1. Check the motor mounts.

2. Test as Shannon has described.

3. Does the overdrive work?? not just the dash light but an actual drop in RPM when OD engages??

The reason I ask is if the OD solenoid is fluid locked on, the cone clutch is held against the brake ring and will slip under initial load as you have described and also at the 1 to 2 shift point.

Since you are on not really safe tires and if the OD is on, do not reverse and test as follows. Ignition on, Engine OFF, in 4th with dash light ON. Under auto, remove the wire from the solenoid on the leeft side of the OD. You should hear a sharp metalic click as the solenodi looses powwer or gets power.

If no click and a spark, your solenoid probably is holding the OD on.

Just below the solenoid is a test port plug. Remove that plug catching the small amount of fluid that will come out. It may be under pressure so remove carefully and be ready for fluid to spray. Repeat wire removal test with plug out. This will release any fluid that may be holding the OD on.

Replace plug and test drive. If shudder has disappeared, time to rebuild solenoid BEFORE you drive auto in reverse.

Hopefully the sliding member is not damaged which also causes shudder just after it has occured.

Other less damage causing possibilities are clutch out of adjustment, hanging pressure plate on shaft. Clutch lever bent or pivot ball damamged. Oil spotted clutch face. Warped or damaged clutch face.

Some of those you can only verify if you remove the tranny.

Good luck,

Duane