For the past months my 1-2 shift is sometimes harsh almost like it holds the cluch too long. All other shifts are nice and smooth dont even notice 2-3 or 3-4. The fluid smells normal and looks cherry red, I dropped the pan and changed the filter last year and refilled with GM dexron 6. It shift harsh even on the first shift of the day sometimes and othertimes it doesnt shift harsh at all for the day. Fluid level is slightly high but hard to tell due to the famous rusty tube it goes in.

 

today it didnt do it at all,its hit or miss when it happens

 

mine used to do the same thing. I think its a band slipping. Mine shifts real hard into 2nd now.

 

Mine does the exact same thing, sometimes it feels like it dont want to shift out of first, on ce it does its fine. I took mine to a Chevy dealership and they couldnt find anything wrong with it, so..... keep us updated if you find out anything and I will do the same. I plan on taking mine to a transmission shop within the next month and let them have it for the week, Chevy said it never did it while they had, go figure.........

 

my rebuilt one does the same thing. It was just rebuilt maybe 20,000 miles ago, but slams into second from first, but the rest is fine. It doesnt even do it all of the time. The previous owner said that the valve body needed adjustment, but he didnt have time or money to have it checked or some bs....is the valve body adjustment something a novice can do, or is it left to the pros?

 

Hey man I found out that it is just some type of (O ring or seal) inside the tranny that is bad. My neighbor works on cars for a living and has his own computers and equipment and stuff, he pulled up the info on the tranny and the diagnostics and trouble shooting guide and figured out that the "O ring" is bad, it allows fluid to leak past it causing a Harsh shift from 1st to 2nd, it is actually very common for the 4l60E tranny. I will try to find out more in detail and let you know how to fix it or what it should cost. He said that you DO NOT have to drop the tranny that you can do this with it still on.

He knows what he is talking about so i will try to get him to write it down so i can reply to this again, so cheer up man, it looks like there is still hope without buying a new one.

 

If the 1-2 shift is delayed and harsh (may not shift into OD):
Check TPS for smooth and linear electrical response over the entire range of motion. If not, replace.

Also check out these threads:
Everyone having 1st to 2nd tranny slams HERE!.!.!
P1870 - Transmission Component Slipping

 

Yeah I dont get any codes thrown or check engine lights,it shifts into overdrive as easily as it ever has. Ive seen that tsb but it almost seems opposite,where mine when it happens which is really hit or miss sometimes it will do it multiple times then others not at all for days, only seems to happen when the tranny is cold. Ive never had a rough 1-2 with the tranny hot. I changed the fluid in the pan again since I only got the fluid in the pan when I did the filter change not the converter or the cooler,ill see if that helps any. How do I go about testing the TPS?

 

Test the TPS with a multimeter by back probing the connections. You should have ~0.5V at closed throttle and ~4.5V at fully open throttle. It should be a smooth transition between those two positions/values in both directions.

 

Where is the TPS is it at the throttle body or the peddal?