Captain Boogaloo

Hello from the( rather hot and sticky, for us, anyway!) UK . Where as we speak the transaxle, torque tube, bellhousing, startermotor, single plate clutch and flywheel from a sadly long dead 1988 s4 928 are in transit to me ( yes, via ebay!). My intention is to mate these parts to a jaguar v12 on down draft weber carbs to go in my replica Ferrari Daytona. It currently runs fuel injection and a conventional getrag 265/ jaguar rear diff which is so nose heavy it's crazy!

The 928 setup would go a long way to fixing this, and the gearshift pattern is even the same as the Daytona!

The question is will the Jaguar V12 lunch the transaxle in short order? I've heard ...conflicting opinions regarding the 928 setup ranging from 'bulletproof, more than capable ' to ' chocolate component parts, prepare for loud expensive noises'. What should I believe? And does anyone still do limited slip diffs for these boxes or other upgraded parts which might be of use to my project?

Oh,and please be gentle! It's my first post!

Captain Boogaloo

Oosty

I hope that you get intelligent answers from those in the know on this forum. Your project sounds pretty incredible.

Disclaimer. I am not in the know. With only internet knowledge and 2 of my own 928's, which have never run under my ownership, but came to me whole(ish) and are both now in 1000 pieces, these transmissions are pretty robust. There are numerous well documented V8 conversions and even a V12 toyota conversion that run or ran the standard transmissions without any major issues.

Good luck.

ptuomov

https://rennlist.com/forums/928-foru...l#post15209097

karl ruiter

The main answer to your question is yes, for sure folks have hookup Chevy type V8s of various types, also folks have extensively modified the stock V8s with bigger displacement and various boost arrangements. In at least one situation a V12 was placed in a 928, but I don't know it the stock trans was retained. You can find a thread about the conversion on here somewhere.
Data Points:
-There are two major generations of the 928 manual trans, and they are very different.
-Early trans is hard on synchros shifting is a little balky even when syncros are good/ not grinding, but said to be strong in race conditions.
-Later trans shifts substantially better, but may not be as strong under really harsh conditions
-Later trans much more expensive and harder to find.
-Early trans easier to find/cheaper, but expensive to refurbish if issues.
-Both generations have succesfully carrried much more than stock HP.
-Extreme performance minded folks are going away from the stock 928 trans to non Porsche 6 speed boxes. I don't know the details, but might be worth looking at going there directly. Have a looks at 928 motorsports' site perhaps. Lots of threads about conversions around here.

icsamerica

Interesting project.

Which Jag v12... 6.0 or 5.3. The 6.0 generates lots of low RPM torque but I would expect the later S4 5 speed to hold it if you're gentile. 5.3 is a dog so no problems there. I have a 928 and still own a 6.0 Jag v12 so I'm kinda familiar. I know what you mean about the Jag IRS being heavy, the diff is strong and heavy but there is a lot of weight to be saved in the lower control arms and axles, I'm machining bits and making tube units as I type for a track car.

Which Daytona? Farrari or Shelby? I would not use a Jag V12 in either Daytona...better to use a stroked 289 in the Shelby or BMW V12 in the Ferrari. The Jag v12 is very heavy, smooth, interesting but not a strong performer in any way and has no prospects. I put a 6 speed TR6060 behind a Jag 6.0 v12 a few years ago for a friend.. It's a great relaxed cruiser. I also have a BMW V12 and compared to the Jag it's from a different planet.

You can see me drive around the XJS 6.0 with a 6 Speed on the track like it's standing still in this video skip ahead to about 7:10. My car has a mild cam Small block chevy.
https://drive.google.com/file/d/1Way...ew?usp=sharing

Sounds like an interesing project, I'd love to learn more about it.

Captain Boogaloo

Thanks for your replies, Chaps; I do feel somewhat reassured regarding the 928 manual transaxle /jaguar V12 mating project, especially since (apart from the down draft carb conversion) I'm not intending to wildly tune the Jaguar lump ( although it's a 'flat head' v12, not the later HE motor, and thus very suitable for big valves and gas flowing) since the build sheet from a ( sadly closed) classic Jaguar race specialist here in the uk clocked the top speed at 185....which is actually quicker than a real Ferrari Daytona!! I've had it up to 160ish and there seemed to be more to come...but I was rapidly running out of carriageway (and if I'm honest the old boumholey was a bit twitchy, too!). Certainly is a LOT of fun on sliproads ( motorway joining road)!! Real millennium falcon\hyperspace stuff!
Anyhoo, the pallet with my Porsche parts is due to arrive tomorrow afternoon, so I should be able to identify exactly which gearbox/transaxle I have acquired (beyond 1988 S4)
For you folks who wish to know a bit more about the Ferrari Daytona replica these parts are intended for, it's a RAM RT Daytona Spyder replica, a dimensionally accurate copy of Ferrari's famous v12 creation, with a chassis designed by Adrian Reynard ( I think he does/did some indy cars too?) I have found genuine bonnet/bootlid and doors, and a complete interior to go in and the gorgeous borrani wire wheels ( and the alloy wheels, too!),but the cherry on the cake is a genuine hard top!!! Rarer than rocking horse doodoo!! Of course, this is all Michael Mann's fault, for making Miami Vice!!! Life would've been much simpler if I'd gone for one of the Mcburnie Corvette versions, I know, but once I saw and heard a real one.....I was hooked, smitten. Just when the prices went bonkers, too.....! If you'd like to know more, Google the Daytona replica Club (moonfruit), there are some pics of the car on there (sorry, can't do links- a bit computer....challenged!)
Happy days!
Captain Boogaloo

The Forgotten On

IIRC the Jag V12 has the same bolt pattern as any chevy that bolts up to a 4L80E or HT400 transmission. So it shares that pattern with a 350 small block. Many of which have found their ways into 928s.

icsamerica

No this is not the case. Jag v12 used a common Borgwarner transmission at first with a custom bell housing that fit the v12. You want to get one of those V12 BW bells and adapt it to the Porsche 928 torque tube with an internal hydraulic release bearing. The auto bell has no provisions for a clutch fork. The BW bell has a flat interface that will easily accept the torque tube with some basic adaption.

In the late 70"s jag swithched to the GM TH400 for the v12 but the case has a unique bolt pattern and is custom to jaguar v12 only until 1993. In 1994 Jaguar now owned by ford refreshed the v12 and used the same 4L80e that GM manufactured for Rolls Royce and to do this Jaguar changed the bolt pattern on the V12 to match the Rolls engine. The v12 was made this way for just 2 year. During this period Ford owned Jaguar and thus is the only Ford product I know of that was sold with a GM tranamission.

The early flat head v12 was a master class in post war low production simplified manufacturing. The v12 head is a rather simple casting that was easy to machine. The exhaust port is very long and exhaust gasses travel through the head a considerable distance which created a lots of time for heat absorption. Combined with a low compression ratio, large bore and short stroke the early V12 is very thermally inefficient. They are basically furnaces with crankshaft. Despite many shortfalls they have a cult following. I owned a 6.0 jag v12 with a 6 speed manual for awhile and it made for a very intriguing driving experience. I'm planning on building another one in the future.