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Has anyone converted the G31 to audi style shift linkage?
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Rocco R16V  



Joined: 03 May 2009
Posts: 497
Location: PNW

PostPosted: Fri Jun 05, 2009 4:28 am    Post subject: Has anyone converted the G31 to audi style shift linkage? Reply with quote

I was looking at the shifters and thought the audi style that mounts to the TT is much more simple and easier to convert to heim joints for a very solid shifter feel.
all porsches efforts to reduce vibration on the G31 seem to just make a complicated system that is prone to fail.
the motion at the tranny is the same, you would loose the push down to access 1st and R but that wouldn't bother me. this is for a racing application.

has anyone done this? any thoughts? TIA
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fiat22turbo  



Joined: 18 Jan 2006
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Location: Portland, OR

PostPosted: Fri Jun 05, 2009 5:18 am    Post subject: Reply with quote

Uh, you could just replace the joint at the back with a sealed universal joint and avoid completely re-engineering something for very little gain.



http://www.empius.com/2009_catalog/empi2009_pg266.html

The other joint on the TT can be replaced with a metal rod end (Heim is a brand name, just like Rose is across the Atlantic) and the front bushings can be replaced with delrin or bronze.

BTW, I know a thing or two about building and re-building shift linkage:

http://pnw-sdac.org/shiftlinkage.html

http://www.pnw-sdac.org/gallery/main.php?g2_itemId=3308

If having the front half of the pivots for the linkage mounted to the chassis with the rear half mounted to moving objects bothers you. One could simply remove the front half bracket from the chassis, and attach it to the TT. It is just steel after all.
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ideola  



Joined: 01 Oct 2004
Posts: 15451
Location: Woodstock IL

PostPosted: Fri Jun 05, 2009 6:34 am    Post subject: Reply with quote

Stefan, you've piqued my interest. This is not something I've given much thought to, but I am very close to reinstalling the torque tube, shift rod, and G31 into my project, so the timing of this discussion is great.

So how would you fix the unversal joint to the shift rod and input shaft on the gearbox? Just drill and tap, and re-use the stock tapered screws?

Poly or delrin bushings...I'm assuming those would have to be custom machined?

As for the front ball socket, are you suggesting a conventional rod end on the shaft itself, and then welding a bolt in place of the stock ball?

Not to pick nits, but you didn't mention the bushing at the front, the one that attaches to the torque tunnel and receives the pointy end of the main shaft...I have two new bushings (one for each car), so not a concern for me, but might be for someone else.

Given your expertise, I would love to hear you expound on this a bit more...how could the whole assembly be made...well, dare I say...the "ultimate" G31 shifter?
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Rocco R16V  



Joined: 03 May 2009
Posts: 497
Location: PNW

PostPosted: Fri Jun 05, 2009 6:55 am    Post subject: Reply with quote

Thanks, it seems you understand the benefits of having a solid shift feel.

Not counting the u-joint at the trans, on the audi style there is only two pivot points the ball on to TT and the selector rod to shift lever. On the G31 style there is one at each end of the guide rod, the bottom of the shift lever, the point where the selector rod attaches to the shift lever. Much more places to fail/replace.

No reengineering necessary, just weld the ball to the TT at the right place and weld rod to U-joint at trans.

No need to locate bushings or have them machined, metal rod ends are easy to get and short shifters are available for the audi style leaving me only to locate a selector rod or make one myself.

any other thoughts, or sources for brass/delrin to make a good G31 shfter?
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Rasta Monsta  



Joined: 12 Jul 2006
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PostPosted: Fri Jun 05, 2009 8:15 am    Post subject: Reply with quote

Those joints are interesting. We just need someone to measure their shaft.
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ideola  



Joined: 01 Oct 2004
Posts: 15451
Location: Woodstock IL

PostPosted: Fri Jun 05, 2009 9:14 am    Post subject: Reply with quote

Rasta Monsta wrote:
Those joints are interesting. We just need someone to measure their shaft.
not gonna fall for that one, Rasta!
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v8carreragts  



Joined: 05 Sep 2003
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PostPosted: Fri Jun 05, 2009 10:53 am    Post subject: Reply with quote

They did this on several race cars. A while back when I had a discussion with Bruce Anderson he told me that they had trouble with the factory linkage causing the trans to pop out of gear during hard cornering. So they went to the AUDI type linkage.
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fiat22turbo  



Joined: 18 Jan 2006
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Location: Portland, OR

PostPosted: Fri Jun 05, 2009 2:30 pm    Post subject: Reply with quote

From looking at the linkage that came off my 79 NA, I can see some improvements right away that can be made.



First, the main joint at the rear of the car (that always fails) that is essentially a U-joint, but they use rubber bushings to isolate vibrations. Similar to some of the Asian cars using a rubber bushing in the gear shift shaft itself. Like I said, replace that rubber joint with a sealed U-joint.



To use the sealed U-joint, you'd have to cut the square end off the shift rod and build an adapter bushing to match the OD of the rod with the ID of the joint. Pins will be needed and the proper angle will need to be maintained unless a method of making it adjustable is designed into the solution.



To make the solution adjustable, one could cut the front off the main rod just before it angles up to meet the gear lever. Weld on a piece of serrated round stock then bore the center of the main rod out to fit the serrated rod. Cut a notch in the top of the main rod then wrap it with a clamp. To adjust, place the car in first gear, loosen the clamp and place the gear lever where it needs to be and then tighten the clamp.



Second, the ball and socket joint at the rear that attaches to the top of the TT can be replaced with a standard metal rod end. Not particularly tricky compared to the other joint. However, this will require grinding the old ball off and welding a bolt or stud in place. For those who are unable to weld, simply drilling and tapping the TT for the bolt could work provided you knew that there isn't a bearing sitting underneath that spot. If one were to use a bolt or a stud, heavy duty loctite would be needed along with a lock nut. Personally, I'd drill and tap to get the proper location and then weld the stud in place.



Third, the other end of the guide rod (mentioned above) fits into the bushings at the front of the car. This is where the main problem lies I believe. The guide rod is attached to the car's body while the rest of the linkage is attached to the drivetrain, this means that half the linkage is capable of moving in a different direction than the rest of it. Not good.



To resolve the issue with part of the linkage moving in different directions, you could relocate the bracket onto the TT, thus the entire linkage is now mounted to the drivetrain. Replacing that bushing with a piece of delrin or bronze isn't a bad idea either.

As far as the gear shift lever itself, in looking through the archives and finding the recipe for the short shifter solution (thanks Lizard!), I'd use that approach to cut and weld the bottom of the shifter.



The shift lever bushings can be left alone or replaced with bronze or even small ball bearings.



I'd also cut off the flat plate and weld on a polished piece of round stock to allow a greater variety of shift knobs to be used.



Keep in mind that removing the rubber bushings from the linkage will cause any and all vibrations from the drivetrain to be transmitted right up the gear lever and could make the transmission come out of gear more often. I would suggest leaving some of the rubber in place or adding some someplace else.
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ideola  



Joined: 01 Oct 2004
Posts: 15451
Location: Woodstock IL

PostPosted: Sat Jun 06, 2009 12:23 am    Post subject: Reply with quote

Good stuff, pretty do-able...

Why not use a standard steering u-joint? They're cheap and plentiful, I can't see the environment back there being any more harsh than what it is in the engine bay, so I don't see the need for a special sealed joint.

FWIW, the cylindrical portion at the end of the shift rod (just prior to where the square part would need to be removed) is ~16mm O.D. I didn't get a chance to measure the actual shifting input shaft on my G31 last night, but the inner diameter of the stock coupler is ~14mm. There are some standard 5/8" x 5/8" smooth bore steering knuckles that could be easily adapted. The one end could be very slightly and carefully taken out to 16mm (5/8" = ~15.875mm); the other end that would attach to the shifting input shaft on the gearbox would need a ~1mm bush.

The question I have is the best method of securing the u-joint to the shift rod and input shaft. Ideally, it seems like using a tapered screw such as the stock item would be better than a spring pin, because it would allow some adjustability at both ends. The question is whether there would be enough material in the u-joint to safely drill and tap for threads, and would it be strong enough to torque down the tapered screw such that things don't slip under load.

The rod end and bolt to replace the cup and ball socket should be a no brainer. The thread is a standard M10 (based on the jam nut listed in PET), so getting a standard M10 rod end and attaching a hardened M10 bolt of suitable length to the torque tube should be easy. Of course, a lock nut should be used on the end.

I'm already looking for options on delrin or brass bushes to replace the plastic ones at the shift lever itself, but the plastic OEM units are easily gotten and should suffice for now. Also, I already have one of Lizard's snailshell short shifters and love it! I'll probably move it from the 941 into the UWB project when I'm ready to put the latter on the road.

Now, the final piece is the front bushing for the guide rod. What I need to figure out is how far above the torque tube that bushing is positioned when it's installed in the car. It could probably be lowered just a touch without too much concern; the best way of attaching it to the torque tube would be to weld a bracket at the correct height, and simply flip over the stock bushing assembly and bolt it to said bracket.

Now, what would be REALLY cool would be to make the primary shift rod length-adjustable. The reason I say this is because I'm putting a Tilton pedal box in the car, and due to the arrangement and slant of the floor pan behind the pedals, the Tilton assembly will be positioned about 3" closer to the seat than the stock pedals. Of course, the seat can always be positioned further back, no problem, but bass gt mentioned that when he did this, he didn't take into account the added reach that was subsequently required to get to the gear shifter.

Having the shifter assembly adjustable by about 3 inches would be way cool. The first thing that springs to mind is to cut both the guide rod and shift rod, remove about 3" from each, install opposite-threaded weldable tube ends on each side, and then connect them with a length of threaded rod (i.e. a Heim-style connection).

Two things need to be check on this: 1) are the rods already hollow (if not, they could be threaded themselves or bored out); and 2) would the opening in the torque tunnel need to be enlarged rearward to prevent the shift lever from interfering or running out of room. Also, the aforementioned bracket for the new mounting arrangement of the guide rod bushing could be slotted to allow some adjustability of the bushing itself, although the guide rod already has about 3" to play with, and positioning within the bushing is not terribly critical from what I can tell.
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ideola  



Joined: 01 Oct 2004
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PostPosted: Sat Jun 06, 2009 2:33 am    Post subject: Reply with quote

fiat22turbo wrote:
Third, the other end of the guide rod (mentioned above) fits into the bushings at the front of the car. This is where the main problem lies I believe. The guide rod is attached to the car's body while the rest of the linkage is attached to the drivetrain, this means that half the linkage is capable of moving in a different direction than the rest of it. Not good.


One more thought on this: I have solid Vibratechnic motor mounts and custom poly-urethane snailshell mounts. Is it reasonable to assume that a more rigid mounting of the engine and trans will reduce, if not eliminate, the concern you raised?


In the meantime, I'm pretty sure I have both early and late style audi shift rods, plus a spare Audi shift lever, and a late Audi-based torque tube, plus multiple G31 shift rods and TTs. This weekend, I'll make a point of doing some comparisons between the various components to see if there might be an easy way to build a hybrid setup from the available bits.
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CÚdric  



Joined: 27 Aug 2004
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PostPosted: Sat Jun 06, 2009 5:29 am    Post subject: Reply with quote

ideola wrote:
fiat22turbo wrote:
Third, the other end of the guide rod (mentioned above) fits into the bushings at the front of the car. This is where the main problem lies I believe. The guide rod is attached to the car's body while the rest of the linkage is attached to the drivetrain, this means that half the linkage is capable of moving in a different direction than the rest of it. Not good.


One more thought on this: I have solid Vibratechnic motor mounts and custom poly-urethane snailshell mounts. Is it reasonable to assume that a more rigid mounting of the engine and trans will reduce, if not eliminate, the concern you raised?


In the meantime, I'm pretty sure I have both early and late style audi shift rods, plus a spare Audi shift lever, and a late Audi-based torque tube, plus multiple G31 shift rods and TTs. This weekend, I'll make a point of doing some comparisons between the various components to see if there might be an easy way to build a hybrid setup from the available bits.


Vibra technics mounts are really stiff, at least the race rubbers. Engine is almost totally still. However its not the most comfortable way. I wont think the movement will such a big problem. Will be interesting to see where this ends. The black bushing part is really not a great solution since it gives a lot of slack and new bushings doesnt help...
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ideola  



Joined: 01 Oct 2004
Posts: 15451
Location: Woodstock IL

PostPosted: Sat Jun 06, 2009 5:47 am    Post subject: Reply with quote

CÚdric wrote:
The black bushing part is really not a great solution since it gives a lot of slack and new bushings doesnt help...

I really think the easy solution is to just replace with a 5/8" x 5/8" smooth bore sealed steering u joint. You can get high quality race versions for ~$50, and probably half of that if you're willing to settle for road-grade VW stuff. It would eliminate the need to fabricate a custom part, and would virtually eliminate all of the slop.

So, as I asked above, what would be the best way to secure such a u joint to the shift rod and gearbox shifter input shaft?
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ideola  



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PostPosted: Sat Jun 06, 2009 5:50 am    Post subject: Reply with quote

Incidentally, the two bushings that go into the stock shift rod coupler are actually a 914 part: 911.424.223.03. I'll do some digging and see if any of the 914 racers have developed a replacement bushing already...
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ideola  



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PostPosted: Sat Jun 06, 2009 5:53 am    Post subject: Reply with quote

Wow, this was too easy. Why didn't we think of this before?!?!?

Check it out:

http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=PEL-BUSH-BR&catalog_description=Shift%20Coupler%20Bushing%20Set%20(Pair)%20-%20Brass%2C%20914%20(1973-76)

Unfortunately, the Pelican site says they're unavailable...but maybe we could get a run produced????
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fiat22turbo  



Joined: 18 Jan 2006
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PostPosted: Sat Jun 06, 2009 6:08 am    Post subject: Reply with quote

ideola wrote:
Wow, this was too easy. Why didn't we think of this before?!?!?

Check it out:

http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=PEL-BUSH-BR&catalog_description=Shift%20Coupler%20Bushing%20Set%20(Pair)%20-%20Brass%2C%20914%20(1973-76)

Unfortunately, the Pelican site says they're unavailable...but maybe we could get a run produced????


Great, but they are going into a cast aluminum housing and you'd want them to be slightly larger OD and slightly smaller ID to be properly machined to fit your piece as they are prone to wear over time (mine has about 1/8" of play at the joint with new bushings)

Making both rods adjustable wouldn't be hard to do. If they are hollow then you'd essentially build a male turnbuckle into the system with the appropriate right and left hand threads. If they are solid then you'd have to build a female turnbuckle after threading the rods. The trick is getting it to work from inside the car.

The standard U-joint isn't a bad solution, I just don't want to ever have to work on that joint again. Using a tapered pin is fine. With the sealed joint, you could build a housing that fits over the outside of the joint's flange and essentially clamps the joint to the rod using the tapered pin.
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