Shift Coupler Question
 

Hello,

I have a '65 and I'm rebuilding the 901 trans. My shift coupler is really loose, and there is a decent gap in it. I know the bushings are old and need to be replaced, but it doesn't look like the gap was caused by poor bushings, but maybe a mismatched part. The casting stamp on the coupler states that it's an '84. It looks like the correct one, but I was hoping that someone might recognize something from the photo.

I know the bushings are cheap, but if I have to replace the whole coupler, I'd like to go with a nicer one, or make my own custom one. (I read the thread where people welded their shaft onto other better non-Porsche couplers)

So what do you guys think? Is this serviceable with new bushings?

Thanks.

-Michael

http://forums.pelicanparts.com/uploa...1299799110.jpg


(for a thread on my restoration: http://voltscar.com)

Bump.

I know someone has the answer to this.

Thanks,

Michael

Yep, time to rebuild/replace. There, I said it! Now do it.

That coupler is definitely serviceable. My 68 had a similarly sloppy coupling. You can get replacement bushings. I'd get the 914 ones as the holes are round and not oblong so less slop. On mine the shaft was really frozen into the housing so tightly I could not punch it out and had to use a hydraulic press. I wasn't careful and ended up dinging the aluminum so I just bought a new coupler from our host. I think it was about $90 or so for a genuine Porsche part. Replacing this and the bushings in the shifter, my car now shifts great. You can get some fancy aircraft style coupler for 2-3x as much but I'm not sure they are worth the cost.

Bryan

I make new bushing to custom fit your coupler....

if you have time to send it to me I will do it free of charge - I am using Delrin

here is the results: Note this is NOT an open offer for everyone to mail me thier couplers!!! PM me if you want

http://forums.pelicanparts.com/uploa...1302700310.jpg

http://forums.pelicanparts.com/uploa...1302700327.jpg

+1 on the 914 bushings...i think you can get them in Brass as well. If money is no object, Stomski is what I am saving for

Nice job Ivan! Do you cut those on a lathe? Are they press fit or do you cement them in place?

I replaced mine with a Stomski unit. I purchased it as a kit along with a Rennshift shifter. One of the best mods I have done. Shifts are precise and snick into every gear. A major transformation from the factory short shifter that came with my car when I bought it. The Stomski shift coupler is available from Pelican too.

http://www.pelicanparts.com/catalog/...mski/SR010.jpg

I actually run them on a CNC mill, it does them in one shot and all I have to do is turn them to length... using Delrin, they take about 3 minutes to make with a single 1/4" endmill and I comp the OD to be very snug and the ID to be a light slip fit...

done about 5 or 6 friends, getting better at them now :)

Busta Rib, I bought a Wevo and took it apart, then returned it...its simply a square block with slip fit dowel pins at 90 degress from each other for $200....I thought maybe it was a bearing or mono-ball... nope... that is why I decided to make my own using the factory parts outside...(looks stock) zero lash means its as good as the Wevo (and most likely the one you picked up) - but that's because I have the means to do it (as do many of these guys) - point is if you can do it for under $10 and some time, and you like to, then it is an option for those who have the machines beit a lathe or mill

BTW the first set I made I just used a dremel to remove the largest outter diameter so they fit in the coupler... now those "ears" are machined in

Ed
Where might i source some delrin?

I am depressed to know that the inside of the Wevo is not good......gee I love the way mine works. You ruined my day!!

The wevo and stromski units are aircraft universal joints. You can get them at Aircraft Spruce and Specialty for about $70. They are then modified by to accomodate the grub screw and shift tube.

I have the Wevo, I like it. It will not fix a worn transmission or sloppy shifter bushings. Replacing the bushings in your coupler will get you 80% of what the Wevo offers.

I use either onlinemetals (local) or McMasterCarr (great website!)

Order Plastic Round Alloys Acetal, Acetal AF100 PTFE Fiber Filled, Acetal LF13 PTFE Powder Filled in Small Quantities at OnlineMetals.com

McMaster-Carr

I just had some 10 mm precision ground rod (3 feet) delivered from McMacster for under $13 !! (making a Seine Shifter)

The Wevo is a high quality u-joint, and Stomski uses an aircraft type balljoint. I view the Ivangene as an improvement over stock :)

Ed, for the price, your solution offers the best bang for the buck. Wish I knew you did this mod. I might have asked you to do one for me. Do you want a spare coupler? I have my old one laying around. Just let me know and we can arrange a time. Jim

Just so there is no perpetuated mis-information, the modification of the stock coupler to tight fitting bushings will only offer one axis of freedom in the coupler - so this is not a like-for-like alternative to the other choices.

The Porsche OE design coupler - with the deliberate built-in clearances, the Stomski unit and the WEVO PSJ, all offer 2 axis of freedom, so the joint can articulate to accept a certain degree of misalignment between the drivetrain and the chassis.

As the drivetrain has the freedom to move on all axis relative to the chassis, there is a need for the 2 axis of freedom at the coupler, otherwise the drivetrain is attempting to swing the shift tube as an extension of itself on the one plane where freedom has been eliminated by the home made coupler modifications.

There are a lot of those out there, home made, short run productions etc, so they do work and will feel better than a stock coupler in worn out condition.

However, the option of using round hole bushes was avaiable to the Porsche factory engineers as well - but they elected to use slotted holes and clearance on the flanks of the bushes too, to allow for a the 2 axis of freedom - it is worth considering that when you decide to modify your OE coupling.

Regards

Hayden

so, some relief slots in the horizontal plane would be a good idea? Excellent!

Hey Jim, that would be great... What I like to do is have one already built then when someone wants one I just swap them and take my time doing thier old one...sort of an exchange without waiting..

If you happen to hit any track days or on the eastside I am always nearby

It seems to me that the gear shift needs to considered as an complete structure rather than be broken down and analysed as individual parts.

With the car stationary the gear lever and coupler need to be able to be adjusted to deal with axial, radial and parallel misalignment which they can clearly do otherwise they could never be fitted.

Once the system has been installed and adjusted and the car is moving then there are movements of the engine/transmission that need to be dealt with and I think that the standard system allows this to happen:

The ball and cup on the end of the gear lever will allow the engine to rock or shuffle laterally.

The angular movement of the gear coupler will allow the engine to bounce up and down or rock vertically

The slot in the coupler bush will allow fore aft movement.

I do agree that standard couplers do seem to have too much clearance but the Delrin bush eliminates these issues and is very cost effective.

I am not convinced that expensive Aeropace standard UJs are needed. A steering UJ for a Group4 Escort for example is about $30 and seems to last for about 10 years of competition before it wears out.

The other minor point is that any change to the coupler that eliminates the axial clearance must result in some ‘wag’ on the gear lever.

The slot in the standard coupler bush allows the engine to shunt back and forth or deal with any change of axial position due to some other complex motion.
If you remove all of this axial clearance then small fore/aft motions must wag the gear stick slightly as there is no other way of allowing for this movement.

If the gear lever has a 5:1 ratio than the+/- 1mm movement of the standard coupler translates to about a total of 10mm movement at the gearknob which is a small percentage of the total movement in a first to second gearshift (less than 10% ?)

If you fit the solid RSR engine mounts this wag will virtually disappear and a solid bush would not be noticed.

I think the secret is to maintain the gear couplers and gear lever bushes and to keep them clean and in good working condition.
From what I have seen these parts and the pedal boxes are the most badly neglected areas of most 911s.