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posted: 6/22/2014 12:01 AM

On rare occasion, old transmission fluid can help

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Q. I read your articles regularly and find them to be very informative. Your recent article on changing transmission fluid reminded me of a concern I have about my car. I have a 2002 Hyundai XG-350 SG with 115,000 miles on it.

The transmission is a five-speed automatic transaxle and it also has a manual shift mode. In the Auto mode there is a minor shift issue going from second to third gears, which I will describe as only mildly rough. It only seems to occur when I drive at a relatively slow acceleration rate, though not always.

If I accelerate at a reasonably fast/normal rate or even tromp on it, the shift is smooth and quick. All other automatic shifts are as good as new. And, in the manual mode, everything is great.

I am the original owner and sorry to say I don't know if my transmission fluid has ever been changed. If it was, it was many miles ago. My concern is, I recall reading somewhere that if the transmission fluid hasn't been changed for a very long time, replacing the fluid may not be a good idea because the new fluid is thinner and dirt free, compared to the old fluid. The implication was, one might be better off leaving things as they are.

I would like to change the fluid if I can do so with confidence that I won't be asking for future transmission issues. If I were to change, it would be a complete exchange along with a new filter. Hopefully you can provide some sound advice.

By the way, this car has been the most trouble-free car I have ever owned and I have probably owned a dozen or so.

A. It is possible that changing the transmission fluid could clear up your shifting problem. As I mentioned in my initial column, dirty transmission fluid is the leading cause of transmission failure, so it's best to keep it clean.

There are times when the fluid is so bad and the transmission so worn that changing the fluid cleans away the dirt that was allowing the transmission to work. The thing that you need to realize, in a case like this, is changing the fluid didn't cause the transmission to fail -- it just allowed to happen what was going to happen shortly anyway.

When the fluid gets dirty it starts wearing on all the clutches and other internal parts of the transmission. This creates an even more abrasive fluid. It is hard for me to judge without seeing the car whether you might be in this type of situation or not.

If your intention is to keep the car whether or not it needs a transmission, I would take the chance and get the fluid changed and then keep it clean.

Let me know how it works out.

• Douglas Automotive is at 417 W. Main St., Barrington, (847) 381-0454, and 123 Virginia Road, Crystal Lake, (815) 356-0440. For information, visit Send questions to

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