'97 4.6 weird shudder

I'm no mechanic, but I'd start looking for something loose that starts vibrating at a certain rpm. Have you checked it when you're not moving? Have someone get in and run it up while you're looking around and feeling for something loose.

" snipped-for-privacy@earthlink.net" wrote in news: snipped-for-privacy@f14g2000cwb.googlegroups.com:

AT or MT?

Speedo reading? Or at any speed?

AT and it seems to do it under light accel, at about 35 mph and above. It's also an intermittant problem, I tried to "make" it do it but it does it when it wants to. Since my last post, I discovered that it comes from under the car, not under the hood. I'm thinking transmission? Thanx again....

Now try it in the D position (or OD off), OD not trying to shift. That is a symptom of Torque Converter lockup problem

How many miles on the car, when was trans last serviced?

Watch the tach... any noticable slippage?

I noticed it does it right around the 30 mph range (18-20,000 on the tach), under slight accel, especially when going up an incline. Seems like it does it just before the tranny tries to shift to a lower gear, like when the motor starts to lug. Sounds exactly like going over rumble strips. 49,000 miles on it, just bought it from a lot so I don't know when it was last serviced. thanx again for the replies...

I'm also with Backyard. Classic torque converter shutter. Look up TSB

Sounds like what Backyard said. I have driven a couple of vehicles where this has happened, have had the tranny serviced and things have smoothed out for awhile.