A newbie's perspective on 915 shifter improvements - LONG!

[Bruce Ayling]

Howdy all,

This is intended to be a quick run down on a series of shifter improvements recently made on a 915 trans. and my subjective impressions of their respective effects. I hope this isn't something that's already been beaten to death and that the following comments will prove both useful and valuable.

For reference I'm new to the Porsche world (as well as this list) and prior to the car in question the only Porsche I'd ever driven was a 996 that I autocrossed once. This is my first experience with the 915 gearbox in any form.

The subject car is a 1980 911 SC Targa that belongs to a good friend. It has the 3.2 engine kit and factory sport suspension, but is otherwise a stock car in overall very good condition. The shifter was factory stock and my first impression was that the Porsche engineers must have had crack in their Spatenbrau when they designed this box - it was probably the worst "shifting experience" I'd ever had.

STEP ONE - Installation of a factory short-shift kit and new shift rod bushing. The first step we took was to order the factory short shift kit from Pelican along with the shift rod bushing that goes immediately behind the shifter. The kit varies from the factory shifter only in terms of a relocated pivot point and the necessary dimensional changes to go along with this. All components are near identical in appearance to the stock parts and are assembled just as you would a stock shifter. Excellent articles have been written on the installation by both Bob Tindel and Scott Booth and I'd like to thank both of them for doing so - some of their tips made the dissasembly and reassembly go MUCH more smoothly than it otherwise could have. Something I found absolutely critical throughout this entire process was the periodic re-adjustment of and experimentation with the shift rod-coupler, but more on that in a bit.

SUBJECTIVE IMPRESSION - there was an immediate and drastic improvement in shift feel. I'm not sure if this was due to the "tightening" effect of the new shift tower components, the new shift rod bushing, or the shorter throw, but the end result was the same. The box still felt pretty darn notchy to me and I wasn't yet thrilled with it, but it was head and shoulders above what it had been.

STEP TWO - Installation of a Stromski Racing Precision Shift Coupler. The shift coupler lives under the access hatch just in front of the rear seats and in stock form appears much like a steering column u-joint. It has two bushings in it that over time can wear and cause an undue amount of slop and a cheap alternative would have been to simply replace these bushings, but we chose to go all out and replace the coupler completely with a more precise aftermarket piece. Installation is a breeze and once the access hatch is removed takes all of 5 minutes not counting fine tuning the adjustment.

SUBJECTIVE IMPRESSION - Our old coupler bushings were pretty worn so anything would have been an improvement, but this was definiteley another step in the right direction. Gear engagement was far more positive and the sense of vagueness significantly diminished.

STEP THREE - Installation of a Robotek "Shift Enhancer". This was the Coupe de Grace of our shift improvement adventure. I hadn't read any of the literature on this piece prior to my friend ordering it and it took me a while to figure out just what the heck it was supposed to do. The 915 gearbox has a decided lack of the "self-centering" effect and the Robotek is designed to address this and in turn further improve shift quality. The kit consists of a longer shifter pivot rod (which replaces the stock piece) and a "spring tension assembly" (my own term) which bolts to the outside of the shifter tower. Installation involves removal of the shift tower and a little minor machining (drilling a couple of holes and notching the shift tower IF you have the factory short-shift kit installed).

SUBJECTIVE IMPRESSION - Wow!! Now we have a box that while still not necessarily my favorite, I can most certainly live with and enjoy. The Robotek makes all gears feel far more solid and particularly helps prevent the dreaded 5-2 downshift. We're still playing with the spring tension (which is fully customizeable) but I actually like this transmission now - a far cry from my first impressions!

CRITICAL NOTE - The importance of adjusting the shift coupler (whether stock or aftermarket) both before you begin and then after each modification is something I can't emphasize enough. We spent a fair amount of time between each mod driving around and periodically pulling off the side of the road to tweak the coupler before we got things the way we wanted them to be. A difference of as little as 1/32" rotation can mean the difference between smooth shifts and a balky box that nicks reverse on every 5-4 downshift.

I hope this proves helpful to any curious about 915 shifter improvements. Please forgive any grammatical errors or less than perfect wording - it's late as I write this and I've been pulling it all of the top of my head as I went along. I'd welcome any questions, comments, and/or corrections.

Bruce in South Carolina

[tobluforu]

Great post, Very informative. I have 2 out of the 3 items you mentioned minus the robotek which i have read about. I agree that the shift coupler takes quite a while to get just right. A little to much one way and away goes 1st and second and visa versa.

[tmctguer]

i recently had a problem shifting from 2nd to 3rd during a track day. i had relatively new "non-swepco" gear oil in the tranny.

i went straight to the gear shift assembly. although i didn't replace any of the bushings, i cleaned and re-greased it. my eyeball look at things seemed to indicate that this wasn't the source of my shifting problem.

i then went to the shift coupler. although the bushings looked OK, i went to a parts store that stocked replacements and bought them. upon comparison to the stock bushings, they were a much tighter fit. the stock units had an "oblong" shape to them which provided for some longditudinal travel of the shift rod. the replacement units did not allow for the front/back travel and seemed like an overall tighter fit.

keep in mind that my car (a '73 911E) has only 60K original miles on it. so the bushings weren't worn -- it was just a different bushing design.

after replacing them, the shifter definitely felt different. it took a few tweaks of adjusting the shift coupler, but i think i finally got it re-adjusted correctly. so far, i've been pretty happy with the shifting performance after the bushing replacement.

i will say that i'm tempted to try the unit you've just installed. i believe that it may have some additional positive benefits to the work i've already done.

also, i have a gallon of swepco that i plan to use in the near future. many folks swear by its miracle properties, but so far, i'm not sold on it as being the next best thing to shifting nirvana. of course, i'm not an expert on the 915 by any means, but so far, i think that my problems have been less from the viscosity of my gear oil, and more from the set-up of my shift coupler.

if i decide to add the shift kit you've installed, i'll report back to let everyone know how it goes. also, if i decide to add the swepco, i'll let everyone know whether it adds any value to my shifting equation.

thanks for your post.

[Bruce Ayling]

"Tmctguer" & "Tobluforu",

Thanks for your comments! As mentioned I don't have a wide basis for comparison, but based on my experiences I would definiteley encourage both of you to "take the next step" in your respective shifter improvements. I took the car out for a cruise this morning and was once again impressed by the dramatic difference these parts made.

Bruce in South Carolina

[DANNOV]

A few years ago I got angry with my 1985 Carrera's shifting and made all of the modifications you described. The biggest single improvement came from adding the Robotek modification. In fact, it was probably the best thing I have done to this car in the 14 Years I have owned it.
The Robotek device spring loads the shift mechanism and gives you much improved feel and preciseness in your shifting. It was simple to install. I can't understand why Porsche did not make a similar modification early in the life of the 911. All the early 911's shift like crap and tinkering with the coupler and adding a short shift helps, but to get some "feel" in your shifting you need a spring loaded mechanism. I now have no fear of doing a 5th gear to 3rd gear downshift from high speeds in Drivers Education events. In the past I would never try such a downshift with the stock mechanism, a mistake in going from 5th to 1st is a several thousand dollar error! Whenever other 911 owner friends try my car they are amazed by the improvement in shifting. You have to try it to believe it. I would never go back to the stock shifting setup again.

[tmctguer]

i have a stock shifter in my '73 911E. how long does it take to complete the installation?

also, where can you purchase the robotech devices? and how much are they?

[DANNOV]

Originally posted by tmctguer
i have a stock shifter in my '73 911E. how long does it take to complete the installation?

also, where can you purchase the robotech devices? and how much are they?

The Robotek Sure Shift costs $299. Installation requires removal of the shift lever housing, only about four bolts. You have to take off the spring holder plate and remove springs, perhaps two more bolts. You replace pivot pin with the Robotek version, a longer pin. Then, you must drill two holes in the top portion of the shift lever housing to bolt on the Robotek spring holder. You then put it back together. The hardest part was depressing the existing shift springs when you put the stock spring holder plate back on. It took me about 1.5 hours from start to finish. In looking at the gearshift drawings in Haynes, I notice that in 1973 there was a design change by Porsche. It doesn't seem like the Robotek can be used on the old version, pre-1973. You might want to check with Robotek to see if the device works on your model. Robotek has an ad in the 11/2001 issue of Porsche Panorama page 107. You can phone them at 815-943-1461. Before I bought mine, I called and had a long conversation about how the device works and how to install. They were friendly and very helpful on the phone. I must admit that the hardware does not look like $299 worth of metal but it does work, and I could not be happier with the mod. I should caution you that before I made this modification I spent a lot of time trying to get the shift coupler (behind the front seat) properly adjusted. It is important that you not ignore these adjustments because while the Robotek works, it will not overcome the the problems of a misadjusted shift coupler.

[Bruce Ayling]

Dannov's reply is excellent and I agree with all that he said. I would add this though - IF you have the factory short-shift kit installed it is also necessary to notch the shift housing to provide clearance for the shift pivot rod - this is because of the relocated pivot point on the short-shift kit. The shift housing is easily machined aluminum and a dremel does the job just fine. The instructions that come with the Robotek device illustrate this and are very clear.

Bruce in South Carolina

[Bruce Ayling]

One more thing I forgot to add - I didn't find it necessary to dissasemble the shift housing to install the Robotek. The springs are locked in place and will not go anywhere when you install the new shift pivot rod. Clearance was a little tight when I went to put the inside nuts on the two retaining bolts, but by holding them to my wrench with a small piece of duct tape it went smoothly. From the point I removed the shift housing from the car it probably took approximately 1/2 hour to fully install the Robotek.

Bruce in South Carolina

[DANNOV]

Bruce
You are correct, there is an easier way than I described. I did this a few years ago and I was trying to remember the procedure. Now, after some recollection, I seem to recall that I did do it the hard way. In any case, it is a simple job but well worth the expense and effort. I now have the slickest shifting 1985 Carrera around and I don't think I will ever sell this car.

[rob justice]

Does anyone have an e-mail address or web site for this Robotek device?

[81Targa]

you can find the kit at http://www.smart-racing.com/ProdCat/Shifter/Shifter.htm

shows it installed

hope that helps

[DANNOV]

Originally posted by 81Targa
you can find the kit at http://www.smart-racing.com/ProdCat/Shifter/Shifter.htm

shows it installed

hope that helps

The Smart-Racing picture shows the Robotek device installed on the outside of the rubber shift boot. I suppose you can mount it this way, but, it would require cutting the boot which may tear over time. In my case I was able to pull the boot over the mechanism so that it is not visible. It is a tight fit but iit can be done.

[Doug Zielke]

The aforementioned website says this about the Robotek gizzmo:

"This gate defining kit defines the 1-2 and 3-4 gate so
unintentional downshifts from 5th to 2nd or 2nd to 5th upshifts are a thing of the past.
Shifting from 2nd to 3rd is also improved because you can "feel" the gate definition by
the spring resistance...gate definition has plagued the 915 shifter since it was
designed.

Mmmm....maybe the Germans dealt me a special 915 or something, but I've never had a problem with "unintentional downshifts" or "gate definition".

It's the (slow) speed of the shift that irks me (and most others) about the 915. So, does the Robotek do anything for that?

[Bruce Ayling]

Originally posted by Doug Zielke
[It's the (slow) speed of the shift that irks me (and most others) about the 915. So, does the Robotek do anything for that? [/B]

The robotek has no effect what so ever on the shift geometry so in that sense, no, it does not do anything for shift speed.

From another perspective though I think one could argue that the Robotek's vastly improved feel and positive sense of engagement enhances driver confidence in the box and leads to quicker shifts. This is definitely true in my case.

The factory short-shift kit does change the shift geometry and the shorter throws should equate to quicker shifts - it's the least expensive of the three mods mentioned and would seem a logical place to start. Since except for the long throws you seem happy with the 915 as it sits, you might wish to install the short-shift kit, rebush and adjust the stock shift coupler (as well as replacing the shift rod bushings), and see how things feel to you at that point. Sum total investment should be less than $200 (plus your labor) and you may find that's all you need to be happy.

In my case I feel the further improvements offered by the AM coupler and Robotek were worth the (fairly large) expense, but shift feel is infinitely subjective and what holds true for me may not be so for you.

Bruce in South Carolina

[Doug Zielke]

Some time ago, both here and on the Rennlist, there was discussion of the short-shift kit.
It was the opinion of a few knowledgeable folks, that such a kit puts undue stress on certain parts of the (915) transmission. Maybe John Walker would care to comment. ("In John We Trust")

[Bruce Ayling]

I'll be very intersted to see if John has any thoughts on this as well, but [as so often seems to be the case of late... ], that doesn't make any sense to me. The factory short-shift kit is identical in every respect to the stock shifter except for a relocated pivot point and the necessary dimensional changes to accomodate this. The only way I could see this happening would be by driver "overcompensation" - that is someone who's used to the long throws and tries to hammer the shifter further than it is now intended to travel.

Bruce in South Carolina

[addictionMS]

one last thing which will make a small difference in the shifting is to go to solid motor mounts, then the entire system is fixed in place and the shifting is even more precise. However there is a price to pay, they are noisier.

Jim

[speeder]

Where can one get the improved,(round), coupler bushings?

[DANNOV]

Originally posted by Doug Zielke
The aforementioned website says this about the Robotek gizzmo:

"This gate defining kit defines the 1-2 and 3-4 gate so
unintentional downshifts from 5th to 2nd or 2nd to 5th upshifts are a thing of the past.
Shifting from 2nd to 3rd is also improved because you can "feel" the gate definition by
the spring resistance...gate definition has plagued the 915 shifter since it was
designed.


Mmmm....maybe the Germans dealt me a special 915 or something, but I've never had a problem with "unintentional downshifts" or "gate definition".

It's the (slow) speed of the shift that irks me (and most others) about the 915. So, does the Robotek do anything for that?

If the owner of an older 911 would drive a BMW or a new Vette, they would quickly understand the meaning of gate definition. This is a real problem with the early 911's. I suspect that over a long period of time you and others have just adjusted to it. How confident are you in doing a 5th to 3rd gear downshift at very high speeds under heavy braking? Not many people are willing to risk such a shift with the stock setup - no gate definition - unless they have a lot of confidence and track experience, as well as being calm and very precise at high speed. I don't know your level of experience, but the vast majority of 911 drivers are probably not that confident with the stock setup.