Improved shifting for side shifters, bolt on? Maybe., Experimenting tonight. Options

[Dr Evil]

I have had this though for a long time to try and remove as much slop as I can in the shifting system. The tail shifter is a bit trickier, but not impossible. I have a side shifter in my new 914 and so, while I build up a transmission for it to drive to Hershey this weekend (this will be the raffle transmission, BTW. Trial by fire!), I decided to see how simple it would be to remove some of the slop.

First, see how much of a gap there is between the shift selector comb and the rod.

This is a huge amount so any bit that can be removed should be an improvement.

Step one was to add material to the sides of the comb faces (Yes, Scotty, I welded). Then, I hand filed the faces and re-formed them to a specific profile. The metal that was added was hardened and a real bitch to file. I figured it was worth it.

The end result was a much tighter fit.


There are a few parameters that I will not go into that need to be respected to get this to work, but the preliminary results were nice on the bench. With the material added and profiled on the faces, the stick throw fore and aft to select gears decreases significantly. There is still refinement that needs to be done on the profile, but so far the preliminary results are encouraging.

Next, I will build a jig so I can directly observe and adjust my profile. And I will also be able to see where I can add material to take up the slack that one feels when they are in gear and can wiggle the stick back and forth.

Once I get this prototype done and tested, I can do this treatment to any side shift console on an exchange basis and it will be a quick bolt on improvement (I hope).
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[boxsterfan]

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['73-914kid]

What kind of clearance are you aiming for between the comb and the shift fork selector? .08-.1"? Seems like too tight might be a problem, but I love this solution... The never ending process of making these cars shift better should interest a lot of people.. (IMG:style_emoticons/default/beer.gif)

[HalfMoon]

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[bulitt]

Seems the play may be "designed in" to compensate for movement of the engine and trans under braking and acceleration ? But finding out how much is too much is trial and error (which I assume is what you are trying to determine). Could be dependent on the condition of your motor and trans mounts also.

[Dr Evil]

What kind of clearance are you aiming for between the comb and the shift fork selector? .08-.1"? Seems like too tight might be a problem, but I love this solution... The never ending process of making these cars shift better should interest a lot of people.. (IMG:style_emoticons/default/beer.gif)

"Seems like too tight.." This is why I actually built and tried it. As mentioned, it works. Clearance will be my secret. (IMG:style_emoticons/default/wink.gif)

No armchair engineering here. Do or do not, no guessing.

[IanS]

So you say this can be similarly engineered for tail shift? Do you have access to a tail shifter to test/engineer?

[CptTripps]

So you say this can be similarly engineered for tail shift? Do you have access to a tail shifter to test/engineer?

If there's one thing I'm certain of...it's Dr. Evil's rolodex of people with tail-shift transmissions.

[mskala]

So you say this can be similarly engineered for tail shift? Do you have access to a tail shifter to test/engineer?

For the -6 version of the tail shift, I did basically the same thing last year:
914-6 shifter slop improvement
It didn't hurt, but I didn't notice any real improvement either.

[Dr Evil]

For a tail shifter you would need the external shift rod, too. You have to add material to the ball. Then, you have to take the whole stack out to get to the internal shift actuator and add material to that. The real problem with the ball on the inside actuator is you have to put some material in a specific place on it (hard to describe) so that you do not get it wiggling side to side when it is in gear. To make a tail work as well as I can make a side.....it would be a task. I am interested in doing it, but do not have a car with this set up. Also, side is sooooo much easier.

[Dr Evil]

So you say this can be similarly engineered for tail shift? Do you have access to a tail shifter to test/engineer?

For the -6 version of the tail shift, I did basically the same thing last year:
914-6 shifter slop improvement
It didn't hurt, but I didn't notice any real improvement either.

Mark, without addressing the internal shift mechanism you will see limited results. The problem with the tail shifter is majorly within the box. If you saw how these things actuate internally, you would be shocked. It is so loose as to be a joke. So much room for improvement. I would love to do a mod on a /6 if anyone is interested. I would throw it in with a rebuild. The stuff that needs to be done to a tail shifter would best be done with the whole box here. If I have the box to play with, I can adjust to the box and its rods. Otherwise, I have to leave a little slop so it will fit all boxes.

[GeorgeRud]

I always looked at that coupling and figured there was room for improvement in the design. Tightening the clearances should help, but I assume there must be some 'wiggle room' to allow the slight angulation as you shift through the gears.

Would a system composed of rod ends allow for the necessary movement and cut down on slop, or is there more clearance inside the gearbox that would negate any improvements to the external components?

[Dr Evil]

My side shift kit would just be the shifter comb. All other factors are being evaluated and controlled for. The fore and aft have been tested. Tight tolerance used and effective. Now I need to see about removing the side to side shift rod play in the cabin by adding beef to the thickness of the comb teeth rather than just the width of them. I need a jig for this and hope to make one tomorrow if I can find my sawsall (IMG:style_emoticons/default/happy11.gif)

[Harpo]

Looks good Doc (IMG:style_emoticons/default/popcorn[1].gif)

David

[Dr Evil]

Thanks man (IMG:style_emoticons/default/smile.gif)

[veekry9]

Dr Evil:
Delicate work,reducing the tolerance and clearances within the shifter forks.
Question:Are you using a jig to determine the distance to the ball detent?
I am about to embark on a re+re of the original tailshift TX that is now on the floor of the shop.Here it is 4 decades hence and I am considering a hydraulic shift mechanism
for the unloved early box.I have seen a number of attempts to resolve the "loose'
shift characteristics with limited success.There's gotta be a better way.

[Krieger]

Cool!

['73-914kid]

Keep on pushing through with this Mike. BTW, if you need someone to do some testing per say with this, I'd be more than happy to.. Being a daily driver, my car undergoes more wear and tear than most, so it might be a good candidate for testing this out.

In all seriousness, I'm not trying to get a free part, but for longevity testing on the tightened clearances, it could be the perfect platform.

[Woody]

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[914_teener]

Doc.


My box will be in transit in a week. I am cleaning it.

I would love a tighter shifting box.

All inuendos intended and true.