440 CVT Auto gearbox

Can anyone tell me where I can get technical and faultfinding information for the CVT autogearbox on my 1985 440CDi? Haynes manual only deals with 4-speed autobox. I am experiencing occasional violent snatching when selecting forward or reverse from neutral or park.The oil level is correct, and the car drives OK. I've overhauled several 340 auto belt-drive models but the system is not the same
Thanks

343GL

Hi sounds like you a serious problem there. The 440 is a fluid box as far as I understand, less it's an early one which were the same as the 300 series DAF belt driven jobbies.

Didn't think a CVT box has fluid, been some years since I blew my 340 up, from what I understand it's similar to the 200 series. If it's a fluid box it need either the internal selector bands adjusted or repaired and or the fluid pressure relief valves may have gone. You probably know, after you have tackled other autoboxes, if you open a fluid box you find a selection of bands with plates that look like ant farms in these there are sprung ball bearing relief valves. I'd suggest finding a good auto box specialist. Some boxes you can adjust externally.

Charlotte

Thanks Charlotte
It gets worse. Sometimes now have to rev. hard to get moving, just like a manual car with a clapped-out clutch, so you are probably right about plates and bands.
Bill

Don't know how you've got on with your problem so far, but information is hard to find for this box.

Suggest you take it to a transmission specialist. Gearbox definitely has oil in it, but is not like a "normal" auto box.

Parts are expensive, and second hand boxes are like the proverbial rocking horse ....... . it took 12 weeks for my mate to find one for his car.

A bearing and the pump was damaged in his, and parts cost would have been £1200, with labour on top.

hope this helps,
Regards,
Nick

[mollusk]

Evenin' all,

Situation normal - confusion reigns over the CVT.

Very difficult to find any information on the 400 series CVT - I don't know of any aftermarket publications that cover the subject and the Volvo factory 'green books' have long been unavailable. What info the main stealers have is computer based.
I will try to clear a little of the fog !!

Firstly the CVT in the 400 series is nothing like a 'conventional' automatic gearbox and nothing like the twin 'rubber' belt drive system of the 300 cars. (the only similarity with the 'Daf/Volvo 300' CVT is both types use a belt/s driving one or more pairs of variable diameter pulleys).
The 400 series has never been fitted with the rubber belt, twin pulley system.

The only 400 series cars to have the option of a CVT were those with the single point injection B18U engine (1.8lt).

As simply as I can describe it, the system works, by giving a seamless, infinite number of gear ratios (between set limits) by varying the diameter of a driving pully linked to a secondary pully by a belt of steel blocks (several hundred) carried on a laminated steel band (when together it all looks like a cross between a car 'fan belt' and a expanding watch strap!!). The whole package is enclosed in a transmission case which is oil filled.
The 400 CVT does not have a clutch (as the 300 system has), nor a torque converter (as has a conventional automatic). Instead the transmission is linked to the engine by a torsional vibration damper fitted to a modified engine flywheel.
Drive take up (and 'in gear creep') is through a multi plate, hydraulic, forward
clutch unit inside the gearbox casing. This clutch is operated by, and bathed in the gearbox oil - it is engaged by pump generated oil pressure controlled by a cable linking the throttle quadrant with the gearbox. (like a so called 'kick down' cable in a conventional auto box). To effect reverse, a separate reverse clutch engages an epicyclic gear train (reversing the direction of the variable driven pulley).
'Up shifting' is achieved by 'squeezing' the halves of the driven pulley together causing the drive belt to 'ride up' (effectively changing a small wheel turning a big wheel (low gear) into a big wheel turning a small wheel (high gear). The secondary pulley 'simply follows' opposite to the driving pulley. The secondary pulley passes the drive to a differential (conventional) and through driveshafts to the wheels.

343GL - your description of the problem initially sounds like a forward clutch failure - but reverse would be ok (different clutch) however if you have a pressure pump problem this would affect both clutches. Its is just possible you have a problem with the torsional damper that links the engine to the gearbox but I doubt it.
One possibility is a problem with the cable linking the throttle to the CVT - this controls oil pressure, which would affect clutch engagement. Note though - low oil pressure would also reduce the boxs' ability to change up (you would seem to be stuck in low gear).
The snatching you describe definitely point to clutch drive take up problems (most likely oil pressure related) rather than a pully and belt problem (pulleys won't move until you open the throttle).
If I had to make a suggestion (diagnosis VERY difficult at long range) I would go for a failing pressure pump - probably spreading contamination around the box. (if you look at the oil on gearbox dipstick can you see little silver particles in the oil). But do check the 'kickdown' cable first.

I hope the above makes some sort of sense,

Good luck - Mac. (mollusk)