Porsche Boxster transaxle

[Nero]

does anyone have any experience with these items? I would like to know if they are invertable and torque ratings. My need is a little different as I would like to adapt a Nissan VQ30DET engine for an ultima type car. G50's are just too expensive and the renault seems a little unpredictable unless uprated (unpredictable in the sense that you have to guess at original condition). Any help would be appreciated
Neil

[Chuck]

I'm not sure they are invertable but I know the ring gear can be flipped. As for load bearing, the Porsche stuff is typically well-suited for its application but the entry-level mechanicals are usually a big notch down from the higher rate stuff. So, I'd lean towards a Boxter S tranny. I do note that 996 tranny prices continue to plummet as there are no natural homes for wrecked ones with only 5 years of 996 production on the road.

Chuck Ward

[Julian West]

Nero,

I beleive Ultima use the boxster trans inverted. If you search the forum I posted a picture of the trans on the ultima stand a while back.

Hope this helps.

[Nero]

I did see that post and I guess that prompted this query, as the boxster transmission is considerably cheaper than the 996 from what I have been quoted. The transmission on the ultima stand did not seem to match the ebay pic or other pics I have of the boxster transmission...interesting no?

[Bill Musarra]

My shop mechanic is pushing me to go for the Boxster S setup. This is a mid engine setup and according to him needs no inverting. Just your pocketbook. There are strong transmissions such as the 930 that yes have to be inverted or ring gear flipped, but the flipping option just requires the drain plug and vent plug being reversed ( a small price to pay) without any bad things happening. Most of them can be had with the posi option. About the 996, my shop forman says that particular trans requires rebuilding after about 40K miles, and is not a cheap deal. I don't know their torque values but all (g50/930/996/boxster) are very strong and should be the least of your $$ concerns.
Bill

[Nero]

Thanks for that Bill. I have been given information about some of the Porsche G50's that seems to indicate that they do not all handle torque well (930 well known to be very good though). However for my application I do not think that I will be generating more than 300-350lb/ft of torque so not so much of an issue. I was thinking of the boxster inversion more for lowering the engine and getting good driveshaft angles. I would like to save as many $$$ here as I can so I can spend more on dampers/tyres/wheels/driving as possible. Besides wife and small children take precedence as always!

[Bill Bayard]

Nero,

Which not so strong, G50's are you speaking of? I had a 392W(514FWHP)in my car for a while, and the only problem with the drivetrain(rebuilt, inverted G50-01), was the inability of the stock clutch, to handle the torque(blew the springs right out of it!). The gearbox was pulled apart shortly thereafter, to re-press an output shaft bearing, that wasn't seated properly, when my LSD was installed, and everything inside looked like new.
Believe me when I say, "I have NOT been very easy on this gearbox!"
Since re-pressing the bearing, and installing a more streetable engine (351W/425FWHP),the box has remained tight, solid, and reliable. And NO, I haven't been any easier on the gearbox! It won't chirp the tires, when shifting from 3rd to 4th at 90MPH+ anymore [img]/ubbthreads/images/graemlins/frown.gif[/img], but it's still a load of fun! [img]/ubbthreads/images/graemlins/cool.gif[/img]

Bill

[Nero]

Bill as with all information by word of mouth and on the net it is difficult to know how factual it is. However some of the information came from the ultima website:

"When used with very high torque engines and large rear tires, the ring and pinion assemblies are prone to premature failure. Differential side cover deflection and undersized ring and pinion gears for the power levels are responsible for transmission failures not generally seen in Porsches used for endurance racing to such a degree. Auxiliary cooling and pressurized lubrication systems are necessary in these applications with this transmission. The G50/50-series is probably the strongest of this generation of gearbox although these are 5-speed units."

Link here:
http://www.ultima-gtr.info/utips.htm#Transmission

And second 'confirming' information came from porsche-a-part who reported transmission failures in some NA model porsches when the box was used in turbo porsche. Whether this is truly reflective of a situation I do not know, but good to hear such thing prior to parting with money.
Neil

[Bill Bayard]

Nero,

What you have quoted, is true, according to my information.
The ring and pinions are the weak links, but some of those Ultima guys are pushing ridiculous horsepower, even as high as 1300HP! With a mere 1300HP, 335 section tires, and a limited slip, I can't imagine why a G50 would blow up,can you? [img]/ubbthreads/images/graemlins/wink.gif[/img]
There are a few companies offering upgrades for the G50 series gearbox, for those who need 500-750HP. That's plenty!

Bill

[Nero]

oh I have no plans for pushing the limits on a G50 with my little plans (don't think I'd know what to do with 1300bhp!), but I do like to be informed (hence this thread) so I can spend more money elsewhere (advanced driving lessons for one!). This transaxle issue has stalled my progress for the past 2 months, hence I am eager to get a resolution. I need a cheap transaxle capable of 350lb/ft torque that is easy enough to get in australia. I was hoping Boxster may be the way to go....but will look at anything!
If there isn't an easy solution I'll bin the drawings and go front/mid engine ala TVR

[gt40rick]

I agree with Bill, I have a lot of 1/4 mile runs on my G50 and haven't had any problems with it yet. The only weak link that I found was the bosses for the clutch throughout bearing pivot shaft were too thin (1/8" thick), and I broke them off when shifting. I am using a Kennedy Eng Prod pressure plate that they say will hold 650ft/lbs of torque. What they didn't tell me was that you have to work out your left leg for 3 months before you can push it in. [img]/ubbthreads/images/graemlins/blush.gif[/img] I had the bosses removed, re-welded and re-machined with a 3/8" thick wall and I have not had a problem since. if anyone else is using this pressure plate with a G50 I would suggest beefing up the pivot shaft bosses before they break.

[Bill Bayard]

Rick,

If your pressure plate was enough to snap the bosses off,
what does your left leg look like since the repair, a tree trunk? [img]/ubbthreads/images/graemlins/wink.gif[/img]
Is it a 3000lb p plate? Which disc are you using with it?

Bill