Why does my 1-2 shift feel like I have a transgo shift kit?

[DrFix2Fly]

Funny thing just happened to me too. I have been dealing with P1870 for a while now and just kept erasing it. Finally after I cracked my torque converter hub last week, (don't ask me how) I had the tranny shop do the TCC valve body mod while I was in the shop. The hard shift problem stayed with the car. The next day, my speedometer suddenly read zero on the highway and I came to a stop. I disconnected the Jet SCU module and I was on my way. Hard shifts were gone too, at least for a few days, but things got better. I think I need my computer reflashed to make all of this go away. By the way, valve bodys produced before 99 will have this problem sooner or later. I just think the SCU 2000 feeds a bad signal to the computer and makes things worse.

[Scott T]

Believe it or not my 1-2 shift was hard when I was low on the rear end fluid. The seal was leaking and my shifts became hard when there was low fluid levels in the differential. I replaced the seal, filled the rear and it went away.