Tuesday, 19 February 2013

911T Project - Gearbox

In spite of the diversions caused by running around in £100k 991s, I'm still making progress on the 911 project. In fact there has been some noticeable 'mission creep' as my initial hopes that the shell was in good condition were confirmed. More details to follow......

With some help from one of the DDK crew, I dropped the engine and gearbox out last week. 

The 911 engine come out from underneath.
First you need to get the car up high.....
Yesterday I took the gearbox to Jez at Carrera Performance in Horsham to take a look at. The synchromesh on 3rd gear is tired so before I re-install the gearbox in the car I want an idea of its condition. Hopefully the cases will be in good nick, and a refresh won't involve serious (or expensive) machining work. 

The 1973 model year cars were built in the last of the completely engineering-led, money-no-object days at Porsche.  From 1962, product development and competition efforts had been led by old man Porsche's grandson, Ferdinand Piech. His energy and determination were incredible, and the level of development applied to the 911 over the next decade were, to modern eyes, extraordinary.  

Increases in engine capacity you would expect, but over time the car got lighter and even more costly to build. A large part of that was a move from aluminium cases for the engine and gearbox to expensive but lighter magnesium alloy - at one point the largest mag alloy casting ever made. Countless other improvements and developments were also applied to all aspects of the cars - it must have had the cost accountants screaming in their sleep. 

The introduction of the 2.4 litre cars in 1972 brought with it a completely new design of gearbox. Known as the type 915, these units were based on Porsche's racing experience, and were used in 911s for the next 16 years, before being replaced by the easier to use (and much, much heavier) G50 'box.

Mag alloy 915 unit. Lovely castings
An anecdote from John Wyer's book illustrates Piech's approach nicely. During the discussions that preceded JWR's 917 factory campaign for 1970, Wyer was asked how many cars his team would need for the season. Basing his answer on his experience of racing Ford GT40s for Gulf the previous year, he answered "Three; two race cars and a spare". 

At that there was a long, slightly awkward silence. 

Wyer learned later that under Piech's perfectionist regime, Porsche had been using brand new cars at each round of the sports car championship, and had built over 30 racing 908s in 18 months as a result. 

In 1972 Piech left Porsche to go to Audi. Internecine politics had clearly become a problem at the company as various members of the Piech and Porsche families vied for influence. Finally an agreement was reached that resulted in all family members leaving the company. 

Piech of course went on to build a stellar career in the motor industry; at Audi he drove development of the Quattro, and then in 1993 he moved on to head the VW group, where his determination to build a 1000PS car capable of 250mph inspired his engineers to create the fantastic Bugatti Veyron. Ironically, as a result of the catastrophic hubris of Porsche CEO Wendelin Wiedeking and his finance goon Holger Haerter, the VW group now own the company, ending 80 years of independence.

Meanwhile, back at Jez's, he had a couple of 915 gearboxes in for attention at the moment. It makes sense for him to do them at the same time, so he'll get mine cracked open pretty quickly and let me know what it looks like.

We also discussed various options for blast cleaning the body shell and zinc phosphate coating the bare metal. There's a local company he has suggested talking to about taking on the work. They have just completed a VW Type 1 van which Jez is restoring and he seemed pleased with the quality of the work. 

After that it was a short drive down the A272 to the painters (passing over the hump backed bridge where I'd briefly got two wheels of my BMW GS off the ground) located in farm buildings on the outskirts of a Sussex village. My brief to them has changed - they now won't be responsible for cleaning the shell, but will be painting both the interior and front compartment. 

The painter seemed pretty chilled, and the price quoted will stay about the same. They also have metalwork skills which might be useful if it saves me from moving the car one more time. In fact they had a race BMW CSL in that was mostly constructed of tackwelded re-inforcement tubes, so much of the original metalwork has been cut out. 

In another corner there was a competition prepared Mk1 Escort shell ready for paint. The lumpen old cast iron Ford gearbox casing was a noticeable contrast to the 911's complex webbed magnesium alloy one. 

More soon.


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