how do i change the gearbox oil on my cvt?
 

i have a 1987 volvo 340 dl with a cvt transmission ...the car recently started making loads of noise as tho it was stuck in low gear or in wrong gear at least .....i dont know much about cars but the engine looked fine so i checked under the car and there seems to be a slow leak from the transmission i am asuming this is the cause of the problem and want to top up the oil but dont know how ....any ideas?....

Hi Spike,

I must confess that despite being register keeper for the 300 series, my knowledge of the CVT system is somewhat limited. When you say loads of noise, as if the car is stuck in a low gear, I assume you mean the engine speed is excessively high, compared with how it used to be?

In that case, the oil probably isn't your issue, although it is well worth checking the level of that anyway. I suggest you get hold of a Haynes manual if you don't already have one to help you with that. I know of a man who has 2-3 spares which he'll be happy to send out for a nominal fee, if you want one.

First question, just to insult your intelligence...you've not hit the 'low gear hold' switch by accident, have you?

The CVT box is controlled by engine vacuum. Vacuum is used to move the 'cones' in which the belts run around, and if this vacuum is not controlled correctly, you will get an incorrect gear ratio.

As I mentioned earlier, my knowledge of the CVT box is limited. I have a copy of Mac's excellent CVT manual, which I will consult if you want some more information on the subject. It's getting a bit late for tonight!

cheers

James

hi ...lol no the low gear hold switch is not on...since i have posted this i have had my uncle who is a mechanic look at the car and check oil levels and so on...he says he cant find anything phisicaly wrong with the car and was actualy pretty impressed with the engine condition:) ..however he knows nothing about cvt's and his best guess now is that the belts may be the problem as he thinks they may be slipping or not alined properly....but he refuses to touch em as he is unfamiliar with the cvt system........so if anyone has any idea howmuch this will probably cost me to put right (asuming that is the problem) as i have a nasty habit of being ripped off....i checked the cars service history and it had new belts fitted in 2001 so i dont think they should need replacing so much as adjusting????/....i hope

the belts whine when worn and you might geta vibration if very worn , are they cracked on the V part which rubs the pulleys? cracks can be 66% through before they are a problem . Belts last about 20000 - 30000 miles . Belts wouldnt cause excessive noise ... Is the engine revving to much or is there a rumbling grating worn bearing sound ?

its reving too much like it isnt finding the right gears

How long have you had the car? CVT's rise up to the maximum torque of the engine and pretty much sit there until you ease off or they run out of ratio. That's not far off 4000rpm and can make the engine sound like its really screaming if you're not used to it. However, if you've had the car some time and its got worse then obviously something's gone wrong.

It may be a gearbox fault or it may be a clutch fault. If you park the car on a very level surface, and put the car in gear with the engine idling and then raise the revs very slowly, at what RPM roughly does the clutch start to engage. You will feel a very slight juddering as it does this. Should be roughly 1100-1200rpm, in other words, not all that much above idling speed. If its significantly higher then your clutch is slipping/worn and you'll probably need a new one.

Other than that it could be a vacuum leak. A quick check to see if the change up is roughly working is to go along fairly slowly, say about 20mph and then switch the low gear switch on. The revs should quite quickly rise up and you should get an accompanying increase in engine braking. If you get that then chances are the transmission is changing up as it should.

havent had it that long....2 month ish... but it has definatly noisyer than when i got it it is hard to know if it is over reving as there is no rev counter lol just a speedo and a clock

tried to do that thing you said where you engage the low gear hold at around 20mph...didnt notice any increase in revs but thats the bulk of the problem....they allways sound too high.....and there seems to allways be a lot of engine breaking.

It sounds to me like the classic CVT problem...the one I've heard more times than any other. Sadly I've not yet got my head around the CVT box well enough to remember what it is, but a failed four-way valve sounds familiar. Can anyone else pipe up along these lines while I find time to read Mac's article...?

cheers

James

Right, it's silly o'clock in the morning and I've got to rack my brains but here goes.

Get the bonnet up and sit in the car with the window open and listening carefully. Put the car in neutral (neutral, remember, not park - never ever rev a CVT in park, you'll burn the clutch out in minutes) and slowly increase the revs to approx 2-2500 rpm. You should hear a pronounced click from the tachometric relay in the 4-way valve. If that valve clicks then fine, if not then you may need a new tachometric relay.

Pull off one tee-piece that holds the two of the thinner pipes that come off the 4-way valve and carefully blow down it. You should be able to get air down them and then it should blow back at you when you let go. Bit like blowing up a balloon. If its too hard then take one pipe off the tee piece and then repeat with the other side. Repeat with the two thicker ones.

To do the rest of the tests you'll need an assistant. Pull off the tee-piece that leads to the thicker pipes with the engine running and the car in neutral. Verify that there is no vacuum coming from the valve. Then get the assistant to press the brakes hard. There should be a click and you should feel vacuum. The engine may want to cut out because you're introducing an air leak by pulling off that pipe...if so don't worry about it, just get the assistant to let go quickly and the engine will recover :) Then release the brake, and switch on the low gear hold switch and verify the same thing happens.

Then pull the thinner pipes now and get your assistant to do the revs test. There should be no vacuum at idle. Sit in neutral and raise the revs up until the valve clicks and hold them there. There should be a vacuum felt there.

Erm I think that's it...if you get any trouble let us know. I've deliberately not put any causes down because there are so many of them and I want you to come back to us with what you've found and then we can work it out clearly.

Hope that helps.