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Tuesday, 08 January 2013 17:24

924, 944, 968 Gear shift issues- Part Two

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So, just to recap, in part one we discussed what is wrong with the 924, 944 and 968 gear linkages, why they wear, what parts wear out and you should now have a good overview of how it all works.

You might also want to rectify an issue with your gear selector issues, which you may or may not have even realised you had until you read part one of this series.

Well, as you are reading this, you obviously want to know what the other options are for repairing your gear linkage, making it a longer lasting item and possibly improving the gear selection action to be better than even the factory gear selection. So lets look at the options.

None of the info in the first article is new information, I like many specialists have known all this for the last 25 years, and over that time there has been many companies who have come and gone who offer repair parts, as well as Porsche who have been selling the original factory replacement parts since the car was originally made, however there is a chance that Porsche may discontinue production eventually.

Until about 10 years ago we were particularity unimpressed with both the standard parts (which become worn very quickly) and even less impressed with the aftermarket parts, such as the plastic block, which if used on its own will be wrecked very quickly.

Then there are the quick-shifts, which were often hand fisted designs which all had compromises in their design, resulting in products which give a new replacement part in one hand, but come with more problems than solutions they offer.

So back in 2002, JMG Porsche teamed up with its sister company 9XX to produce some proper solutions.

9XX is a team of engineers, including myself, as well as ex-employees of Penske Racing (designers and builders of indi500 race cars, the Porsche RS Spyder and more), who also have access to advice from the Porsche Motorsport engineers when needed. As such, the team believe in making parts to the same standard or design as you would expect from Porsche Motorsport, and parts which would not look out of place when fitted to your pride and joy, your Porsche sports car.

Over the years, 9XX have developed many products for all Porsche cars, both for the road as well as the race track, and indeed we have developed not only products for manufacture and sale, but also custom parts for particular one off applications such as Porsche race cars. So solving the issues with the Porsche 924, 944 and 968 gear selection assembly has need been hard for us, and over the years has proceeded through many revisions of evolution.

For the purpose of this article, lets talk mostly about replacement parts with standard performance specifications, in other words, we will touch on quick shifts just to show the evolution, but in the next part of the series will be an article more dedicated to our quick shift designs.

The first part we designed was a replacement for the front gear lever, or as we like to call it, the front shift.

As you can see, the 9XX FrontShift looks very much like the original factory part, however with one very special difference. Rather than a mild steel pin (as seen in the centre of this picture) it has been fitted with a pin made of stainless steel.

What we do is take your original worn out gear lever, clean it, blast all traces of corrosion from it, inspect it, and if it passes our inspection it is then sent off to an engineering works to have the original pin removed, the new pin fitted and the whole assembly repainted in black to protect the main part of the assembly from rust or corrosion.

This does mean that we need a supply of original gear levers, but luckily we keep many in stock so that we can send you one, charge a small surcharge and then refund the surcharge when you recieve your old one in the post to rebuild for another customer.

The result is a replacement front lever which is not very much more expensive than an original lower quality Porsche part, looks the same as a Porsche part, but will not suffer from wear and corrosion (or erosion) as the original part.

The other benefit of the replacement pin is that it has been made from billet stainless steel, much stronger than the original mild steel item, much less susceptible to wear than mild steel and of course impervious to corrosion.

Where the pin locates, into the main gear selection shaft, there is a tubular orifice to accept the FrontShift pin, it is unusual for this to wear, and it is almost impossible to remove without completely removing the gearbox. However, in the unlikely event that your one is worn out, we offer a service of drilling and reaming this orifice and installing self lubricating bushes into the main selector shaft without having to remove anything other than the Front gear lever and the leather gear knob, or we can supply the self lubricating bushes with technical support of how to drill and ream the main selector shaft.

Once the 9XX team had designed and had tested (in several customers test cars) we moved into the rear assembly.

Originally, the demand was not only for a replacement rear linkage, but for a replacement which was of a shorter throw for track and race use, also the value of the cars was quite high still, so customers were happy to have the very best part that money could buy.

As a result, it was decided to work on a replacement rear linkage, suitable for fast road, track and race use. Development of this product was over the course of a year in 2002.

As you can see, the original design is a quantum leap from the original Porsche rear gear selector mechanism. All parts are custom made from either billet stainless steel, billet aluminium and aircraft quality spherical bearing rose joints.

None of the parts used in this component can rust. Every moving part is a spherical bearing, so in theory, it should last forever!

Not only this but this item, like all our rear linkages benefit from one additional feature, which we believe is unique to 9XX gear shift linkages, an adjustable cross brace bar.

When the 944 was originally designed, it was designed as a left hand drive car, as such, you may notice that the gear lever is biased to be most comfortable in the left hand drive configuration, with a centre point slightly biassed towards the left. With our 9XX rear linkages, the crossbrace bar is adjustable (on the car), just loosen the two lock nuts, and turn the main shaft and the centre point of the gear lever will move one way when you turn the shaft one way, and the other way when you turn the shaft the other way. Once you are happy with the position of the gear lever inside the car, just tighten the two lock nuts and you can enjoy a gear lever position most comfortable to you. Especially important to race drivers, but also enjoyed buy our customers with road cars also.

These parts are available in two configurations, a RoadShift and a RaceShift. The RoadShift is designed to provide a shorter throw between gears than the standard Porsche part, and the RaceShift was designed to have as short a movement as possible at the gear lever end to change gear. So two different products as a replacement of the rear gear linkage.

Expensive to manufacture, this product is still available, however it has been superseded by our new RoadShift and RaceShift. But more of that in the next article.

More recently we have had many enquiries from customers wishing to keep their cars completely standard, wanting a crisp and precise gearshift, but with the original distance between gears at the lever end, which prompted us to develop our new product, the precision shift.

The PrecisionShift is designed to look very similar to a standard item, and to offer the same distance at the gear lever as a standard gear linkage, but with one major benefit of employing spherical rose joints in place of the rubber mounts on the cross brace, which reduces any sloppiness in the gear linkage than even a new Porsche part.

In addition, every part of the gear linkage is made of stainless steel, Aluminium or billet composite material (except one part, but we will get to that). So absolutely no chance of rust and very little chance of wear.

To maintain the original look of the part, as well as keeping the price down, 9XX have employed the choice of using one original Porsche part, the main clamp assembly onto the transmission shaft. This does have the drawback that a little like the FrontShift, we have to charge a surcharge when you buy these units, which is refunded when you send this part back to us.

This clamp is not just reused though, they are cleaned, inspected, blasted and then sent to an engineering works to remove the original mild steel pivot pin that runs through the composite pivot block which is replaced with another custom machined billet stainless steel item.

When you send back your clamp for the refund of the surcharge, you need not send back the whole assembly, just the clamp assembly shown above will do, we do not mind how rusty or even broken the original mild steel pin is, as long as the rest of it is in serviceable condition is good enough for us as it will be complete remanufactured for building another kit.

All moving parts in the PrecisionShift are completely serviceable (unlike the original Porsche part) which means we will be happy to sell you a replacement composite block, or replacement spherical bearings should they ever wear out, but we fully expect these kits to last almost forever!

There is one part which we have not mentioned in this article, or the previous article, which is the front gear selector ball cup. This part is inexpensive from the main dealers, however, even though it is often mentioned on forums as being the cause of some sloppiness, we have always found that the problem is always due to the front gear selector pin and the rear gear selector assembly.

So, with this article we hope you have discovered some solutions to some of the problems with the standard 924. 944 and 968 gear linkages as mentioned in part one of this series. In the next instalment we will discuss further improvements, in particular, how to shorten the throw as seen at the gear lever when you are diving the car, the subject of Quick Shifts!!

 

Read 10318 times Last modified on Monday, 18 March 2013 16:16
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