17 replies to this topic

[lildeucecoop72]

Gearbox gurus your advice again please!

I might have solved this myself, but wanted to check (and understand) as it's my first gearbox build.

Its a remote box with a close ratio setup. Its currently on the bench.

The facts:
Selector rods in and movement checked OK
Reverse gear in correctly and checked
Checked the compatibility of the gears/layshaft: all OK.
Everything throuroughly cleaned and assembly-lube used under assembly
All needle bearings new and carefully put in
Locking rings are set
All gear spun on the shaft before installation.
Baulkrings are new
All gears and syncros double-checked that they are the correct way around.
Main bearings are carefully banged in and hit home, with snap-ring inserted.
1st motion shaft is new.
Double roller bearing ring inserted, and carefully banged in and hit home.
Layshaft is new along with new bearings - endfloat at 0.0025" (within tolerance)
Retainer for double roller is shimmed, gap is 0, and torqued up to 18nm.


So the problem is when turning the input gear to test the motion of the gears:

Neutral: Gears all spin OK feels as it should, perhaps felt others that turn slightly easier, but put this down to new bits and the assembly lube that is quite thick…
Reverse: Once engaged, nearly impossible to turn. It took two hands and takes all my strength - surely not good!?
1st: Still took two hands but a little easier, again not good.
2nd: Easier still, one hand
3rd: Much easier
4th: Still resistance but nearly as neutral

I started to wonder what could make the resistance happen and which (though I guess logical and consistant) they got easier 'up-the-gears'?
could it be something to do with the selectors, or the synchros?
If everything spins ok in neutral then surely no resistance from the bearings. I resisted the urge to tear everything out and start again.
A mate suggested I torque up the input shaft, and pinon nuts to the correct torque (150ft/lbs). I couldnt see how that would help, but thought I would humour him.

After torquing both of these main nuts to 150ft/lbs (207NM).

Neutral: Gears all spin OK feels as it should - perhaps easier than before.
Reverse: Still resistance but possible to turn with one hand with no real issue, but not 'free' like neutral. Perhaps still a little stiff.
1st -3rd: Easier to turn with each change
4th: Same as nuetral.

Questions
Of course I am relieved...but how?
Surely torquing from both ends would make it even stiffer pushing everything togther? Or have I missed something?
Should the box behave this way (when changing up the gears)?
Is there something I could/should do that would make it even easier to turn?

Again this is mostly to check and understand-
Cheers

(I edited to correct a few typos)

Edited by lildeucecoop72, 01 May 2023 - 07:28 PM.

[timmy850]

Yes, having the bearings on the end torqued to spec will help everything settle in place properly.

The gears should have some kind of resistance when spinning, but no binding or tight spots

[Spider]

Tightening the 1st Motion Input Gear and Mainshaft Pinion Nuts seat the shafts to where they need to be, Then can appear seated, but until those Nuts are done up they won't be. Doing the Nuts up, pulls the shafts away from each other. 1st, 2nd and 3rd Gears are all on a common shaft (the Main Shaft), however, with the Pinion Nut not torqued up, the shaft naturally will sit a few thousands towards 4th / 1st Motion Shaft. If you have also fitted new Selector Forks, these will be in the wrong relative position and will likely press against the Hubs resulting in 1st and 3rd Baulk Rings dragging. A similar situation occurs with the 1st Motion Shaft when it's not seated that it will be positioned a few thousands towards the Mainshaft, which results on the Baulk Ring for 4th dragging.

 

So, before the built up box can be checked properly, those big Nuts need to be fully torqued up.

[lildeucecoop72]

Very grateful for your comments Timmy850 and Spider!
This sort of info is invaluable to a novice gbx builder. :)

Yes, I see why torquing will make the difference. For some reason I thought they pushed the main shaft and 1st motion shaft together, but of course they do the opposite.

The rolling resistance is the same, no binding or tight spots that I can ‘feel’.
Selector forks are not new and used with the same hubs as before. These seem to be smooth.

The fact that reverse gives most resistance and 4th gives least is normal then?

Thanks again.

[Ethel]

Reverse has the highest ratio, so it'll be trying to turn the main shaft most, relative to the 1st motion shaft. fits in with everything Spider said about torqueing the nuts up.

 

As it's on the bench I guess it's still missing one component - oil.

[DeadSquare]

You mention that you have just built up the gearbox with close ratios, but don't mention whether the cogs are new or whether they are straight cut.

 

At low RPM, straight cuts that have not bedded in will have more resistance than helical gears that have done 30,000 miles.

 

Reverse rotation is obtained by the addition of an extra straight cut cog in the gear train , which will always be an additional resistance to the transmission of power from the crank shaft to the drive shafts.

[lildeucecoop72]

You mention that you have just built up the gearbox with close ratios, but don't mention whether the cogs are new or whether they are straight cut.

At low RPM, straight cuts that have not bedded in will have more resistance than helical gears that have done 30,000 miles.

Reverse rotation is obtained by the addition of an extra straight cut cog in the gear train , which will always be an additional resistance to the transmission of power from the crank shaft to the drive shafts.

Hi Deadsquare.

All helical. All used, except for the 1st Motion which is new, 18tooth. The laygear (Dam3168) is from a different box, so not used with any of the gears before.

[Spider]

Reverse can feel tighter as in all the forward gear, those that are not engaged and 'freewheeling' are all mounted on the Mainshaft and while there's a difference in speed between those Gears and the Mainshaft, they are all turning in the same direction.

When in Reverse, all gears are 'freewheeling', however, the Mainshaft is turning in the opposite direction to the Gears, so there is some more drag via the Bearings under the Gears here. If the Selector Forks aren't exactly aligned where they should be, you may find some additional drag via a baulk ring.

 

One important check (of probably a hundred !) is that when assembled with the Interlock correctly in place, when in Neutral, that the Baulk Rings are all loose and not dragging on any of the gears. 3rd can be a common one here. You can get a small screwdriver in to flick the ears on the Baulk Rings to check for this.

[lildeucecoop72]

OK an update here after I took another look last night.

I got a hold of another box  (lets call that 'Box B') to compare it to my new build ('Box A'). 

The only differecne is that 'Box B' is a rod type with std. ratio, (I cant seeing this being a massive issue in the comparison).
Other than that they are of roughly the same same era (late 60s on Box A and 1973 Box B). Both pre A+.

Box B is untouched from the factory and full of very black oil, but works as it should, with nice smooth motion.

 

Both boxes are side by side on the bench and minus the diff.

I tested Nuetral and Reverse as a comparison.

I also got a second opinion from a chap who I share a garage with, who also builds engines and gear boxes (but has no experience with minis). 

 

The conclusion is that Box A still too stiff, especially in reverse. In his opinion reverse should offer only slight resistance and should freewheel without issue just like Box B does.
He reckoned the ammount of resistance would see my bearings and box innerds out very quickly and I would have a very short summer season!
So far this fella's advice had been sound on other issues, and my own gut feel especially when I compared the boxes agrees with this.

 

I decided to take a closer look at my build on Box A.

I found that slackening off the x4 3rd motion retainer bolts suddely loosend it up and reverse felt like Box B, so beginning to lean towards the assumption that this was incorrectly shimmed.

 

Does that sound like a logical cause?

 

 

Also, I had also used the retainer from another box as it was 'cleaner', but I didnt think anything of swapping these, so will go back to one that was on before.

I also removed the laygear to see if the issue might have been there, that was fine. It's possible that some of the sticky engine lube is also adding to the initial resistance but there was a huge difference when undoing those retainer bolts, and the gears spun like they did before putting in the box.

 

As Spider mentioned, I checked the cynchros/baulk-rings these are fine and move of their own accord.

 

I will investigate and post my findings. Found this old thread link useful.
 

https://www.theminif...ainer-shimming/

Edited by lildeucecoop72, 03 May 2023 - 11:18 AM.

[DeadSquare]

OK an update here after I took another look last night.

I got a hold of another box  (lets call that 'Box B') to compare it to my new build ('Box A'). 

The only differecne is that 'Box B' is a rod type with std. ratio, (I cant seeing this being a massive issue in the comparison).
Other than that they are of roughly the same same era (late 60s on Box A and 1973 Box B). Both pre A+.

Box B is untouched from the factory and full of very black oil, but works as it should, with nice smooth motion. The   

 

Both boxes are side by side on the bench and minus the diff.

I tested Nuetral and Reverse as a comparison.

I also got a second opinion from a chap who I share a garage with, who also builds engines and gear boxes (but has no experience with minis). 

 

The conclusion is that Box A still too stiff, especially in reverse. In his opinion reverse should offer only slight resistance and should freewheel without issue just like Box B does.
He reckoned the ammount of resistance would see my bearings and box innerds out very quickly and I would have a very short summer season!
So far this fella's advice had been sound on other issues, and my own gut feel especially when I compared the boxes agrees with this.

 

I decided to take a closer look at my build on Box A.

I found that slackening off the x4 3rd motion retainer bolts suddely loosend it up and reverse felt like Box B, so beginning to lean towards the assumption that this was incorrectly shimmed.

 

Does that sound like a logical cause?

 

 

Also, I had also used the retainer from another box as it was 'cleaner', but I didnt think anything of swapping these, so will go back to one that was on before.

I also removed the laygear to see if the issue might have been there, that was fine. It's possible that some of the sticky engine lube is also adding to the initial resistance but there was a huge difference when undoing those retainer bolts, and the gears spun like they did before putting in the box.

 

As Spider mentioned, I checked the cynchros/baulk-rings these are fine and move of their own accord.

 

I will investigate and post my findings. Found this old thread link useful.
 

https://www.theminif...ainer-shimming/

 

Please forgive me,  This may sound foolish and I do not wish to infer foolishness on your part, but when building your close ratio gearbox. your Main shaft cogs are matched to your Lay shaft ?

[lildeucecoop72]

 

OK an update here after I took another look last night.

I got a hold of another box  (lets call that 'Box B') to compare it to my new build ('Box A'). 

The only differecne is that 'Box B' is a rod type with std. ratio, (I cant seeing this being a massive issue in the comparison).
Other than that they are of roughly the same same era (late 60s on Box A and 1973 Box B). Both pre A+.

Box B is untouched from the factory and full of very black oil, but works as it should, with nice smooth motion. The   

 

Both boxes are side by side on the bench and minus the diff.

I tested Nuetral and Reverse as a comparison.

I also got a second opinion from a chap who I share a garage with, who also builds engines and gear boxes (but has no experience with minis). 

 

The conclusion is that Box A still too stiff, especially in reverse. In his opinion reverse should offer only slight resistance and should freewheel without issue just like Box B does.
He reckoned the ammount of resistance would see my bearings and box innerds out very quickly and I would have a very short summer season!
So far this fella's advice had been sound on other issues, and my own gut feel especially when I compared the boxes agrees with this.

 

I decided to take a closer look at my build on Box A.

I found that slackening off the x4 3rd motion retainer bolts suddely loosend it up and reverse felt like Box B, so beginning to lean towards the assumption that this was incorrectly shimmed.

 

Does that sound like a logical cause?

 

 

Also, I had also used the retainer from another box as it was 'cleaner', but I didnt think anything of swapping these, so will go back to one that was on before.

I also removed the laygear to see if the issue might have been there, that was fine. It's possible that some of the sticky engine lube is also adding to the initial resistance but there was a huge difference when undoing those retainer bolts, and the gears spun like they did before putting in the box.

 

As Spider mentioned, I checked the cynchros/baulk-rings these are fine and move of their own accord.

 

I will investigate and post my findings. Found this old thread link useful.
 

https://www.theminif...ainer-shimming/

 

Please forgive me,  This may sound foolish and I do not wish to infer foolishness on your part, but when building your close ratio gearbox. your Main shaft cogs are matched to your Lay shaft ?

 

 

Hi Deadsquare, not foolish at all  .  

 

It's questions like that could well reveal the answer, and I would rather that, and look 'a bit foolish' and learn from it. That's why I value this forum. 

 

The laygear DAM3168 is swapped out with the appropriate 1st motion shaft that has18 teeth 22G1371.
As far as I can see that is the only difference between that and the standard laygear 22G927 and 17th tooth 1st motion: 22G1093

 

If I am correct, DAM3168 / 22G1371 is the setup mini coopers used in pre A+ boxes, along with standard 1st-3rd gears, or at least they are compatible as far as I have been told on this forum.
This is something I also checked myself. I counted the number of teeth and checked the tooth forms. against the previous box that also had this setup and where my DAM3168 laygear originates from. (that box went bang for other reasons).
I also tested the rolling motion/meshing once the gears were 'in' and everything rolls as it should, nice and smoothly except for the afore mentioned problem when tightening the retainer bolts and 1st motion/3rd motion end nuts.

 

Here is the thread an the question of compatibility. https://www.theminiforum.co.uk/forums/topic/357753-22g1371-pre-a-1st-motion-compatible-with-dam3168-a-laygear/

 

If this is wrong, please let me know. I can then (though would rather not) revert back to the original laygear and 17 tooth 1st motion shaft.  It would be a shame as it would have been a rather expensive excersice (I bought a new 18th tooth 1st motion to fit the DAM3168), but better to have a functional box, and get driving. Norwegian summers are short! 

Edited by lildeucecoop72, 03 May 2023 - 02:26 PM.

[Spider]

I've found when they are tight or have drag when all the Mainshaft Bearing Retainer Bolts are slackened off, it's been usually 3rd Gear Baulk Ring dragging. If not on 3rd Gear, it's been the Ring on 4th Gear.

 

It might seem odd that 3rd will do this, but that's from the Synchro Hub 'staying put' and the Mainshaft being pushed towards the 1st Motion Shaft. There's more end float on the 1st / 2nd Hub, so that one tends not to have this issue.

This can come about for one, or several reasons that I've found;-

 

    One Baulk Ring being out of round (or more),

    One (or more) Baulk Ring out of spec and too small on the ID or having the wring taper angle,

    While I've never had one, it could be an incorrect size and / or taper angle on the Cone of a Gear,
    Selector Fork(s) out of Spec,
    Gearbox Case machined wrong,
    Mainshaft Bearing out of Spec,
    1st Motion Shaft Bearing out of spec

As the Gearbox is assembled, I'd suggest starting by doing the retainer bolts back up, then select each gear in turn and spinning over the Gears as you have been. If you find it suddenly frees up in one particular Gear, then it's most likely that one that's dragging (if dragging is the issue).

Set it back in Neutral, then flick the ears of the Baulk Ring to check it's actually floating free, not just rocking back and forth, but floating. If it's not floating, then there's the start of getting closer !

Check the Clearance between the Baulk Ring and the Gear Dog Teeth, when there's light pressure on the Baulk Ring, you should be able to do that by pushing the Hub towards the gear. If that's more than about 0.040" Then the fit of the Ring here is likely the issue.

If the Clearances here are OK, then the Selector Fork maybe out of spec, setting the Hub(s) not quite in the right position, though, I've only had that maybe a couple of times over the years. I know that you haven't changed these, but I would suggest not falling in to that trap, assume nothing, check everything ! You don't know what 'tweaks' were done in the factory.

The last check here, the Casing, I have found most late cases to have this error. The register for the Mainshaft Bearing that it's Circlip lands on is machined around 0.020" too deep. This sets the Mainshaft too close to the 1st Motion Shaft. I measure them this way;-

 

 

That's from the Register for the Mainshaft to that for the 1st Motion Shaft. That needs to be 7.400". At 7.395" you might be OK, but less than that, and you maybe getting drag on 3rd Gear. There's a few 'fixes' I have done to get around this, but my preferred method has been to make a shim to fit between the Mainshaft Bearing Circlip and the Register in the Case in order to set the assembled shaft in the correct location.

 

Fitting shims to correct this, between the Bearing Retainer and the Case is not the solution here. The Bearing is not then held firm (might feel that way from the fit in the Case, but it is not), then it will float back and forth on the case between the Register and the Retainer. As the Gears are Helix there are forces generated that will drive this. When driving and the shaft is thrust against the Retainer, happy days, but when it thrust the other way, it will drag on which ever Baulk Ring it's bind up on, resulting in burning out of that Baulk Ring. It will also wear the Tunnel in the Case in which the Mainshaft Bearing is in, resulting in a fully and freely floating Bearing.

[lildeucecoop72]

Thanks Spider!

 

I will certainly look at these points too. The baulkrings all are loosly-flickable and I will check how they are with the retainer bolts done up again.   

Most of the parts in the box have been used together before, and it was fine. (The casing, the main shaft, all gears, selector forks, synchro-hubs.)

 

Though that said, the list below shows a lot of  brand new or stuff not used in this box before, perhaps then, enough changes to cause an issue.

 

All shaft bearings, including 1st motion and layshaft NEW

First motion bearing RHP, NEW
Double roller bearing RHP, NEW

Layshaft is NEW (and of the A+ type for DAM3168 i machined my casing a little to accomodate

Laygear, DAM3168 (USED)

Layshaft/reverse lock NEW

Retainer USED ( from another box)

1st motion shaft 18tooth NEW

Circlip - possible used from another box (i picked the slightly thicker of the two, that were more or less the same)

Baulk rings NEW

Top hat for 1st gear USED - from another box as the original was slightly worn/pitted

 

As to whether case was badly machined, I will check this if it come to it.

'Box A' was before I started the rebuild, was not a factory setup, but rebuilt by a 3rd party when I got it, (Mini speed - something they got right for once) and it was fine before I dismantled it but they may well have tweaked something, that i haven't seen as I am still very much the novice here.

 

Again, thanks to everyone for the info so far!

[lildeucecoop72]

Ok...looks like I did incorrectly shim the retainer. After shimming it correctly, and torquing retainer bolts / the end nuts box A seems to behave as it should, and like box B.

All the gears turn as they should and baulk rings looks good. Phew!

Though I have a question though it might seem strange.

 

Should there be a tiny amount of axial end float along the shaft to allow oil into all the areas it should? Even though everything moves nicely now, It seems pretty 'tight', no play if I tug/push on the 1st motion roller and the main shaft at the 3rd motion end. Perhaps it should be that way.

I see there are oil galleries between the teeth on some of the gears to get oil to the needle bearings, but if there is no end float then would there be areas that could suffer from oil starvation? The obvious point is it all sits in oil, but if oil can't get in where its too tight...then that wont help.

 

Where on the box is end float measured and what should it be? I couldn't find any info in the Leyland workshop manual.

 

Thanks again.

[lildeucecoop72]

Ok...looks like I did incorrectly shim the retainer. After shimming it correctly, and torquing retainer bolts / the end nuts box A seems to behave as it should, and like box B.

All the gears turn as they should and baulk rings looks good. Phew!

Though I have a question though it might seem strange.

 

Should there be a tiny amount of axial end float along the shaft to allow oil into all the areas it should? Even though everything moves nicely now, It seems pretty 'tight', no play if I tug/push on the 1st motion roller and the main shaft at the 3rd motion end. Perhaps it should be that way.

I see there are oil galleries between the teeth on some of the gears to get oil to the needle bearings, but if there is no end float then would there be areas that could suffer from oil starvation? The obvious point is it all sits in oil, but if oil can't get in where its too tight...then that wont help.

 

Where on the box is end float measured and what should it be? I couldn't find any info in the Leyland workshop manual.

 

Thanks again.

 

 

Can anyone answer me on this? 

 

To put it another way, after :

 

The retainer is correctly shimmmed and the retainer bolts are torqued to 18NM

The main nuts (1st motion and 3rd motion) are torqued to 207NM 

The synchros move freely along with no issues with gear selection

And most importantly all the gears turn without resistance, especially in reverse.

 

All this is acheived on my box now. :)

 

Is it then correct that there should be no 'play' if you push/pull from the 1st motion end, and push/pull on the main shaft pinion end? Its currently 'solid', with no play.

 

As I mentioned this may be normal and the desired result, and due to the gears being in the sump in the mini and submerged in oil.

But I wondered if there should there me a tiny, tiny ammount of play so that needle rollers and gear.ends that face/meet eachother on the shaft have a small end-float gap to allow sufficient oil in the first instance?  

 

 

 

Again, just trying to unserstand the workings and and save myself time if I have not correctly set up before I go further with the build. :)

 

Thanks for your comments  so far :)