1999 GMC....Powerless :(

[2TheSky]

Hello Everyone,

 

Recently I sold my rice burner and purchased my father's truck a 1999 GMC 1500 3-door ext. cab. It has a 5.7L engine I believe. I'm 17 yrs old so naturally I lifted the truck with a 6 inch Tough Country suspension lift then added 18x10.5 rims with 315 10.5 cooper tires. Before the truck had some guts and now after first gear I might as well get out and push the poor thing. I was wondering if there was any hidden power waiting to be unlocked perhaps with an exhaust or intake. also I've noticed some sag in the lift in the front of the truck. I was wondering if I could adjust the Torsion Bars to compensate for that? And how I would go about doing that.

 

thanx all!!

Bryan

[Nice rig]

Performance loss is to be expected when you put big tires on it.

[2TheSky]

For Reals???? huh. anyone have a "good" answer

I'm not asking if there will be a power loss because that is obvious. I'm asking what I can do for more power.

[asilverblazer]

There wasn't a "loss" of power the gears NEED to be lowered in order to compensate for the taller tire. No amount of power add ons will compensate for too tall of a tire.

[drumset5994]

He prolly needs close to 3.73's or 4.11's in the rear...they're right...those tires are too big for stock gears. Am i in this statement fellow members?

[Nice rig]

I didn't say "power loss", I said performance loss. How about doing a search and you will find an endless stream of intake/exhaust/pcm tune threads. Have a nice day....

[67ChevyRedneck]

Aren't you supposed to have the PCM re-tuned when you significantly change tire sizes?

 

Nice rig has a good idea

[asilverblazer]

I didn't say "power loss", I said performance loss.  How about doing a search and you will find an endless stream of intake/exhaust/pcm tune threads.  Have a nice day....

 

<{POST_SNAPBACK}>

 

 

 

Sorry, wasn't exactly quoting you per say, but more along the lines that he had lost get up and go since putting larger tires on, which is not a motor/power problem so much as it is gearing.

 

Aren't you supposed to have the PCM re-tuned when you significantly change tire sizes?

 

If he wants the speedo, ABS, and other items that work base on speed sensors to work correctly he has to, but it won't change the lack of get up.

 

He can add all the tunes and power add ons he wants, but in my opinion that will mask the problem of too high a gear ratio, rather than solving it.

[OnyxMAX]

yep gears will wake it back up, the increase more or less made your 3.08/3.42 a 2.50/2.83.

 

hidden power can be unleashed with a tune, intake, exhaust, electric waterpump, underdrive pullies, electric fans, nitrous, forced induction, basicly all the same stuff as riceburner would use.

 

you can adjust the T-bars but it's kinda complicated in a simple way and could throw off the alighment (not much but just a smidge) think their's a how to in the how to section.

[gtj]

Hello Everyone,

 

Recently I sold my rice burner and purchased my father's truck a 1999 GMC 1500 3-door ext. cab. It has a 5.7L engine I believe. I'm 17 yrs old so naturally I lifted the truck with a 6 inch Tough Country suspension lift then added 18x10.5 rims with 315 10.5 cooper tires. Before the truck had some guts and now after first gear I might as well get out and push the poor thing. I was wondering if there was any hidden power waiting to be unlocked perhaps with an exhaust or intake. also I've noticed some sag in the lift in the front of the truck. I was wondering if I could adjust the Torsion Bars to compensate for that? And how I would go about doing that.

 

thanx all!!

Bryan

 

<{POST_SNAPBACK}>

 

 

 

Hi Bryan,

 

There is a good chance the performance loss is due to the tire diameter change you made accompanying the lift install. The larger diameter tires will effectively change the ratio and also your speedometer readings which affects the transmission shift patterns.

 

You can figure out you're new tire diameter and ratios using this calculator. http://www.ringpinion.com/content/calculators/RPM.asp

or here

http://www.4lo.com/calc/geartire.htm

 

Then select a new gear set. Precision gear or Yukon Gear are good choices.

 

The speedo fix is easiest with something like this:

http://suvworld.tenmagazines.com/tenarticl...?aid=2195&sid=9

You can also modify the DRAC controller or get a custom tune.

 

 

You can crank the T bars up to level out the ride height in the front very easily to adjust within about 1' to 1.5". You can get about 2", but the CV angles get steep and cause premature parts wear. Remember to get an alignment done after any T bar cranking. Procedure is basically to measure a refernece distance such as the top of the front wheel wells to the ground, jack and block the front end, get under and tighten the adjuster bolts pushing against the T bar keys located in the cross member, tightening them the same on both sides (maybe 2 turns to start), drive it around a bit to let things settle in and recheck height measurements, once you get it corrected get an alignment.

 

Hope this helps.

Glenn