Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Automatic Transmission shifting

My KIA diesel has difficulty shifting into the highest gear especially when it’s cold. I live in the Philippines and mechanics who understand automatic transmissions are unavailable in my area. I have had the fluid and the screen replaced but it doesn’t seem to help.

What are the possible causes of this behavior?

Is there anything that I can do (personally) to improve the performance?

How cold is cold? Is whatever is going on a new behavior? Sometimes by design all transmission functions don’t operate until the fluid reaches a certain temperature.

If this is a new kind of behavior then one thing that would help is if you describe it better. What exactly does “has difficulty shifting” mean? It revs to high in the prior gear and then jerks or jumps into the next? It leaves the lower gear and the engine revs up high before the next gear really kicks in? It won’t shift at all?

A transmission specialist might be unavailable, but what about any mechanic with a decent scantool? Find the shop with the best scanning equipment you can and have the computer scanned for error codes.

We need more info here like, what year is the Kia, how many miles, ever been serviced before?? How often??


I’ve had the same problem for about six months. I also changed the fluid and the screen, and it didn’t help. For what it’s worth the car is an 87 Corolla FX-16 with 137,500 miles on it.
The problem is a new one, and in my car’s case it could be caused by a button on the shift that enables/ disables the overdrive gear. Could be, but I doubt it. The switch seems to work just fine. Why it’s there at is a mystery to me, seems like just one more thing that could go wrong.
The problem is generally minor in hot weather, say 75 degrees f and higher. The car will shift into fifth gear pretty easily and stay in fifth gear at highway speeds.
If the temperature is around 50 degrees, it takes about twenty minutes of driving before the car will shift into fifth gear, and it will maintain the gear at highway speeds. At forty degrees, it will shift into fifth gear after twenty minutes, but suddenly shift back into fourth gear after maybe five minutes, and stay in fourth gear.
Less than forty degrees it almost never shifts into fifth.
The CEL has not come on, and the reason might just be the age of the car - the CEL doesn’t come on unless there is a serious problem.

I offer this information since I think our two cars share the same problem and hope that the information will help you tranny experts diagnose the problem or at least offer suggestions. I never took apart a transmission and don’t plan on ever trying it.

The rest of the transmission seems fine, although it does seem to have trouble deciding on which gear to use while accelerating, especially uphill. The transmission doesn’t slip in any gear.

bknier1, does all of this sound like your problem, or do you have different symptoms?

The Kia is a 1998 (I think) with about 250 thousand km. I bought it used about 2 yrs ago from an outfit that imports used cars from Korea to the Philippines (where I live). I have no record of the service before I bought it.

I did not notice the problem for a long time since most of my driving was local at speeds below 50 km/hr so the top gear was rarely required.

I now make regular trips of about 20 km on a two lane road where traffic moves at 60 - 80 km/hr. Starting “cold” (about 75 F) the van will accelerate normally and shift through the gears smoothly but the last shift occurs at about 40 km/hr so that at speeds above 70 km/hr the rpms are above 2500. After about 5 km the transmission will shift (smoothly) into the top gear. After the that shifting to the top gear happens at 60 km/hr until the engine is shut off and cools.

At first I tried to figure out whether the problem was solved by the time the engine was running or by the distance the van traveled. Eventually I realized that I could predict the behavior based on the temperature gauge on the dash. Normal running temp is one line below center on this gauge (4 lines from the bottom) and shifting starts 1/2 a line below that (at 3 1/2). This seemed to work well. In the rain, for example, the temperature of the engine rises more slowly and it takes longer (in both time and distance) until the shifting begins.

But I recently had the fluid and screen changed and the behavior has changed. I have made only one trip but I went the entire trip (out in the morning and back in the afternoon) without shifting into the highest gear. That’s why I’m worried.

Everything else is fine. The lower gears shift smoothly all the time; it downshifts when I push it to pass–and, like I said before, below 60 km/hr you would never know there is a problem.

Kizwiki’s reply seems to outline the same problem with an 87 Corolla. My situation is different (better, actually) than his since it never gets very cold here.

Mechanics here are mostly of the backyard variety so finding someone with a decent scantool may be difficult. But I’ll give it a try.

Thanks for your suggestions.

B Knier

I don’t know this van or transmission (and probably wouldn’t eve if I was a mechanic since I doubt it is sold in the US). But it actually sounds to me like this might be normal behavior.

You do have to take what I am saying as a guess rather than specific knowledge of this transmission. But I think that what you’re taking to be the top gear is probably your torque converter lockup clutch (TCC). It is probably programmed to remain off until a certain transmission fluid temperature is reached.

However, it would be helpful to seek out someone with a good scantool that can access transmission functions.

Thanks for your input, it helped a lot. I finally solved the problem and it might work for you as well. My Kia’s computer–control unit (CU)–does not permit the transmission to shift into the highest gear unless the engine is hot. The CU has its own temperature sensor–separate from the dash gauge sensor. Both are located in the waterhose connector to the head. On my car the gauge sensor has one wire and the CU sensor has two wires. Your problem sounds similar and could be a faulty sensor or a faulty thermostat. Take it to an auto electric shop and they should be able to sort it out for you.