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Old 11-02-2004, 09:19 PM   #1
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Swapping of Tiptronic to Manual Transmission

Just how difficult is this procedure assuming I can get my hands on a reasonably cheap 6 speed transmission? I know the ECU control modules interfaces to the tip control module so that's one thing that needs to be taken care of. Any documented articles on this?

Reason I'm considering is because there's absolutey no manual Boxster S where I'm living. All are tip. I'm just a sucker for manual cars, especially 6 speed ones. But I'm also a great fan of the Boxster. So I compromised and am now on a Boxster S Tip.

Thanks for any response.

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Old 11-03-2004, 08:04 PM   #2
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Keep in mind the Instrument Cluster should be changed out also.

ABS and PSM talks to the Tiptronic Control Module to control downshifting on full ABS stops and holding a gear in other situations.

Find a good Wiring diagram for a Tiptronic and Manual of the same year to see if there are any pin out differences on the ECU connector and will deleting the Tiptronic Control Module dead end other necessary circuits.

The Tiptronic Control Module has several inputs including the usuall, TPS sensor, RPM, MAP, ABS, PSM, Temp sensors. Outputs are to the Trans, Cluster, ABS, PSM and the ECU. I'm referring to a non-MOST car. Finding a ECU for a manual S 6 speed should take care of most of the issues. Your automatic/tiptronic cluster may fail to operate properly once the Trans Control Unit is deleted. (had this happen on VW and Audi auto to manual conversions). Some pin outs may need to be moved in the cluster connector also.

I'm learning how MOST works on the Boxster at this time, but I am familiar with it on the Mercedes-Benz side. Here's an educated guess...

If the Tiptronic Control Module is on the MOST fiber optic "Ring"
and is removed without a bridging fiber optic harness in its place, you are breaking the ring and all of the other modules will not communicate with each other. You will be "dead in the water".

If the fiber optic bridge harness is in place you will have to have the "ring" reprogrammed to think its now a manual. Provided all of the wiring is correct, the replaced ECU and manual instrument cluster should communicate properly.

All modules and Control Units on a fiber optic system or a twisted pair data bus relay commands back and forth. The modules are programmed to pick up certain bytes of information sent arond the ring. If a command is intended for a certain module, the data is captured and the function is performed. If the data command is not for that module, it will pass it on to the next module on the ring and so on.

For example, the head of the "ring" in a Benz is the radio. it is responsible for "waking up" all of the other modules and control units on the ring. If one module is malfunctioning, it can interrupt communication to all of the other modules on the ring or fail to pick up the command. I have seen the Becker radios do this causing odd problems or bring a car to its knees.

Best advice, do you homework on the electrical side and grab any harnesses and parts from a doner car if possible. Best of luck, it can be done.

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Old 11-03-2004, 09:17 PM   #3
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Thanks for the detailed writeout. Like you said, the 'easiest' way out is to get the ECU together with the transmission, not forgetting the instrument cluster.

A major job and the keys will also need to be re-programmed or grab off the donor car again.

Sigh.... why isn't there a manual over here

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