Clutch slip query

[Crockett]

Can anyone tell me how to tell the difference between overdrive clutch slip and plain old "ordinary" clutch slip?

The problem appears to be most noticeable when pulling away from stationary in 1st then changing into 2nd gear, although it does also slip in 3rd if you are heavy with your foot. The clutch slip is worse the harder you press the accelerator and less if you ease off the accelerator slightly.

I was told that this was overdrive clutch slip but I'm not convinced. This is happening when overdrive isn't engaged (it doesn't engage in 1st & 2nd gear in any case) and seems no be no worse when the overdrive is engaged than when it is not.

Once up to speed in 3rd or 4th gear, the overdrive can be switched in / out and can be heard and felt to be engaging / disengaging properly. If you engage overdrive when climbing a steepish hill in 3rd ghear however, then the clutch will slip for a few seconds before returning to normal.

So my thinking is that this maybe isn't overdrive clutch slip at all but just ordinary clutch slip. Anyone have any input on this one?

Cheers
Daryl.

[2420DH 2.5PI]

sounds like ordinary clutch slip to me not overdrive problems.

[gilesdive]

I agree with 2420DH, sounds like the clutch. You would expect it in all gears roughly equally as it is screwed to the back of the engine. If it is the overdrive slipping (which is after the gearbox) you would expect it to be hugely worse in the lower gears.

Looks like gearbox off for you, you lucky chap. What else where you doing over the bank holiday?

[Crockett]

[quote by=gilesdive link=Blah.pl?b=2000,m=1178387452,s=2 date=1178398624]Looks like gearbox off for you, you lucky chap. What else where you doing over the bank holiday?[/quote]

Thankfully, this isn't occurring on my own car but on a friend's. I'll be helping out with this no doubt but that will end up being deferred for a while, on the grounds that I don't want to contribute to an increase in the divorce rate, by getting involved over the bank holiday weekend :)

The only thing that now worries me though, is you comment about it being worse in the lower gears if were an overdrive problem. It is pretty bad in the lower gears (such as when pulling away in 1st or going into 2nd) but I thought that may be because that's when there is the higest level of inertia and the car is therefore, pulling at it's hardest.

I'm not really certain how I can be sure whether it's the clutch or the overdrive that has the problem.

[Doig]

On the later J type overdrives I think you can remove the casings to see the internals. Not sure however if you'd be able to check the conditions of the clutch cones though.

I hope I haven't experienced overdrive clutch slip (although I have an annoying recurring judder when pulling away in 1st) but your friends problem sounds exactly like the clutch slip I had in my old Avenger - but thats another story.

[Alex]

try putting car in second and see if you can let the clutch out with the brakes on. When my cone clutch in the overdrive went it was a lot more intermitent than a normal clutch slip.

[Crockett]

I checked the fault diagnosis chart in the manual and it only lists four, for overdrive faults:

o  Lack of engagement (No - it engages fine)
o  Lack of disengagement (No - it disengages fine)
o  Clutch slip when overdrive selected (Yes but also when not selected)
o  Clutch slip in reverse or free-wheeling when overdrive selected (No)

So basically it seems to be none of those. That almost leads me to think that the clutch slip isn't overdrive related. Could the overdrive clutch be slipping even when overdrive isn't engaged? I don't know enough of how type J overdrives work, to be able to answer that. One thing I'll be doing over the bank holiday weekend is lots of reading up on type J overdrives..

I'll try that 2nd gear (with the brakes on test) and see what that reveals. If it slips then I'm still not entitrly certain how I'll know where the problem is.

[Deleted User]

It can be overdrive clutch slip.
There are TWO cone clutches in an overdrive and a unidirectional, but people rarely look for the internal cone which sits on the annulus,- only the external cone which contacts the brake ring.

The symptoms you describe could easily be caused by a defective unidirectional, and this happens when the overdrive is in fact "disengaged".
Just because you tell it to run direct ratios doesn't mean there's not a clutch in the overdrive transmitting drive. This is one of the weak points of the overdrive system, because if the unidirectional clutch is faulty or you break a sunwheel (the pinion in the middle of the planets) you get either no drive or slippage.

[Crockett]

Okay. That makes things a little bit clearer to me. I also looked at the description and diagrams in the BL workshop manual which makes understanding your comment much easier as I can now see what you arte referring to.

I am puzzled though, as the diagram (attached) seems to show that power transmission, when the overdrive is engaged, bypasses the unidirectional clutch via the sunwheel, planet gears and annulus route. When the overdrive is disengaged then the power  transmission is via the unidirectional clutch and the annulus route, with the cone clutch and annulus preventing the unidirectional clutch from allowing freewheeling. Do I have that right?

Based on this, would the clutch slip problem be exactly the same regardless of the overdrive being engaged or not? If not then this may help me to decide where the problem lies. How's this for an idea - find a hill and compare direct 4th against O/D 3rd, with a heavy foot? I would have thought it unlikely to have a worn cone clutch AND a broken planetary gear. If the symptoms are the same for both direct 4th and O/D 3rd then I'll start my investigations with the main clutch.

Otherwise the most  useful thing in this exercise will be a coin, which I'm going to need to toss in order to decide which one to check out first :)

[Deleted User]

hmmmmm....usually an overdrive clutch problem is accompanied by a bit of shaking and vibration. Also it's very intermittent.

Remember when in Overdrive the difference of speed between the mainshaft and annulus makes the unidirectional non functional in drive (maybe not so obvious!).

When out of overdrive the gears of the sunwheel and planets being angled force the clutch back onto the annulus with a force proportional to torque applied.
Obviously if it can, this could overcome slippage and it works again.

A main engine clutch (low clamp load) usually manifests itself by slipping at the slightest touch of the clutch pedal, but particularly low revs where there is max torque.

[Nick Jones]

Dunno about overdrive slip, but in my experience normal clutch slip is worse in higher gears and the car will often drive normally in the lower gears at first.  For this reason I would be inclined to blame the overdrive.

Nick

[Crockett]

Well - here is no vibration (in fact it slips very smoothly) and the problem can be duplicated more or less at will, by accelerating hard. It seems most noticeable when pulling away from stationary but can also be duplicated when in 2nd gear under heavy acceleration and in 3rd when climbing a steep incline.

Funny you should say that even touching the clutch would worsen any main clutch slip. I seem to remember observing something like that at one point. Certainly, when I have experienced main clutch slip in the past, it was worse when pulling away in the lower gears or in higher gears when climbing hills, when torque would be at its highest.

I think my best course of action would be to try the direct 4th versus O/D 3rd test, up a steepish incline. I think if the slip behaves in much the same way (direct 4th and O/D 3rd are pretty close ratios) then it has to be the main clutch that's at fault. Such a test seems to make sense to me, anyway. I guess we'll see what happens in practise :)

[trackerjack]

Okay when I recently had the engine and box out of my car (Jtype) the box hit the ground hard on the drive flange, despite solenoid working correctly the overdrive does not engage, is it rammed into the cone and can it be freed?

[Deleted User]

I doubt very much if an OD problem can be caused by dropping the box.
The only thing you can do is crack the case or break the solenoid off.
Did it work before?
There's about 500kg force pulling the clutch onto the brake ring and there's a fat lot will resist that. (although I have seen the annulus corrode onto the clutch)
The number of OD faults with J type are fairly limited but they usually come with a blockage or simple old age.
There is an advantage,- you can get at pretty much all the valves, oil pump and filters from underneath.

[Crockett]

Another problem they also suffer from is the poor manufacturing of the later units. Type J overdrives manufactured after 1978 apparently use a lower quality centre for the unidirectional clutch, which tends to wear out after about 30,000 miles, resulting in clutch-slip symptoms. (http://www.canleyclassics.com/infodatabase.asp?article=overdrivesjtype)

[Deleted User]

[quote by=dd829 link=Blah.pl?b=2000,m=1178387452,s=14 date=1178546958]Another problem they also suffer from is the poor manufacturing of the later units. Type J overdrives manufactured after 1978 apparently use a lower quality centre for the unidirectional clutch, which tends to wear out after about 30,000 miles, resulting in clutch-slip symptoms. (http://www.canleyclassics.com/infodatabase.asp?article=overdrivesjtype)[/quote]

Actually they don't wear out they are just complete rubbish!
I always put the early ones in, but they are not cheap any more.

The centre part for cheapness was made out of a forged material which has unmachined ramps, so the little rollers stick in one spot and wear a tiny round spot into what should be a ramp.
As the cage tends to wear a little, it then stops working altogether.

This became a giant problem in production on Ford transits, which as luck would have it often were used as ambulances with all the excess weight  ::)

The later plastic cages stopped this happening, and that's all there is today  ;D

[Crockett]

The latter ones not as good as the originals? That's what's called "progress"  ;D

So, assuming it does turn out to be the UDC in the overdrive that's causing my clutch-slip problems, and I order a replacement UDC, what am I likely to receive? I guess I don't need worry for another 30,000 miles  :-/

[trackerjack]

[quote by=GTEVO link=Blah.pl?b=2000,m=1178387452,s=13 date=1178523377]I doubt very much if an OD problem can be caused by dropping the box.
The only thing you can do is crack the case or break the solenoid off.
Did it work before?
There's about 500kg force pulling the clutch onto the brake ring and there's a fat lot will resist that. (although I have seen the annulus corrode onto the clutch)
The number of OD faults with J type are fairly limited but they usually come with a blockage or simple old age.
There is an advantage,- you can get at pretty much all the valves, oil pump and filters from underneath.[/quote]

It worked fine GT before I thumped the end on the ground when the tackle gave way! so perhaps it dislodged some sludge or something. I was just going to put another one on as I have three that all worked.

[Deleted User]

[quote by=dd829 link=Blah.pl?b=2000,m=1178387452,s=16 date=1178556049]The latter ones not as good as the originals? That's what's called "progress"  ;D

So, assuming it does turn out to be the UDC in the overdrive that's causing my clutch-slip problems, and I order a replacement UDC, what am I likely to receive? I guess I don't need worry for another 30,000 miles  :-/[/quote]

errr..............exactly >:(
They fitted NO END of defective ones to the MG LH units, then the FORD transit etc.
Luckily MGB ones are the same as the old A type 2000 too, and it made us no end of money too! ;D

If you get a new one today, it comes with a nylon cage and all the rollers are captive (so you don't need the tool or violin fingers to fit the darn thing!).

I never liked the new style ones but production is production and I'm told they work fine.
The rollers are forged too now, not machined on the ends.

I won't sell the good "old" ones, there's hardly any left.
Funny thing "progress" eh?!

[shenderson]

Clutch slip is usually worse in higher gears so I reckon the O/D is the problem.  When mine packed up I had virtually no drive in any forward gear but, as the UDC was still OK, reverse was not a problem.  I was able to reverse one side of the car onto the kerb and one rear wheel up onto my spare wheel so I could remove the O/D (I was still a student them and couldn't afford ramps!)

Steve

[Crockett]

Sounds more to me like it was actually the UDC that had failed. It would have been the cone clutch that allowed you to reverse, I think.

[Crockett]

GTEVO wrote:

...the little rollers stick in one spot and wear a tiny round spot into what should be a ramp....

The attached is not the best of photos but I think it's clear enough to show exactly what you described. This is the centre from the bearing of the overdrive I've been having problems. with.

It's now been replaced and just needs a proper road test. My first impression is that the clutch is no longer slipping but I now need to make sure the overdrive still works :)