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TOPIC: 928 auto gearbox upgrade

928 auto gearbox upgrade 08 Feb 2021 09:08 #21753

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Hi all,
In March last year I brought a barn find 1985 928 S2 as a covid lockdown project. The car had been off the road a few years and was a non-runner.
After a bit of time and money the car was road worthy and I really like certain aspects of the car. However I am not happy with the auto gearbox and wonder what other 928 users feel about the quality of the auto gearbox. To me, the 928 looks and feels very modern but the auto 'box feels dated.
The auto gearbox in my car is working OK but is typical of an auto gearbox of this technology level.
I am considering replacing the gearbox with a more modern auto gearbox such as a 6,7,or even 9 speed tiptronic unit. It is a heck of a lot of work but it might just bring the 928 right up to date.
Does anyone have any comments? Does anyone know of a similar conversion? Clearly this will fly in the face of purists.
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928 auto gearbox upgrade 09 Feb 2021 12:18 #21754

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i have a 1984 928 that was off the road for 8 yrs, like you i recently got it back on the road. i notice a jerk or abrupt upshift with accelerating. i am also interested in tip on how to smooth out the upshifting. safe travels
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928 auto gearbox upgrade 13 Feb 2021 20:41 #21758

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Approximately 80 percent of Porsche 928s were shipped with automatic transmissions. The automatic transmission in the Porsche 928 was sourced from Mercedes Benz, from 1978 – 1982 is a 3 speed and 1984 – 1995 is a 4-speed. It is the same type used in the Mercedes S Class of the time so it is a very high-end design, robust and reliable. The tuning/valve body is different from Mercedes so it isn't a straight swap, however a rebuilder that is familiar with the Mercedes transmission would be able to repair it.

The Porsche 928 uses a transaxle, so a 100% identical fit would be necessary. I can't imagine of such a swap. There have been some pretty involved transplants of 6-speed manual shift Corvette transaxles into the 928. I'm not familiar of such a swap of an automatic transmission.

A bumpy upshift/downshit may be cured by an adjustment that a qualified mechanic can cure.
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Last Edit: 13 Feb 2021 20:42 by Rich928.
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928 auto gearbox upgrade 16 Feb 2021 05:54 #21770

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Thanks for your comments Rich928.
I am not really talking about faulty transmission on standard 928's but more so reimagining the automatic transmission of the 928.
2 years ago I would have been against the reimagining of any classic car. I do own an 1969 Jaguar and love the old world quirkiness of it. However as a profession automotive integration engineer I have recently been involved with the Californian company Singer who reimagine the Porsche 911 range. This experience has confused my outlook somewhat.
The best way I can explain this is that my old Jaguar is old in everyway, the door shut are clunky, the seating position is not comfortable, there is no ergonomic sympathy to any of the controls. The list goes on. But this gives the car great character, which I love, but this does become tiresome on longer journeys.
The 928 is a totally different car, it still feels modern and fresh. It has good road presents and the interior space is a fine place to spend time. Indeed the near on 20 years of automotive development between the 2 cars has gone a long way. And that is my point regarding the automotive transmission, although the 928 did have state of the art transmission in the early 1980's that is a long way from the automotive standards of 5 to 10 years ago.

The question is if, electronically controlled automotive transmission with 5, 6 7 or 9 speed and better level of human interaction of the ratio selection via tiptronic control, would this have been fitted to the 928 in production?

Doing this type of conversion is a massive job. Not just with the physical alignment of mechanical parts, which will almost certainly require new parts being manufactured, but also the electrical control with modern transmissions using a CAN (controller area network) architecture.
This would be a huge task, hence the reason for the discussion. Understanding other 928 drivers point of view is very interesting as well as the potential donor parts which could be used.
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