Feels like driving on a rumble strip.

[workinmanfred]

I have a 95 Crown Vic LX(not police car). 120K miles. I have a "rumble" in the car while trying to maintain about 35 or 40 mph. It's not at the shift point. It feels like you are running over a rumble strip. If I speed up or slow down it goes away. I have replaced plugs and wires. Maybe the COP? Anybody have any ideas? I hope it's not the tranny. Tranny is full and still a nice red color.

[Blue)(Fusion]

It COULD be the transmission. To help diagnose, get up to the speed in which the rumbling occurs. While holding the accelerator in the same position to maintain speed and with no other cars around, lightly press on the brake pedal. You just want to lightly press the brake enough to make the brake lights turn on but not actually start braking. When the brake lights turn on, the transmission disengages the torque converter clutch. When this happens, the RPMs will increase slightly but speed will remain unaffected. When this happens, if the rumbling goes away, it is your TCC slipping.

The TCC is known to wear out and when it can't grip well enough, it will cause this effect. It can also be caused by bad automatic transmission fluid. If you are not using strictly MERCON V, it is very likely. Dexron III/MERCON is NOT the same and does not contain the required friction modifiers. Anything that says universal is not going to work. There are concentrated friction modifiers on the market you can try, but if you find out it is the transmission after that brake test, then try replacing the fluid completely with fresh MERCON V first.

[Dreyko]

The same thing is happening on my 04 Civic. I had the hardest time figuring out whether it was the road or the car. After listening to it for a few days, and narrowing down the space it happens in, I believe it is my car as well. It might be just in the early stages though. Is there something I can do to get it fixed now cheaper, or should I just wait till the whole thing goes down, then get it fixed? I'm just wondering what would be my best bit fiscally. Thanks!

[Blue)(Fusion]

Did you try the lightly touching the brake while holding constant throttle when your symptoms occur? If it goes away when you press the brake pedal just enough to make the brake lights go on, then your TCC is slipping.

Try new ATF first. If ATF is worn, this will solve it. Use ONLY MERCON V Automatic Transmission Fluid (ATF). Never Use MERCON/DEXRON III or anything that says "multi-vehicle." Castrol, Valvoline, and of course Motorcraft MERCON V work well and are cheap enough.

I dropped the pan myself and removed the valve body to get as much fluid out as I could. I could have drained the torque converter too, but my fluid wasn't THAT old. After cleaning the valve body and letting the transmission drip out over night, it took about 9 quarts to fill it back up.

If the ATF refresh does not solve the problem, you may need a new torque converter.

[DeltaP]

Reply to Dreyko: Honda uses their own special trans fluid also. Best bought at Honda. Not the same as Mercon V. HTH

[Dreyko]

Yeah, I drained and refilled 3 quarts of Hondas DW-1. However, the noise is still there :\.

[Blue)(Fusion]

Whoops I didn't catch the "civic." My mind read "c-vic" as in crown vic...

[workinmanfred]

I just wanted to post a reply about my tranny problem. We dropped the pan and drained the torque converter and replaced filter and fluid with Mercon V (12 Quarts) and that fixed my problem. You guys are awesome. A tip: Dont use the cheap ass rubber gasket from Autozone or you'll have a nice slow drip from around your tranny pan.

[Blue)(Fusion]

Thanks for letting us know how you fixed your issue. Drive safe