I recently put a D1SC on my 5.3 with 44# injectors and a westers tune.It is running great but I have one issue.Sometimes when I have it at WOT in 2nd it will shift at 5200 and not at my set rpm of 5800.I had my pcm tuned twice by Lyndon in the last 3 weeks and everything is set up right.He said it might be a dirty MAF sensor [so I cleaned it].It runs perfect most of the time but then it will shift early.I don't think it is pcm related.So can these early shifts be caused by belt slip?

 

Do you have any way of scanning? Do you know what TPS% your WOT command is set to? PCM may not be seeing correct WOT parameters. I had an isuue once befor when the pcm was shifting at about 500 rpm below commanded. Can't remember what it was right now, but I'll think about it. Also sometimes the gauge may read slightly different than the RPM the PCM sees but 600 rpm seems like alot.

 

What does it due if you try T/H mode? My old 02 would short shift with out the T/H on.

 

I think it is something besides the pcm because sometimes it works fine.That's why I was asking about belt slip.

 

Mine did the exact same thing after I first had it tuned by nelson. We were at the track and had shift points at 6600 rpm and it would short shift sometimes. Solution, command shifts based on speed and not rpm. It sucks having to dial in shift points based on speed but this is the only way my truck will listen.

Belt slip should have absolutely nothing to do with it.