ALFAGTV6.COM

[manuel164]

Hello,

I have some vibrations in my GTV6` propshaft.
The story:
After new three engine rubbers, i wondered about the alignment of the engine, the crank axis was showing a little bit to the right rear wheel.
After setting with a laser the engine straight to the gearbox entry with an extra fitted support in the engine's back, i assembled all other parts.
Then i started the engine and the propshaft was vibrating
I think i should bring it all back to the old positions....???
Before i started with the conversion, the propshaft was very nice and had no vibrations!
First donut is new (1000km two years ago), middle and rear donut is in good condition, redassembled with marked position.

Does the engine or the propshaft with the donuts need a "disalignment"?

Thank you for your help.

Manuel

[Giuliettaevo2]

The engine is originally placed in an angle in the engineroom. Under load the engine pulls straight.

[MD]

Man, all this drama we have with these prop shafts all because the Bean Counters wouldn't spend ten more bucks to fit torque tubes for the original design. Bean Counters. My favourite people on the planet. They know the price of everything but the value of nothing.

[Duk]

Man, all this drama we have with these prop shafts all because the Bean Counters wouldn't spend ten more bucks to fit torque tubes for the original design.

The thing is, the current (not the 'new' anymore ) Nissan GTR doesn't use a torque tube and it uses a 1 piece carbon fiber tail shaft with a uni joint at the engine and a CV joint at the TA.
With your comments MD, about about the solidly linked tail shaft ringing like a bell, I wonder if CF is an acoustically dead material???

[MD]

Duk, the only way you are ever going to fit a one piece shaft in a GTV (or any other transaxle)is to have an inboard shifter or massage the tunnel big time with a 10lb hammer.

Now if we dream a little and say you actually joined me in that quest and you are now shifting upstairs, the coupe is the most suitable for a one piece shaft as it is about 100 shorter than the sedan (don't quote me). The all steel one I had made seems to be working well. Could do with some sharper balancing but otherwise working ok.

I would see that a carbon fibre one piece shaft with BMW donut up front and either a CV or UV at the rear would be the bees knees, the ducks nuts and whatever else says bonza !

Not using a front donut is just too harsh on the gearset for no appreciable gain.

[Duk]

Duk, the only way you are ever going to fit a one piece shaft in a GTV (or any other transaxle)is to have an inboard shifter or massage the tunnel big time with a 10lb hammer.

Now if we dream a little and say you actually joined me in that quest and you are now shifting upstairs

This I have thought about. But being a road car, getting you shifter mechanism to integrate nicely and compactly is a little off putting. I thought about trying to apply something like the piccy (found on GTV6.com), but........

I would see that a carbon fibre one piece shaft with BMW donut up front and either a CV or UV at the rear would be the bees knees, the ducks nuts and whatever else says bonza !

Not using a front donut is just too harsh on the gearset for no appreciable gain.

I saw a picture of a BA Falcon sedan tail shaft on Ebay. They use a rubber coupling at the gearbox, so must use a pilot bush on the shaft. These couplings slide onto the V6 flywheel but would require bolt sleeves like you made, to allow for the Alfa's skinnier bolts. A uni joint in the middle and CV joint at the diff.
So if the shift mechanism is mounted inside the car, the BA sedan tail shaft could/should be a decent supply of required parts to build an unbustable (well, you'll smash the TA before 1 of these) tail shaft for a V6 and maybe a 4 banger, even if it is still a 2 piece shaft.

Another thing I thought about was a single piece, 3" diameter Chromoly shaft.
3" x 0.095" $35.00Aus/foot (bloody drag racers ). Where's Mats for some input about suitability of Chromoly for single piece tail shafts?

[MD]

Manuel,

I hope the topic isn't straying too far from what your interest is but if it is please say so.

Duk,

For this shifter to have half a chance of doing what it is supposed to for an Alfetta (cannot tell what it is servicing) it needs the modification where I have indicated.
This part needs to rotate. ( in addition to stuff happening at the other end)
If it does the job, then it should be made up from much more robust components. (apologies to original owner)

[MALDI]

the Bean Counters wouldn't spend ten more bucks to fit torque tubes for the original design.

Actually, there is no torque tube as a weight saving measure.

I have an interview somewhere with an Alfa engineer from the '70s (not Busso) that discusses all the trouble they had with the drive shaft including building prototypes that did have a torque tube.

Also, talk to any Porsche 944 owner: renewing the drive shaft bearings mounted inside the torque tube is extremely difficult: if they are misaligned even slightly they wear out in 1000 miles.

[kevin]

k

[kevin]

I would still choose a torque tube any day and attend to any problems and upgrades on that.
Manual 164 . Alignment does not cause vibration on the prop unless you way out as mentioned the gtv prop is far out of alignment in horizontal plane and to align it up you have to centre the engine with new mounts , then centre bell housing bush(as it is offset)then centre middle bearing as its also off set .
Is the vibtation at Idle , all through rev range etc . Have you been changing anything in clutch or gearbox as it could be your thrust bearing on wrong size tube in gearbox .
if thats ok its normally centre bush that has not positioned properly.
A 105 series vibrates heavily if prop is out of alignment and vibrates more faster you go.

[MD]

Manual 164 . Alignment does not cause vibration on the prop unless you way out as mentioned the gtv prop is far out of alignment in horizontal plane and to align it up you have to centre the engine with new mounts , then centre bell housing bush(as it is offset)then centre middle bearing as its also off set .
Is the vibtation at Idle , all through rev range etc . Have you been changing anything in clutch or gearbox as it could be your thrust bearing on wrong size tube in gearbox .
if thats ok its normally centre bush that has not positioned properly.

Kevin, you left off attending to the partridge in a pear tree.
Maldi, what makes you think that doing all the above would be simpler than aligning some bearings in a tube and then making it more reliable?

You are forgetting the basic bible rule of engineering:
"The fewer the movig parts, the greater the reliability".** Sorry but the Porche solution wins hands down. Having said that I will never give up my transaxle Alfas, I just keep improving them.

** qualification
That statement does not refer to JK's moving parts as some of them have actually fallen off from lack of use..

[MALDI]

Hey, my only point was that the lack of a torque tube was not a cost saving measure but a weight saving measure.

Also, no one has given a good reason why the Nissan GT-R does NOT have a torque tube. What do they know that we don't???

[Duk]

Also, no one has given a good reason why the Nissan GT-R does NOT have a torque tube. What do they know that we don't???

Personal guess is that they restrain the engine and TA MUCH better than what Alfa Romeo did.
Japanese performance cars of the last 20 years always seem to have better engine and transmission locating without the noise transfer.
Alfa (and FIAT) used blocks of rubber that instantly began disintegrate once exposed to air and allowed everything to flop around with bumps, tidal movements, moss growth on rocks in the tropics and engine torque.

All of that, plus engineers who think designed the GTR.........

[75evo]

The only 2 problems with the Alfa's setup are:
1) Alignment
Not such a big problem to overcome, but not exactly easy either.

2) QA or QC of giubos
I wish we could easily interchange them with Corvette units or even BMW units. I've had giubos blow up within a few thousand miles. The new manufacture is shite.

Otherwise the system works well and is easily serviced. Other means of transmitting the power could be better, but it's much easier to work with what we have.

[Bruce]

From my experience, the propshaft can run quite smoothly even in an appalling condition. Front had a missing section, rear was starting to split, and centre hanger bearing spilt. Nevertheless, it was smooth. When I changed the couplings, I was brutal with the removal, split the propshaft a few times from the middle, did not the put the nuts and bolts back as I took them off. I had an issue with a new centre hanger, purchased from a "reputable" UK seller, which caused me no end of vibration problems, this XXXXer was too stiff, old split one back in and OK.
How I install, everything loose, tighten rear coupling slightly, rev engine a few times up to 2k, tighten rear, tighten front pinch bolt and then tighten hanger.