I have a 98 with a 4.6L and the 4R70W tranny. The other day I noticed that I will be cruising down the interstate at about 70 mph and the tranny will down shift and the RPM's will hit about 3 and 1/2 for about two seconds and then drop about 400 RPMs and then kick back up. It is still pulling right and I do not think that it is changing gears what is it. I feel the actual shift at about 80 mph. What is this RPM drop?

 

you need to be more specific about what you are talking about...but it sounds like the torque converter clutch unlocking/locking. this will cause rpm fluctuations...completely normal, or at least from what i can glean from your limited info.

 

Not to sound like a smart @ss but I thought I gave very clear information. What more information can I put. I will try this way. At 70 mph and I hit the passing gear the RPMS will raise from 2000 RPMS to 3500 RPMS with the throttle in the same position the RPMS will lower 400-500rpms and then raise back up to about 3900RPMS and then shift gears. I have an extended warranty on this transmission but I wanted to know if this was normal or not. Believe it or not some dealer will lie to people about problems

 

That's normal.

When you step on the throttle the transmission will downshift from fourth to third, and the torque converter will unlock. After a few seconds the torque converter will relock. That's the 400-500 RPM drop. Then the transmission will shift back to fourth gear.

Mark

 

Thanks for the information. Reading this sight about my tranny has me worried