this has been buggin me since i got this tranny, even if you hold it in low 1 it will shift into second right around 4900rpm. i've heard all 400's do this. adjustable modulators don't fix it. oh well. i was just curious why gm made these trannies do this. i got a manual valve body for mine to put in soon anyways.

 

Most shift kits cure that. I'm sure you've noticed that when it shifts that way it shifts so hard it knocls your teeth out... it uses the band instead of the clutches when it does that.

GM did it to protect motors from being over-revved.

 

If you hold the shifter in manual low, it will automatically go into second if the rpm,s go high enough. GM did this on all TH400's. If you want it to stay in 1st, then you will have to install the Trans-Go Performance Shift kit (400-1-2). This will leave the transmission fully automatic, but with the ability to hold 1st or 2nd to any rpm you like.

 

You 700 guys may be surprised to find that your will do that too! Not everyone notices this, depending on several factors.

 

Yep, I was just going to add that the 700r4's will do that. With my old comp T/A's I had a burnout get out of hand while I held it in 1st gear--it shifted to second.

 

At what rpm does the 700 do this? I have a superior kit in mine, it goes at least to 6200 without shifting. I have been having trouble getting the trans shifting the way I want it to. I know a guy that run our local trans shop. We've been messing with the tv adjustment tring to get it right. With the tv adjusted like the superior instructions say, this trans won't shift at wot till you let off the gas. He is claiming that the reason is because I used a 2.8 valve body and separator plate in my rebuild. Are the valves differant in the 6 cyc. valve body? Separator plate?