DDK - Die Deutschen Klassiker

Advice please!

matteo68 wrote:Advice please!

…and thoughts on precision shift joints and shifter spring kits too please!

I have Rennshift [Jwest] in Jaffa 911- and tango 914 [not a 915]

This is just my experience on this subject.

I've had a 915 in my 73T for the 34 years I've had the car. I have seriously hillclimbed it for 14 years and now it is a cruiser.

I have tried the stock parts and wanted a 'short shift' to go quicker.

I tried the factory conversion kit of parts; awful, and removed it after 4 events back to stock.
I changed the coupling bushes for round holes new bushes, not slotted, and they are still in the car 20 years on. Recommended.
I renewed all the shift ter bushes at the same time, absolutely required.

I modified the stock tower to a bolt=on/weld system from the USA, can't recall the name, but French sounding, and that was good. Sold to a DDK'r.

Bought a Rennshift system which is a very well engineered item. Found it 'tight' to adjust correctly and found it made 3rd to 2nd hard and notchey, but good, and reduces gear knob movement by about 30%. It can be adjusted to be about 50% less.

Sold it not long ago and fitted a well used stock shifter bought last year at the Autojumble.
Fitted a new bush at the base and carefully adjusted it.

The box is an absolute dream now. Long shift as ever, but for a simple road car and traffic, perfect.

The gearbox was rebuilt about 15K miles ago by Mike Bainbridge. With the Rennshift I thought the box was faulty, with the stock shift tower the box feels rebuilt!

In conclusion:
Good gearbox condition
Stock shift tower
All new bushes, coupler with round holes
Very careful adjustment to get the position of the lever in the tower correct to the gearbox gear positions, but this applies to any shifter you choose.

Thanks Graham, that’s really, really helpful.

So no Wevo 915 internal gateshift kit (https://www.twinsparkracing.com/shop/we ... shift-kit/) or PSJ required then?

A short shift in a 915 box is not a good idea in my opinion. By shortening the throw you are lessening the time that the synchros have to do their job. Fine in a race car where you are prepared for regular rebuilds but not so good for cars in normal use.

As said above make sure all the factory parts are in tip top condition and that it is adjusted properly and live with the slightly long throw, your gearbox will thank you for it.


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Don't bother with the gate shift.
I have one in my 915 box in my racing only Lola, no real difference!

Thanks. Short shifting is not as important for me as precise shifting / reducing the 'soup-stirrer' feel of the 915 box compared to the later G50, so this is why I added my subsequent request for advice on PSJs & springs etc.

I had a Porsche short shift kit that I inherited with a later gear tower on a 915. It was the most horrible gear change I have ever experienced. Been driving for almost 60 years. The gear tower has been reverted back to standard and the 915 box is lovely to use. I would not agree that the 915 has a "soup stirer feel". Careful adjustment set up by someone who knows what they are doing and fresh standard bushes give a precise change. In any event what ever the feel of the change it is part of the character of the car. I also use a 'dogleg box ' in another car which has a totally different feel to the 915 but I would not wish to alter it. If you want a modern feel to a gear change best buy a modern car.

Suitably told!! I’ll go and crawl back under my rock…

The biggest improvement to my 915 came about 11 years ago when I fitted a Wevo shifter. This added much needed, spring assisted precision to the shifting. It doesn’t make it faster, I don’t believe you can or should rush a 915, but it gave confidence in where the shifter was due to the spring loading. I added a Stomski coupler which is the same construct as the Wevo and the main difference is more noise in the cabin, it only added a small amount of extra precision. A bigger improvement (than the coupler) came with the fitting of a new shift rod bush that I saw on Pelican. It gets excellent reviews for something so simple and cheap. https://forums.pelicanparts.com/porsche ... shing.html

A lot has to do with what you want from it all.
I actually extended the gear lever on my old Renneshift, and that (40mm) extension is now on the stock shifter. This increases the throw!

Work Done = force x distance.
The 915 needs work done to shift gear, lets call this 100 N.

If you reduce the distance (short shifter) then the force has to increase to achieve the same work done, so to get 100N and a 30% shorter shift distance you need to increase the force, and this is where things get tricky, as some level of force is ok, more is too much.

My extra 40mm increases the distance, thus I need less force for that 100 N.

I just rumble around in my 911 now, i want it safe, reliable and easy to drive.

These mods can affect these qualities.

If you have a hillclimb car (say) and need to thrash the b+lls off it for 50 seconds, these forces, roughness are not a priority, BUT, you do want to get the gear every time.
The WEVO/Renneshift systems have quite strong springs which hold the gear lever in the 3rd/4th plane of the H pattern, just like a modern manual box does.

The short shift also narrows the H pattern as well as the fore/aft throw, so it is a very precise movement that demands precise adjustment, but all these shifter need precision in adjustment and the new bushes etc all reduce play, but there has to be some for things to move.

On that note, one mod I did on my 911 was to fit poly bushes in the trans and engine mounts. This stops the drive train moving around significantly, it weights about 300Kg after all.

This introduces noise/harshness but really helps on precision in changing gear.

I now have stock rubber mounts now I just cruise.

Thanks again Graham. As you’ll be aware this is for GeLo, which is going to be a race car on the road, and won’t be droning away / sending me deaf on long journeys on motorways. Rather I will be blatting around on the glorious twisty, undulating roads of the Cotswolds (A361 Charlbury to Burford is on my doorstep if you know it - Harry Metcalfe’s fave), with plenty of 2nd / 3rd / 4th gear changes and red-lining out of corners. So a precisely adjusted gearbox with new bushes, couplings and maybe polybush mounts, but retaining a stock shift, may well be the answer.

always had a stock shifter on my 2.4S . Box rebuilt by Mike bainbridge. I drive it hard and never wanted for a short shift. The only shift I do take steady is the 5th to 4th . 1st to 2nd is also never going to be a lightening shift .. but neither is 1st to 2nd in my 964. When I've driven early cars with short shifts I've hated them. I'm not blinkered though, as arguably the shift in our old ratty mgb is better and more precise, but the a stock 915 shift suits the car well. I'm looking at things from a road car point of view though

I’m not changing anything in Gina’s box - she’s a road car through and through. Mind you, there’s no mention of any competition shifter / linkage parts for the 2.5 SR in the parts list, so maybe nothing doing there either, apart from just following Graham’s original advice.