Auto gearbox "snatching" problem

5,000 miles ago, I had a reconditioned auto gearbox fitted to my Citroen Xantia.

Everything was fine until last week when I noticed it has started "snatching" at the drive transmission.

This only happens from a standing start. With the gearbox in Drive, I take my foot off the brake, put the usual degree of revs on and the car will move forward gently, but not as strongly as I'd expect.

Add more revs and a couple of seconds later, the car will jerk forward and take up the transmission power fully. After that it's fine until the car comes to a standstill again. Once moving, subsequent gear changes are perfectly normal and smooth.

Can anyone advise me where the problem might be? In the gearbox, the torque converter or perhaps the automatic clutch (which is integral to the torque converter anyway, isn't it?)

regards andy

snipped-for-privacy@hotpop.com

Reply to
andy
Loading thread data ...

I assume that you've checked the fluid level in the torque converter, as per your manual? Could just be a slight leak which needs rectifying.

Reply to
Malcolm Stewart

Further to that, I fitted a scrappy autobox to my Carlton (not quite the same I know but the worky gubbins inside follow the same principles I believe) a couple of months ago. It took a week or 2 of checking and topping the gearbox up every so often before the fluid level stabilised. Despite filling it to "full" each time, it would drop below minimum and do funny jerky things (kickdown when cold and going uphill was its favourite) when there were no apparent leaks. The fluid level is rock solid now.

I have since heard that this topping up is reasonably normal, and it takes some time for the fluid to work out all the airlocks and get fully round the system if it has been drained.

5000 miles is a fairly long time though.

Douglas

Reply to
Douglas Payne

No - the torque convertor *is* the 'automatic clutch' in the way it operates - below certain revs it transmits no power, and as the revs increase it allows the engine to run faster than its output - then as the revs increase further it gradually brings its output speed up close to that of the engine.

It sounds like one of the gearbox clutches is sticking - it should engage firmly when you select drive - this is why most cars will leap forward slightly if the brakes aren't on. It could either be a sticking clutch or low fluid pressure. I assume you've checked the fluid level is correct?

A torque convertor fault would show up in other ways - not least in the same effect in reverse.

Reply to
Dave Plowman

Weird. I've never come across this. Were you adding the fluid with the engine running or stopped? The fluid is pumped round at pretty high pressure, so air locks shouldn't be a problem.

Reply to
Dave Plowman

Mixture of both running and stopped I think. I didnt have any idea of the history of the 'box though. The written off Senator it came from had been crushed shortly after someone bought the engine so I didnt know how many miles it had done. Plopped it in my car and it worked so I was happy.

The drop in levels was more pronounced in the beginning, got more subtle over maybe 1000 miles and now it doesnt seem to lose anything.

My boss said he'd had similar experiences with autoboxes on a couple of Volvo 240's he had and advised me to keep a close eye over 2 or 3 weeks.

One thing I did notice was that when I had the torque converters off (got a spare one with my scrap box) they seemed to have a lot of fluid in them and they drained very very slowly, and once you emptied it and sat it down again, more fluid would trickle in to the hole in the middle from somwhere. This worked over several draining "cycles".

I don't know what the internals of a torque converter look like so theres probably a good reason for this behaviour and I wondered if this was the reason for my fluid level dropping.

Douglas

Reply to
Douglas Payne

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.