CV-joint propshaft?

[sonus]

I just bought a one off car that has had a engine transplant. I'm trying to track down the reason for some vibration that appears during acceleration and on the over run (engine braking). I've measured the crankshaft angle and pinion angle and they are 12 degrees out of alignment in the vertical plane. The gearbox tailshaft points downwars and the differential pinion is level. It even looks like the prop is out of alignement horizontally as well with the gearbox tailshaft pointing towards the left rearwheel and the pinion entering the pumpkin at the right side. The transplant was done in the 70s so the car has been like this since, but I am wondering if this can be the cause of the vibrations?

If so could a propshaft with CV-joints instead of the U-joint possibly help me cancel the vibration without having to realign the engine/gearbox and differential?

[v8ian]

without a doubt that will cause vibration, they should be the same angle, depending on what axle use, My leaf sprung axle was set up to have about 3degs of nose down on the diff.

[sonus]

Thanks V8Ian, but what kind of vibrations would this cause? And would a CV-joint propshaft cure the problem?

There's not enough room to shift the engine over nor the diff.

[DWDarkWheels]

A few degrees of offset of a UJ is a good thing. 12 degrees sounds more than usual, especially if 12 degrees is all at the front joint. The horizontal offset sounds like it's adding even more to that. Am I reading that right : the engine and gearbox are angled off-centre? Bike-engined cars get away with that, but have 3 joints, the middle joint well supported.

If the angle is too large at a joint, it'll pulse. At least, it will if the joint at the other end isn't at a similar angle, or the yokes at each end haven't been aligned with each other. While the gearbox output shaft rotates at a constant speed, behind the angled joint, it will speed up, slow down, speed up, slow down within a revolution. Is that of sort of vibration you notice? Is it a professionally made prop?

How good are the joints on the prop-shaft? If they've been working hard to deal with the angles, perhaps they are worn?
Is the tube bent : if you jack up the back of the car, put it in neutral and spin the prop by hand does the tube rotate around the centre-line?
Any play in the gearbox output shaft?

You haven't mentioned what this car is yet, so hard to know how it's been put together

Oh, and to answer the original question (oops), if pulsing is the issue, yes CV-joint type shaft would dial that out, but it's worth looking for the simple things like wear first. Then I'd talk to a prop specialist for their thoughts.

[sonus]

Thanks Darryl, none of the u-joints have any play in them, nor does any of the drive shafts. The diff has had an LSD fitted and I'll check if the back lash on the pinion and ring is correct to see if this might cause some vibration.

Yes the vibration is a very clear pulsing/shaking that disappears when the drivetrain isn't under load.

The car is a Daimler v8 powered TVR Vixen with a Jaguar E-type diff.

[colnerov]

Hi, this is a common problem on the front props on lifted Land Rovers, and the usual remedy is to move the sliding joint round one spline. If this doesn't do it either move it two. or move it one spline the other way. Just try it until it improves.

Colin

[scimjim]

Is there room to lift the rear of the gearbox (and/or drop the engine on its mounts) or shim the diff mounts? The flanges (diff input and gearbox output) need to be parallel (not in-line). Fitting a CV may mask the symptoms for a while but it's not fixing the fault.

[sonus]

Thanks guys
I can probably "lift" the nose of the diff by lowering the rearmost mounts 8mm to bring the pinion closer to parallell to the gearbox output shaft. However there is no way in h*** I'll be able to move the engine to combat the sideways misalignment. There is approx 3mm clearance between the frame and exhaust manifolds.

The problem as I've understood it is the use of u-joints with their non linear rpm transfer through angles. So if I change to CV-joints the problem isn't masked but gone (?).

I'll see if GKN can make or suggest what to do today if I get the time.

[sonus]

Spoke to GKN in norway and they can make me a new propshaft with CV-joints that will cure my vibrations/problems. It'll be 40mm shorter than the one I've got now and supplied with two 20mm adapters from Jaguar flanges to CV-joint. Only for the princely sum of £700+VAT

Any suggestions where I might source this in the UK?

[colnerov]

Hi, Rover SD1 propshafts are fitted with CV,s each end. However the gear box end flange has the usual asymmetric hole pattern while the axle end has a symmetrical pattern so two of the holes will need redrilling.

Colin

[sonus]

Mar 4, 2014 20:20:01 GMT colnerov said:

Hi, Rover SD1 propshafts are fitted with CV,s each end. However the gear box end flange has the usual asymmetric hole pattern while the axle end has a symmetrical pattern so two of the holes will need redrilling.

Colin

Thanks Colin I'lllook into if I can have one shortened.

[ChasR]

Dolomite Sprints and Triumph Stags (on a Manual Overdrive gearbox) also came with CV joints.

You could always try David Mac Propshafts in Coventry (www.davemacprops.com).

Whilst the angles will not help (I managed to smooth out the Stag's drive by checking the basis, I would still be tempted to check the rear driveshafts (I can appreciated with an IRS setup these can be tricky to check since IIRC are they not also a locating member as well?), since the vibration under load does sound alot like a driveshaft with worn CV joints (although IME the vibration only tends to start at around 30MPH upwards.

[sonus]

Thanks ChasR

It's only the diff that's e-type, driveshafts, wishbones, brakes and uprights are TVR.

I've had a good tug at the driveshafts and could not feel any slack. Neither in the prop was there any slack.

[rascaltl]

Try Bailey Morris in the uk 01480 216250. They manufacture driveshafts. The max working angle for uj type joints is 16 degrees unless you use a double cardan type then it is 32 degrees.

[vtecpowergt]

Land rover freelanders use a CV joint on there propshaft at the front where it connects to the gearbox output loads of those have been scraped check a scrapyard .

[drprop]

Hi,

You can give us a call, Dr Prop on 07920 130022, we can shortern a shaft for you, or make a new one up.

Cheaper than GKN by a mile.

Thanks

The Dr

[425ci]

Apologies to all if I am stating the blindingly obvious here, but have you checked the axis of each universal joint (assuming one at each end of the propshaft) to make sure that they haven't been fitted on the same plane and are fighting with each other? That is, whatever position one is at one end of the propshaft, the one at the other end has been fitted identically, rather than rotated ninety degrees to it.

This is something that I have come across on Land Rovers when the propshaft has been removed and worked on to replace the universal joints without first taking note of the relative positions of the universal joints before removing the propshaft.

[colnerov]

Apr 7, 2014 22:44:46 GMT 425ci said:

This is something that I have come across on Land Rovers when the propshaft has been removed and worked on to replace the universal joints without first taking note of the relative positions of the universal joints before removing the propshaft.

Hi, this is as I said deliberate on Land Rovers to move them out of phase because the angle of the gearbox is different to the axle so it pulses. Some times they are fitted with double carden joints as a cure as well.

Colin

[425ci]

Ahh, okay. Noted! I thought it might be worth a mention. Back to the drawing board!