This winter I was looking forward to putting my 1986 Porsche 951 into a heated garage and hopefully taking it under the knife. Putting the 968 Door handles, mirrors and the hatch on. Now this is where it gets tricky. I have heard that it is possible to switch my 951 transmission with a 6-speed from a 968. Is this true? And if so, exactly what procedures am I looking at taking on?

Any reply is great, this being my first post, I hope I can come to rely on everyone as much as possible.

 

Yes, it is possible. The procedure should be simple, just the same as a normal transmission removal-and-replace, which can be found on Clark's Garage.

I'll let others chime in on whether or not its worth the effort and the money.

 

The 968 gearing should keep the 951 in its powerband more, I believe you also have to swap out the drive axles in the back (maybe just one side), and you'd also have to come up with some solution to make the speedometer work

 

GPS!

 

Thank you for your quick replies. What exactly would be the problem with the speedometer? Is this simply a problem with a different model transmission?

 

I think its something about the sensors that are used to determine speed work differently between the 951 and 968 and are not compatable. I've heard that getting the speedo to work requires some ingenuity, but is not impossible.

 

Sounds like a solid explanation. Has anyone here completed this project before, or have a link to walkthrough on how this is possible.

 

I'm pretty sure John, fast951 here on the forum has done this. He posts mostly in the 944 turbo/s forum, so you might want to post over there or send him a PM

 

If this is your first post you should search for the 968 archivies for 6 speed transmssion failures. I wondered when my 968 6 speed would fail its ring and pinion bearings until the day I sold. I think there are many other upgrades for the 951 before a 968 6 speed. I have had seven 951/952 project cars of which I sold three to German Auto Dismantlers for parts. But that is another story.

 

The speedo problem comes down to this:

The early 944's ( < 85.5 ) have a mechanical speedometer driven by the rear wheel (transmission swap won't affect this)

The late 944's ( >= 85.5 ) have an electrical sensor in the transmission which provides a spedometer signal

The 968's have an electrical sensor in the wheel (ABS sensor) which provides the spedometer signal.

Whatever solution you choose, it likely won't be easy. I imagine your best bet would be to rig something off of a 944 ABS sensor, combined with some type of 'signal massager'.

 

how difficult would it be to conver to a mechanical speedo a la early 944?

also, I don't recall hearing anything about 968 tranny failures....

 

For a discussion of 968 pinion bearing failures and a 968 owners' protest letter to the President of Porsche go to 968.net. Also, Audi 6 speeds of a similar design in this time frame suffered the same problem. One Porsche dismantler pays a premium for 968 6 speed crashed cars because the demand for replacement 6 speeds always exceeds his available parts cars supply. Also, he has purchased crashed 968s to find out that the 6 speed transmission had been swapped out for the 951 5 speed. I guess he deserved that though for all his other "evil deeds". The 968 6 speed failure is reported as the pinion bearing preload being too low according to those that have studied the problem.

 

The 968.net discussion actually claims the 6 speed pinion bearing problem was too much preload not lack of preload. Also note the discussion of how expensive it is to repair damaged 6 speed transmssions.

 

interesting

 

So I gather that going with a 6speed will not only be hard, but would be unwise as well? If this is true, then what am I looking at doing next? I heard the mention of a 952, and I am completely unfamilar with the term.