Hello all. Have a 1995 Mustang GT that is being sold but a trans issue just popped up. Bought the car about 1 year ago. Has 69,000 miles but found a receipt in glove box saying trans was rebuilt about 15,000 miles ago. So last year I put a Trans-Go shift kit in it but inadvertently put 2 of the plugs on backwards for 2 of the solenoids. Felt to me like the convertor was locked up as it would bog at the 1-2 shift and when stopping. It would also shutter at stopping. I dropped the pan and swapped the plugs and all was good. Put 4000 miles on it with no issues. Drove it a few times this year then bought a 2005 Roush Stage 1 so sold the 1995 to a family member. Buyer drove it home about 50 miles and all was fine. A couple days later it started doing that same exact thing. Tonight I dropped the pan hoping to see a plug came loose but all looks good. No CEL either but it's OBD1 so not sure it would set a code? Anyway, everything in the pan looks good. My plan is to replace the TCC solenoid to see if that fixes it but aside from that I'm out of ideas?
Any help would be greatly appreciated! BTW-I'm not a trans guy so I'm flying by the seat of my pants here.