Mating splines

[Charles Levien]

Have spent most of this afternoon struggling to get gear box back into 37 Opal ie from the inside of car.   ( who needs a gym)
I’ve got a couple of 5/16 whiworth taps and am thinking I might fit these to the top stud holes on crankcase to act as a guide. I don’t have any suitable bolts. Any tips please on spline alignment— is it best to have mating groove on top or bottom?

Charles

[jansens]

I'd be careful using taps as guides. They are very hard and brittle and you really don't want one breaking off inside the hole!

Can you use 5/16 UNC bolts instead as guides? From memory they will fit although the pitch angles are different. I might have that wrong so wait till someone else confirms. I know I have definitely mixed up 1/4 Whitworth and UNC before.

Simon

[John Mason]

The best way For me I have no Charles, Have you disturbed the clutch as it is most important that the clutch plate is central. I do this by measuring from the dimple in the end of the splined shaft on the clutch plate to oppersite bolts on the bell housing . Once they are equal tighten all bolts up. Line up both blind spline and corresponding spline in the gearbox to the top. Offer up the gearbox to the spline trying to keep it square and in line. With the gearbox in gear slowly rotate the round end drive of the gearbox (the bit where the prop shaft bolts)whilst still putting pressure on the box to push it onto the spline. Once on the splines rotate the box to line up with bell housing studs and continue to push. Once there is enough thread to put a nut on the bell housing studs pull on by tightening the nuts.

John Mason.

[dickie65]

Hi,
I often assemble the clutch with the clamp bolts loose enough to move the plate around but just nipped.
You can turn the output flange with gear engaged and wiggle things about and rotate till things line up.
Once all is in accord put a couple of nuts to hold the box to the engine then rotate the flywheel and tighten up the cover plate bolts.
Result a self aligning A7 clutch.

[Colin Morgan]

Hi,
When lining up the splines, I found it helped to mark a radial line on the gearbox output flange so it could be turned back to where it started if it got knocked during assembly.  Prior to assembly, once the box was in gear, a trial rotation showed how the blind spline moved with respect to this mark.   A mental note was made of the orientation of the mark before the gear box was moved forward with the splines lined up.  Without the mark, I easily lost the track of position of the blind spline, but with it I could always set the blind spline back to the required angle.

Colin

[Charles Levien]

I'd be careful using taps as guides. They are very hard and brittle and you really don't want one breaking off inside the hole!

Can you use 5/16 UNC bolts instead as guides? From memory they will fit although the pitch angles are different. I might have that wrong so wait till someone else confirms. I know I have definitely mixed up 1/4 Whitworth and UNC before.

Simon

Thank you Simon and others who have responded — I won’t use the taps. It’s a fresh day and maybe a new approach will be successful.  I can’t see the practical purpose of that mating spline. Was it just always done that way or is there a reason for it?

Charles

[GK5268]

Hi,
When lining up the splines, I found it helped to mark a radial line on the gearbox output flange so it could be turned back to where it started if it got knocked during assembly.  Prior to assembly, once the box was in gear, a trial rotation showed how the blind spline moved with respect to this mark.   A mental note was made of the orientation of the mark before the gear box was moved forward with the splines lined up.  Without the mark, I easily lost the track of position of the blind spline, but with it I could always set the blind spline back to the required angle.

Colin

That is what I do, last year I had the gearbox in and out about 5 or 6 times over a space of a few days (clutch disengagement problems - resolved by fitting a spacer between the gearbox & the crankcase) so I was getting proficient at doing this...

The correct clutch alignment tool is very useful indeed!

A little patience is required, or lots of it, never use force, I found the gearbox more manageable without the gearlever fitted.

[Colin Morgan]

Hi - There has been a lot conjecture on why a blind spline was included. The best suggestion I have seen for it being there, is that it ensures the drive is less prone to wear than one with no blind spline. It certainly makes putting it back together much harder, so I hope there was a good reason! - Colin

[Charles Levien]

Hi,
When lining up the splines, I found it helped to mark a radial line on the gearbox output flange so it could be turned back to where it started if it got knocked during assembly.  P rior to assembly, once the box was in gear, a trial rotation showed how the blind spline moved with respect to this mark.   A mental note was made of the orientation of the mark before the gear box was moved forward with the splines lined up.  Without the mark, I easily lost the track of position of the blind spline, but with it I could always set the blind spline back to the required angle.

Colin

That is what I do, last year I had the gearbox in and out about 5 or 6 times over a space of a few days (clutch disengagement problems - resolved by fitting a spacer between the gearbox & the crankcase) so I was getting proficient at doing this...

The correct clutch alignment tool is very useful indeed!

A little patience is required, or lots of it, never use force, I found the gearbox more manageable without the gearlever fitted.

I have a cente plate and agree it is very useful. Will be getting some 5/16 UNC threaded rods today to screw into top holes on bell housing — to act as guides and possibly help reduce some of the blasphemy.

Charles

[Robert Leigh]

Hi,
When lining up the splines, I found it helped to mark a radial line on the gearbox output flange so it could be turned back to where it started if it got knocked during assembly.  P rior to assembly, once the box was in gear, a trial rotation showed how the blind spline moved with respect to this mark.   A mental note was made of the orientation of the mark before the gear box was moved forward with the splines lined up.  Without the mark, I easily lost the track of position of the blind spline, but with it I could always set the blind spline back to the required angle.

Colin

That is what I do, last year I had the gearbox in and out about 5 or 6 times over a space of a few days (clutch disengagement problems - resolved by fitting a spacer between the gearbox & the crankcase) so I was getting proficient at doing this...

The correct clutch alignment tool is very useful indeed!

A little patience is required, or lots of it, never use force, I found the gearbox more manageable without the gearlever fitted.

I have a cente plate and agree it is very useful. Will be getting some 5/16 UNC threaded rods today to screw into top holes on bell housing — to act as guides and possibly help reduce some of the blasphemy.

Charles

Why not use 5/16" Whitworth bolts for alignment, screwed finger tight in the stud holes and with the heads removed they will provide a fairly smooth guide compared with threaded rod.
Robert Leigh