advice needed

hi i have a problem with my propshaft front its a 96 p38 2.5 diesel manual ....
it hasnt had a front propshaft on so i bought a new one. and i have fitted it .
the problem is it vibrates and also there is no information on fitting 1 exept for marking your old 1 when taking it off
is there a spacific way of fitting them does the sliding joint go front to the axel or rear to the hand brake drum mine at the moment is at the axel side i was told this is wrong as the axel is lower and the grease would come out which sounds right but no advice anywhere any help would be greatfull thank you :doh:

The prop was probably removed because the VCU has seized.

mmm the new one has new vcus on it and thay are nice. not sure if its cause its backwards but it still drives ok. but for the vibrating and i carnt see any lineup markes on it confused and it was alot quicker with it off but its poo in the snow

chip2366 said:

mmm the new one has new vcus on it and thay are nice. not sure if its cause its backwards but it still drives ok. but for the vibrating and i carnt see any lineup markes on it confused and it was alot quicker with it off but its poo in the snow

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The VCU is in the front of the transfer box, it sounds like you are talking about the Hardy Spicer UJ's. The usual reason for removing the front prop is a seized VCU

yes you are right i was talking about the ujs sorry

The thin bit of the prop to the front (check that, it like that on my Series II) there are no line-up marks on it, it will revolve anyway you like on to it (you cant twist it around the wrong way) if that's what you mean, there are different types I think for Manuel and auto box though, and different engines, and a rubber coupling as well, never done the job on a P38, have on my Series II but have a look around and make sure its the correct prop you have on, and always put new nuts and bolts on (I have always been told to do that as a matter of course)

thank you dopey i do have the thin bit to the front thats the end with the slider on i will get under again tomorrow and make sure all the nuts are tight as i know it was cold and i was rushing will give it some more greese to thank you

I thought I'd better check before opening my big mouth, the slider end of the prop goes at the gearbox end.
Now, you obviously have not listened about the VCU. If it has seized, now you have put the prop back on, you will be back on here in a week or three asking why your front diff has exploded
Still if you want to ignore it and wait and see that's up to you.

I would concur with Datatek...

Check your VCU (Viscous Coupling Unit) first....

The VCU ensures that the Front and Rear propshafts can turn at different speeds on tarmac roads when cornering (similar to the axle differentials do from wheel to wheel - due to different speeds during the turn) when on the slippy stuff the VCU locks up due to slip in the rotar/stator vanes inside stirring up the viscous fluid and this has the effect of locking the two axles to turn at the same speed thus maximising traction....

If the VCU has seized it will not allow the front and rear shafts to turn at different speeds and this will cause what is called transmission wind up, and the weakest link if you are lucky will be one of the Diff's....if not the next thing is the Gearbox....£££

Check the VCU first....can't remember the exact procedure but goes something along the lines of jack up one (or two) wheels and try turning them agaisnt the resistance of the VCU...if they turn alls good, if the lock up...alls bad....but I can't remember which wheel(s) or whatever....

Check on here with a search first.....

ok thanks saint v8 i will go out tomorrow and check the coupling in the transfer box as you discribed in both ways thank you for that and thank you datatek for checking which end the slider goes TO THE GEARBOX i did not ignore your comments as it has been very bad weather today i have not been able to go and spin it round but it will be done before the diff explodes all information recived is much appreciated from all senior members so therefor
the checks on the vcu will be done and i will spin my propshaft round so the sliding bit goes to the gear box
thank you...........
just found a few examples on you tube for checking vcus will do it tomorrow thanks again everybody

To check the VCU, jack one front wheel, you should be able to just about turn it with a great deal of effort. If it does not turn, the VCU is seized.

Datatek said:

To check the VCU, jack one front wheel, you should be able to just about turn it with a great deal of effort. If it does not turn, the VCU is seized.

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I knew it was something like that....

right just jacked up the p38 and checked the vcu as described by datatek and saint v8 thanks guys and it turned ok with a little effort not a lot but it is working .....i then removed the front propshaft and spun it round so the sliding joint is at the transfer box no all fitted properly BUT i still seem to have a vibrating feeling at about 35 but goes away at about 45ish and also under load when the vibrating starts if i release the throttle a bit it also stops could this be just an imbalance in the prop

If it turned with a little effort something doesn't sound right, should be really hard to turn. You did only jack one wheel? Vibration could be out of balance prop, duff front diff etc.

I have just tested my VCU this past weekend and it would not turn under my weight using only the wheel brace. I used the jack's extension over the brace and then I was able to turn it slowly. Certainly not just a little effort

mcapinha said:

I have just tested my VCU this past weekend and it would not turn under my weight using only the wheel brace. I used the jack's extension over the brace and then I was able to turn it slowly. Certainly not just a little effort

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That's about right

mcapinha said:

I have just tested my VCU this past weekend and it would not turn under my weight using only the wheel brace. I used the jack's extension over the brace and then I was able to turn it slowly. Certainly not just a little effort

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VC should turn at 90degrees per minute with a 27 pound feet load applied to the nut on the front output shaft. Multiply that by 3.54 to get torque required to be exerted on nut of front driveshaft. Around 95 pounds feet i think. So considerable effort is needed. And the wheel only needs to turn 25 degrees in the minute.

Probably having a thick moment but something doesn't compute. If the VCU allows front and rear propshafts to turn at different speeds and as Saint said axle diffs allow opposite wheels on the same axle turn at different speeds, then how does raising and turning just one wheel at the front test the vcu? Or are we seeing if that wheel can turn relative both to the one opposite AND the rears? As I said, sorry for being thick, all the auto-mechanics I know is being learned from the great university of P38 ownership!

By keeping 3 wheels on the blackstuff....and raising one, you are using that one wheel to turn the VCU as the others are in effect locked up...if you had two or more up in the air, the turning of one wheel will be transfered to another wheel through the drive system via the VCU...

What you are testing for is to ensure the VCU isn't seized....if it was seized, you couldn't turn one wheel in the air as it is trying to turn the VCU which has seized to the other wheels via the propshafts....

hi all just had the vcu checked at my local lr steelers and it turns out that the vcu is fine it was £20 quid to have it checked and they did the same as i did as advised by you lot only they did both of the front wheels 1 off the ground .they said it could just be the prop out of balance as it only vibrates between 35 and 40
I THANK YOU ALL again for your help