I need some help. I was at the drag strip and noticed a rasp from my exhaust at each shift and the trucks stops pulling . I have a custom tune from James at running with the devil. (Diablo Sport). Anyways I was wondering who the best tuner is and what gains I can expect with a good custom tune rather then the diablo sport junk. I have a 03 gmc sierra excab 4x4 5.3 and have long tubes full boltons and ran a best of 15.7 with my 18 inch wheels. The shifts suck and it taps off of rev limiter somtimes. I would like to raise my shifts to 6100 and my rev limiter to 6400. I need your opionions. Thanks, Jared

 

6100 is too high for what you have. I don't know alot about the Diablo tunes but a custom (mail order or dyno) tune will be much better. Torque management sucks...

 

I had a problem with my 00 silverado that was somewhat similar to what you are expereincing. It started after I installed my headers and a difffernt muffler on my truck. I had a custom dyno tune done to my truck and while the tuner and myself were driving down the road logging the truck we noticed that when I got on it WOT it would throw a false knock and retard the timing. The tuner fixed the problem and the raspy sound when it shifted gears went away.

 

jared he could have zeroed out the mph in the tune and have it shifting off rpms only and that could be causing the rev limiter hitting. check your a/f and timing in that diablo or have him do it to make sure it all appears correct. Oh and an easy fix to that is to raise the rev limiter. And 6100 is not to high. Actually he might want to try to shift it a little higher, might help cross the traps a little faster.

 

From personal experience with my truck when I had similar mods, anything over 5800 was useless as far as power. He could put the limiter at like 6200 so in case he is close to crossing the line in second he could manually stick it out...

 

Are you in Mobile? Did you see James in person or order a Predator offline?
I'm near Pensacola. I know a place you can go if you're close by.
Your truck could stop pulling because thats just where it maxes out. The stock intake is only good to about 5800 as well as the stock cam. I have a crap load of mods and mine stops pulling at 6200 so it really just depnds on your setup. A custom dyno tune is the best option to find out what your truck can really do.

 

If your close to mobile/pensacola area, i would go to xxx motorsports and get John to hook you up with a dyno tune. Im pretty sure thats who 1SlowHoe is talking about as well.

I've dealt with both John and James and i'd choose John hands down. Much more impressed with the tune and the company.