RAVE says to make sure that the prop is marked on the IRD and rear diff before removal so it goes back in the same place. The prop sections are balanced and they will vibrate if put back in a different orientation.
I think.
In my opinion yer right. This has been an on going debate on ere for years. Ere's my theory:
Each prop shaft is balanced at the time of manufacture one would eggspect. It has a little metal plate on it to balance it as required. The plate isn't always in the same place due to the needs of balancing.
A brand new vcu is machine welded. It's true the viscous fluid inside falls to the bottom of the vcu if left standing. But those like me who have drained a vcu know the fluid moves. Not as quick as water but it does move faster than you would think, considering it's similar to slime. So that won't make it vibrate unless the fluid has turned solid/hard.
Marking the ird/props/vcu when you take it oft means you can put it all back together in the same orientation. Some would say this isn't needed but if you do, and you put it back, in theory there shouldn't be a problem. If there is a problem then you can rule out fitting it differently as it's the same. If there was a problem before then eggpect it to happen again.
It's true the props rotate at a different speeds to each other under normal driving. The tip-ex test proves this. But what does that really mean? It means yer can't rely on one prop to counter balance the other prop. But marking the prop does allow the rear prop to connect to the rear diff as before. Also connection to the vcu is the same. Same goes for the front prop being connected to the ird the same. If there's any imbalance on the front prop/ird connection then aliging the re-fitted prop in the same way it was taken oft means yer should be able to rule out problems. Same goes for fitting the rear prop the same. The worst thing that can happen is taking it oft, then putting it back an hour later and it then vibrates. Especially if the Freelander hasn't been moved. Id the prop to diff/ird mounting perfectly central or oft set slightly?
A recon vcu isn't a brand new vcu. Some like to call it a genuine LR re-con vcu but that's a play on words. If it's been cut open for re-con then it will need to be welded back together. They won't have an automated machine to do this, with a precision jig like the manufacturer. They will have a jig but the weld just isn't the same quality as a new vcu. You can spin them in a lathe and clean up the weld. But there isn't the same guarantee the vcu is put back together perfectly straight before welding.
My old vcu is bent slightly. Imagine you support both axles of the vcu and give the vcu itself a whack with a big hammer. It's not bent by much, but at speed you may feel it. Turning it against a datum whilst it's oft ma hippo proves this. If I can find the video I will put it up. Can't film it again as it's already cut open.
I've known people to have bent props. Also one filled with mud when it was cut in 2 after it rolled on it's own on the floor. (don't know how he achieved this - dried out muddy water oft road?). If you take it oft road and land hard on an axle twister etc you risk hitting something underneath. Like the vcu (I think this is what I did) or the props. The vcu supports are surprisingly strong. I had one of my props rebalanced. Only needed a slight adjustment. If was cheap as the uj was being done at the same time.
Comparing this to the OP's problem of vibrations at 60mph+... He has a recon vcu which may be bent slightly. His props may be secure to the rear diff and ird but what if they're not perfectly central? What if the prop is bent? He doesn't know the history of his props. If they were his and he'd taken them oft then put them back and this problem occurred what does he do? Say there can't be a fault...
The vibration is only very small. The prop has to be turning very fast to notice it. that proves it must be small. Therefore the cause is only very slight. He either continues his quest or waits for it to get worse. Could this be resolved by disconnecting then reconnectiong the props to the rear diff and ird? Remember it's only a slight vibraton. Not like a house brick in a washing machine (goo gle it). Could it be his props/vcu are bent? If it were mine I would imspect and wobble all connections. Then turn one of the prop connections 90 degrees to the next bolt hole, and reconnect. Hence reconnect the prop to the rear diff by 90 degrees. The diff should spin central but a vibration would occur if the 2 mounting faces (diff/prop weren't central to each other. It's worked before. May just have been better alignment when disconnecting/reconnecting. Only other option is to lift the wheels oft the ground and set it driving (make sure yer vary safe when doing this) and check for vibrations. The engine will get hot far quicker than normal due to no wind cooling. In my opinion marking the props rules out a lot of guess work and makes fault finding easier. Going mondo would be a shame. Especially as the OP's already paid out for the parts. Waiting for it to get worse so it's easier to detect may be the only way. Could an unevenly fitted uj be just slightly out so it only causes this problem at speed...
Rant over.
