in these cases it's the Mainshaft seat that's been machined too deep, Off hand, I forget the exact number it's out by, by I think it was around 0.020".

 

This, as you've said, causes either the 3rd or 4th gear (or both) baulk rings to bind up on the gears. If left, it just burns the baulk rings and the cones on the gears out.

 

One cure I have done is to grind (in the surface grinder) the inner race of the Mainshaft Bearing to move the Mainshaft back to where it should be. Another cure would be to fit a shim of the appropriate thickness in to the seat of the case before fitting the bearing.

[AlexMozza]

One thing I do is measure the baulk rings.
I had a batch a while ago from a well known mini specialist which were terrible. They seemed physically to big. With the gear set assembled the gears would lock up.

[jonlad]

i appreciate the responses folks. The first motion shaft bearing did indeed bottom out leaving only just enough space for the circlip to go in, it was tight.

 

The mainshaft bearing bottomed out also (in the case) such that no shim is required when the retainer is fitted. And yes i fitted the circlip type ring on the mainshaft bearing

 

I think the best thing to do is carry on and torque everything up and see if it frees up. I didn't measure the bulk rings, they were mini spares items.

 

Thanks again for the thoughts folks, i will let you know how it goes if i get time to play in the garage one night this week...  <fingers crossed>

Edited by jonlad, 15 October 2017 - 07:20 PM.

[jonlad]

I forgot to add... i checked the laygear end float with new thrust, it was good. It just feels like the laygear is pushed off its axis by the meshing with the main gears so its difficult to get the layshaft in. This in turn locks everything up. I'll have another go and report back!

 

One other point... i managed to damage the bearing retainer. In the guide i'm following it says to torque the retaining screws up to see if a shim is needed. Foolishly i torque up the nut on the side of the retainer which is over the lay shaft lock tab which is not fitted by this point. The fact that there was a gap between the retainer and case (where the screw is) bent and cracked the retainer before the screw reached torque.

 

One to look out for folks! Good job i have a spare box to scavenge parts off.

 

The guide is locked (its in FAQs) so i can't leave a comment to warn others...

Edited by jonlad, 15 October 2017 - 07:41 PM.

[Rorf]

Most manuals do NOT say torque the bearing retainer bolts to check for the shim gap, they says to hand tighten the bolts. And this is after the third motion bearing has been tapped fully into the casing. Make sure you are using the correct RHP full width bearing.

[Racer_Pete]

New baulk rings will make the geartrain tight at first especially if fitted on 3rd/3th as Moke said. due to the bigger gap now created where as your old ones where probably nearly touching the face of the gears? I wouldnt worry to much about that as when it has been driven down the road they will soon bed in. Have you checked the lay bearings slide nice and freely up and down the layshaft before fitting?

[Spider]

Not suggesting others follow what I do, but I never fit the shims under the Mainshaft Bearing Retainer.

 

I assembly my boxes in this way (and compensate for it) to firmly anchor the bearing from any movement. Allowing this bearing to move is one of the leading things that occur towards cracking the centre gearbox web. I also loctite this bearing in place.

[jonlad]

Good news, and it was just as you said

 

Tightening the pinion nut and the input gear nut solved the problem...

 

All spinning freely.

 

Thanks for the help guys!