75 TS Drive Shaft Question

[shane wescott]

Hi Guys

One of my next jobs on my 75 TS is the drive Shaft. I need to replace all the rubbers, and was wondering if I need to be worried about the orientation of the metal parts.

Should I mark them all up and reassemble exactly the same, or doesn't it matter.

I know with standard propeller shafts, balancing is a big deal but is it the same on these drive shafts??

Thanks in advance Guys.

[MD]

Absolutely. I mark every connection and every bolt, nut and washer. Then reassemble in reverse order if the assembly was in a good and smooth running order. If it was vibrating before, well, it doesn't matter because you will need to rebalance it anyhow.

Matter of fact, I am currently doing a conversion on my GTV6 to configure it like the race car with a BMW coupling in the front, CV in the middle, slip joint at the rear and finished off with a universal joint coupling the clutch input shaft. The slip joint is particularly useful as you don't have to drop the gearbox to separate the shaft for removal. Just undo 3 bots and off she comes.

The BMW coupler will give me some grief I know already because all holes for mounting are in the same radius,  bigger diameter bolts and different PCD to the Alfa unit so there will be some hair tearing soon. I dont know how many guys are aware that the front Alfa donut has 3 holes of one radius and three holes of another longer radius which just adds to the complexity of trying to adapt a foreign part.

On the race car we remade the flywheel end and the prop shaft to take the different PCD but that is more drama than I need at the moment so I will see if can do a short cut..

[shane wescott]

Cool.

When you say rebalance. Does that mean I take the shaft with the new donuts to a specialist and he gives me back a balanced shaft ??

If this is the common thing to do then that takes the hassle away. I remember getting a VH Commodore V8 shaft balanced and the difference was amazing.

catch ya and thanks for the reply. Sounds like a decent job you have chosen to do for the GTV6.

[MD]

Shane,

I don't know about Melbourne but in Brisbane there are bugger all places that can properly balance these shafts. To be perfectly honest, I have never had a shaft correctly rebalanced here-not even for a Volvo !!

So if you have a well balanced shaft now, I would just change the donuts over and refit it. Your chances for a close enough balance may be as good as you will get anyhow.

The problem seems to be due to nature of the two piece shaft that has to be balanced as a set. It should also be balanced to its full rpm range but this is never done. The combined shaft has a resonant frequency with 2nd and 3rd harmonics so you typicaly start with a vibration around 1600rpm followed by 3200 rpm and a third one either inside your upper rev range or out of it if you don't rev the motor that high. These numbers are not exact and will vary with every car but are somewhere near the usual.

There are also alignment related vibrations due to sagging and aging engine and transaxle mounts.

I once had some local morons balance a shaft had a bent front section. Just too stupid for words.

Ask around the Club which local companies do a good job and you may strike it lucky.

[Darryl]

So far as Brisbane goes Driveline services managed ok (but not perfect) on mine - I had a shaft that wanted to shake the car to bits. However, I put this down to damage done before I pulled the shaft etc not assembly problems. The shaft came out after I destroyed the front donut and bent the tailshaft bolts on the flywheel...

After replacing every donut + the bearings in the shaft as well as engine mounts and front transaxle mounts it shook A LOT. Much better after rebalance but not perfect. Not sure how much to blame the remaining vibration on the quality of the balance vs any alignment changed and/or increased vibration transmission due to the "less stuffed" rubber bits...

Oh - and the shaft is straight. Had that checked first...

I've never had a problem before. All I've done in the past is to marking the shaft halves. Before is only 3 times (on 3 different cars). I'm suspecting the issue is that this was the first time there was some real damage done before disassembly, so if yours is all in one piece now I think you will be fine...

[Al Campbell]

I think Benincas do shaft balancing.

AL.