ok, recently i had a thread about why my car vibrated. it is a pulsing vibration. vibration...fine....vibration...fine. it has about 1 second of vibration, 1 second of no vibration. then, theres another vibration that feels like your riding in an old clothes dryer. this vibration kicks in at about 30 - 40 mph.

after getting all kinds of replies, i had the driveshaft balanced and replaced the u-joints, balanced the tires and it is still happening. the engine is balanced by a good shop. it never did this before the swap so im thinking the tranny or maybe the torque convertor is vibrating. any ideas, stock th-400 and TQ convertor.

 

cracked flexpate?

 

sounds like my 94 at 90mph..Driveshaft...factory flaw, in my case...Checked the rear fluids lately?

 

my car did that over around 40mph pretty bad and it turned out the tires were bad. (cupped) SP? got new z-rated tires and it was all good

 

First see that the vibe is auto movement related or engine only related. Note speed and rpm when the vibe occurs. Put in park and run engine to rpm to see if it occurs. If so, engine related, if not, drivetrain related. If driveline related, put 50 psi in tires to rule out the tires and go validate speed for different gear position. Try to isolate the vibe to the rear or front. Mine has engine vibe, but still working it. You could check the engine or torque converter by removing the TC cover and disconnecting the TC from the flexplate. Push TC rear to tranny and run car to see if vibe persists. If so, disconnect belts to see if it is related to the components. Run only short time here. If it persists then it is really engine related.

 

My car had real bad vibrations in 5th gear from 35-45 mph. I changed my plugs and one of them was CAKED with oil. So I was only runnin on 7/8 of my engine. Now it runs like a champ at 35-45 in 5th gear... Not sure if that will help you..helped me though.