Another Gearbox Question

[builder]

Howdy Y'all...

Us "Yanks" are familiar with the PowerGlide, Turbo Hydromatic 350 and 400s, T56 Corvette 6 speed transmissions, etc. But where can a guy get a good explaination of the entire Ultima transaxle drivetrain?

Of course, I have been searching around on the Internet and it seems there's sparce little available. I am trying like HE** to understand what happens from the crankshaft to the wheels. Any links you have in your bookmark files would be greatly appreciated.

I have the PHII site and www.rennsportsystems.com/1-d.html

Thanks!

-- Scott
Reno, NV

[steve_D]

Scott
Is this a detailed description you want or just the basic principles?
steve

[Builder]

Hi Steve,

Sort of both, but I would like to start more basic. I can find specs on the components (i.e. the torque and bhp ratings of a G50/52 are available). But, I don't yet understand all of the components required.

I presume the rear axles are part of the GTR kit, or part of the transAXLE? I am getting the impression that there is some kind of (limited slip?) differential as well ?? (what we call "the pumpkin"). I gather there is no "driveshaft"?

Are you getting an idea about my level of confussion? I can build an SBC from the core, but what's a transaxle???

Thanks,
-- Scott

[bigmack]

Ah the good old days... I can remember having all of your same questions. Basically, a transaxle is a wimpy piece of garbage that can't take over 600ft. lbs of torque.
Just kidding. Seriously, though, these cars use a Porsche G50, G50/50,G50/52, or some other variant of G50 gearbox. We're talking 1987 G50 forward. You can also go with a newer 6-speed getrag gearbox. The g50 was offered in both a 5-speed and 6-speed version. You'll need to tell the factory what gearbox you decide on. We all have our own theories as to best box and choice to use(limited slip, non-limited slip). It uses brass synchros and gears very similar to a transmission. The transaxle is nothing more than a transmission without the driveshaft output. Instead, it has two half shaft outputs. These half shafts are offered by the factory and are supplied by GKN. You'll also need a pressure plate, clutch disc, a modified flywheel, adapter plate to mate the Porsche to a Chevy, and a slave cylinder to engage the "push" type clutch. Nothing real mysterious, don't worry, its just another way of doing things. Cheers!
-Mack

>> Edited by bigmack on Friday 9th April 04:29

[steve_D]

Mack may still have been on the technical side.

Start with flywheel complete with starter ring gear.
This is not flat like a normal manual box (MB) with a pressed steel pressure plate. This is dog bowl shape with the clutch disc in the bottom and the pressure plate putting a lid on the bowl.
The transaxle (TA) has a bell housing, as normal, which has to be mated to your engine using an adaptor plate. The input shaft, as normal, goes into the splines in the clutch disc. In this area is the release lever.

So far this is not much different to a MB.

What you know is that the input goes via the various gear clusters and come out at the back, onto a drive shaft, into the diff which then puts it out sideways to the wheels.
In a TA all this happens inside the box.
From the outside the boxes look about the same size and shape. On a TA the output flanges are one each side halfway down the side of the box and where the MB output spline should be is normally the TA gear selector.
Because the drive shafts now come out halfway down the box makes it possible to create a mid engine car without it being the length of a bus.
Steve

[builder]

Great stuff! Okay, I'm beginning to get it. I'm picturing this gear box. It's got the clutch, dif, and gears all in one with two outputs to GKN half-shaft axles. And, there are options as to what goes in there...Yes?

So, what (in general) are the options? :::

Positraction -- Limited Slip -- "Locker"? I am thinking Limited Slip for the road courses I intend to run.

Strength for torque (Stage 2 or 3 internal components)?

Clutch manufacturer options?

What about having to (apparently) flip the unit up-side-down? What has to be done to make sure it is properly lubricated?

What about ratios? Certainly, a stock Porsche ratio isn't going to work behind an SBC, is it?

And, since the output flanges are not at the end of the TA, what are the bits further back? And is GKN one of the reliable best for shafts?

So many questions. I guess I should find a run-out unit and open it up. Better yet, order a GTR! Does the factory address these issues in the builder's guide?

Thanks, guys. This is a great board and I appreciate that you share your experiences here. Mack, I am going to take your word for it brother! Steve, GTR bus? Adds new meaning to public "Rapid Transit".

-- Scott
Reno, NV

[builder]

steve_D said:

Also check with some of the Porsche gearbox sites. steve

Steve, I am above quoting a reply posted to "propricer" regarding the flipped 930 gearbox question he had. For some reason, I can't find many sites. Perhaps American search engines only work on American cars. If you have any favorite TA links, would you be so kind as to send them my way?

Thanks!
Scott

[steve_D]

Have you done the FAQ at the top of this page?
Most of what you want is in there. If not then search here for G50 or gearbox as most of these things have been done.
The G50 comes in a number of ratios, some have LSD.
Different ratio gears can be fitted but need special tools.
The upside down is actually better as it puts the gear clusters in the oil where they would normally only be splash lubed.
Steve

[builder]

steve_D said:

Have you done the FAQ at the top of this page?

I have tried to get to the FAQ and only get errors -- "Oops Invalid Forum Specified." I thought perhaps there were no FAQs for the Ultima board. This is from the "This Forum >> Show FAQs" tab above. I will perform the search on the board, too...thanks.

That's good news about the flipped gearbox. Sounds like a design improvement!

Thanks!
-- Scott

[steve_D]

If your FAQ is still not working try this www.pistonheads.com/gassing/topic.asp?t=25930&f=20&h=0

Steve