Propshaft Question

[v8granada]

Gents, after you opinions/experiences with propshafts.

Currently about 3/4 of the way through a Jag IRS conversion on my Mk1 Granada Estate, when I done the engine swap originally I just had a new yoke fitted to the existing prop, but now gonna need one a tad longer as the Jag IRS does not have a nose extension like the ford diff did.
So here’s the question:

Straight or centre bearing???

Currently the propshaft has a centre bearing bolted up to the floor, should I stay with this style setup, or go for a straight g/box to diff prop? As the Diff and Box are fixed no need to worry about slide joints,

Engine: Ford 351ci Windsor
G/Box: C4 Auto
Diff: 2.88:1 XJS LSD

The propshaft will be circa 1500mm long!!!!
I know a prop loop will be in order if it's straight!!!

Thanks in advance, Steve.

[JJMclure]

I'd go for a straight, just make sure your diff pinion and box output shaft angles are the same and I don't see a problem, although a centre bearing would be just as good, not really helping much am I?!?!!

[CastleMGBV8]

Steve,

I would still retain a sliding joint at the front with a one piece shaft as you will still get some flex somewhere between the engine and diff and it will also make it a lot easier to fit as the length will not have to be 100% accurate.

Kevin.

[v8granada]

Thanks for the replies guys,

JJ - Your not helping me decide one advantage I can see to having the centre bearing is it acts sort of like a prop loop and makes it so the prop is not such a long unsupported length.

Kevin - The prop slides into the gearbox on a yoke so there is no need for a sliding joint as such, saying that the yoke needs to be inserted into the box pretty spot on otherwise the bearing in the tailsahft wears (speaking from experiance on the first attempt )

The main thing I'm worried about is the centre bearing not being man enough to cope with the job, ford only designed it for a 3 litre V6.....

Steve.

[kiwicar]

I would use a centre bearing, it will hold the prop shaft and stop it acting like a big heavy skipping rope, also it won't have to be so well balanced. the bearing itself will be under very little load so should not be a worry. It also allows for the diff moving relative to the gearbox when the chassis twists.
best regards
Mike

[topcatcustom]

I'm sure a manufacturer like Bailey Morris will be able to advise you instantly on whats best

[stevieturbo]

There absolutely must be room for movement with any shaft. So there has to be a slip joint somewhere. Either at the box, the shaft, or the diff. Unless of course the engine/box was bolted solid into the chassis, and likewise the diff.
Even then, chassis flex could cause push or pull on the shaft.

1 piece or 2 is easy. Can a 1 piece shaft be safely spun to the speeds you will require ?

If Yes, get a one piece. If no, get a 2 piece.

And a centre bearing is certainly not a form of propshaft loop. But it IS another potential area of failure.

And who said you had to retain any Ford parts of any shaft ?

The Ford item on mine, really was a weedy piece of crap. ALthough, the entire ford shaft was a weedy piece of crap lol

Given the setup will be fully custom anyway. Use the biggest/best centre bearing setup you can find, from whatever vehicle it needs to come from. and have that shaft adapted to your box and diff.
Or just go complte custom from start to finish.

[v8granada]

Thanks Guys,

Mike - The skipping rope effect was my thinking behind possibly keeping it,

TC - I will be taking a trip to my local manf, Propshaft Services in Feltham, they are part of the Bailey Morris group now, so should be able to advise, was just after some real world experiences from other members, didn't want to get one made then have to redo it again if possible

Stevie - With the origonal shaft there was no slip joint, all you had was a donut at the box end to put some flex into it.

To take up the movement on the current setup I have a slip yoke like this in to the grarbox:

As the Diff is solid mounted this will allow the flex in the engine to be take up,

Not sure about what is the safe speeds for a shaft to rotate at, max RPM from the box should be nor more than 5500, so will have to ask the Manf for advice on that one,

I think whichever way I go a prop loop will be fabricated to fit as well, just incase

[stevieturbo]

Max shaft speed isnt a gearbox issue.

Its rear diff/road speed.

eg, when I first had a 1 piece shaft made for my car, I couldnt go above about 120mph or there was serious serious vibration.

I had the shaft re-balanced....and still the same. The place that supplied me it in the US sent another, and it was still the same.
You'd think the idiots would have mentioned critical speed to me at the time of ordering !!!!

Basically...from memory, shaft speed was limited to around 5800rpm or so due to its length, diameter, material etc.

Totally bloody useless !!!!

Larger diameters can spin faster before the problem occurs. As can shorter shafts. Composite materials or lightweight materials can also spin faster before it occurs. ( ie carbon or Alu. )

I'll assume your car will use a fairly long shaft still, as mine does. Hence a 2 piece becomes the only option if highish speeds are to be used.
Again, this is shaft speed....which will be much greater of you have a short diff.

So a 1 piece steel was useless around 5800rpm....so far, I think my 2 piece has been spun to a good bit over 9000rpm with no problems.

As effectively it is 2 very short shafts

[stevieturbo]

http://www.hotrod.com/howto/52718_drive ... index.html

And a small chart based on 3" shafts etc. Its rare to find much smaller than that in the US

http://www.pstds.com/driveshaft_critica ... _chart.htm

[v8granada]

Thanks for the links and the info Stevie,

If I were to go for a straight prop looking at the chart it would need to be at least 3.5" tube as the prop will be approx 59" long!!!

The max RPM at the engine is gonna be circa 5500rpm, with max power around 4800 (from looking at cam specs) the C4 auto is running at a ratio of 1:1 in 3rd and the diff has a ratio of 2.88:1. running it through a gearcalc app gives me the following:

Gear---Mph per 1000 RPM----Mph @4800 RPM----Mph @5500 RPM

1--------------10.03-----------------------48---------------------55
2--------------16.90-----------------------81---------------------93
3--------------24.67-----------------------118--------------------136

Not that i'd fancy trying to push it to 136mph (unless on a really long runway!!!)

I reckon that orginally the shafts on our motors were probably virtually the same length when standard, if not the same

From what you and other have said, I think it's gonna have to be a 2 piece prop with a new centre bearing. Rather than get the existing one modded (as you have previously said they are a bit weedy) I'll have a word and see how much a completely new one will be, hopefully will be able to up the tube size depending on clearances.

You say yours is a two piece, I presume you still have a centre bearing of some description in there?

Thanks again, Steve.

[stevieturbo]

2 piece has to have a centre bearing

Mine is just a big 3" steel 2 piece, with the biggest centre bearing I could fit, and 1350 yokes.

Although even trying to get that made was a nightmare. So few places would commit themelves to making a 2 piece shaft in case it broke ffs.

Like wise up !!! I wasnt asking for any warranties etc.

And again, engine rpm is irrelevant. As shaft speed is dictated by wheel size and rear diff, and obviously actual road speed. The 2.88 diff will be a big help in that respect.

I had been using a 3.55 rear at the time of my problems, although I'm now on 3.27. Doesnt matter much, as the 2 piece is more than capable either way.

My first 2 piece was crom Carolina Driveline, and they were very helpful, and pretty cheap !!
I subsequently found a place with a bigger bearing on offer, which allows a larger shaft through it, and hence stronger.

http://www.iedls.com/Center-Support-Bea ... Trucks.asp

These guys made me another shaft to suit with the bigger parts. It was pretty expensive though. But given the nature of my car...I wanted the strongest I could get.

I actually should have most of the bits of the old 2 piece here which shouldnt be too difficult to adapt to your car ( well, for a prop place to alter shaft lengths etc. )

It may or may not be cheaper than going full custom from scratch. I'll have a hoke to see what I have

[v8granada]

Thanks again Stevie, your a gent.

Just been looking at the carolina driveline shafts, they are some serious pieces of kit some of them with some serious price tags as well, but with what your running i can see why you went for one like, as my old shed is not quite so powerful, I reckon I could probably get away with getting one made up by local manf.

Sorry if I sounded a bit dense when thinking rpm was shaft speed i've done some more reading and see what you mean now

My reason behind going for a 2.88 was previously with the standard ford diff (3.45:1) I was doing 3500rpm ish @70mph, wanted to lower the cruising speed a bit, saying that though it did take off like a bat out of hell, just runs out of steam quite quickly,

So in conclusion, at the moment I think I will atempt to get a new 2 piece shaft made, using the biggest centre bearing I can lay my hands on and using the biggest tube I can fit int the tunnel.

Stevie, are you using the original mounting point for your centre bearing or did you fabricate a new one??

Steve,

[stevieturbo]

It should be very easy for any capable shaft place to make what you need.

Places like that just dont exist over here, hence I sourced from the US. Carolina was very cheap !!

The other place was about 3x the price, but I simply couldnt get anyone else do make me one.

3" shaft fits easily in the tunnel, and Ive a live axle.

I use the original ford mounts on the chassis, just adapt the centre bearing mounts as required. they dont need to be mega strong, as there arent really any loads placed on it.

The big yellow one in the link. I just cut and butchered up up so it was pretty much round, then made new mounting lugs to bolt it to the floor.

[v8granada]

Thanks Stevie,

Hopefully by the end of next weekend the axle will be all fitted and bolted into place, so I can take the measurements and attempt to get one made up...

I know what you mean about places like that not existing over here, it can be a nightmare sometimes finding "custom" stuff, and when you do find it you need to remortgage to buy it.

Once I got the prop all i got to do then is sort out the torque arms, handbrake cable and brake lines then we'll see if its been worth the hassle

Steve.