It doesn't happen all the time but occasionally. I have noticed that when my Mark VIII is driving around 40 mph the rpm dropped to 1000rpms this is apparently normal for this car the overdrive is kicking in to conserve gasoline. I will cruise at this speed for a while. The problem I have noticed is that when crusing at 40mph the rpm drop if I then ask the car to go faster I hear a grinding noise. It sounds like the ridges you run over on the expressway to tell you to slow down. What should I do? Is my trans going out? Is there a part that I should immediately change? Could it be a vaccuum leak? If so where should I look? If it turns out to be my trans can I pick up a new one from Ford and how much can I expect to pay? Thanks for all the advice. You guys are great.

Sounds like torque converter shudder to me.

What year is your car?

It sounds like the ridges you run over on the expressway to tell you to slow down.

Take about 13 quarts of Mercon V and call me in the morning.:D

You should start with a transflush. Most dealers will have the Motorcraft MerconIII/V combo fluid, so contamination won't be a problem. If you use straight Mercon V, you must flush all of the old fluid out. Mercon V is not compatible with Mercon III. It may also take up to 50 miles of driving for the condition to go away. If it doesn't, you will prolly need a converter replacement. If its that, I recommend the Marauder converter.

And you might as well put a new trans filter in there as well. One other tip I use is when in traffic at 40 MPH and under I puch the shifter button that stops the tranny from going to 4th ( it stops the hunting syndrome) and provides a much better performance experience.

Yup, T/C shudder.


Like everyone else stated.... have the ranny FLUSHED with MerconV, and have a new filter put in. While your at it... 1-2, 2-3, and OD shift accumulators, should be checked/ replaced.


Mike

Actually Merc V is compatible with Merc III, but Merc III is not compatible with Merc V.

In other words, if a trans is full of Merc III and you add a even quart (or less) of V you will have some major issues. But when putting V in a trans, its not necessary to flush all the III out, the small amount left over is fine and wont cause a problem. Just make sure you drain the TC also!

A good flush, not refill, would be necessary to get the real value out of the more expensive V though. So, if you take it to a shop, make sure the don't just drain the transmission and refill it. They must drain the large torque converter and flush the cooling lines too.

Also- just make sure your plugs and wires are good. That can also cause a bit of a rumble-strip type miss.