340 CVT Problem

Post by **Ian Macaulay** » 25 Apr 2006 01:21 pm

Hi, I'm new to the forum but not to 340's - I've had about 5 or 6 of them over the last few years. I've just bought a 1990 340 Auto which has covered a genuine 28000 miles and is generally superb throughout. However, I have one concern in that for any given roadspeed the engine seems to rev too high (I've had an auto previously so I'm fairly familiar with them, however, the previous one didn't have a rev counter). According to the rev counter the engine is pulling 4500 rpm at 70 mph and this seems excessive. The transmission operates perfectly in all other respects, ie; kickdown, low gear old, engine revs decrease as roadspeed increases although it is slightly difficult to move away from stationary with a slight jerk. Any ideas or info would be appreciated. Thanks, Ian

Post by **redline** » 25 Apr 2006 01:24 pm

Hi Ian and welcome aboard . wjp01908 ( Will ) is our resident vario expert and your lucky in that he has just returned to the fold after a long absence , try and p.m. him if you get time

Post by **petefarrell360** » 25 Apr 2006 05:47 pm

Hi and welcome to the forum! I have a low milage Variomatic too, but as yet it's not on the road, so I can't be 100% sure, but I'm pretty sure at higher speeds they are fairly thirsty and high reving. You're lucky with a variomatic to have a rev counter, as not many do I believe, so sometimes other owners cannot be too sure of what figures they are at compared to speed. I seem to think someone else was rather worried at the high revs on the motorway, but sadly the variomatic isn't a high speed car, just a relaxing drive, most suited to town and country road usage. I'm sure one of the more knowledgeable vario owners can give you a better answer! Enjoy the 300.
Pete

Post by **wjp01908** » 25 Apr 2006 07:26 pm

Slight deja vue on this one - have a look at this thread:
http://www.volvo300mania.com/forum-uk/v ... sc&start=0

I seem to remember that the maths worked out that this was about right but if anybody has any better information......

As regards the jerk when moving off, the cvt has a centrifugal clutch. This means that the speed at which the clutch engages is a function of the speed at which the revs are increasing. The trick is to feed the gas in gently until the clutch bites and only then give it a bit of welly (the cvt will surprise at fast get aways - the upside of low gearing)

Will

Website · Post by **antiekeradio** » 25 Apr 2006 09:23 pm

As regards the jerk when moving off, the cvt has a centrifugal clutch. This means that the speed at which the clutch engages is a function of the speed at which the revs are increasing. The trick is to feed the gas in gently until the clutch bites and only then give it a bit of welly (the cvt will surprise at fast get aways - the upside of low gearing)

if I may step in; the trick is to have the clutch readjusted at minimal clearance. that way the clutch catches at 950 rpm already, instead of around 1050 to 1100. if done properly there won't be any jerky clutch action!

Greetings Wouter

Post by **Ian Macaulay** » 25 Apr 2006 10:20 pm

Thanks everyone, this would seem to confirm that its pretty well normal - looks like I'm stuck with 25mpg on the motorway then...

By the way, mine is 340 GL Auto, 1990 on a G plate and it has rev counter, clock in the centre console, heated seats (which work), electric front windows and mirrors and a top tint front screen. 28000 miles with a full history - not bad for £370 !!

Post by **petefarrell360** » 26 Apr 2006 12:31 am

Not bad at all, same spec as mine, except yours is 1990 not 1989, however you thought your low mileage was low, how's 10514! Enjoy it and look after it! Yeah the high fuel consumption on the motorway is one of it's downsides.
Pete

Post by **wjp01908** » 26 Apr 2006 08:18 am

Wouter has a point that this adjustment would smooth out the action a fair bit. In fact an overly jerky start might indicate a problem with clutch adjustment.

It is however out of spec and I suspect that it might cause some issues such as engaging (causing the car to creep) when running on fast idle (choke) and possibly with gear selection depending on other adjustments and state of wear.

Might a similar effect be achieved by simply adjusting the idle speed of the car - perhaps to the spec for the manual transmission.

Will

Website · Post by **antiekeradio** » 26 Apr 2006 09:52 am

hi Will,

the CVT versions have a slightly lower idle RPM, just for this reason. if you would adjust it to the MT idle speed, it would indeed be risky for the clutch.

normally, there is no problem with gear selection at any RPM lower than 2000. however, the clutch limiting mechanism does fails all too often.

what do you mean by 'out of spec'?? according to the workshop manual the 'air gap' between either plate and flywheel or plate and clutch plate, should be in the range of 0,1 to 0,5 mm.
Even experienced CVT mechanics (there are some left in holland) tend to fail on this point; quite a few think that 1,5 mm is OK as well (NOT!!)
at such gaps the clutch starts slipping slightly at elevated revs, wearing out very very fast.

connected are problems with CVT clutch lifespan; some people honestly think that a CVT clutch will only last for like 70.000 miles. (when adjusted timely and properly, it has a longer lifespan than a manual clutch!!)

Greetings Wouter

Post by **wjp01908** » 26 Apr 2006 02:33 pm

" the CVT versions have a slightly lower idle RPM, just for this reason. if you would adjust it to the MT idle speed, it would indeed be risky for the clutch."

Yes I know this - I was suggesting it as an alternative to Wouters idea of adjusting the clutch so that it engaged at about 950rpm.

By "out of spec" I meant adjusting the clutch so that it engaged at 950rpm - just above the 850rpm idle speed setting for the cvt. As you are probably aware it should come in at about 1100 rpm.

I think doing this might cause problems and agree with you that leaving things as they should be is the thing to do if you want long life from your clutch.

Regards

Will

Post by **ebdl** » 26 Apr 2006 03:05 pm

I would be very wary of setting the clutch to come in at lower revs simply because of the high likelihood of vacuum leaks and consequent idling problems. If you get stuck like I am at the moment, then you find that most of the time your idle is ok (but with a very rich mixture) but occasionally the vacuum leak seals up, the revs rocket and you can't engage drive until the leak comes back. I wouldn't want to make the clutch engagement too sensitive just in case... [edit - plus we all know the problems you can get with the Weber carbs]