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Hyundai Sonata Auto gearbox erratic

Car is a 2.5 V6 Hyundai Sonata with about 100k on the clock. I have no idea what oil changes etc have been done on the car in the past.

A couple of weeks ago my Sonata autobox dropped out of top gear. On arriving home I checked the oil level to find it low. I topped the oil up and everything ran fine for the next week.

However I now have a problem.

I can start up fine in the morning and gearbox changes quite happily on my 40 mile to work. However if I spend a long time stop start in traffic (well about 5 minutes) The gearbox will drop down a gear from top with a jolt. It then proceeds to drive the rest of the way in that gear with no changes. If I stop and switch off and start again. It seems stuck in bottom gear until I get to about 3000 to 4000 rpm when with a jolt it will change to one down from top it then stays in that gear all the time.

However after been parked all day or for an hour or so I can drive nearly all the way home again without a problem until again it drops out of top.

Any ideas. The oil in the gearbox looks a little on the brown side. Would an oil change help?

I only need this car for about 3-4 weeks more is it likely to hold together that long for about 3000 miles?

Reply to
david.cawkwell
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Sounds like one of the shaft speed sensors is failing. They are quite common on these. A quick trip to a dealer to read the codes might reveal this - usually a 'Pulse A' or 'Pulse B' error.

Reply to
Andy Hewitt

Reply to
david.cawkwell

The snsors are not cheap, but fitting them is very easy. Depending on the exact box you have fitted (they vary a bit), it can have a pair of siamesed sensors on a single loom, or two separate sensors. They are bolted onto the top of the casing with 10mm bolts.

These sensors are actually very akin to ABS or Crank sensors. As such they are also around the £100 mark.

As they are a fairly common problem, I wouldn't opt for second hand either.

It's not likely to be dirt, they normally get weak and can't build up enough signal.

Reply to
Andy Hewitt

Andy, are you still going to be around in October? I may need some advice on a Ford autobox depending on what I find.

Don't go away.

:-)

Reply to
Conor

Ok been to Hyundai and they say it needs pulse generators. Well I didn't take the car in but that is what it says on the engineers report.

They quoted some silly price of 317 pounds fitted.

Is it possible to get these pulse generators from any other source? Like a gearbox specialist who is likely to charge a more reasonable figure?

Andy Hewitt wrote:

Reply to
david.cawkwell

If it's a pair then that's about right I'm afraid. Probably about £100 each, plus some labour, usually an hour for diagnosis and fitting £60? + the VAT.

They are easy to fit though, so you could do them yourself, or get a mechanical mate to fit them (a 10mm bolt on each one). You'll need to return to the dealer for the code reset though.

You could try Auto Transmission specialists, but Hyundai use a rare American made box, and it's hard to find anybody outside the dealers that can fix them. IIRC there was only one company that was listed for repairs by their extended warranty company.

Any experience I had of independent repairs was not good though. We found a specialist in Watford that would tackle them, but tended to f*ck up more than they fixed.

Reply to
Andy Hewitt

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