Marina 4 speed gearbox gearchange extension.

[meverett]

Starting this thread again as we had sidetracked to this in a different thread 'another update'.
Anyway DC and Darth Vader has given us a great idea and a challenge to fabricate the gearbox extension to save on scraping knuckles on the dash.
DC, could you add you photos to this again please.
I had a spare selector extension as it looks like two will be required to make the extended version.
The housing between the propshaft flange and the gear selector will need to be cut and if two extensions were used then the second could be sacrificed to ensure the housing wall thickness is still there on both parts.
I have separated the selector housing and cleaned it all up.

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Unfortunately had to sacrifice the rest of the casing to maintain the wall thickness in the selector housing.

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After a bit of origami to get the dimensions.

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Then transferred this to scraps of aluminium that I had hanging around.

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[meverett]

Re: Marina 4 speed gearbox gearchange extension.

A quick trial fit before I continue then decide whether to hack up my gearbox that is already on the engine ready to fit.
Also took some measurements to make sure it clears the prop shaft and think I will have about 10mm. May need to raise it up and move more centrally to clear the prop and move centrally in the narrow part of the tunnel and use a universal joint to connect the selector rod as hairydave suggested.

IMG_4031.JPG

[meverett]

Re: Marina 4 speed gearbox gearchange extension.

A quick trial fit before I continue then decide whether to hack up my gearbox that is already on the engine ready to fit.
Also took some measurements to make sure it clears the prop shaft and think I will have about 10mm. May need to raise it up and move more centrally to clear the prop and move centrally in the narrow part of the tunnel and use a universal joint to connect the selector rod as hairydave suggested.

IMG_4031.JPG

[meverett]

Re: Marina 4 speed gearbox gearchange extension.

Forgot to add this will move the gear lever back by 7".

[dcunn]

Re: Marina 4 speed gearbox gearchange extension.

As requested, herewith pics - email me at home if you need higher res ones

Looking good so far Martin

Rgds DC

[meverett]

Re: Marina 4 speed gearbox gearchange extension.

Thanks Dave,
I am now at the stage where I need to remove the selector housing from my existing gearbox already bolted to the engine, do I or don't I? If I b&lls it up I will have to source another extension and partially strip the gearbox down (again) to replace.
DC, looking at the pics of KEX the tunnel looks parallel where mine narrows to 100mm'ish where the gearchange will be. The gearchange is off centre on the original and to make it central to the tunnel will mean using a universal joint connecting the gearchange shaft.

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[stevejgreen]

Re: Marina 4 speed gearbox gearchange extension.

Would it be totally impractical to simply extended the single rail, even by machining a longer one, and devising a clamp or fixing that is less destructive to the standard gearbox?

[dcunn]

Re: Marina 4 speed gearbox gearchange extension.

Martin
Yes KEX tunnel has a slight taper from the front but mostly parallel sided - note that the lever is off set anyway, and the handbrake lever is not in the normal place either

I would have thought it possible to get the extra width by cutting the top few inches off the tunnel where you need to and "plating" new straight bits either side, leaving the bottom of each
side untouched for rigidity and "plating" over the top and down to the floor level ?

[meverett]

Re: Marina 4 speed gearbox gearchange extension.

I have taken the plunge and cut the old selector off to be able to take some more measurements. Unfortunately to keep the selector shaft in line the modified selector will catch on the prop.

IMG_4039.JPG

One question, is the prop shaft reverseable as it would fit no problem if it could be. Ignore the 15mm copper fitting, that won't be used, just there to maintain a straight selector shaft.

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[dcunn]

Re: Marina 4 speed gearbox gearchange extension.

Crazy thought...why not weld the back part of the selector shaft onto the top of the old one, then you could put the selector higher up and this would give you the lift required to clear the propshaft - would you still be able to select all gears ?????

Propshaft probably OK t'other way round, but remember also the rear axle moves up and down so you need a bit of room between your selector thingy and the propshaft, maybe you could also file off a mm or two from the bottom lip ?

Hope these thoughts help

Rgds DC

[meverett]

Re: Marina 4 speed gearbox gearchange extension.

Both halves of the selector shaft needs to be in line as it needs to turn, having one on top of the other will force them to try to turn in a circle around each other.
I am going to try a 15mm universal joint and tilt the new frame upwards at the same point as the u/j. I will have about 20mm to work with between it catching on the prop and the top of the tunnel.

[h_m_cumming]

Re: Marina 4 speed gearbox gearchange extension.

No problem with the sliding joint of the prop shaft at the front, mine's been like that since I built it as with less bouncing around it doesn't wear as much. That will give you a bit more clearance.

[meverett]

Re: Marina 4 speed gearbox gearchange extension.

Hmmm, not sure this is going to work.
Waiting for a universal joint from Banggood, think it's coming from China as ordered it last week.
Thinking about this, by using this universal joint to raise the selector will be ok for the side to side movement between 1st/2nd and 3rd/4th but not sure it will work well for forward and back movement, they are designed for turning and not push and pull. Have to wait and see.
Adrian, how are you getting on with yours?
Martin.

[listerjp2]

Re: Marina 4 speed gearbox gearchange extension.

Will be going to my mates week after next.

Have cut selector and gearbox and have dressed both so all parts are ready for fixing.

Interested in the work your doing and had the same idea as you with regards reversing the drive shaft.

Decided that's the way I will be going.

Adrian

[stevejgreen]

Re: Marina 4 speed gearbox gearchange extension.

Hmmm, not sure this is going to work.
Waiting for a universal joint from Banggood, think it's coming from China as ordered it last week.
Thinking about this, by using this universal joint to raise the selector will be ok for the side to side movement between 1st/2nd and 3rd/4th but not sure it will work well for forward and back movement, they are designed for turning and not push and pull. Have to wait and see.
Adrian, how are you getting on with yours?
Martin.

I thought that it might be practical to machine a complete new shaft but it appears to be difficult.
Be aware that under load, the standard propshaft, though being reversible, deflects a great deal, your calculations must co sides the maximum vertical bump stop.

so far as UJ's are concerned, two, rotated 90° apart, would give the best 'feel' theoretically, one may be oK provided it is centred about the rotation of th selector shaft, otherwise unacceptable forces might be indipuced.

I am watching with interest, real possibilities if a design kit can be produced and sold, not just for Marina based cars but Triumph too.