P38A Front Prop died!

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O Bife

O Bife

Active Member
Posts
409
Location
Almada, Portugal
Hi there,

Last Saturday, luckily on a roundabout, my front drive-shaft decided to part ways with the transfer box. Made a bit of noise too.

Now my question is what might have caused it. My main train of thought leads me to the Viscous Coupling in the transfer box, but at the mo I cannot get to it to check if it has seized. No point in saying jack the front up etc as the offending prop has already been removed.

Wouldn't the transfer box have given me some sort of sign the the VC was on it's way out or would it have simply gone bang?

If it is the VC, what are my best options?

Yeah I know I could always by one from Ashcroft, but I was wondering if I could get away with just fitting a new VC to the Borg I have fitted (about 100,000Km old). As Ashcroft no longer sell the VC units I have been looking around and I have seen them both as new units and reconditioned units (for less than £200). Would a re-coned unit be worth it being it's less than half the price of a new one?

Cheers in advance.
 
Where did the propshaft part company was it the UJ or the flange on the viscous coupling ? you don't have to jack it up to see just look at the propshaft.
 
it could indeed be your vc,but if you think about it the prop is the weakest link. Thank god it wasn't your front diff that failed!! I would replace the prop and test your vc before shelling out, it could just of been a duff prop!
 
Mark Piercy said:
it could indeed be your vc,but if you think about it the prop is the weakest link. Thank god it wasn't your front diff that failed!! I would replace the prop and test your vc before shelling out, it could just of been a duff prop!
Click to expand...
From what I understand you should be able to check out the VC anyway, apply the handbrake and climb under the vehicle with a large(ish) lever and see if you can rotate the front output shaft from the transfer case, it should be hard to turn but still should give, when the VC fails I believe it fails in the locked solid condition, so if it will not give at all, you know that there is the problem.
 
The universal joints on the propshaft are usually the first things to let go if they have never been changed, or greased/serviced... but they usually give a driveline vibration well before they go pop.

As Gazbo says, you can check the VC with it in the transfer box still with a big socket on the nut, and decent breaker bar and it should turn slowly, but smoothly.
 
ovalandrover said:
Where did the propshaft part company was it the UJ or the flange on the viscous coupling ? you don't have to jack it up to see just look at the propshaft.
Click to expand...

As I said above, my front drive-shaft/propshaft decided to part ways with the transfer box. As to wether is was the UJ or the flange, by what I saw after the mech removed it, I would take a guess it was at the UJ join. The two holes where the UJ seats were no longer holes, more like "C"s. They looked like had had what ever was fitted into them, the UJ, ripped out of them. In the attached image where the red arrow is pointing to has an opening like that where the yellow arrow is point to.

Bust-Prop.png

martyuk said:
The universal joints on the propshaft are usually the first things to let go if they have never been changed, or greased/serviced... but they usually give a driveline vibration well before they go pop.
Click to expand...

The vibration you speak about is exactly what I had been noticing the past few weeks, but after I had asked the mech to see if I needed some new UJs and he told me they were fine... well I took his word and started to wonder what the heck was causing it. I have had the same vibration before which did turn out to be the UJs, hence me asking him to check them.

I don't know if the following could have caused some sort of problem, but about 5 months ago I swapped out both my rear and front diff. The front one was very much on borrowed time so I decided to refit both at the same time. What I put in were a pair of Ashcroft's LSD's (ATB). Could that have cause some sort of stress to the drive line. I have noticed a strange knocking sound if and when I turned at full lock. Now, when I drove the beast home after the mech had removed the front prop (having to wait for the new one to get here) I noticed when I put her into full lock there was no noise. Saying that, that knocking noise didn't apear every instance I put full lock on.
 
Last edited:
O Bife said:
As I said above, my front drive-shaft/propshaft decided to part ways with the transfer box. As to wether is was the UJ or the flange, by what I saw after the mech removed it, I would take a guess it was at the UJ join. The two holes where the UJ seats were no longer holes, more like "C"s. They looked like had had what ever was fitted into them, the UJ, ripped out of them. In the attached image where the red arrow is pointing to has an opening like that where the yellow arrow is point to.



The vibration you speak about is exactly what I had been noticing the past few weeks, but after I had asked the mech to see if I needed some new UJs and he told me they were fine... well I took his word and started to wonder what the heck was causing it. I have had the same vibration before which did turn out to be the UJs, hence me asking him to check them.

I don't know if the following could have caused some sort of problem, but about 5 months ago I swapped out both my rear and front diff. The front one was very much on borrowed time so I decided to refit both at the same time. What I put in were a pair of Ashcroft's LSD's (ATB). Could that have cause some sort of stress to the drive line. I have noticed a strange knocking sound if and when I turned at full lock. Now, when I drove the beast home after the mech had removed the front prop (having to wait for the new one to get here) I noticed when I put her into full lock there was no noise. Saying that, that knocking noise didn't apear every instance I put full lock on.
Click to expand...
With respect, I'd be ashamed to admit that I'd driven any vehicle to the point where the driveshaft uj's had been trashed to that degree, I have to ask, how is your hearing? Your mechanic must be a classic to tell you the uj's are all ok, my first job would be to take that driveshaft to him and smack him with it, both him and his guide dog.
Your front diff could be causing a problem I have heard that the differing speeds of turning corners etc plays havoc with them but I would think you would feel the car dragging, i.e. not rolling freely when the engine is not pushing it, also the tyres would be squealing on the pavement because of the lock up condition, same as an ordinary 4wd if driven on the hard surface with the centre diff locked up. I put in a previous post how I think you could check the VC in the centre diff, but if you are still able to drive the vehicle without the front shaft in that has already answered that question, it must be solid locked, cactus, stuffed.
What usually will happen when the VC fails is you start breaking axles or on something fitted with Salisbury diff the axle/hub drive members splines strip out.
Seeing as how the diffs are not broken in this circumstance, says a lot for the Ashcroft product.
 
Gazbo said:
...but if you are still able to drive the vehicle without the front shaft in that has already answered that question, it must be solid locked, cactus, stuffed...
Click to expand...

Are you saying that if the VC was ok I would not be able to drive at all without the front prop in place?
 
With 15 lb ft of torque applied to the front transfer box drive flange nut. VC should turn about 90 degrees in a minute. Propshafts CANNOT be checked for wear with load on them. A wheel MUST be lifted.
 
Mark Piercy said:
it could indeed be your vc,but if you think about it the prop is the weakest link. Thank god it wasn't your front diff that failed!! I would replace the prop and test your vc before shelling out, it could just of been a duff prop!
Click to expand...
wammers said:
With 15 lb ft of torque applied to the front transfer box drive flange nut. VC should turn about 90 degrees in a minute. Propshafts CANNOT be checked for wear with load on them. A wheel MUST be lifted.
Click to expand...
echo!!
 
Is that a picture of the propshaft end with the sliding joint on it or with the solid end .If it was the solid the prop was fitted the wrong way round if that was the gearbox end.
 
O Bife said:
Are you saying that if the VC was ok I would not be able to drive at all without the front prop in place?
Click to expand...
Upon reflection I cannot say for sure, some of these other chaps have more experience in the models with VC's, the test method as described by @wammers is how I understand you can see if in fact the VC is functional.
Obviously you have been able to drive the vehicle without the front prop shaft in, I would have thought that if VC was still functioning as it should some slippage would be detected but that probably be imperceptible with an auto box.
What I understand for sure is that the VC "failure" condition is a fully locked up unit, and that gives the whole drive line a bad work out.
 
The transfer box applies drive to front and rear wheels via the VCU. With normal tyre pressures the front and rear wheels turn at different rates so there would be constant slip in the VCU. However steering inputs negate this difference to some extent giving an almost constant 50%-50% distribution of drive front and rear.
 
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