Transaxle weakness's

[105gta]

Just out of curiosity, for those that have broken their transaxle, usually the diff. Under what conditions did it happen? And if anyone can remember, what gear where you in when it broke?
Ben

[aggie57]

You mean when the spider gears strip?  When people are pulling donuts all over the place .  Or at a motorkhana on a hard surface...bang!!  Lots of lurvly metal bits in the bottom of the box....

CV's can go as well but gather you're talking about the internal bits.

[105gta]

Hi Aggie, yeah I'm more thinking what breaks inside, I've heard that diff pinion breaks but not actually spoke to anyone who has broken one.

[LaStregaNera]

Have heard of a few higher HP cars stripping the teeth off the pinion on hard launches.

[jazig.k]

My understanding of the transaxle weakness is the actual case moving under torque, misaligning the gear tooth mesh and shredding/wearing excessively.

[105gta]

That was my thinking too, just thinking of ways to add some strength if at all possible.

[MD]

No real problems with late model transaxles. Reliability would max out at 300bhp. Custom clutch would be mandatory for that sort of power. Standing start big power launches will kill any box eg. hill climbs. However power shifts on the move should not be an issue.

I'd be more concerned about shredding donuts...

[jazig.k]

Well, in the gearbox, most of the forces are spreading the 2 gear shafts away from each other. A gearbox strengthening plate works here, to a point. Here's a link showing good pictures [conveniently I googled a Alfa 164 gearbox haha]. This can be applied to the transaxle gearbox too.
If the plate is 3mm thick, then you have 3mm removed from the case join faces so everything internal still lines up.

http://www.turbonutter.net/gearbox

The diff though is harder, with the diff having more axial load the strengthening plate doesn't work here.

I've seen people build exoskeletons for the transaxle before. More recently I seen someone make a clutch housing brace/exoskeleton for the transaxle. I can't find the threads via google right now, but I'll keep looking for a bit.  They're interesting conversation pictures at the least...

[jazig.k]

Heres the clutch exo'.


Link to the thread here-
http://alfagtv6.com/phpBB3/viewtopic.php?f=9&t=4354&p=45019

[105gta]

Hi MD and Jazig. Yeah the clutch housing bracing is a known mod. I think the problem with the transaxle is the distance between and type of bearings used.  The main pinion bearing is a needle roller type which offers no pre load for the shaft or immediate support at the pinion other than for radial loads. The next bearing is at the intermediate flange at the other end of the gearbox which also sets the pinion depth/height. Which was fine for its original purpose being a 1.8l 4cyl. And it holds up quite well for most applications, including low boost v6's. I'm just thinking of ways to add reliability. Depending on cost of course!

[jazig.k]

Well... You seem fairly aware of the 'problem'... Time to get out the SKF book, do some cross referencing and measuring.

[105gta]

Yeah I've already been all over reading about preload benefits and setup.
Looking for as much info as I can get about the issues with the gearbox so as hopefully not to miss anything.
Ben

[Mrme4u]

I was using an Alfa 75 1800 INDY in the Netherlands during my race license training. On the 2nd 5 hour session the whole tooth of the Crown Wheel cleanly grinded off leaving me with no drive.  Engine was practically std. Only sport air filter added and exhaust

Sent from my GT-I9082 using Tapatalk

[MD]

That's freaky and a condition I have never heard of before. I have been pounding transaxles for thirty years and the typical issues are much like any gearbox. Synchro sets , LSD packs and oil seals.

[Duk]

Just thinking out loud, but if case flex is an issue, how about vacuuming resin enfusing some carbon fiber cloth around (a thoroughly cleaned and slightly etched) case? Basically a carbon fiber exo-skeleton.
Steel like strength, bugger all weight penalty and apparently CF is pretty reasonable conductor of heat (no that you wouldn't have an external oil cooler at this stage).