Heading out to work today, the trans in my 94 TA made a howling/shuddering sound on the 1-2 shift. The best way I can descibe it is the sound that an Auburn cone-type differential makes when it's failing and causing a one-wheel peel. Leaving work, I tried a couple of light-throttle 1-2 shifts with the performance button both off and on. Problem was worse with the reduced line pressure in the off position. It feels as though it's slipping, then engaging, and the 2-3 shift seems normal. I haven't had it up to highway speeds yet, so I can't comment on the status of 4th gear. I will say that the 1-2 seemed a bit too soft with the performance button off, so I've always left it on.

I did a little reading, and there are only a couple of posts that describe this issue, so I'm not sure how dire the situation is. The little info I did find seemed to suggest a crack in the accumulator piston, broken sun shell or a failed shift solenoid. I don't drive the car very hard since it's currently my DD, so the failure was unexpected. Looking to hear from vendors and other 4L60E experts on whether this is a simple pan-dropping operation or a full R&R. I realize an internet diagnosis is difficult, but hoping it's a common enough failure that the cause can be narrowed down.

In the event I'm looking at a rebuild, I'll likely be sending it to Performabuilt, as they are the closest to my home (NE Ohio.) I used the well known shop in eastern OH in the past and shattered 2 input drums within 500 miles of a rebuild, so although he is technically closer, I'm gonna try my luck elsewhere. Thanks in advance guys.

 

Got a little more information on the drive to work today. From a stop, the engine revs up a bit before moving, slamming to a start (like a clutch dump on a manual.) The growl in second appears to only occur during the 1-2 shift; once it engages fully, it seems to hold the gear without slipping. Since my job is close enough to walk to, I haven't had the opportunity to check for 3-4 operation, but 2-3 seems normal. That said, I haven't driven it long enough to get everything up to temp, so I've kept it well under 50% throttle to avoid shocking the cold tranny with any abrupt shifts. I do have a spare trans that was functioning correctly when removed from its former vehicle, so I may be able to get by on it long enough to rebuild this one. Still looking for some input before I go suffer through swapping a tranny on the garage floor in the middle of a typical sh!tty Cleveland winter.