Last year I purchased a rebuilt THM375 tranny off the net. It was listed as rebuilt with a stage 2 shift kit and came with a 2500 stall.
I hooked it up to my rebuilt 350 with a tall cam (450 lift, 224 duration, 206 lobe centre). When first driving it I didn't like the stall so replaced it with a brand new 1500 stall so I wouldnt scare the neighbours too much (unsconstricted exhaust + high stall = loud!).
Everything works great except the tranny shifts really hard when you go into drive or reverse. It is not so bad if you let the entire package warm up good (i.e. 5 minutes in idle).
Now, I assumed it was normal and the truck has been running great for the past year. Tranny fluid is still pretty pink and tranny temp always runs normal but....
rear seal has started to leak a little and as the fluid went down the shifts have gotten smoother and smoother. Add more fluid back to normal zone and shifts are hard again.
1. I got the transmission without a dipstick and tube so I sourced one from a wrecker but he got it out of truck so he may have mistaken the 375 for a 375B (which is a totally different beast) so is it possible my hard shifts are due to too much fluid and when it went down it was more in the 'normal range'?
2. I like the smoother shifts at low tranny fluid (i.e. it's just below the 'add one quart' on the dipstick), is that hard on the tranny? (assuming the problem is not as noted in quest 1)
3. Is it possible that something is sticking (governor valve)?
4. Am I using the wrong stall for that cam and causing that hard shifting (I read that you should use a high stall with a tall cam)?
5. Am I just paranoid and the shifts should be this hard so just fix the rear seal, put fluid to normal zone and live with it
Thank You very much for any assistance.