My wifes 3.3 auto Chrysler Voyager sometimes won't select a gear but sometimes it goes into gear, I'm driving off the estate and the engine revvs up because the car has jumped out of gear. I then need to select the gear again and again for it to go back in but then seems to be ok for the rest of the drive. Only seems to happen when cold.

I checked oil level a couple of months ago and it was just below max. I was told I have a leak under the car so checked engine and gear oil, had to top engine up a bit but gear oil was over the max a little?

Puzzled!

Any ideas?

Atleast you can check the fluid level!

Autoboxes will hold the lowest gears for longer when cold to aid start up.  By making the engine rev higher before changing gear warms the cat(s) up and the engine and gearbox. 

Does the selector lever move out of D into N when it comes out of gear?

Measuring fluid level in an autobox needs to be done with the car parked on level ground with the engine running with both the engine and autobox up to temp.  Before measuring while the engine is running pull the selector lever from P to L or 1 of what ever your lowest setting is then push it back to P.  Some manufacturers say to do this 3 times before checking the fluid level.  It gets the fluid moving around all the parts of the box .

Changes in air temp and autobox temp will make the fluid level rise and fall.

Park the car over some clean sheets of ply or a clean surface so you can monitor it for leaks. Autobox fluid should be dark red and it smells very different to engine oil.  If you have oil that is black and smells like it is burnt (some folk describe the smell as toast like) then I'm afraid your autobox has seen better days.

Sounds to me like something is slipping in the box.

I don't suppose you know if it is a GM transmission that is fitted your Chrysler?  If it is then it will be a 4 speed box with torque converter lock up in 3rd and 4th with an electronic brain with 3 modes, normal, Sport and Winter.  These boxes have been fitted to Vauxhalls and other GM cars (as well as some DIEsel BMWs) for years and are generally bomb proof for 150,000 miles.

If it is a GM electronic box it will have a removeable sump which you can drop yourself and change the fluid filter.  That may help esp if the filter is clogged.  A clogged filter will lower the fluid pressure which may cause something to slip resulting in loss of drive.

If it isn't a GM box then all you can do other that check and top up the fluid is take it to an Automatic Transmission Specialist for a service. 

Keep us posted

Andrew

When the engine revved up, the car came to a halt completely, like I'd taken it out of gear. The lever was still in D as was the light on the dash to it should have still been in gear. I took it out of D into N then back to D again but nothing. It was only after I'd repeated that for about the 4th time it went into gear and off I drove.

It did a similar thing back in the winter when we had the snow. I'd moved the car off the drive to get my car out and when I put it into R to get it back up the drive, the same thing happened. The engine revved but no drive. Again, I had to move the lever in and out of gear several times before it finally selected reverse and I got drive again. I assumed in that case it was perhaps the cold, maybe something had frozen (it was minus 9!) but it has happened 3 or 4 times since.

I'll try your method of checking the fluid. When I dipped it a few weeks ago the oil was a very clear light red so looked fairly new.

Perhaps once I've checked the level, if it's ok, I'll try doing a service to see if that helps.

Annoying thing is, when she had the Galaxy, there was a few great forums but there seems to be nothing for the Voyagers which is a shame because they are fairly simple, uncomplicated cars to work on so self servicing should be easy. Perhaps I should search for a bentley/haynes manual.

Cheers

Mike