Sometimes not in overdrive on the highway. How come?

**SiskMan** · 11-04-2014, 08:05 AM

I bought this 2000 WS6 A4 about a month ago with 118,000 miles and it runs great. I took my car on a trip yesterday and it drove fine. I just did a fluid and filter change a few weeks ago and the car shifts great. Driving around, beating on it, whatever the case its always in the right gear with no slipping or anything. However, sometimes when I am on the highway sometimes the rpms will be a few hundred higher than normal. Then when I let off or coast down a hill it will "lock" into overdrive. It will stay in overdrive after this for most of the time. Then I will look back down and it will be in 4th again with the rpms a little higher. Shouldn't the car be in overdrive on the highway the whole time when just cruising? Or am I just being paranoid?

Car is supposed to have a shift kit but I have no way of knowing. It shifts relatively firm I guess. I have never ridden in another car like mine to compare.

**JayTA98** · 11-04-2014, 11:22 AM

is the SES light on? Have you checked for codes?

**Too Fast** · 11-04-2014, 02:12 PM

It's possible you have a torque converter lock-up problem. So what exactly happens? You're driving at normal operating temp on the highway, what does the RPM do? Your torque converter (TCC, torque converter clutch) should lock up in 3rd and 4th gear, over ~45 MPH. When just cruising, you can feel it and watch the tach drop a few hundred RPM when it does, which should be right away. When you give it some gas, the first thing the car will do to help you accelerate is unlock the TCC, then if that's not enough, downshift to 3rd or 2nd, depending on your right foot and current speed.

When you let off the gas in gear, like coasting down a hill, the fuel injectors almost shut off, you may be feeling that, it's like a light application on the brakes.

**SiskMan** · 11-06-2014, 07:56 AM

Well it hasnt done anything like I described since I posted this. It has been locked on the highway ever since. I think it might be just the thermostat not letting the car warm up like it should. I doubt its ever been replaced. The trans is shifting fine now and doing what it should on the highway. Even up a super steep hill it stays locked with no problems. Sorry guys didn't mean to cry wolf here.

**0rion** · 11-06-2014, 08:49 AM

just in case.....what known mods are done to the car? There's a couple things that will keep that converter from locking up or cause it to unlock randomly. Is it the the stock stall converter?