Staff Car Sagas
Danny’s 29k-mile minter… has a few issues
Read the latest progress on the PC team’s projects.
When I bought this car, I thought it was too good to be true. How right I was. Don’t get me wrong, it is still a beautiful example of a rare car, but it’s time out of use has not been beneficial to its health. I managed to get it running, driving and stopping well enough to pass an MOT. But driving it home, it was obvious all was not well in the CVT (Continuously Variable Transmission) department.
I got in touch with the always helpful DAF Owners’ Club, for the 340 (especially in CVT form), is really a DAF underneath. It put me in touch with a wizard called Graham Meinert who has been working on cars with belt transmission for 35 years. He agreed to come and have a look.
I am ready and willing to attempt almost anything in the privacy of my own workshop, but rummaging around in the nether regions of a CVT equipped Volvo gives me the fears. It is a brilliant idea though, and once I learn it I will be all over it with spanners. Until then I am simply going to learn it as best I can and it is worth learning.
CVT varies the drive ratio continuously by changing the operating diameters of two pulleys that are linked by a (on the 340) pair of substantial drive belts. The transmission can alter its ratios without any interruption of drive. It has the comfort of an auto box with the efficiency of a manual. No torque converter is used so there is no hydraulic slippage. Throttle pressure creates an instant response providing smooth and rapid acceleration. That’s the theory at least. It should work a treat, in fact it has been proved in Formula 1. So successful was Williams’ use of CVT in its F1 car on test in 1993 that the FIA effectively banned it for the 1994 season – it was that good.
Not a belter!
Mine really wasn’t that good. I was revving at 4000rpm and not managing to get over 40mph, it was like being locked in second gear. Transmission was continuous, but not very variable. So Graham popped in to the PC workshop for a tea and a look. The first thing he did was condemn the belts, which were cracked and wouldn’t last more than a 100 miles before destroying themselves. A call to Danny Muijtjens at dafhobby.nl had new belts delivered in three days. Next it was time to look at and adjust the clutch. On the 340 the engine drives the primary pulleys through a centrifugal clutch and propshaft. The belts then drive from primary to secondary pulleys and these, in turn, drive the rear wheels through a differential.
The automatic centrifugal clutch has a vacuum-operated servo which is activated by the direction selection lever so as to raise the clutch engagement speed except when forward or reverse are fully selected. It sounds a bit complicated but actually it isn’t when you see it in action. For instance, really there are only two items on a CVT that should ever need adjustment, namely the rear pulley gaps to
‘It was revving at 4000rpm and not getting over 40mph’
maintain correct belt tension and position (Graham did this after he fitted the new belts) and the clutch clearance.
Boomerang shims!
The clutch is conventional in that there is a clutch plate gripped between a steel pressure plate and the rear face of the flywheel. However, where in a conventional car, the clutch is normally closed and the operation of the foot pedal opens it, in a Variomatic, the clutch is open when the engine is at rest or turning slowly.
So Graham grabbed a feeler gauge and bit by bit measured the clearances between flywheel and clutch plate and clutch plate and pressure plate all the way round the clutch plate through a rather convenient hatch. Clutch adjustment is achieved using shims, shaped rather like boomerangs, which are adjusted with Allen keys. It is fiddly and time consuming but not complicated once mastered.
The complication for me was that the car still revved its nuts off. Graham and I replaced the centre panel mounted switch that locks the CVT in high ratio… no change. Then Graham changed his focus to the vacuum system that controls the pulleys. He replaced ten vacuum switch. Still no change. ‘It must be electrical’ said Graham. A check with a multimeter found no feed to one side of the switch. So we pulled out the dashboard to look at the wiring loom that controls the vacuum switch and servo. Here we found the culprit. A fossilized mouse, still with its teeth in a live feed, had fried some of the loom. New wiring in and still no joy though. By now we had been at work for two solid days of, mainly, swearing.
Last throw of the dice
We had a look at the tachometric relay that controls the feed to the vacuum switch. We carefully took it apart and, sure enough, the burn marks showed us that the problem was solvable. A specialist sourced a replacement circuit board that improved matters but it is still stuttering. I shall drive it and revisit after a week or two.
One essential change was the fitting of new tyres. With some pride, the vendor had explained that the Michelins on the 340 were the original items from 1983. I fitted a set of Falken Sinceras that look right and have a profile and width that will not to mess with the excellent handling.
danny.hopkins@practicalclassics.co.uk Bripart, britpart.com DAF HOBBY, dafhobby.nl Graham Meinert, 07543 076673