Torque Tube

[gtv6sv]

Hey Alfisti,

Was reading the sequential transaxle post, thought I'd start a new one about a torque tube.

Anyone ever added a torque tube to their GTV/GTV6/75 etc?

I heard Claude Botti was working on making a kit for it but I could be wrong!

If this is true, I'd think he'd get a fair few customers!

[Duk]

Not seen or heard of 1, but I wonder about its value in such modestly powered cars.
You'd be adding many kilo's to an area that's not got much room to start with, to fix what problem?

MD created the best fix to prevent breaking the clutch housing.
There are multiple solutions for the tailshaft, with a carbon fiber 1 being the best.
Transaxle and engine mounts can be modified or made from scratch to better hold the engine and TA in alignment.

It would be interesting, but I'm just not sure it's needed. And the cost of even just an aluminium 1 would be pretty flippin high!
Imagine 1 from carbon fiber??? 

Mazda used a sort of ladder type frame to link the gearbox to the diff in the FD3S (Series 6) RX7s. Maybe something like that would be more doable?

The Nissan GTR doesn't use a torque tube and they whack out well over 500hp.

[gtv6sv]

This is a good point Duk. Correct me if I was told wrong, but I heard it help strengthen the car as from the bellhousing to the gearbox it's all held together by the outer tube which would also eliminate any room for vibration (providing it's done right) and that the bearings on the inner shaft need to be replaced every 25+years (which seems like a good return!) The weight is an interesting point!

With the aftermarket carbon fibre/aluminium shaft, is that made as a one piece or is it still 2 pieces?

[Duk]

The photos of carbon fiber tailshafts that I've seen are 1 piece and so needed an in cabin shift linkage.

A suitable torque tube would need to replace the rear engine mount/bell housing, a new design or heavily modified clutch housing would also be needed. Aswell as an in cabin shift linkage.

Without a massive lathe, you wouldn't be able to create a torque tube with internal bearings for the tailshaft.
Acceptable missalignment of couplings for heavy industry motor/gearbox/pump/what ever that spin upto 2000rpm is 0.07mm.
I can quote that 1 'cause I did a laser alignment at work recently for something that spins a bit under 2000rpm. Faster speeds requires more and more accuracy. Worse than acceptable accuracy and your bearing life plumets.

[julianB]

Duk, did you ever see Kevin's posts on gtv6.com regarding one vs Tw
Piece shafts?
It seems that the one piece option may not work with the length of an Alfetta shaft (even in short form) due to the harmonic it sets up.
The torque tube solution worked so well in Porsche's transaxles that it can't be something to simply dismiss on weight grounds, surely?
They had the clutch up front, so the tailshaft doesn't spin as fast until
You hit the top of 5th, but the idea of having the two locked in "plane" has some merit.
It would also help take the beating when the donut lets go hahaha
May be a bit of a hard maintenance situation.

[Duk]

The tailshaft will always spin as fast as the engine in a transaxle car, regardless of where the clutch is.

Kevin's answers are excellent and revolve around him removing any sort of rubber couplings in the tailshaft. The rear section is made in 2 pieces, with the inner piece (from the engine) bonded to the outer piece via rubber.
Note that the key is to keep dangerous and noisey harmonics out of the hollow tube that is the tailshaft and rubber isolation (of the correct natural frequency) does this much better than any other material.
You can actually see this (bonded together inner and outer rear section) set up on some trucks.

Something to bear in mind, rubber coupling, when done well, are more than capable of doing their job.
The C5 onwards Corvettes use rubber couplings in the drivetrain. Yes they also use a torque tube, but they also churn out a lot more power at their highest levels (about 620hp).

As for 1 piece tailshafts, they work just fine SO LONG AS either the diameter of the shaft is sufficient or the material it made from is rigid enough.
The more rigid the material that the tailshaft is made from, the lower the required diameter for a given length.
So the Alfa's tailshaft diameter in (mild) steel, probably wouldn't be large enough.
You may get away with making a 1 piece tailshaft for the Alfa in the same diameter from 4130 Chromoly.
But in Carbon fiber, in the same diameter, EASY.

Incidentally, the R35 GTR uses a carbon fiber tailshaft, no torque tube (as mentioned), but it doesn't use any rubber couplings and the tailshaft is 1 piece............. It has a spring loaded drive hub, exactly the same as a conventional clutch disk, that attaches to the engine's flywheel. The springs absorb the pulsations from the engine.

[Mrme4u]

I am planning to do up a torque Tube but I will install a V8 in my GTV6 also will be moving the engine further inwards moving the steering rack in front of the axle not behind to also create more space for the exhaust etc and easy maintenance on the steering.

Cost I am thinking of doing mine within the €2,500 and €3,500 range so cost not so bad as people might think.

Sent from my MI MAX 3 using Tapatalk

[julianB]

I can confirm there is a torque tube conversion underway for an Alfetta box and I am looking at another option involving a torque tube for my 3.7

Photos to come, hopefully a few months away

[MD]

Hey Jules, your twelve months are up. Cough up with your torque tube already. 

The Dukster is right. Very close tolerance is crucial. Bit of lateral thinking. Instead of starting from scratch, if Porsche has done it before, how problematic would it be to cut and shut an original Porsche set up an adapt it to an Alfa transaxle for a racing experiment?

Ferdinand would turn in his grave I know.

Beninca has advised that an open one piece is not on.

[MD]

If get through the COVID-19 challenge and find myself naval gazing, I just might make an open chassis using the transaxle dimensions. Position the engine at one end and the tranny at the other in an accurate fixed location- then start doodling with a Porsche torque tube in between.

Of course don't let me stop all you CAD merchants doing all your own doodling in the meantime ! 

[julianB]

Hey MD! Turns out I need more than 12 months!

I can confirm I've seen a Porsche torque tube fitted to a 75 transaxle with an adaptor plate, in australia...

I still don't think the box will be happy about the turbo torque it's going to get

[MD]

I'm still navel gazing too.
Too many projects.