Torque converter locks up when cold. Chatters and vibrates when hot?

Perhaps bad engine mount?

Hello Carl, Yes, I have seen this. New torque converters are balanced before they leave the factory. I think yours slipped past Quality Control. Did they replace the flex plate at the same time? Flex plates are also balanced. Maybe that is your vibration. Either way, the repair shop should redo the job right for free. Good luck. Let us know.

Absolutely heard of and seen out of balance torque converters do exactly as you are describing. Since you just had it replaced before you picked up on the vibration that is the first place I would look.
Let us know how it goes with the transmission shop?

I do not know if this vehicle has a torque converter lockup or not, but sounds like it. Does the transmission stop shaking when you go over 65? Some vehicles have a torque converter lockup, which means when the vehicle is traveling at a certain speed in high gear the torque converter "locks" and there is no slippage to the transmission resulting in better fuel economy. if the torque converter doesn't "unlock" when you slow down to say 45 then the engine will "lug" causing vibration. If this is the case you are not hurting anything by driving, just shift to 3 when it shakes then upshift under lighter load, or take it to a shop that replaces transmission sensors.

I think you are right, since in park the only thing turning in tranny is torque converter. had same trbl with an impala once.

run the fault codes
the torque converter clutch operates almost immediately on gear selection
indicates a servo/solenoid problem

VIBRATION - DRIVELINE RESONANCE/VIBRATIONBETWEEN 1400 AND 2000 RPM WITH CONVERTER
Clutch ENGAGED DURING MEDIUM TO HEAVY
THROTTLE CONDITIONS - VEHICLES WITH 7.3L DI
TURBO ENGINE AND TRANSMISSION BUILT PRIOR
TO 11/13/95 (5L13)
^ TRANSMISSION - E40D - DRIVELINERESONANCE/VIBRATION BETWEEN 1400 AND 2000
RPM WITH CONVERTER
Clutch ENGAGED
DURING MEDIUM TO HEAVY THROTTLE
CONDITIONS - VEHICLES WITH 7.3L DI TURBO
ENGINE AND TRANSMISSION BUILT PRIOR TO
11/13/95 (5L13)

FORD:
1995-1996 E-350, F-250 CREW CAB, F-350 CREW CAB
Article 96-26-21 is being republished in its entirety as part of a consolidated 7.3L diagnostic aid booklet.
ISSUE
Some vehicles with transmissions built prior to 11/13/95 (5L13) may exhibit a driveline resonance/vibration between 1400 and 2000 RPM with the torque convertor engaged. This may be caused by the torque converter.
ACTION
Prior to torque converter replacement, refer to the following Service Procedure for details to verify conditions.
SERVICE PROCEDURE
1. Verify the resonance/vibration does not occur in neutral and is most noticeable between 1400 and 2000 RPM with the converter clutch engaged during medium to heavy throttle conditions. Also watch for the vibration to diminish at engine speeds lower than 1400 and higher than 2000 RPM. If the concern meets all of these conditions and the transmission has a built date prior to 11/13/95 (5L13), replace the torque converter. Refer to the appropriate Service Manual for removal and installation procedures.
2. If the vibration concerns do not meet the conditions, check for non-factory installed items that could affect driveline and verify proper installation. Also refer to the appropriate Service Manual, Section 05-00 for diagnosis and testing.

change the torque converter

The torque converter clutch solenoid on the GM 125 transmission will stick when it gets hot and not let the torque converter clutch disengage. It has to be replaced. It is under the side cover. Quite simple to replace once the cover is off. The side cover however is fairly difficult to remove (usually involves dropping the left side of the transaxle).

Hi....i just bought this same model......i am having the same problem but not only at first drive......its all the time......now......im not positve that its the torque converter.....but im leaning that way.....reason why....i used to have a mitsubishi galant.......after pulling my hair out and even rebuilt the engine.........comes to find out it was the lock up converter slipping ...but it didnt vibrate.....the RPM gauge was always moving up and down as i drove and it slipped in and out of lock up.....im about no narrow this down....if i find more....ill reply.