Thought the VCU on my wife's 2006 TD4 (64K miles) was getting a bit stiff so I thought I would replace it just to be on the safe side. Ordered a new GKN unit & GKN bearings a couple of weeks ago but due to the snow I put it off until this weekend.
Saturday morning I set about it and apart from the front prop being fairly well stuck on the splines it all went very well. All done I took it for a trundle around the estate and I was a bit disconcerted to find that it felt just as tight and indeed when turning on full lock the rear tyes were slipping on the tarmac which is something they hadn't done before. In addition, when I got it on the open road I discovered that from 50MPH onward I had a vibration which was never there before. As there was little else I could do I checked the alignment of the VCU and tried it again but it remained the same. What a pain, give up and have lunch!!!!!
Sunday, day of rest & visiting family.
Monday I thought I would try a process of elimination to discover if it was the new VCU at fault or if perhaps I had damaged one of the props (knocked a weight off or something?). Front prop only, vibration still there as before. Rear prop only, vibration still there but slightly reduced. No props fitted, no vibration.
Ok, the fault appeared to be with the new VCU or bearings so I decided to put the old VCU back on. One of the original bearings is a bit noisy but still runs ok and is only on there while I carry out the comparrison. Old VCU & bearings, all ok with no vibration.
The only thing I could possibly have done wrong on assembly was to somehow damage the new bearings or fit them incorrectly but on both counts I am certain I didn't (to be honest, it isn't rocket science) and with all parts being new and the surfaces being clean & smooth they went on very nicely. One thing that did strike me as strange when I was fitting the new VCU was that it seemed tighter than the old one. Using a bar through the UJ I found it almost impossible to turn the new VCU but when I did the same to the old one, while still being difficult it wasn't so tight.
I'm stumped now and the only thing I can think of is that the VCU is unbalanced (maybe this ties up with it being so tight?) however before I reject it and speak to the supplier I am going to check the bearings but it all looks ok and indeed it isn't until over 50MPH that any imbalance can be noticed.
Anyone else had a similar issue?
I have done a search and read of a couple of cases but those seemed to be down to poor quality bearings being used.
As a postscript, I think that the original VCU was probably perfectly servicable anyway. Ok a bearing is worn and is in need of replacement but the VCU turns ok so maybe all this was for no purpose anyway!
Saturday morning I set about it and apart from the front prop being fairly well stuck on the splines it all went very well. All done I took it for a trundle around the estate and I was a bit disconcerted to find that it felt just as tight and indeed when turning on full lock the rear tyes were slipping on the tarmac which is something they hadn't done before. In addition, when I got it on the open road I discovered that from 50MPH onward I had a vibration which was never there before. As there was little else I could do I checked the alignment of the VCU and tried it again but it remained the same. What a pain, give up and have lunch!!!!!
Sunday, day of rest & visiting family.
Monday I thought I would try a process of elimination to discover if it was the new VCU at fault or if perhaps I had damaged one of the props (knocked a weight off or something?). Front prop only, vibration still there as before. Rear prop only, vibration still there but slightly reduced. No props fitted, no vibration.
Ok, the fault appeared to be with the new VCU or bearings so I decided to put the old VCU back on. One of the original bearings is a bit noisy but still runs ok and is only on there while I carry out the comparrison. Old VCU & bearings, all ok with no vibration.
The only thing I could possibly have done wrong on assembly was to somehow damage the new bearings or fit them incorrectly but on both counts I am certain I didn't (to be honest, it isn't rocket science) and with all parts being new and the surfaces being clean & smooth they went on very nicely. One thing that did strike me as strange when I was fitting the new VCU was that it seemed tighter than the old one. Using a bar through the UJ I found it almost impossible to turn the new VCU but when I did the same to the old one, while still being difficult it wasn't so tight.
I'm stumped now and the only thing I can think of is that the VCU is unbalanced (maybe this ties up with it being so tight?) however before I reject it and speak to the supplier I am going to check the bearings but it all looks ok and indeed it isn't until over 50MPH that any imbalance can be noticed.
Anyone else had a similar issue?
I have done a search and read of a couple of cases but those seemed to be down to poor quality bearings being used.
As a postscript, I think that the original VCU was probably perfectly servicable anyway. Ok a bearing is worn and is in need of replacement but the VCU turns ok so maybe all this was for no purpose anyway!
