axeman wrote:
simon's difflocks failed as well. as have many others when they were needed by the drivers. reduce the wear and increace the life span of wearing components simples!
neil
Neil, read through it all again as I dont think you understand or dont want to understand. If anyone is going to defend something they have to acknowledge what has be discussed and resolved through discussion. If someone is under the illusion of something being beneficial and the myth has been busted then it needs acknowledging so it can be accepted and not brought up time and time again and we have to go through all this again and again. If people have taken time to explain things that go against the opinion of, (in this case a Decoupler owner) then its only polite to acknowledge that what the decoupler owner is under the impression of is wrong. Again the reason these things never come to an end is because they arnt acknowledged and fingers are put in ears with the attitude of I am not listening, I am not listening, I am not listening, I am not listening....... Or just say they are board with it when their understanding of something isnt quite right. Not acknowledging the result that goes against an understanding of something and just sweeping it under the rug, before swiftly moving onto the next thing is resulting in this re appearing so I am going to save this post to pop up every time a decoupler thread crops up to save the same old same.
It could also stop the next generation of people who didnt understand how something worked before they bought it arguing about something just to justify there outlay on an unnecessary item and falling back on the already discussed and not acknowledged myths that have been busted all ready.
I wont bother directly quoting people as there isnt really any point but this is what has been discussed and havnt been acknowledged so far. Its all black and white stuff and the then grey areas have been rubbed out this is how we are looking.
A The magic figure has been give, thats 5%. This is how much drive that is said to be given to the front via the VC when a decoupler is not fitted Its not hard to understand that 95% goes to the rear wheels via the gear box.
B When a decoupler is fitted, 100% of the drive is given to the rear wheels through the gear box.
Pro's of fitting a decoupler
1,
Q.
"reduce the wear and increace the life span of wearing components simples!"
A. True, by fitting a decoupler you are putting 5% more wear on your gearbox that was designed to work with a VC sending 5% up front (it is not a 2wd gear box), this also means 5% more on your rear CV joints that mysteriously failing and you not understanding why are getting 5% more wear..
2,
Q.
Jed wouldnt have had to remove his prop with a failed UJ if he has a decoupler fitted.
A. When a decoupler is fitted the prop still turns even though the 4wd is disengaged meaning a failed very graunchy UJ is still turning on the prop and the same unbearable vibration would still be going through the prop. 5% of the the drive is going to the front wheels (it will be helped along with the free turning of the drivetrain too so more like 3% in real terms but I am no expert) it isnt enough to wear out the UJ's on a prop, no way. What about front engined cars with rear wheel drive they go for hundreds of thousands of miles with 100% of the power going down a prop..... and when I do get the full whammy through my prop that is when my 4wd is engaged and is needed when the back wheels spin, or when in your case you would be pulling the knob on your decoupler. Jeds van has done 339921KM more than likely and not unreasonably, general wear and tear caused a UJ to go and the prop having to be removed, if a Decoupler was fitted or not.
3,
Q.
Can a decoupler fail and leave you stuck in the middle of nowhere without 4wd?
A. Yes it can, if one was fitted and it broke (because it is a mechanical part and aftermarket) and you are alone and remote you would be in trouble. No decoupler = No failure.
4,
Q.
If you put new tires on your van you will cook the VC without a decoupler.
A. In the unlikely event you get a total blow out twice in one trip and you have to get a garage/tyre shop to fit two new tires you dont need a decoupler. If you dont want to take 10 minutes and take the prop off (remember you will be on a tar road more than likely) put them on opposite corners so the rolling radius would have stay the same. If you have to put only one spare tyre on with a deeper tread than the rest would not the diff on that axle take up any difference in rolling radius so they stay the same between the front and back axle.
5,
Q.
Can a decoupler stop wind up on long drives?
A. Yes. You will have a stiff VC and it is not working like it should, I have personally seen a stiff VC fail open (will only work as a 2wd) much quicker than expected this year (infact it was quite early) due to its stiffness, it worked quicker but became hot quicker and failed quicker. I have video to prove this happens and actually the fact is your VC will be failing if your getting wind up and is getting stiff. A VC is an automatic clutch that sends drive to the front wheels when needed on its own, if you fit a decoupler to disengage the 4wd so you dont get wind up you have still got a VC that is failing and you run the risk of it letting you down big time. A Decoupler is about the same price as a reconditioned VC so I would think its better to fit a new VC and have a working van than to use one of my personal favorites, "put lipstick on a pig" or fit a decoupler to protect a broken VC . Think of your normal clutch on your van or car, when you feel it slipping and on its way out you get it changed so your vehicle works properly.
6,
Q.
Does fitting a decoupler mean you will have a knob and a green light?
A. Yes, you will..... But like has been said already by defenders of the decoupler if you have a perfect VC their is no need for a decoupler. If its a willy waving compensation for anyone fitting a green light and a knob then you would be best sorting your Shlong out first.
7,
Q.
Does fitting a decoupler make your steering lighter?
A, No, I took the prop off my van due to a failing UJ, is maintained as it should be and the steering is no different. I fitted a spare prop borrowed from my Doka just this minute and the steering is exactly the same.
I hope this helps with any future discussions on the Decoupler as these are the points that have all ready been talked about time and time again and I hope this bit of time I have taken to type this lot out will act as some sort of confirmation of it being talked about and the answers have been given. An engineer with a long career and adequate actual qualifications has contributed to these discussions as well as keen amateurs such as myself and others.
Jed
It's only the gearbox that I have had real issue with.
and you have problems with your gearbox 
oh dear must be that extra 5% extra wear from running a decoupler