I'm new here and need some help. My truck has been driving me nuts.I have a 1999 Chevy Silverado 4x4 5.3L. I’ve got 305/70 (32”) tires on it and I just finished putting 456 gearing in it. I have a Hyper-tech (sp) tuner and have set the tire size to 32” and the gearing to 456 this should make my speedometer correct. Here is the problem. Stock (373)if you were running less than 70 and stomped on it would gear down into 2nd and go. Now if you are running 50 it won’t gear down and is extremely sluggish until you reach about 60 or so. If you are closer to 45 and it will shift down and wont shift out of 2nd till 65 or so. Why is this and what can I do to make it shift down in my opinion correctly. Any help would be greatly appreciated.

 

I don't know about that particular programmer, but some have a kick down adjustment for the shifts.

 

Thanks, but my tuner does not have that adjustment. That would be to easy. It never seem to be that easy when it comes to me and anything I do withmy truck.

 

#1 aren't 305's closer to 33 or 34"?
#2 You should have a 1-2, 2-3, 3-4 shift speed adjustment on your programmer.
#3 Your programmer should have a firmer shift adjustment that should help too.
#4 You should have a cable beside your throttle cable on your throttle body that you can adjust. (Tighten it a little for firmer shifts)

 

i wouldnt of geared im tucking 33(technically 32.8s) with 3.73 gear and it runs like a champ, my speedo is of 2 mph big whoop, i would buy a shift kit for your truck if i was u that helps alot andfor jcbst12the number 305 is the thickness of the tire, like my tire is 285 thick by 75 percent of 285 that is the the thickness of the sidewall by 16 the rims and my tires are 33

 

Thats right, Im thinkin bass ackwards again! Sorry! ( and the scary part is I used to sell tires for a living )

 

yeah the 305 is a tij shorther than the 285, i was runnin 305s with 373 gears and had no probs, but i would look into the shift kit idea tho