B18 Overdrive Clutch Slipping

[maggie]

Hi,

The overdrive clutch in my Amazon Estate started slipping over the w/e. After 2hrs of driving on the motorway yesterday then switching out of O/D and back in after a roundabout the O/D would engage (light on and shift feeling) but the cluch was slipping.

After leaving the car for 30 minutes the problem has gone away.

I consulted Mr Haynes manual who suggested:

Low oil level - checked and OK
Faulty or Badly Adjusted Operating Valve - Any tips on how to do this are most welcome!
or Worn Cone Clutch Material - As it does not slip when cold I assume this to be ok.

Any thoughts, similar experiences or remedies most welcome!

[Clifford Pope]

I am not sure which kind you have, but I have a bit of experience with the J-type on a 240, and also an A-type on a Triumph 2000.
Basically there are two kinds of slipping:
1) when it is reluctant or slow to engage, caused by the oil pressure being slow to build up. This is most commonly caused by low oil, old oil, oil filter clogged, or worn pressure valve O-rings.
2)slippage of the cone clutch, caused by wear.

The first is characterised by being more likely when going slowly, or downhill. The second commonly happens when you apply torque when the O/D is already engaged, but you feel it starting to slip unless you ease off. Overheating, eg caused by not noticing it beginning to slip,will make it worse.
It may first show itself only when you apply torque too soon after engaging, but be OK once engaged. One is supposed to declutch, but I never have.

My line of attack would be:
Clean the filter. This may need fabrication of a simple tool to unscrew the plug - depends on model as to what's involved.
Renew the oil
Check the solenoid adjustment and operation
Try overfilling the box slightly, by tilting the car away from the plug.
Try a thicker oil
and lastly,
Think about removal and overhaul.

[Mike Arnold]

I had a similar problem many, many years ago and it turned out to be the main clutch (ie not in the Laycock unit). It was only when o/d was engaged that the torque demand was high enough to slip the clutch itself. The o/d unit itself was not at fault.

[GL]

Solver the problem by switching from 30W oil to Castrol 80-90 Hypoil.

[TomTom]

Interesting topic:

mine starts to slip after about 2-3 hours hard driving, and always when torque is applied, usually going up a hill. It will give me 2-3 chances, slipping into 4th and regaining overdrive when I take my foot off, and then it will finally go out and stay out.

However a break of about an hour will make everything right again. I'll check my cone clutch and try the tip of changing the oil weight.

Tom

[maggie]

I first posted this thread back in the summer - since then I have done nothing mechanical to the car. I now belive the problem to be low oil pressure to engage the O/D caused by low viscosity of the oil when it get really hot. During all the recent colder weather I have not had a problem with this at all. I think I will go down the route of heavier oil - although I do want to find out why all Volvo publications say to use 20w/50w and all Triumph publications say EP80 /90 when they both seem to use Laycock D type O/D - Anyone know why?

[Clifford Pope]

It is curious. I have asked this question whenever the topic of overdrives and the correct oil comes up.
Volvo persisted with the difference down to the J-type overdrives on M46 boxes on the 240 and 740. Here they specify ATF rather than 20/50.
Have you ever read the information at Brickboard by the overdrive guru, Duane Holberg I think he is called? When I suggested curing slipping by swapping to 80/90 a la Triumph he was quite adamant that it would cause severe damage. I swapped all the same, and 50,000 miles later the overdrive continues to work better than it ever did before.

Another oddity is the Volvo advice to declutch when engaging or disengaging overdrive. Triumph offer no such advice, and go further than Volvo in allowing engagement in 3rd and sometimes even 2nd gear. The torque from a TR6 flat out in O/D 2nd must be vastly greater than in the Volvo. No one would dream of declutching in a Triumph - clutchless engagement is the whole point of an overdrive in my opinion.

[GL]

I and many other people I know use 89-90 in overdrive and gearbox. It just seems to engage more positively and it doesn't kick out of overdrive any more. I believe that there is less friction with higher viscosity fluid. As I live in Las Vegas and only see snow on the mountains in the distance, heat is a problem for me. If I lived in cold weather, maybe the thinner oil would make sense. 89-90 DOES NOT cause ANY damage to tranny parts in my experience.

I clutch out of but not into the overdrive as I don't like jolts and I think this causes less wear and tear on the driveline. That's just my opinion though. The overdrive was designed to be clutchless and I know of many people who never clutch in or out and have had no problems.

[Clifford Pope]

I should add I don't just flip the button regardless. With years of practice I instinctively adjust the engine speed as the O/d bites. ie engaging, I ease off, disengaging I increase the revs a little. Done slickly there is no jolt at all.