Builder

Howdy all,

New to list...

I am building a kit car and would like to use a Porsche Transaxle in the process. In reading through some of the posts, there are bits and pieces about the various codes, ratios, and stats.

Is there a website somewhere that is the definitive guide to the units? I am looking for a list of model numbers (i.e. G50/xx), what year and model Porsche it belongs to, and gear ratios along with torque specs.

Also, I have never driven a car without LSD. But, I understand that non-LSD diffs are better for the track. Any comments about your experiences with non-LSD and what to use (instead) would be welcomed.

Thanks!

John D.

Hey Scott!

Welcome to Rennlist..!!!

Hmmm - OK - you will find the gearboxes as follows:

901
915
G-50

What do you have for an engine you'd want to mate with the box - and then maybe a few of us can assist with the "conversion bits"???

Also - I've driven both LSD and Non-LSD on the track? Yes - I liked the LSD in the 915 (with a 3.2) a bit better then the 3.0 - 901 - non-LSD, but given the suspension mods, not sure it made a whole lot of difference (at least to me?)...

Let us know what you are thinking for a conversion for your kit car (and what kit you are building!!!!)

Best to ya!

John

Builder

Thanks, John. I am going to build an Ultima GTR, which uses a Chevy 350! The kit is set up for a G50.xx, so I am trying to figure out what's best... G50.01 02 50 52... and what the options are for R&P and LSD. I presume I can add the LSD in the future, if I don't like it without.

Here's a section from something I have found on the Web:

The G50/52 series were used in the 3.3 C2 Turbo and 3.6 C2 Turbo cars. These transmissions also have stronger differentials and cases and a type of Limited Slip differential that locks 20% under power and near 100 % on the overrun to minimize trailing-throttle oversteer. All of the G50 cars use the 240mm clutch size introduced on the earlier Turbo cars and they are now hydraulically actuated. In 1990, the infamous dual-mass flywheel was introduced on the C2/C4 series. These flywheels were intended to help reduce low-speed gear noise however they have proven to be problematic on these cars. A popular conversion invloved installing the single mass, lightweight flywheel from the Euro Carrera RS into these cars for a performance increase and much improved durability. The well-known stalling issues can now be resolved.

G50/00 = 911 Carrera, R.o.W.
G50/01 = 911 Carrera, USA/CND/J/AUS
G50/02 = 911 Switzerland (very short gear ratios)
G50/50 = 911 Turbo world wide, 1989 only
G50/52 = later Porsche turbo boxes ZF ltd. slip

So, I am leaning towards the 1989+ G50/52, but want to find the list of stock gear and R&P ratios to plug them into my spreadsheet.

Any idea as to where a guy could find such info?

The kit company provides the adaptor mount for Chevy small block to Porsche Transaxle, as well as all of the linkage.

Thanks for the info!

DJF1

If you do a search on this board you will come accross gear ratio charts that have been posted from time to time. Sorry i dont have the direct link but a quick search and you will find it.
The motorsports LSD is 40%-100% and for sure on a 911 it stabilizes the rear end especially under braking, trailbraking and exiting a corner at throttle. On a 911 it actually increases a bit the initial understeer but the benefits outweigh the negatives. Since you are building an Ultima 911 chassis setup tips are out of the window due to the differences of the two but stil for a track car you should have LSD.
Have you thought of mating a Porsche flat six back there? Can it be done? It would sure sound very sweet with a heart of a Porsche!
Good luck! The Ultima's sure look to be great toys!

Builder

Thanks, Danny. I will continue to search around on the board, too. Your vote is in favor of the (Motorsport) LSD. Will definitely take that into consideration. Do you have an opinion on the Torque-Sensing differentials?

Danny, you are reading my mind. The SBC is the engine of choice due to availability and cost. A guy can build a Small Block Chevy 700 bhp engine with 600 ft. lbs. of torque for under $8k. I don't know what the equivlent Porsche engine would cost, but the weight would probably be less...so the power could be also. However, my plan is to build 4 Ultima GTRs. The first will have a Chevy-8, then a Porsche-6, then BMW-12, and lastly a Ferrari-12.

I will be very happy with the Chevy for a while. It will be a fun road toy for sure!

DJF1

Yes my vote goes for the Porsche motorsports LSD. Its bullet proof and it gets the job done. The stock LSD at least on the 993's is not that durable for track use.
I think that HP/cost ratio for sure the chevy beats hands down the flat six.
Of course going the TT way and mounting a twin turbo 3.6 aircooled flat six there mated with a 6 speed gearbox will give you a very sweet package indeed but the price of admission from what I have seen is at least 20K for the engine alone and another 3-4K for the gearbox. I would also imagine that the flat six would be better suited as the center of gravity is much lower than the V8 and on a car such as yours it will be a dynamic combo indeed.
BTW this is the G50/20 and 21 gear ratio chart:
http://members.rennlist.com/david_t/gears.htm

As for the V12 monsters ...my my my... they will be awesome for sure!

Builder

That's a very cool set of graphs, Danny. And I also checked out your album...very sweet!

There have been many good comments about the Motorsport LSD, so I guess I will seriously consider it. I sure would like to drive a car without LSD to see how it handles...

The first engine will be Chevy, for sure. I can hardly wait to build with an exotic "lump" though. There's a guy in Canada that just put one on the road with the BMW 850i v12. See the attached photo. I don't know where I would get a Farrari engine!!!

Thanks for your input and I will post some shots of my build.

Regards,

Tour18

Greetings Builder and welcome to Rennlist. This place is rich with knowledge and information...

Although garbage compared to any Ultima, I have a Mirage shell which might turn into a street legal neighborhood terror one day.

Builder

Hello there, Tour18. Greetings to you...

Yes, I have been reading until my eyes are shot! This is a very good list. If I every own a (complete) Porsche, I know I can find answers here.

For me, building is all about the craftsmanship and the accomplishment. Build quality into your Mirage and you will be very happy with it. Remember, though...East Indian rug weavers always put a tiny error in their rugs, because only their deity is perfect.

Regards,

DJF1

wow Scott, that is a thing of beauty! I do not know what I would do more with it, drive it or stare it!

IMO with so much HP I would should not consider driving the beast without LSD. It is money well spent.

Good luck and please post pics of your finished product when you are done!

Builder

Haha!! I know what you mean...it borders on pornogrphic. And, at 2100 lbs, it's a rocket!!! Finally drove one last week. Can't get the smile off my face. Sure, I will put some pix up when ready. It will be a while...

Thanks again and drive fast!

Regards,

Tour18

Yeah, you need to make this place a regular hangout. Lots of good gearhead folks around here. Especially when it comes to things with transaxles... hehehe...

JC in NY

Remember if you run the G-50 in a mid-engine configuration you are going to have to run it upside-down.

Builder

LOL, yes I would guess so. You folks probably know these transaxles pretty well. I appreciate the invite...even though it won't be in a P-car. My creation will be sort of a mixed marriage of German, British, and American engineering. Should be interesting!

Perhaps, the second build will have a flat 6. I think that would be a good combination.

Regards,

Builder

...Which is, from what I have read, the way it was intended, according to history. Upside-down, the gears are wallowing in lube...

I have a lot to learn about these boxes. Not even sure yet what all of the parts are from the crankshaft - back. I have been looking for an "exploded view" without any luck. I know there's a diff and clutch, but where do they fit exactly. And, what's that funny looking flywheel? Is that a dog bowl with teeth?

Any pointers to websites would be appreciated. I plan on picking up a Microfiche on eBay once I finally decide on a specific box. Thinking G50.20 right now and waiting for someone to give me a good reason why that's not the right one.

Thanks,