Hi, im new here but not to z31s... i bought an 88 n/a auto 2 weeks ago dirt cheap but runs great. ive never driven an automatic z till now and ive noticed when im driving around town at real low rpm like under 2000 the trans feels like it slips when shifting from 2nd to 3rd the rpm jumps like 500 during the shift. if i give it more throttle tho and have it shift higher rpm it shifts great. this issue is only from 2nd to 3rd. it has 163000 miles on it but the last owner said he had it rebuilt and he only put 30000 miles on the car since he bought it. i checked the fluid and it was over full but clean... i pumped some out through the cooler line and added a bottle of lucas and it didnt do anything. i also noticed some very fine metal shavings in the oil i took out. i have been told(dont know if its true) that its normal for a new trans to have some shavings in it from it breaking in but i dunno. ... i took a trans out of an 84 olds stocker once that was brand new only like 4 runs on it and it had shavings too so im guessing thats normal. i cant afford a new trans and dont really wanna do all the work to change it to a stick even though i have everything to do it. my other one is a stick and id like to keep it that way once i fix the motor. and help would be appreciated i just hope its something stupid and easy to fix

oh and also the car sat for at least 4 years before i bought it since it still has an 08 inspection sticker

 

If the radiator has not been replaced, I would get an external cooler at O'reillys for 40 bucks. The cooler on the radiator may have some gunk in it and well if you overheat you wont have to worry about cooking your tranny. I have the same issue you do with an 85 that I popped my 87 tranny into but 50,000 miles later its still going strong. May not fix the problem but it cont make things any worse.