Porsche 944: Actually there is a substitute

[Fitz]

Originally Posted by sparkydog

Here's the car and the PO. And a picture of what the engine bay looks like with the LSX in it.




Hee hee!

I'll take two! No, not the car, the Blonde.

[sparkydog]

Trial fit #3. Took the oil pan off. Headers are now resting on the Mustang engine mount brackets. Throttle body is mashed up against the firewall. I’m guessing that this is about where it will end up +/- 1” in any direction.

[sparkydog]

Forgot the hood shot.

[sparkydog]

I bought an '01 Grand Prix GTP that one of my daughters will drive and it might also end up donating some parts to the 944 some day.

It has the typical fails for the w-bodies: engine mounts were shot and oil pan gasket leaking like a sieve. Here's a shot of the dead PS motor mount. I am replacing with solid body rather than the OG design with fluid.

[TexasLS1]

Don't know how I missed this thread, but I'll be watching. My first car was a 914 in shambles, so I have a fondness for Porsches. Awesome work and will be a fun car!

[FRENCHBLUE72]

Any updates?

[sparkydog]

Thanks for checking in French. No progress but not dead is about all I can say. When I do get back on it I'll work on the IRS stuff. Trying to mate the Ford diff with the 944 swing arms. I'll also be trying to gather more info about the CARB rules here in California and whether I can realistically make it to approval if I modify the intake and exhaust as much as I would like to. If not then I have two other options. 1) "sell" the car to an Oregon relative and then buy it back and bring in as an out of state car that can pass emissions. 2) Rig it with L36 RWD stock components, get the CARB sticker and then swap in the L67 gear. I want the car to be legit as far as polluting goes - just don't understand why it's bad to change plumbing as long as it still passes emissions.

[made2drag]

Wow... amazing work man....love it!

[sparkydog]

Back on it!

I lay claim to be the first guy to ever hang a Ford 8.8 diff and drive line up inside a Porsche 944. (Can't prove it but what are the odds, eh?)

[sparkydog]

I'll have to do a little research but I'm thinking the 8.8 diff is not going to work because for the drive line to clear the 944 swing arm torsion bar housing it puts the CL of the diff about 3.5" higher than the CL of the wheels while at approx ride height.

I doubt the axles would like running with that much offset all the time. Does anyone have advice?

I think that I either have to see if there is a way to mod the center of the 944 torsion bar housing so that I can run the drive line right through it, or - scrap the 944 suspension altogether and stuff the Mustang straight axle setup in.

[sparkydog]

Originally Posted by sparkydog

I doubt the axles would like running with that much offset all the time.

Maybe I will be OK on this. I did a rough calc and it looks like the axles would be at about a 10-11* angle with the diff up where it is in the pictures above. From what I can tell off the internet this amount of angle is OK for a CV joint.

[sparkydog]

There it is boys and girls! A Ford TBrid IRS hub, axle and 8.8 diff mocked up inside a Porsche 944. The stock TBird axles are a little too long for the track of the 944 so to achieve these photos I just slid the diff over to the side until I could get everything to fit. This allows me to get an idea of how much I would need to shorten the axles (or maybe find something OEM with about the right length). The pics also illustrate the 10-11* axle angle I would have to run.

[ejn74]

Looks good! Keep it up.

[ricott]

Would it be possible to "section" the Porsche crossmember so the driveshaft/differential could sit a little lower? The side shaft angles look a little severe and would it be outside the working limits in certain situations (rough roads, hard cornering?)

[sparkydog]

After doing the mockups with the Ford IRS diff and looking at the tradeoffs I would have to make I've decided this is not the way to go. As we've all noticed the CL of the driveline wants to run right where the 944 Tbar housing sits. It is possible to do a "Tbar delete" (as the Porsche guys call it) and run coil overs but there are other mods that accompany it. Even then I would be running custom shortened axles so when the CV joints wear out I'm faced with expensive replacements. Since my goal is to try and have a car that is affordable to maintain and repair I think my best option is to ditch the 944 rear suspension and graft in the Mustang setup.

So I pulled out the Mustang junk, disassembled the axle from the floor, cleaned up the floor and then studied where to do some trimming in order to get it down to the essential structure that needs to go into the Porsche.

I ended up with this plan and set about doing the trimming.

[sparkydog]

My basic plan with this 1st trim was to use nothing off the Mustang aft of the shock upper mounting points so that there was as much 944 as possible rear of the axle - mainly so that the 944 spare tire stowage would be left. The Mustang front trailing arm attachment points end up just behind where the 944 torsion bar housing currently sits (that is if I measured correctly). I will trim more out of the Mustang but this was close enough for now.

Next up is to remove the 944 Tbar assembly and trailing arms, slide the Mustang metal under the car and stare at it for several hours.

[sparkydog]

P stuff is out. Different F stuff ready to try and go in.

[TexasLS1]

Looks like a lot of work done this weekend. Good to see the updates on this!

[firethorn]

very interesting build

[sparkydog]

I realized that I needed to get some kind of reference datums going before I got too carried away with stuffing the Ford sheet metal up inside the 944. So I assembled the axle and linkages back onto the sheet metal and then set it up at the correct angle. (When this stuff was still in the Mustang long ago - I had recorded that the lower arm sat at a 2* angle.) With the lower swing arm at 2* down I then made marks on the sheet metal where the CL of the axle is. Then removed the heavy axle and linkage so that I can wrestle with the structural metal more easily up under the car. Next I'm going to add some temp bracing and then whittle a little more of the excess metal off this thing.

[sparkydog]

I also came to realize/remember that the input to the Ford rear diff is shifted about 5/8" off to the passenger side of the car - the drive shaft isn't on the CL of the car. The Porsche is symmetrical und vee know zee Germans like zee perfection, ja?! So the 944 drive line tunnel is centered and that will be an issue I have to contend with and solve somehow. Can anyone confirm what the exact amount is? Any Ford rear end experts lurking around here?

[sparkydog]

It was a rough week at work so I gave myself a little fun time this morning. I decided to do some more prep work to the Mustang structural metal while it was easier to work on. So... the axle went back on again, then some more conduit bracing. Then the axle came off again. Then I marked up where I wanted to improve upon the Ford factory spot welding. And then it was stitch-o-rama for an hour or so until I ran low on shield gas.

[sparkydog]

I shaved more off of the Mustang frame section and did my 1st stuff up under the 944. Then I stared at it for awhile and made notes on what to do next. The upper shock mount pockets are going to come off. They may go back in after the graft surgery or I may do a slight mod on where the shocks route. And now I have a rough idea of about how much of the 944 frame has to get sectioned/removed. I need to prep the 944 for surgery so that nothing moves on me while I cut up it's rear frame horns.

[sparkydog]

More shaving. The upper shock mounting brackets came off as well as the last of the OG Mustang floor skin. Then another stuff up under the 944 and of course more staring. I began to envision how I will fit a small exoskeleton up under the 944 so that I can cut into its frame horns without causing anything to distort. And now that the shock brackets are off I lost my axle location reference marks... so I put the axle back on (getting good at it) and clamped the shock mounts back so that I can create some NEW locating reference points. And so it goes.

[sparkydog]

This is what I came up with for a system to give me handy reference points as I start working to mate the Mustang metal into the 944's hiney. With the axle, linkage and mock shocks on and the lower arms at their 2* down angle - I welded in 2 of these reference bracket things. Now I can remove the axle but have the inner edges of the brackets to measure fore/aft and up/down location of the axle center line. And with the rear faces of these brackets I can clamp a level and know that I have the whole thing at the right "pitch".

I also added some gussets to stiffen up the areas that will see stress.