The Torque Tube Restoration Thread (4200/GS/Spyder)

[FIFTY]

Small update from me

I took the tube up to the guys at Augment. David and Tom Barker kindly spent a couple of hours examining the TT. They pressed apart to find that nothing has slipped or failed prematurely. We put the shaft on engineering V blocks to check the straighteness and it's true with nondetectable round out.

The drive shaft is extremely flexible, the guys at Augment theorised that the play off the gearbox input shaft created a "corkscrew" effect into the TT which is what created the rounding out on the shaft. Once the drive shaft was pressed back into the tube the rounding out on the shaft was back to being minimal again.

The gearbox has just been rebuilt, I had a look at the failed bearing and it had a tiny bit of play in it but very difficult to tell it's a knackered part while in hand which is all down to the sheer forces at play on these perishable items..

Here is a short video with the shaft on v blocks showing how easily this flexes, not a huge amount of force merely resting your hand on it does this

 

[Zep]

Hopefully that will sort it. Interesting that it is so flexible. Must be winding up and releasing all day on a mountain pass.

 

[Ebenezer]

Is it an early attempt at a form of DRS?
Eb

 

[CatmanV2]

Hopefully that will sort it. Interesting that it is so flexible. Must be winding up and releasing all day on a mountain pass.

Does the flexibility mean it'll twist easily?

C

 

[Zep]

Does the flexibility mean it'll twist easily?

C

Not easily, but it indicates to me anyway, that the material has a lower elastic modulus, so it will deform elastically under stress and the bearings will control the deformation. There are two ways of doing this, one is a high modulus shaft which won’t twist but permanently deform under high load (like a prop shaft) this will thicker and heavier, or low modulus which will deform elastically but return to its normal shape after the stress and potentially be a lot smaller and lighter.

More of an observation than a criticism.

 

[FIFTY]

Not easily, but it indicates to me anyway, that the material has a lower elastic modulus, so it will deform elastically under stress and the bearings will control the deformation. There are two ways of doing this, one is a high modulus shaft which won’t twist but permanently deform under high load (like a prop shaft) this will thicker and heavier, or low modulus which will deform elastically but return to its normal shape after the stress and potentially be a lot smaller and lighter.

More of an observation than a criticism.

In contrast the Porsche 964 and 944 drive shafts they had there were a solid extruded bar that had no flex and are about 50% fatter. The bearings are positioned inside the tube and the shaft is pressed through the bearings into the tube.

The Maserati drive shaft is machined into shape with the wider parts that the bearings are attached onto using internal snap rings. They said it was more fiddly to disassemble/reassemble but pressing it into the tube is a lot easier than the Porsche design.

One thing for sure is that this design with the amount of flex in the Maserati drive shaft doing things like burnouts, doughnuts and full throttle standing starts is a great way to destroy the bearings on the drive line as well as the clutch/flywheel.

 

[Zep]

In contrast the Porsche 964 and 944 drive shafts they had there were a solid extruded bar that had no flex and are about 50% fatter. The bearings are positioned inside the tube and the shaft is pressed through the bearings into the tube.

The Maserati drive shaft is machined into shape with the wider parts that the bearings are attached onto using internal snap rings. They said it was more fiddly to disassemble/reassemble but pressing it into the tube is a lot easier than the Porsche design.

One thing for sure is that this design with the amount of flex in the Maserati drive shaft doing things like burnouts, doughnuts and full throttle standing starts is a great way to destroy the bearings on the drive line as well as the clutch/flywheel.

I thought as much, interesting. Thanks.

 

[FIFTY]

Unfortunately the Torque Tube rebuild did not work for some reason. The car has gone back to AV for a used tube to be fitted which is being done as we speak.

I have asked for some of the GS bits to be removed and I intend to sell the car over the summer as I need something more reliable as a second car.

 

[digitaladam]

Sorry to hear, can you share a bit more about what didn't work?

This is something I'm planning to look into more this season, it would be helpful to know if there is some approach to reduce/eliminate drivetrain vibration, or if it's a 'live with it' condition

 

[FIFTY]

Sorry to hear, can you share a bit more about what didn't work?

This is something I'm planning to look into more this season, it would be helpful to know if there is some approach to reduce/eliminate drivetrain vibration, or if it's a 'live with it' condition

Everyone involved is at a loss to explain how it didn't work because it is very basic engineering, it was pulled apart and inspected but the first TT bearing after the bell housing started making a noise after a stress test on the lift and progressively got louder... It sounded like a whirling grinding noise.

AV rebuilt the car one step at a time by putting the exhaust back on after installing the clutch, (new) thrust bearing finally the TT and it only started grinding with the rebuilt TT installed so the diagnosis is solid.

 

[boomerang]

Sad to hear it did not work out.
Years ago i allready worked on this torque tube issue, in the end exchanging it for a very mint one.
But the 10k kms tube did the same.
When i asked my very experienced Maserati specialist, i was told that i would just have to live with it. ( mild 4000 rpm vibration)
Recent designs show CFK tubes, that do not need those support bearings inside the tube. (AMG GT/Corvette C7)
No vibrations, less drive line losses, no bearings that go wrong.

 

[Nibby]

Sorry to hear it didn’t work on the torque tube and your thinking of selling. Whoever buys your car will have one well sorted car.

 

[digitaladam]

When i asked my very experienced Maserati specialist, i was told that i would just have to live with it. ( mild 4000 rpm vibration)

Given that, is it generally okay to push past the vibration up into the higher revs?

 

[boomerang]

Yes, that is exactly what he told me.
But on high ways it still bothers me, when you are in that speed region for longer times.

 

[boomerang]

Funny though, the resonance damper shown in the first postings, seems to be a two piece bolted version that I do not recognize.
The later shafts have a one piece damper if I am not wrong.
Both my old one and the replacement had the one piece damper.

 

[FIFTY]

Sorry to hear it didn’t work on the torque tube and your thinking of selling. Whoever buys your car will have one well sorted car.

I really don't want to but I have not really had the opportunity to enjoy the car for over 2 years yet I am still ploughing money into it - annual services after barely doing 1k miles PA on a car that has never been a garage queen, I have ended up insuring it for business miles so I can run it to some meetings to get some extra miles on the clock. Time for someone else to enjoy it - I have my eye on something that will keep me smiling (guess what it's not a Maserati)

 

[TimR]

Sorry to read this mate...! I cant believe you wont change your mind, after all the time and money you've put into the car.

 

[Nibby]

I really don't want to but I have not really had the opportunity to enjoy the car for over 2 years yet I am still ploughing money into it - annual services after barely doing 1k miles PA on a car that has never been a garage queen, I have ended up insuring it for business miles so I can run it to some meetings to get some extra miles on the clock. Time for someone else to enjoy it - I have my eye on something that will keep my smiling (guess what it's not a Maserati)

Best of luck FIFTY.

 

[Oishi]

Fernando, I'm sorry to hear that you will be selling your sweet Coupe.
When I was trying to determine what to buy for my last Maserati, all your posts on the rebuild of your car helped tip me toward a 6mt 4200.
I can't overstate the value of your posts to me and others who struggle to keep our cars on the road.
Thank you very much for taking the time to show us how it's done.
Ed.

 

[Alan Surrey]

Sorry to hear that you feel you no longer have any option but to sell the car. Sad day.