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Old 03-27-2024, 03:07 PM   #1
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Reducing play in gearshift mechanism

I have my G87/21 gearbox ready to install along with a shifter from a 987. It will go into my 986.

Shifter and box are now connected together outside the car and the combination feels a whole lot better than the 986 shifter and G86/00 coming out of the car. There was a lot of play on the shifter and possibly even more on the box. Not only the mechanism on the gearbox, also inside.

But even though it feels much improved, it doesn't feel as good as my high mileage BMW diesel gearbox (which really is a pleasure to shift). So I want to get even closer to that.

With all out of the car it is much easier to see what happens. Some main observations;
- The fork actuation (forward / back) is made to have play, on purpose. There are 4 rubber pins between the gearbox shaft and the lever where the cable attaches. It moves quite a lot.
- The fork selection (left / right) has quite a bit of play / movement due to the rubber connection between shaft and ball.
- There is a lever to rotate cable movement to shaft movement. This has a bit of play as well, mostly up and down.
- The weight wheel (or what the steel wheel on the gearbox is called) has play on its own access as well as a little play on the shaft.

I think the top two points are the main contributors and can easily be fixed. I plan to make a new shaft with steel cups on the balls. Easy and cheap and worth a try to see whether it reduces side to side movement. Forward/ back I'd like to improve by replacing the rubber pins with steel ones.

Two questions remain;

- What have others done (racers for instance?)

- Why did porsche design in so much movement? If we remove it, does it really become uncomfortable ?(I don't notice that in the BMW). Already the G87 gearbox itself should prevent feedback / wobble of the shift fork to the shaft.

Any input well appreciated.

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Old 03-27-2024, 06:02 PM   #2
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Mark, I have never experience it, but heard great reviews of the Numeric Shifter and Cables combination, you may want to check them out

https://store.numericracing.com/collections/cayman-boxster-987-transmission/products/986-987-transmission-bundle
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Old 03-28-2024, 01:31 PM   #3
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Hi Gilles,

Thanks for the suggestion. Looking at their product offering I see a new shifter, but the 987 seems decent already (room for improvement, but not bad at all), and new cables. I don't feel any slop in the cables, but I can imagine a new set being smoother.

What did catch my eye though is that they have made part of the linkage similar to what I intend to do:
Name:  Shift_mechanism_rod.jpg
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So replacing the rubbery stock part which does allow a lot of movement side to side with a solid part. Easy to make and try, and easy to swap back to stock if it does turn out to be too spartan. Seeing their part being so equal actually makes me confident of this improvement.
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Old 03-28-2024, 11:49 PM   #4
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My S shift is fairly indistinct and I’d like to refresh it. Mind you I had a new Boxster (not the one I have now) and I’d not call it the sharpest shift even then.

I’ve had other mid engine and remote linkage cars too - older like a Matra Murena.

I’d not call them brilliant compared to the Mk9 box on my Caterham (Lotus 7) where shifter comes out the back of the box.

What bothers me about all the after market solutions is the long term impact on the synchros and forks. I often wonder if that play helps cut out shifter vibration into the box (even though it’s cable shift) and allows for some give in the shift rather than forcing it down a precise path with knock on to adversely impact the massively fine tolerances in the box itself.

I can say that’s a theory made up in my head so people who understand things like backlash far more than I are invited to shoot me down. However for present having the gearbox oil changed next weekend at the same time as the clutch (apparently they are very sensitive to the right oil) and seeing if there is a new OEM shift bearing are top of my list.

Last edited by Porboxs; 03-28-2024 at 11:51 PM.
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Old 03-30-2024, 09:18 AM   #5
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I have tried a few things in my 2001 S.

1. Replaced shift console with a 987/997 oem - helped a little
2. Adjusted the cables with the factory alignment tool. Tricky because the stock blue cable was not long enough and needed to be pulled forward about 1/4Ē to fit in. Pulling the black cable forward the same amount seemed to help somewhat.
3. Changed the motor mount to 987 version. This was a huge improvement in vibration and clutch engagement (particularly disengagement, car would sort of lurch). Did not help with shifting for me.
4. Changed the gear oil using oem stuff. No change in feel but still glad I did it.
5. Raceseng circuit sphere shift knob. Attaches to the lever with set screws. Highest quality part in the interior, but is a little taller than stock and still getting used to it. The rubber inside my stock shifter was a little loose so this feels tighter to me.

Fixes I may try next:
- rennline shift cable retainers to hold the cables on the tranny side tighter.
- gbox second gear detent (stiff shifting into second gear and sometimes third, but no pop out)
- numeric racing cables and possibly the shifter as well.

I do have concerns about longevity either detent or numeric shifting cables, but I think there is still enough slop in there that everything will work fine.

My late 80s 3 series was a dream to shift and Iím still chasing that dragon 🐉
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Old 03-30-2024, 11:02 AM   #6
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I think what Phazed did is the smartest. Smallest outlay and it seems like side to side is the biggest problem:

https://www.boxa.net/topic/99432-shifters/
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Old 04-02-2024, 10:03 AM   #7
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Good to see I'm not the only one thinking it needs a bit of improvement.

Quote:
Originally Posted by Porboxs View Post
What bothers me about all the after market solutions is the long term impact on the synchros and forks. I often wonder if that play helps cut out shifter vibration into the box (even though itís cable shift) and allows for some give in the shift rather than forcing it down a precise path with knock on to adversely impact the massively fine tolerances in the box itself.
I'm not really worried about that as the cable ends are still rubber and allow a bit of 'give'. The G87/21 box I have is actually a Porsche version of the Audi 0A2 (which I also have, to go behind the audi V8 at a later stage). The audi linkage is much more solid, more comparable to the way BMW operates the gearboxes. If that is good enough in comfort and durability in an Audi, it should be good enough in a Porsche.

When I bought the car, the shift was extremely imprecise, it felt like shifting a lorry, aided by the ultra-stiff worn-to-bits clutch. It had more side to side play than the gates are apart. Main two culprits were the 986 shifter which was simply worn, side to side linkage as well as the bushings. The box itself was also very loose.

I like the idea of the feeler gauge / shim on the 987 shifter. Mind you, his first step was to move away from the 986 shifter if I'm not mistaken.

My rod for the linkage on the gearbox is done. I'll look at the fore-aft as well before I put it in. Fresh fluid is going in as I don't know the history of this box. It also needs a new reverse sensor as the connector suffered a hit. Will steal it from the 0A2 for now.

Also a fun detail on the G87/21 or 0A2 box is that it actually has two detends. One holding the shift fork in position, the other holding the selector rod. This way the fork has a little play when engaged (not when in neutral position) to isolate the wobble of the fork from the shifter.
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Old 04-02-2024, 10:09 AM   #8
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@Porboxs ,@Danimal I guess you both have the 986 6-speed (G86/20 if I'm not mistaken). I can't comment on that box, but would advise to locate the source of play / slop first.

And good info on the motor mount. I'll add it to my list as judging by the movement the engine now has without the gearbox attached, I'd say it has had better days.

Indeed, once you have had a car that really shifts nice, you appreciate the joy it gives in driving. And that is all this 986 is about for me.
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Old 04-03-2024, 07:38 AM   #9
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The new engine mount was the best project cost/time per upgrade Iíve done on the car so far. It was pretty easy. I changed the fuel filter while everything was open as well (stinky and messy).

I would recommend using a scissor jack to lower the engine with a board across the front of the oil pan. I did it back where the transmission and engine join (at the cable) and it made it hard to raise the engine back up and I squished fluid out of one of the tranny mounts. It was just too far back to effectively raise the engine in the front.

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