How to recondition a VCU yourself.

OK, I can now report back on this method of reconning a VCU.

I had Bertie at an off road course yesterday going up and down some seriously steep hills in very wet and slippery conditions and the VCU worked flawlessly transferring drive to the rear wheels. At no time did I feel the car was only 2WD or that the rear wheels were not being driven. This combined with a OWUT time of approx 20 seconds and we can now say this method is a success.

Cracking result

GrumpyGel said:

Cracking result

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+1 - and of course we want more pictures!!!

I didn't get any more photo's at the event but this is Bertie at my mates house afterwards.

Shame - next time!

I think this is how I will do my next one

Probably with grease nipples so I can force white spirit in and accurately refil with fluid

Kayos said:

I think this is how I will do my next one

Probably with grease nipples so I can force white spirit in and accurately refil with fluid

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I'm not sure how critical the exact amount is since we only think we know how much is correct anyway. From previous experience the most important thing is to test how tight it is after a few miles driving. The last one I did was too tight giving a OWUT time of around one minute until I let a little fluid out bringing it back down to 20 secs or so. If you plan on using it off road a lot then you might want it a little tighter so put a little extra in from the start as it is easy to let out.
As for accurate filling, I think you'll find it's very difficult to avoid spillages even if injecting from a grease gun as some is bound to escape from the open hole but try it and report back. The more people who do it this way and report back their experience the better we will understand it.

Well I have a welder and I have stripped and rebuilt one the "old fashioned way" but when I did my clutch I could see some seepage so wasn't sure how much had leaked out.

Because of that I am currently in 2wd mode as I imagine no fluid won't be good

I'm thinking a refillable cartridge type gun would be best, put say 200ml in to allow for the nozzle and spillage, at least with nipples it will be easy(ish) to adjust the level in situ

Kayos said:

Well I have a welder and I have stripped and rebuilt one the "old fashioned way" but when I did my clutch I could see some seepage so wasn't sure how much had leaked out.

Because of that I am currently in 2wd mode as I imagine no fluid won't be good

I'm thinking a refillable cartridge type gun would be best, put say 200ml in to allow for the nozzle and spillage, at least with nipples it will be easy(ish) to adjust the level in situ

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Did you try to reweld it? I've had to do that to mine as well which was the main reason for doing it this way this time.
Welding with the fluid in is fun as it keeps pushing up through the weld like a mini volcano.

I didn't try to reweld because I was unsure how much fluid I had lost

When mine was the same I rewelded it, put it in a vice and turned it the same way I showed earlier in this thread. After cranking it for a couple of days and no more leaks I filled it again and refitted. Then after a few days I tested and in my case it was still OK but if it had given a high OWUT time I would have let some fluid out.

I have done a few VCUs and i plug the holes with grease nipples. The advantage with this method is that the friction can be easily adjusted: Too tight: press the ball on the nipple's valve and let some fluid out. Too loose: Press some more fluid in. For 2WD drive during summer: Unscrew one nipple and let the fluid drain, then fit the nipple again. When 4WD is desired: pump the fluid back in.

jonaf said:

I have done a few VCUs and i plug the holes with grease nipples. The advantage with this method is that the friction can be easily adjusted: Too tight: press the ball on the nipple's valve and let some fluid out. Too loose: Press some more fluid in. For 2WD drive during summer: Unscrew one nipple and let the fluid drain, then fit the nipple again. When 4WD is desired: pump the fluid back in.

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Lol, not sure I'd ever want it 2wd, can't think of any good reason to go that far but fully agree about adjusting the tightness by adding and removing fluid. It was your posts in a previous thread made me think to do that.

Alibro said:

Lol, not sure I'd ever want it 2wd, can't think of any good reason to go that far but fully agree about adjusting the tightness by adding and removing fluid. It was your posts in a previous thread made me think to do that.

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And created quite an argument at the same time, with one particular person

2WD saves fuel, tyres and drivetrain wear. Letting out sufficient fluid to make the VCU loose is done overnight and putting it back in takes only a few minutes.

jonaf said:

2WD saves fuel, tyres and drivetrain wear. Letting out sufficient fluid to make the VCU loose is done overnight and putting it back in takes only a few minutes.

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Have you ever worked out how much fuel it saves? It's been mentioned and mocked here in equal measure so I figured it wasn't worth the effort.

jonaf said:

2WD saves fuel, tyres and drivetrain wear. Letting out sufficient fluid to make the VCU loose is done overnight and putting it back in takes only a few minutes.

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It would definitely stop the possibility of those things, but would it not also damage the VCU? If there's no fluid I'd have thought the plates would rub against each other and over heat. I suppose it depends how much fluid is left in there - none and problems will occur with the plates, too little and problems with both plates and the remaining fluid being degraded, to much and you're not achieving anything. Where is the range between too little and too much

GrumpyGel said:

It would definitely stop the possibility of those things, but would it not also damage the VCU? If there's no fluid I'd have thought the plates would rub against each other and over heat. I suppose it depends how much fluid is left in there - none and problems will occur with the plates, too little and problems with both plates and the remaining fluid being degraded, to much and you're not achieving anything. Where is the range between too little and too much

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It'll never all drain out so shouldn't do much harm to the plates but like you say it might speed up deterioration of the fluid.

GrumpyGel said:

It would definitely stop the possibility of those things, but would it not also damage the VCU? If there's no fluid I'd have thought the plates would rub against each other and over heat. I suppose it depends how much fluid is left in there - none and problems will occur with the plates, too little and problems with both plates and the remaining fluid being degraded, to much and you're not achieving anything. Where is the range between too little and too much

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Getting the last drop out of a VCU takes weeks so I think there will be plenty fluid left to lubricate the plates if 50-100 cc is drained. The fuel saving will probably be a few percent so long mileage non-offroad drivers may save enough to justify the effort. Myself I only use the FL during the hunting season in the autumn and for winter driving so I like to keep the friction fairly stiff.

I've actually calculated it, reset trip and fill up and I get 26mpg with or without a prop