Jump to content
Sign in to follow this  
Ian of Chorley

Hill start disaster from stationary

Recommended Posts

1 hour ago, Jaydug said:

 

Not me, for sure.   I do exactly the same thing.   My longest tow is down to southern Spain each winter and I dread having to do hill starts.   I leave as big a gap as possible and crawl in first gear as slowly as possible to avoid having to come to a stop..   Even when boarding the ferry, I wait till the ramp is clear before beginning the climb. 

That is the technique my father taught me: "look ahead, and keep it rolling slowly".

  • Like 2

Share this post


Link to post
Share on other sites
3 hours ago, DACS said:

In effect, the CVT transmission belt is your friction clutch and may be subject to wear during hill starts etc..

There should be no belt slip in a CVT transmission, the 2 adjustable cone pulleys just allow the ratios to change as the steel belt climbs or descends inversely in the cones. The ZF VT1 has 2 auto clutches, one for FWD and one for REV, they are multi plate wet clutches and work on engine RPM/output shaft RPM with a transmission pump and valve proportionally adding pressure to the clutch packs allowing the slip/drive.

 

The early BMW Mini autos and Rover/MG used the CVT ZF VT1,  it could also be used in semi manual mode where the auto box programme gave 6 defined fixed ratios, so you could up/down shift with the gear lever to have a six speed box, or on the MGF/TF with switch paddles on the steering wheel; in my younger years a lot of fun to drive.

Other versions of CVT still retain a torque converter for take up or slip of drive. 

 

Auto boxes in cars have been out for a long time, early days normally only 3 speed with a lot of drag and frictional losses making them a lot heavier on fuel and if you were using an auto for towing you would have a transmission cooler fitted as an extra due to the oil getting easily overheated when pulling away with a load.

 

Nowadays we have dry and wet internal clutches, up to 8 speeds, computer controlled speed shifting that can throttle down the engine as the ratios change for a smooth shift and built in oil cooling plus the high quality of the transmission fluid.  You can never be in the wrong gear and you only need one foot; what's not to love!

 

 

  • Like 1

Share this post


Link to post
Share on other sites

Thanks for the advice! A number of ideas which I can take on board now. My mileage is now just under 31k which I feel isn’t bad - it was 26k when I bought it in November. As you say you can’t tell how the previous owner handled it but now I have a new clutch that should be a new baseline. I am using maps now rather than using satnav though the main issue I had was moving straight from roadworks with controlled traffic lights ending with a hill leading up to a junction with a busy A road! Obviously those who designed the roadworks had no understanding of caravan owners! 

I bought the Mondeo because of its green credentials- just trying to do my bit for the planet! Not convinced that any electric cars are up to the job yet or would have considered that. Will definitely go for an automatic next time- but hopefully I won’t be forced into doing that for a few years!!

Share this post


Link to post
Share on other sites

Having towed with a “proper” (I.e. torque converter equipped) automatic car for the last 12 months there is no way on the planet I will EVER return to a manual. ESPECIALLY when I hear how much my friends are having to pay to replace their DMF’s when their clutches need replacing!

 

I know some say there is no need to replace the DMF at clutch change time, but it’s a brave man who risks it as they do SEEM to have a lifespan very similar to the clutches fitted to them, and the labour cost to replace a DMF on its own is the same as that for having the clutch changed, i.e. A LOT!  and no-one wants that bill twice in a short period of time. 

 

Andy

Share this post


Link to post
Share on other sites

Yes - forgot to say that I had the DMF replaced at the same time- hence the expense!

Share this post


Link to post
Share on other sites

Just say this Joe Blogs , they dropped the motor cc down to 1.6 on both F1 and WRC as they were becoming to powerful for safety reasons I think , so somebody must think more capacity means more power even these days ?

Share this post


Link to post
Share on other sites

As a general rule, if you can smell the clutch it usually indicates its been hot enough to damage the DMF and often happens when some reveres onto pitches.

My Mondeo diesel is slightly over 80,000, I've had the cam belt changed but the clutch is fine (touch wood) however I tow a 1300kg MPLM caravan, if I was to tow the OPs caravan I would want a bigger car.

Share this post


Link to post
Share on other sites
9 hours ago, Mr Plodd said:

I know some say there is no need to replace the DMF at clutch change time, but it’s a brave man who risks it as they do SEEM to have a lifespan very similar to the clutches fitted to them, and the labour cost to replace a DMF on its own is the same as that for having the clutch changed, i.e. A LOT!  and no-one wants that bill twice in a short period of time. 

 

Andy

 

Absolutely, and to add I know many people who have replaced the clutch because the DMF has gone in advance; 80-100k seems to be common.

 

We had a clutch replaced on our old C4 Picasso, Citroen covered the cost even though it was out of warranty as it had a FCSH and only 45k on the clock - the release bearing had collapsed and there was no sign of premature wear; they didn’t replace the DMF, which looked fine, but as I didn’t pay that didn’t bother me!

 

I’ve developed a technique pulling away which may or may not help - quite a sharp initial release of the clutch followed by immediately dipping it again; now the car is moving I can bring it up as normal. Clearly this doesn’t work on hills but having only 1300kg on the hitch I’m probably not pushing the car much

Share this post


Link to post
Share on other sites

Having read a fair bit about DMF failures it would appear that a common cause is that the hefty springs that act as a “cushion” between the two main components lose their temper (springiness) This loss of temper could well be caused by the whole assembly being subjected to too much heat. That heat coming from slipping the clutch, a common bad habit.

My son in law is a serving traffic cop so I asked him to enquire at the police workshops what their experience with DMF’s is. The response was “interesting” 

Traffic patrol cars, which are only ever driven by officers who have undergone extensive driver training rarely suffer DMF failures. Local response cars (formerly known as Panda cars) eat DMF’s for a pastime. 

So, from that I would suggest that perhaps driving style has a significant influence on DMF durability. 

My experience with a modern manual, to reduce clutch wear when pulling away from rest when towing was........... First to remember  that a modern car has “anti stall” built into the ECU.

So when moving off from rest initially leave the accelerator alone,  slowly bring the clutch up with NO ADDITIONAL REVS, (that greatly reduces the slippage and therefore the heat generated)  the car WILL start moving without any throttle (because the ECU will prevent a stall) once it’s moving and the clutch fully engaged THEN depress the accelerator.  Try it, it DOES work, but not when doing hill starts though!!

Another thing to remember is to NEVER hold your car on a hill using the clutch more than momentarily, use the handbrake, that’s what it’s for! A slipping clutch is wearing out. If you can smell it you have created a huge amount of heat and THATS what weakens the springs within your DMF.

Best advice?? 

 

Buy and automatic, a“proper” auto with a torque converter not a robotised manual that will still have a clutch (and by default a DMF)

 

Andy

Share this post


Link to post
Share on other sites

A conventional auto (not dsg / auto clutch type variants) has significant advantages due to having a torque converter as it's name suggests increases the torque at the wheels while ever it is 'slipping'. As the drive is transmitted through oil there is very little wear taking place. Amazing devices and very old technology!

  • Thanks 1

Share this post


Link to post
Share on other sites
Posted (edited)

Whilst small capacity diesels can now deliver high powers and here more important high torques, these are not there at the idle revs, if the engine is not "working" there is no gas to drive any turbo charger.

And all IC engines have to be spinning to give any torque, which means to start moving a stationary vehicle, there has to be slippage, that unavoidably is generating heat.

Add onto that the scantlings of domestic car conventional clutches etc, are optimised  to be a "domestic car" not a load hauling tractor.

Therefore, whilst it is understandable it is expedient to use one for towing a caravan,  if a friction clutch its at the expense of its abuse.

Job here for hybrids where their electric motor torque can be there at zero revs, no "work" done, no waste heat generated.

Or a lovely big torque converter auto, designed to handle the tractor duty.

 

 

Edited by JTQ

Share this post


Link to post
Share on other sites
24 minutes ago, AJGalaxy2012 said:

A conventional auto (not dsg / auto clutch type variants) has significant advantages due to having a torque converter as it's name suggests increases the torque at the wheels while ever it is 'slipping'. As the drive is transmitted through oil there is very little wear taking place. Amazing devices and very old technology!

I agree with that theory, but hot stranded will once when an Aisin Warner box at 50k started selecting any gear it fancied, with a heavy bias to neutral. Car had never towed... 

Share this post


Link to post
Share on other sites
1 hour ago, Mr Plodd said:

Having read a fair bit about DMF failures it would appear that a common cause is that the hefty springs that act as a “cushion” between the two main components lose their temper (springiness) This loss of temper could well be caused by the whole assembly being subjected to too much heat. That heat coming from slipping the clutch, a common bad habit.

My son in law is a serving traffic cop so I asked him to enquire at the police workshops what their experience with DMF’s is. The response was “interesting” 

Traffic patrol cars, which are only ever driven by officers who have undergone extensive driver training rarely suffer DMF failures. Local response cars (formerly known as Panda cars) eat DMF’s for a pastime. 

So, from that I would suggest that perhaps driving style has a significant influence on DMF durability.

 

My understanding is the springs were damaged if the clutch is ‘banged’ together which causes premature wear.

 

As for trickling a diesel off the line, I’ve always done this but it’s almost impossible in the Passat as the clutch is very sharp and it will happily stall at will - never sure if it’s the stop start causing the issue in some way though because if you depress the clutch it automatically restarts itself. Stop start is turned off when towing and I don’t recall this particular issue so it could be related.

Share this post


Link to post
Share on other sites

I had a Corsair auto in the 70’s, so that would be a torque converter box.  It was playing up, can’t remember the symptoms but I think Is was sluggish to change.

 

An x policeman close to us opened a business specialising in auto boxes.  He took it for a test in which the rev counter was an important feature.  Quickly he diagnosed the problem as ‘front clutch’. As I never thought a clutch was involved I was surprised.  He surprised me even further when he told me it was an easy and cheap job. 

 

I imagine (but don’t know), that that clutch does not take the main loads.

 

John

Share this post


Link to post
Share on other sites
On 21/05/2019 at 16:49, Ian of Chorley said:

 .......  Moving awning into car to help ......

 

 

On a hill start no it won't make any difference! Its all down to weight, gears, steepness of hill, and tyre grip. It really doesn't matter where the extra weight is in a front wheel drive car.  The answers are simple:

 

1. Reduce the overall weight by either towing a lighter caravan and/or take less junk with you.

2. Avoid steep hills.

3. Get a car with more bhp and torque, and if tyre grip is an issue, go for a 4x4.

4. Generally 4x4s have a lower top speed, and therefore are geared lower. This means there is less need to slip the clutch in very slow moving traffic.

Share this post


Link to post
Share on other sites

With my 2 tonne caravan sat on the back of my Shogun on a steep incline I can select drive, let my foot off the brake and it will just there all day, brilliant!! I'll never buy another manual again. 

Share this post


Link to post
Share on other sites
1 hour ago, JCloughie said:

I had a Corsair auto in the 70’s, so that would be a torque converter box.  It was playing up, can’t remember the symptoms but I think Is was sluggish to change.

 

An x policeman close to us opened a business specialising in auto boxes.  He took it for a test in which the rev counter was an important feature.  Quickly he diagnosed the problem as ‘front clutch’. As I never thought a clutch was involved I was surprised.  He surprised me even further when he told me it was an easy and cheap job. 

 

I imagine (but don’t know), that that clutch does not take the main loads.

 

John

The clutches in conventional automatic are used to engage different gears, either by braking part of the epicyclic gear train or locking sections together.  However, they normally engage and disengage very quickly with little or no slipping.  The torque converter does all the slipping required to move from rest.  Unlike a conventional, friction clutch, there is no friction surface to wear.  While a torque converter is slipping it is churning the transmission fluid and generating heat.  This is not normally a problem although the fluid can be burnt by prolonged abuse.  Even then, it is easier to change the fluid than to change a clutch.

Share this post


Link to post
Share on other sites
52 minutes ago, DACS said:

The clutches in conventional automatic are used to engage different gears, either by braking part of the epicyclic gear train or locking sections together.  However, they normally engage and disengage very quickly with little or no slipping.  The torque converter does all the slipping required to move from rest.  Unlike a conventional, friction clutch, there is no friction surface to wear.  While a torque converter is slipping it is churning the transmission fluid and generating heat.  This is not normally a problem although the fluid can be burnt by prolonged abuse.  Even then, it is easier to change the fluid than to change a clutch.

The clutches you refer to are Brake Bands and they are easily changed and adjusted. The real gain with a torque converter is that it too acts as a gearbox and increases the torque available when moving off.

Share this post


Link to post
Share on other sites
1 hour ago, Borussia 1900 said:

With my 2 tonne caravan sat on the back of my Shogun on a steep incline I can select drive, let my foot off the brake and it will just there all day, brilliant!! I'll never buy another manual again. 

Much the same with our LR Discovery !

 

Share this post


Link to post
Share on other sites
1 hour ago, AJGalaxy2012 said:

The clutches you refer to are Brake Bands and they are easily changed and adjusted. The real gain with a torque converter is that it too acts as a gearbox and increases the torque available when moving off.

I think most auto boxes no longer have adjustable brake bands. The likes of Borg Warner 65 or the Torque Flite were of that type.

The ZF box used in the some Discovery uses clutches and brake-clutches. All are mounted axially and cannot be adjusted.

Share this post


Link to post
Share on other sites
Posted (edited)
17 minutes ago, Gd485 said:

I think most auto boxes no longer have adjustable brake bands. The likes of Borg Warner 65 or the Torque Flite were of that type.

The ZF box used in the some Discovery uses clutches and brake-clutches. All are mounted axially and cannot be adjusted.

ZF make some pretty impressive gearboxes, in a former life I was a REME Tank Mechanic, many of the gearboxes fitted in Armoured Tracked vehicles are made by ZF (and others), these things are huge and not only have to handle massive amounts of torque they also steer the vehicles through the gearbox too (the speed of the outputs relevant to each other turns the vehicle) some types also have the main vehicle brakes inside the gearbox, very reliable though and no problems with hill starts.

Edited by Borussia 1900

Share this post


Link to post
Share on other sites
21 minutes ago, Borussia 1900 said:

ZF make some pretty impressive gearboxes, in a former life I was a REME Tank Mechanic, many of the gearboxes fitted in Armoured Tracked vehicles are made by ZF (and others), these things are huge and not only have to handle massive amounts of torque they also steer the vehicles through the gearbox too (the speed of the outputs relevant to each other turns the vehicle) some types also have the main vehicle brakes inside the gearbox, very reliable though and no problems with hill starts.

 

I bet they would tow well also.

 

John

Share this post


Link to post
Share on other sites
5 minutes ago, JCloughie said:

 

I bet they would tow well also.

 

John

If memory serves me well, a  CRARRV  (that's a REME version of a Challenger Tank with a winch and crane on it) weighs about 62 tonnes, I have in the past towed a broken down CRARRV with a CRARRV so that's 124 tonne cross country at around 30 mph, not sure what the MTPLM or User Payload was but I'm glad I wasn't paying for the Diesel :o

Share this post


Link to post
Share on other sites
1 minute ago, Borussia 1900 said:

If memory serves me well, a  CRARRV  (that's a REME version of a Challenger Tank with a winch and crane on it) weighs about 62 tonnes, I have in the past towed a broken down CRARRV with a CRARRV so that's 124 tonne cross country at around 30 mph, not sure what the MTPLM or User Payload was but I'm glad I wasn't paying for the Diesel :o

 

Ah, but we’re there any hills?

 

John

Share this post


Link to post
Share on other sites
Just now, JCloughie said:

 

Ah, but we’re there any hills?

 

John

Often up steep sand hills on various training areas around the world, never rolled backwards when setting off and with huge torque converters no clutch to burn out either (although some older military vehicles have centrifugal clutches instead of TC's))

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...