727 having a few issues

Hey guys, I think my rebuilt 727 might have a problem. Here's some info and backstory. Warning, long post, but I want to give as much info as possible. My 71 Dart has a 360 (stock rebuild), and rebuilt 727 (again, stock). I had the 360 balanced during rebuild with the B&M flex plate to account for the externally balanced 360. The 727 was rebuilt (stock rebuild) and I had the transmission builder give me a neutrally balanced converter like off a 318. I believe the converter was used. I personally didn't rebuild the 727 I had a shop do it, same shop that did my 904 on the daily driver and it worked great for 10 years. But still that's not saying anything, anyone can screw up at any given time.

Due to changing jobs all of this was done across country from me and oversaw by a friend. After the engine & transmission were in the car it was broken in for a few hundred miles and then shipped my way. I've had the car a couple months. Apon receiving the car I noticed it was shifting soft, so right away I checked the kickdown. The Lokar kickdown cable basically wasn't doing anything (!!!!) and it was driven for ~200-300 miles like this. The throttle cable also wasn't opening all the way. I fixed that as well so the kickdown lever was all the way forward at WOT.

Bad friend, I know, but it is what it is and I had to move away from work on short notice. Moving on after I adjusted kickdown all the way forward at WOT this made it shift wayyyyyyyy late, excessively late, so I backed it off a little. I adjusted it so it's about 1/4" or so from being all the way forward at WOT. Oh also I have a very light return spring down on the kickdown lever to ensure it pulls off properly. I ensured that the fluid was checked warm and in neutral and at the correct level. The cooler is a m7b and I ensured that's working (it gets warm and so do both of the lines). I drove it like this for several weeks with no issues. The only driving I do is around down with short drives on the freeway.

The problem started a couple days ago and it happened right away in the morning. The car would have this odd shudder/hesitation if it's BARELY moving in R or D. Like if I'm stopped and i'm BARELY taking my foot off the brake it would shudder for a second. I can't stress enough how I have to barely be moving, if I take my foot all the way off the brake it's fine, unless I'm on an incline or something. It's a very small "sweet spot" that would cause this shudder. I tried revving the engine to up the RPM, let foot slowly off the brake, and the shudder still happens so it doesn't seem RPM related. At first I thought it could be the rear end, but it's a sure-grip, and the results aren't consistent that it's a rear-end problem. It feels like transmission. The shudder/hesitation is worse in the morning when it's cold vs when it's warmed up. When it's warm i can just barely feel the shudder when i start to let off the brake. Even though it's not as bad when it's warm it is a consistant problem when starting out. I am trying to describe the feeling, it almost feels like motor/transmission mounts if you will, but mine aren't bad, they're new and I verified this today. If it's cold sometimes the shudder/hesitation is pretty strong when at that sweet spot of just barely moving and will even shake the car.

Then today I noticed another issue. I was driving and I could have sworn I was feeling a few random slips. Like it would slip for a split-second and then be fine, not during any shifts. I remember I was driving around a corner, car was in 2nd, and I felt a slip for a split second. I was later going up a hill, car was in 1st for longer than usual since it was going up a hill, and it slipped for a split-second, then was fine, then a few seconds later it shifted into 2nd.

I got home and right away checked the fluid and tried to smell for burning. The fluid smells fine, isn't low, and is normal color. Later I decided to check the kickdown adjustment and I adjusted it more forward at WOT, so now there's maybe 1/8" of play. I also added half a quart of fluid since it was towards the low-end of acceptable range. These changes didn't make a difference.

Car uses Dex VI fluid if that helps at all. That stuff isn't cheap. No leaks either.

Anyone have any idea what this could be? I know I've heard that if the clutches are burned up the fluid would be bad and I don't see any signs of bad fluid. This transmission has maybe 400 miles on it total. Could this be a bad converter? I have no idea what bad converter symptoms could be.

I know the car was driven for ~200-300 miles with the kickdown not even doing anything, but could that really cause this? I know have a miss-adjusted kickdown is BAD, but I've also read posts of people saying there's wasn't adjusted right for years and finally fixed it, and now it works fine. Then again adjusted somewhat is better than none at all, and mine wasn't doing anything those first few hundred miles..

As usual thanks guys!