Decouplers another con?

[jed the spread]

Whats were those sage words you once said

Your bang on it this morning mark

jed

[jed the spread]

Good post Jed

Thanks,

I will add to the list too about steering allegedly being lighter with a decoupler. My prop is off right now and it isnt. Its good this thread has gone full circle and through this discussion and jotting down a few of the facts one can stand back, look at the text and think mmmmmmm you know what it might have some negative effect on a gearbox designed to have its load balanced out between 4 wheels.

jed

[syncrosimon]

Did you write your post Jed, it's very good, and you are right this is how we are going to resolve this issue.

I essentially agree with that synopsis, but having covered so many miles in syncros over the last 15 years I feel more comfortable on the long trips with the 4x4 de-coupled. I have never liked the even slight wind up you get even with a good VC. I have always said that this is a personal choice thing, like big lights and winch's, and my perfect syncro would have a big diesel engine, a sports VC and a decoupler. I have never really known how long my tight Vc would last, and now have the materials to rebuild one should it ever fail open. According to the SDP factory workers the only VC alternative offered by them was a softer one for those that dont enjoy the wind up. There is a great deal of variation between VC's so I guess some are soft and some are not. My dads T4 syncro does not have any wind up, but you really have to get the fronts spinning to get the rears moving. If I were to buy an new VC without decoupler I would rather err on the side of caution and go soft.

My family have owned 3 syncros and around 6 2wd T3's 3 from new, and the only problems encountered by these vehicles was gearbox failure 2wd, VC failure (8 year old syncro) and CV joint failure. When the first VC failed we did not even know really what was wrong (this was after the return trip from france with unequal sized tyres) and VW were not really any help. I just feel happier driving around de-coupled, and that means peace of mind which means trip enjoyment.

Other advantages of the de-coupler is that you can have a full brake test at MOT, which I consider to be really important.

If you do have to have new tyres on a trip you can put them on the rear axle, which is where the tyre industry recommend you put new tyres. This is because new tyres grip more in most situations, and grip at the rear prevents oversteer which is a nasty cause of accidents.If you have new tyres spread across two axles you are adding unknowns into the emegency braking situation. My family are worth more than that.

Ease of servicing. When decoupled you can spin the wheels to set up the handbrake, put the CV joints on, listen for knackered wheel bearings etc. This I also consider a great advantage in long trips.

When I purchased the de-coupler I took advice from CJ. His comments were that the VC's available at the time were of unknown pedigree, and were more expensive than they are now. Also he stated that for off road driving he preferred a tighter Vc than a standard one. I have noticed that the combination of a tighter VC and a heavier van makes for very little wheels spin and great traction. CJ still in my mind is the best pilot of syncros I have seen, and I have spent 2 days sat next to him and he is good.

The last factor for me is that I, like most, dont use the 4x4 very much, and as the VC really seems to wear out the most at high speed when the temps can get really high. So it seems natural to me to use 4x4 only when needed. as I have said VW built many more 2wd's than syncros and they seem to manage in most situations. Other 4x4's I have owned have been selectable, and I prefer this option.

I totally agree that a new vc equipped syncro is fine, but I prefer the ability to overide the sometimes eccentric VC and make that decision myself when I want the VC working.

It is horses for courses, as I would not be seen dead with all the lights up front that Jed has, I guess they light up the road better than standard, but I can see very well with mine (especially now they are getting 14.8v from the Sterling) it is just personal choice, and I have not liked the way that proper discussion like this has been avoided for a cheap laugh.

I dont know what sort of engineer paddy is, but I bet it was not in the development of a VC drivetrain. Engineers now do not use the Vc like we do in the syncro, so you could say that modern engineering has superseded this set up. It is a compromise that somehow works. I But there are plenty of rear wheel drive vehicles out there in production, so I will stick with that. I am looking forward to when my VC does expire, and I can rebuild mine. It will make testing a rebuilt one much easier, and so far I have spent 120 quid on all the parts required, and have enough fluid for possibly 2.

Thanks for your synopsis Jed, this is forum chat at its best and most useful without it being just a slagging match or an I am with him fest.

I wish I had more time to E D I T this up nicely but I have got too much to do at the mo.

Simon.

[jed the spread]

Did you write your post Jed, it's very good, and you are right this is how we are going to resolve this issue.

I essentially agree with that synopsis, but having covered so many miles in syncros over the last 15 years I feel more comfortable on the long trips with the 4x4 de-coupled. I have never liked the even slight wind up you get even with a good VC. I have always said that this is a personal choice thing, like big lights and winch's, and my perfect syncro would have a big diesel engine, a sports VC and a decoupler. I have never really known how long my tight Vc would last, and now have the materials to rebuild one should it ever fail open. According to the SDP factory workers the only VC alternative offered by them was a softer one for those that dont enjoy the wind up. There is a great deal of variation between VC's so I guess some are soft and some are not. My dads T4 syncro does not have any wind up, but you really have to get the fronts spinning to get the rears moving. If I were to buy an new VC without decoupler I would rather err on the side of caution and go soft.

My family have owned 3 syncros and around 6 2wd T3's 3 from new, and the only problems encountered by these vehicles was gearbox failure 2wd, VC failure (8 year old syncro) and CV joint failure. When the first VC failed we did not even know really what was wrong (this was after the return trip from france with unequal sized tyres) and VW were not really any help. I just feel happier driving around de-coupled, and that means peace of mind which means trip enjoyment.

Other advantages of the de-coupler is that you can have a full brake test at MOT, which I consider to be really important.

If you do have to have new tyres on a trip you can put them on the rear axle, which is where the tyre industry recommend you put new tyres. This is because new tyres grip more in most situations, and grip at the rear prevents oversteer which is a nasty cause of accidents.If you have new tyres spread across two axles you are adding unknowns into the emegency braking situation. My family are worth more than that.

Ease of servicing. When decoupled you can spin the wheels to set up the handbrake, put the CV joints on, listen for knackered wheel bearings etc. This I also consider a great advantage in long trips.

When I purchased the de-coupler I took advice from CJ. His comments were that the VC's available at the time were of unknown pedigree, and were more expensive than they are now. Also he stated that for off road driving he preferred a tighter Vc than a standard one. I have noticed that the combination of a tighter VC and a heavier van makes for very little wheels spin and great traction. CJ still in my mind is the best pilot of syncros I have seen, and I have spent 2 days sat next to him and he is good.

The last factor for me is that I, like most, dont use the 4x4 very much, and as the VC really seems to wear out the most at high speed when the temps can get really high. So it seems natural to me to use 4x4 only when needed. as I have said VW built many more 2wd's than syncros and they seem to manage in most situations. Other 4x4's I have owned have been selectable, and I prefer this option.

I totally agree that a new vc equipped syncro is fine, but I prefer the ability to overide the sometimes eccentric VC and make that decision myself when I want the VC working.

It is horses for courses, as I would not be seen dead with all the lights up front that Jed has, I guess they light up the road better than standard, but I can see very well with mine (especially now they are getting 14.8v from the Sterling) it is just personal choice, and I have not liked the way that proper discussion like this has been avoided for a cheap laugh.

I dont know what sort of engineer paddy is, but I bet it was not in the development of a VC drivetrain. Engineers now do not use the Vc like we do in the syncro, so you could say that modern engineering has superseded this set up. It is a compromise that somehow works. I But there are plenty of rear wheel drive vehicles out there in production, so I will stick with that. I am looking forward to when my VC does expire, and I can rebuild mine. It will make testing a rebuilt one much easier, and so far I have spent 120 quid on all the parts required, and have enough fluid for possibly 2.

Thanks for your synopsis Jed, this is forum chat at its best and most useful without it being just a slagging match or an I am with him fest.

I wish I had more time to E D I T this up nicely but I have got too much to do at the mo.

Simon.

I did write the post myself nobody else has access to my computer and glad you liked it.

There is so much to say about this it is difficult to put it into words for everyone to understand clearly, but their we all have it. I have saved it so the next time this comes up by someone else (doing "research") it can be posted up and we can all talk about something more creative now, maybe springs, spot lights or my winch


jed

[axeman]

Ok so what is the evidence for de-coupler failure.

Mine stopped working because the non VW vacuum lever broke.

I am aware of one time when someone else could not engage 4wd.

Thats all I am aware of. And they are not fragile. Simple yes.

sorry i assumed wrongly that there was a vacuum leak which would render the whole system not working, so i asume (again) that it was just the switch that was broken but still kept the vacuum in the system allowing the diff lock(s) to still engage?
this is an emotive subject with pros and cons, but like most emotive subjects it boils down to personal choice.
my reasons for buying one are
1 i have a stiff vc but to date it has not failed open nor closed ever , when this fails i will buy a recon vc.
2 i use the van daily and dont need 4wd most of the time
3 no more tyre rotation, not a big deal i know but one less thing to do
4 i look at it as a wear reducing item.
5 i got a good price on it and i had the spare cash so why not. (and it is tax deductible)

neil

[syncrosimon]

The only modifications that I would make are that the Prop will last longer decoupled, a spinning prop will not wear like a loaded one.

The steering is lighter on a decoupled, you can always tell you are driving a syncro by the slightly heavier feel compared to 2wd in my experience.

No transmission vibes ever when decoupled

The most versatile syncro will be a sports VC de-coupled one. (the tight VC mimics this whilst it still works, and in my case that is 5 years and 70,000km.

I have really come to find that the basic and fundamental perception that you need 4x4 is wrong. I find now that I even forget that the syncro has 4x4, on tarmac you just dont need it. I find that the economical sense in me says that using something for the sake of it is akin to glutony, and it is always better to make do without.

We feel we are daring doing a 4000km trip across Europe, this is only because of the fear of mechanical failure. Mine is less when de-coupled.

On my 3 4000km Euro trips I suffered no mechanical failures. I had a CV bolt come undone which I believe I never had done up in the first place. I attribute this reliability partly to the de-coupler.

I would not contemplate a syncro without a de-coupler and if I was to do this again, then the sports Vc and de-coupler would be my choice. I guess you could say I am just waiting for my old 160,000km Vc to give up. I wonder when it will.

[jed the spread]

Ok so what is the evidence for de-coupler failure.

Mine stopped working because the non VW vacuum lever broke.

I am aware of one time when someone else could not engage 4wd.

Thats all I am aware of. And they are not fragile. Simple yes.

sorry i assumed wrongly that there was a vacuum leak which would render the whole system not working, so i asume (again) that it was just the switch that was broken but still kept the vacuum in the system allowing the diff lock(s) to still engage?
this is an emotive subject with pros and cons, but like most emotive subjects it boils down to personal choice.
my reasons for buying one are
1 i have a stiff vc but to date it has not failed open nor closed ever , when this fails i will buy a recon vc.
2 i use the van daily and dont need 4wd most of the time
3 no more tyre rotation, not a big deal i know but one less thing to do
4 i look at it as a wear reducing item.
5 i got a good price on it and i had the spare cash so why not. (and it is tax deductible)

neil

Read again,

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

jed

[jebiga41]

As per usual this is an emotive subject (the forum needed a bit of spicing up as was getting a bit jaded IMHO ) and I hope that all understand how a certain slagging obviously comes in to play in trying to keep it somewhat a lighthearted discussion. Hopefully at last we can maybe put this one to bed in terms of the pros and cons of decouplers (i may try and put together a brief unbiased synopsis of both sides of the debate in the wee hours of the morning when its quiet at work). I think that both sides of the debate have been clearly and logically expressed by all parties and it is now up to the individual to make their own decision in such an intelligent way

[syncrosimon]

The fact is if someone said "i will fit a de-coupler to your van" you would have to be a proper nob to turn it down. It is a luxury addition to the syncro which makes living with one easier. If you want to convince yourself that you dont need one, it is easy to do, but to have one is better than to not. There is only one situation where not having one is better, and that is in a fail situation. But the chances of that are so small, and as we all know 2wd gets you 99% of the places a syncro will that it is not really worth bothering with. At worst the removal of the nose cone and fixing it in 4wd is a worse case senario as it is the antiquated vacuum system that fails more often than not.

People without a de-coupler need to get over the people that have and just shut up and get on with enjoying their syncro's.

[syncropaddy]

Well done Jed, that was a good post, well put and quite useful.
Simon good post from you as well but .... and there is a but ..... as Ive said before, a working VC is a de coupler and de coupling a de coupler does not make sense. Another thing that doesn't make sense is saying that "No transmission vibes ever when decoupled" - transmission vibe come from the prop as well. You have chosen to have a de coupler and thats fine but there is a more factual argument for NOT having one than having one. But you made your choice and thats fine.

For the record Simon, I served my time with Leyland Cars as it was at the time, from 1972 to 1978, and ended up with a degree in Engineering and a job as a Prototype Build and Development Engineer working on the models to come, but you know this cuz the first time we crossed swords you asked the same question and I pm'd you the same! Since then I have spent my time in the Machine Tools Industry and assembly manufacturing so my career has taken me from product conception,design , through homologation, financial argument to final assembly. No I didn't work for SDP..... and yes , I would loved to have. So now you know what sort of an engineer I am - and so does everyone else!

You told us you were a traffic warden .... but you're not really are you?

Like Jed says, this debate will go on and on and on but the only people who really know the truth are now no longer with us.

[jed the spread]

Well done Jed, that was a good post, well put and quite useful.

Thanks...

All the prop stuff was covered in section two so no point in going back there. Thanks for sharing your career details very impressive

jed

[toomanytoys]

Good post Jed

Thanks,

I will add to the list too about steering allegedly being lighter with a decoupler. My prop is off right now and it isnt. Its good this thread has gone full circle and through this discussion and jotting down a few of the facts one can stand back, look at the text and think mmmmmmm you know what it might have some negative effect on a gearbox designed to have its load balanced out between 4 wheels.

jed

Dont forget that the box is only the 2wd design modified.... so it was never "designed" to have load balanced.. 95%/5% isnt "balanced" is it....

Any additional wear could be attributed to the higher torque loadings from running in "G" and the shock and localised loading that WILL happen when you go off road...

[jed the spread]

Dont forget that the box is only the 2wd design modified.... so it was never "designed" to have load balanced.. 95%/5% isnt "balanced" is it....

It can be if "modified"



jed

[jebiga41]

The fact is if someone said "i will fit a de-coupler to your van" you would have to be a proper nob to turn it down. It is a luxury addition to the syncro which makes living with one easier. If you want to convince yourself that you dont need one, it is easy to do, but to have one is better than to not. There is only one situation where not having one is better, and that is in a fail situation. But the chances of that are so small, and as we all know 2wd gets you 99% of the places a syncro will that it is not really worth bothering with. At worst the removal of the nose cone and fixing it in 4wd is a worse case senario as it is the antiquated vacuum system that fails more often than not.

People without a de-coupler need to get over the people that have and just shut up and get on with enjoying their syncro's.

Just when you thought it was all over here we go again
Simon you have obviously convinced yourself you need one so why enter into a slagging match with people who don't have them. Obviously if someone volunteered to fit one for free I'd say yes but then if someone offered me a rockton I'd take it aswell but I do not need either. Also as we all know MG is actually removing his from Limey as he thinks its a factor in his gearbox wear which is what the original post was about so how do you explain that?
Regards to

But the chances of that are so small, and as we all know 2wd gets you 99% of the places a syncro will that it is not really worth bothering with

That is so completely untrue Simon, ok andy simpson did manage to to go all over syncropendence in the dry but the places where we go offroading in Ireland are a very diferent kettle of fish and a 2wd wouldn't have a hope of getting through but maybe thats the 1% for you, for me its a lot more plus on ice and snow the syncro leaves 2wd's standing oops slipping.
Regards 4,000 mile trips i did dublin to croatia via a syncro meet, a festival in devon, a detour through switzerland onto slovenia and down to split then vis and back again with a good working VC and had absolutely no issues regards wear, wind up, bearings,cv joints or gearbox on top of trips to syncro 25 numerous trips around Ireland and england etc
So why would I bother with a decoupler and blow 650 sterling or the whereabouts on something I do not need and may increase wear on my gearbox , just to have an additional Knob and light on my dash whilst not replacing a part which is worn i.e. VC as opposed to spending less money on renewing the part that if not working properly will wreck my gearbox ?

95%/5% isnt "balanced" is it....

in some cases it is

[KarlT]

F'k me, Leyland! Can we have a real engineers view please?


I've had five syncros now, none with what I'd say is a tight VC, no scrubbing on tight turns. But all have got wind-up on fast long runs (although can't really tell with the Tristar as P/steering makes it harder to feel). Have I just been unlucky?








Anyone want to buy a decoupler? Hardly used.