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> What are all the things I can do to make 901 shift better
grantsfo
post Nov 20 2006, 04:51 PM
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If there is one thing that slows me down its the way the 901 tranny and its associated linkages shift.

What are all the tricks to making the linkages better for a race car? Is there good aftermarket shifters, linkages etc that make things a little more positive?
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brant
post Nov 20 2006, 05:25 PM
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- there are better shifters out there
(rennshift, wevo, ajrs)
- straightened shift rods
- custom firewall bushing
- custom shiftrod knuckle
- custom rear shift console bushing
- custom rear shift cup (for cup bushing)
- custom motor and tranny mounts.

brant
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Brad Roberts
post Nov 20 2006, 06:31 PM
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Brant,

I have been thinking about a two piece shifter cup for the rear shift console made from stronger material than the soft plastic.

What are your thoughts on this?

Something that is actually held together by the shift coupler as it slides over it??

If you look at ErikM's Hewland/MK box, it has a steel ball in a steel socket. I would like to mimic this in some form or fashion.

The other thing we do Grant: extend the shift rod and support it in another bushing at the back side of the console. This is VERY similar to what Hewland does in their boxes.


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groot
post Nov 20 2006, 06:37 PM
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Not to wander too far off the path, but I've been thinking about this, too.

That whole ball slider in a cup thing is wacked. It's taking fore-aft motion and making it rotate the shifter in the trans. There's got to be a better way.

It's got me thinking I'd be better off with a 901 from a 911 from a shifter stand-point...
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Brad Roberts
post Nov 20 2006, 06:51 PM
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Kevin,

The actual motion inside of the 901/914 tailshifter is better than the ball/cup shift console. The main issue with it is how the shift rod engages the shaft hanging out the box.

You are correct. You could easily do a Monkey Motion like the Hewland on the back of a 901/911 box (cause the 901 is very very similar to the Hewland VW boxes)..it says VW on the case for gods sake!!..lol


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brant
post Nov 20 2006, 07:23 PM
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I stole erics picture for over here..
I think thats a very interesting idea Brad.
it wouldn't be that hard to try it.

my cup is modified but still uses the stock plastic slider bushing.
at full range of motion, the bushing is pulled about 1/8 of an inch beyond the edge of the stock metal cup.

so my cup has been extended
the extension is welded on and then the inside is re-machined and honed to make it seamless on the inside sliding surface.

this provides a tiny bit more rigidity during full range of motion.

but I like the metal ball idea.

brant
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brant
post Nov 20 2006, 07:24 PM
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ooops...


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Joe Ricard
post Nov 20 2006, 08:06 PM
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Why not just learn how to shift the damn car.
seriously Snug up the bushings and adjust the shifter.

I don't have a problem shifting my car. however other 914's I have driven are a bit wierd.
Some I agree are like shifting with a bowl of chocolate pudding for the connection.
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Thorshammer
post Nov 20 2006, 09:01 PM
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Joe, PLLLLEEEEEEAAAASSSSEEEEEE. They suck, We all can do it, but why should we.

These cars can be made to shift very well.

Heres what I have done recently and am VERY happy.

RENNSHIFT. The best I have tried, I know Brad is partial to another, but I really like this one.

Side shift only:

Measure the tab on the front of the console and then the distance for the hole from the plate. Fabricate a tab to be welded to the rear of the console.

Mill some .380 plate so that it is the same. Don't drill the hole yet. Basically you have made a tab that is the same as the front tab. Weld the tab to the rear section of the shift console after removing it from the transmission of course.
Then drill the second hole in the back tab that you welded on. You may have to choose a drill size that will clean up the front hole by making it just a touch larger.
Now you will have a shift console that will have two holes in it so that a rod will slide fore and aft in the same plane.

You will need a machinist to spin up another shift rod (the piece that the shift knuckle attaches to) it should be much longer now because it will now pass throught the rear tab that you fabricated, The front part of this rod which is a straight piece that is larger (.580). Most of the shift rods I have seen are hammered and if you run them in delrin, the bushings will get wooped quickly. What you are making is ONLY the straight part of the shift rod, not the curved part.

Build two delrin bushings for the shift console tabs. Be carefull the fore and aft motion is critical, and the forward motion is very close to the front tab so make sure the bushing shoulder on the inside of shifter console is fairly thin. This is one of the areas you will eliminate a ton of slop. Not to mention changing the way the shift action at the transmission works.

You will now need a 5/8 APEX joint. Weld the apex over the top (be sure to use the cooling paste they sell it really works) of the large step of your straight shaft. Now you will need to assemble everything and mark the shaft you made so that you have enough fore and aft throw. The rotational angles are really not important at this point. Mark it and you will have to drill it for the set screw. i think I used a #30 drill bit and a tapered reamer until I got the desired angle and depth.

Next, You should now have a straight shaft that is supported at the back and the front of the shift console, assembled on the transmission, and the shift knuckle and shaft held in position by the original set screw, with the bushings installed and held in place by a washer and circlip.

Now you need to connect your original shift shaft to the apex joint. I like to machine a small slug that welds to the apex joint and is "fittted" (ie... cut and weld) to the original shift shaft. Once you have centered the shift shaft and welded it. Paint it. Adjust it inside the car.

Enjoy it. When i did it, I could not believe how good it was.

If you want to, you can also add an APEX joint to the front coupler. I did not but you could.

I would take some photos, but the car is nowhere near me.

The difference is amazing. The gates are where they are supposed to be everytime. it works good. Hope this is clear enough.

Erik
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Brad Roberts
post Nov 20 2006, 09:44 PM
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Damn,

did you have some free time tonight?? LOL The only thing missing from your post was the engineering blueprints (IMG:style_emoticons/default/biggrin.gif)

All jokes aside, thanks for the writeup. The person Grant uses to maintain his 914 will understand what we are talking about. I'm trying to locate a pic of a shift console so I can photo edit what we are talking about.



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Brad Roberts
post Nov 20 2006, 10:05 PM
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Here we go.. this should make it a little more clear for those of you scratching your head about adding a second support and extending the shaft.




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Brad Roberts
post Nov 20 2006, 10:10 PM
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We are also talking about making/replacing the white plastic piece with a metal two piece unit.


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Thorshammer
post Nov 20 2006, 10:49 PM
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Now thats What I am talking about.

Except for the plastic bushings. Since the shift rod will rotate and slide in the same plane, the clearances can be much tighter. But what Brad has photo shopped is the exact thing I have built. Works very well.

Erik
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Brett W
post Nov 20 2006, 10:51 PM
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Replace it with a better tranny.

Can't think of anything else.
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Brad Roberts
post Nov 20 2006, 11:04 PM
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Brett,

I think you missed his original question (IMG:style_emoticons/default/biggrin.gif)

He didnt ask if there was a BETTER tranny (duh! of course there is)

He asked if we could make a 901 shift better. (duh! of course you can!)


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Brett W
post Nov 20 2006, 11:33 PM
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Actually here is something that Brumos does on their cars.


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Brad Roberts
post Nov 20 2006, 11:36 PM
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There you go! That is actually what I'm talking about. Good shot of it. If you had been around earlier.. I wouldnt have had to exercise my photochop lack of skilz!!


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Brad Roberts
post Nov 20 2006, 11:42 PM
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I played "admin" and cropped/resized it for you (IMG:style_emoticons/default/beerchug.gif)


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Brett W
post Nov 20 2006, 11:42 PM
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For some reason I was just being an ass.
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Brad Roberts
post Nov 20 2006, 11:52 PM
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Leave that to me! I'm better suited and more well known for being an asshole!!

Watch this:

Grant,

I think you should build a big type 4 for your car..LOL


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