2 peice Tailshaft versus 1 peice - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

Cobra · 10-26-2002, 22:41

Why is the 2 peice better? What are the advantages of both? Is having the two peice on the new BA's a contributing factor in attaing a higher top speed? Reduced road noise? Every new model as reduced road noise, and that is eveident with the BA over the AU, but there has been abit of discussion about the new Tailshaft beeing two peice.

YuGoStaR · 10-26-2002, 22:59

Perhaps it is to do with the positioning of the engine. Or maybe the diff....not really sure why they chose the 2 piece in BA.

Rabnud · 10-26-2002, 23:04

A single Tailshaft is hard and expensive to balance to a high standard.

The balance on the old single tailshaft was imperfect, and Ford couldn't justify spending the money on balancing them. So They put the speed limiter on so the tailshaft wouldn't vibrate itself, and everything connected to it, to pieces.

2 tailshafts solves this because each is shorter, and thus easier and cheaper to balance.
So now the tailshafts are better balanced than the old. Less vibration equals better, quieter ride. Also allows the speed limiter to be lifted.

WBT56 · 10-27-2002, 00:50

Quote:

Originally posted by Rabnud

The balance on the old single tailshaft was imperfect, and Ford couldn't justify spending the money on balancing them. So They put the speed limiter on so the tailshaft wouldn't vibrate itself, and everything connected to it, to pieces.

The balance on the factory shafts was good. The problem is that as average diff ratios go down tailshaft revs at a given speed go up. A perfectly straight and balanced 1400mm shaft is only good for about 4800RPM on paper,(about 168km/h with 3.45 diff) hence the limiter. Above this they risk suffering from harmonic whip. This is not a NVH issue, it is to prevent the risk of sudden catastrophic failure. A correctly designed two piece is much better, but much more expensive to fit. I say correctly designed because wait till all the VX commodores need a centre universal and the customer gets told it's a "staked in" design and they need to buy a complete new shaft.

T3man · 10-27-2002, 02:07

Quote:

Originally posted by WBT56
The problem is that as average diff ratios go down tailshaft revs at a given speed go up.

You are assuming here of course that we don't have overdrives - but in fact we do - so in real terms, todays vehicles, in top gear, have less revolutions on the tailshaft than in previous times. In any event, what the tailshft speed is at a given speed is pretty irrelevant - it is simply reflecting engine speed and (max) engine speeds have not gone up. Well, I guess the BA has, but by about 500rpm only.

Quote:

A perfectly straight and balanced 1400mm shaft is only good for about 4800RPM on paper,(about 168km/h with 3.45 diff) hence the limiter.

So how do you explain the old Falcon GTs of the 60s and 70s that had 3.5 diff (optional), 1:1 top gear (no overdrive), and a single piece tailshaft that was spinning at 5,800 rpm at 120 mph?

The difference of course was the old tailshafts were steel - not the aluminium crap they are using now. And I say crap because it is obvious that they can't do the job that the steel ones were doing 30 years ago.

XR_Strider_GuY · 10-27-2002, 02:28

Yes it's correct to mention that the steel tailshaft promotes that whip at high speed as it's purely due to the length of the tailshaft, especially more so in the wagons and utes.

With the release of the AU's Ford developed an alloy tailshaft that was suitable for high speed, hence the XR's have them and are not speed limited. However as many of us have noticed due to the lightness of the shaft theres a great deal of clunking, and driveline noises associated with the alloy shaft, though apparently theres a revised shaft that will cure these problems.

So i guess Ford designed the two-piece tailshaft to have the best of both worlds.

smciner1 · 10-27-2002, 02:38

The question beggs to be asked how Ford managed in the 70's with a single piece tailshaft in a car that pulled close to 150 mph down Conrod Straight??

The old GT-HO Falcons never had tailshaft problems!

WBT56 · 10-27-2002, 02:42

Quote:

Originally posted by T3man
You are assuming here of course that we don't have overdrives - but in fact we do - so in real terms, todays vehicles, in top gear, have less revolutions on the tailshaft than in previous times. In any event, what the tailshft speed is at a given speed is pretty irrelevant - it is simply reflecting engine speed and (max) engine speeds have not gone up. Well, I guess the BA has, but by about 500rpm only

Sorry, but this is incorrect. Overdrives drop the revs before the output shaft only. Using your example, a GT with a 3.5 diff and a 1:1 top gear is doing 5800 engine RPM and 5800 tailshaft RPM at 120MPH. If you were to fit an O/D box with a ridiculous fifth gear of say 0.61, at 120MPH the tailshaft is still doing 5800 RPM, it's just that the engine is now only doing 3538RPM.

I agree with the comment on alloy shafts. The GT's got away with it using a large diameter steel shaft. The larger diameter resists whip.

XR_Strider_GuY · 10-27-2002, 03:07

Another way to get around it is to have a carbon fibre wrapped tail shaft like the EL GT. So driveline is smooth and no limiter is needed, but then the cost of the tailshaft is expensive.

ebxr8240 · 10-27-2002, 03:57

[QUOTE]Originally posted by XR_Strider_GuY

With the release of the AU's Ford developed an alloy tailshaft that was suitable for high speed, hence the XR's have them and are not speed limited. However as many of us have noticed due to the lightness of the shaft theres a great deal of clunking, and driveline noises associated with the alloy shaft, though apparently theres a revised shaft that will cure these problems.

Ah the first E.B X.R has a alloy drive shaft tmk they all have.. I have no limiter and have done well over 200 klm well over!! Remember??...

The idea was to make it lighter and prevent whip ??"In theory"
without the weight of a steel d/shaft..
The clunking has nothing to do with the d/ shaft, more to do with backlash etc in final drive etc..
The funny thing that I can't understand you'd think that i.r.s would stop most of these troubles due to final drive being held in the body so can be set up to drive in straight line..Yes they are spining faster and making them lighter, the transmision housing strength doesn't help either compared to a top loader..