[N0tt0N]

Added some more pictures to Aero/Cooling.

[HoodPin]

To me....it always daunting to consider cutting into perfectly good body parts..........but you guys have done great! Plus, nice work on the radiator(s) shrouding.

[N0tt0N]

Originally Posted by HughA44s

More info on the diff install please. You know, the limited slip diffs on M3s are know to be clunky and erratic even when new. I was thinking of a triple plate replacement. Was this difficult? I think I would stick with the stock 3.67 (I think) but the idea of a 3.91 looks neat too. Did you reuse the stock ring and pinion? Do you really need to do the calculations to 7 significant digits? Seriously I would like to hear more about this. I may have an advantage as I have a separate diff and not a transaxle.

I know jack diddly about BMW mechanicals except that V10 M5s cost a fortune to maintain for occasional track use. Someone else can chime in with specific advice as there are quite a few BMW racers here.

Was it difficult? If you haven't worked inside a transmission before it can be intimidating mostly because you second guess everything with images of shrapnel flying everywhere coming out of T10. I was lucky enough to have BillC mentor us when we put the WaveTrac Torque-Biased Diff (TBD) in the Blechster. He had the tools and the know-how and generously shared them with us. So, we were a bit better prepared to undertake this ourselves. Its not actually that difficult as far as the steps.

The ring and pinion are a matched set. Ours showed no signs of wear. We did not really consider switching them out for a different ratio so I can't provide any feedback. I think in the case of a Cayman changing the transmission gearing would be more beneficial to tuning the performance of the car as 2nd gear would be completely useless with a higher ratio diff but maybe that would be replaced with using 6th. Hard to say.

7-significant digits is cutting corners for Team OCD (as Vranko calls us) but the answer is no. We were actually curious what the variability in the shims was given we were making our own.


We also went with a Guard diff. We consider it an heirloom investment - in that you would remove it before bequeathing the car to your next of kin. Mihnea didn't want to put it down.


We racked up the transmission on an engine stand (weird how it works for both, right?) and drained the oil.


We then levered off the axle stubs (there is a circlip that pops free) and the access plate to expose the diff. The diff lifts right out (but it is heavy given its size).


The ring and pinion showed very little wear.


The pattern of the wear indicates whether or not the pinion is correctly positioned relative to the ring. If you change the pinion then there are some extra steps to go through for measuring and positioning the gears. Since we were sticking with the original set we reduced our problem space to shimming the diff side to side to match the correctly set OE setup that is wearing well.

We did go ahead and replace the bearings since we had the case open. We drove out the outer race with a brass drift.



And then pressed in the new outer races, which in our case are unique for each side. The shims go beneath the races. On the 986 I believe it was the opposite setup of shims that went under the inner races on the diff. Know where they go! The access plate bearing is easier to manage on a press.


Double checking the target offset


For the other side its a bit trickier. With the shims in place.


And with the outer race in.


Getting the inner races on the diff is one of the 'tools are important' things (besides the shimming process). BillC turned us on the the Miniductor so we used ours (we ARE NOT tool whores - more like tool Call Girls) to heat up the inner race and then drop it over the pre-frozen diff. Drops right on, tap, tap, tap, done. Very difficult to get on and correctly seated otherwise.


Make sure it is super clean


And put it back in


And seal up the case


And drive through T10 with your butt cheeks clinched.

[N0tt0N]

Originally Posted by HoodPin

To me....it always daunting to consider cutting into perfectly good body parts..........but you guys have done great! Plus, nice work on the radiator(s) shrouding.

Believe me we stared at it for days before cutting....

[HughA44s]

NOTTON,

Thanks for the great response. Obviously the configs are different but I think many of the basics are the same. Yup not changing the ring and pinion reduces the number of equations and unknowns.

Incredible work and coverage.

[N0tt0N]

I mentioned that we had to fab custom coolant hoses in order to mount the CSF center radiator for a Cayman in the reversed GT3 mount. They all share the same end connector but the hoses are either starting from somewhere else, going somewhere else, or oriented differently. Since we couldn't find a source or tools for creating Porsche coolant hose connectors we decided to splice in a section of aluminum tube to extend or reorient the ends to where they needed to be. We wound up using some pieces from the original Cayman hoses and some pieces from the GT3 hoses we originally purchased thinking they would fit.

After several mental exercises trying out different combinations of ends (before cutting them in half) we set out to make the tube joints necessary:


and roughing up their ends to accept hose clamps:


We attached the end connectors from one of the sets we cut:


And viola!


The other side mounted:


We also wanted to take the opportunity to reduce as much thermal transfer as we could between the intake air and fuel as it travelled through the very hot engine compartment.

We applied some gold reflective tape (that is supposed to reflect away 80+% of radiant heat) to the manifold crossover tube:


the underside of the manifold runners:


and the airbox:


We also wrapped the fuel supply lines and the crossover line with velcroed heat protecting material:

[Vicegrip]

Originally Posted by HoodPin

To me....it always daunting to consider cutting into perfectly good body parts..........but you guys have done great! Plus, nice work on the radiator(s) shrouding.

No such thing as a "perfectly good body part" on a track car. At best everything is "A good start"

Interesting to see how much plastic has replaced metal in the transition from air/oil cool to water cool.

[cmartin]

less weight, lower ET. Wait....

[thelittlemrs]

Is anyone else thinking "Forget the car, just organizing all the pictures would do me in!"????

[Fumes]

why didn't you de-snorkle? that giant plastic thing weighs 20 lbs...