How do I get my horsepower back?

truck rider · August 1, 2004

ok guys I need your help!

I have a 2003 chevrolet silverado 2wd 4.8 L, and I just got a 6" fabtech lift with 305/70R16 Bf's, it really looks nice, but to be honest with you guys I lost a lot of horsepower. I went to the dealership and ask them if there was something I could do, because my speedometer was no very accurate and my horsepower went down. the guy there told me that sometimes they have to adjust the computer, but a friend of mine told me thats a lie, that what I need to do is to re-gear my differential. who is right?

and if I need to re-gear what kind do I need?

GF7PE · August 1, 2004

you havent lost any horse power you have just changed your final drive ratio. Get a Westers tune and that will help more than I cant tell you

Valsport · August 1, 2004

Both. since you're running 33 inch tires your final drive ratio has dopped significantly. I'm going to assume that you've got a 3.42 ratio right now, so a good gear to get would be a 4.10. If you do not re-gear, you will put much more stress on your trans and motor, possibly causing premature wear. After you've regeared, you'll want to get your pcm up to speed by either getting a custom tuned pcm like a Wester's or a Nelson tune, or you can buy handheld programmer like the Diablosport Predator and do it yourself. Either of these will both correct your speedo, and put your shift points back where they are in the meat of the powerband for your 4.8 liter.

truck rider · August 1, 2004

thanks

I totally new in this field.....!

what would be the difference between 4.10 and the 4.56?

where can I get the westers tune and around how much should I be expecting to expend?

GF7PE · August 1, 2004

there are group buys all the time posted by Tbyrne. Not sure that yoy would want the 4.56. thats a bit drastic

BDZ71 · August 1, 2004

Both are correct.

Re-Gearing will get you your HP back and give you back the mechanical advantage over those tires. 4:10 would be nice for the tires you have now, but 4:56 would be even lower if you thought you might ever want to go to a larger tire.

Getting the computer reprogrammed is on the list of things to do aswell. He did not lie to you. When you put on the bigger tires it WILL throw off the speedo like yours did. Also when you regear (if) the computer will need to be told what new gearset you are running b/c it will still think you have stock gears. This will throw off your Shift points and it will shift funny.

truck rider · August 2, 2004

hey guys!

I just want to thank you all for your advice!

I think I'm gonna go with the 4.10, cause I don't think I'm ever going to put bigger tires in this truck.

Thanks!

I AM STILL OPEN FOR MORE SUGGESTIONS

Smokey420 · August 3, 2004

Don't forget about your odemeter either I found mine to be off by a little when going up one size.

Shotgun · August 3, 2004

Don't waste time or money installing anything less than 4.56 gears then re program your PCM for the new tires and grears. I have the same size tires and it's a perfect combo.

truck rider · August 3, 2004

hey guys ! guess what

I just find out I have 3.42 in my truck and some truks like the 4x4 and the Z71 have a 3.73

you think that if I just get the 3.73 will help?

Frank S · August 3, 2004

Nope,go to atleast 4.10's on that truck if you intend to off road in it at all.With the width of those tires your truck will have more difficulty turning them in mud or anything else that presents resistance so 4.10's would definitely benefit you more than 3.73's.

Couple in the fact that your truck has a 4.8 and I would go with 4.56's if it were mine.

BDZ71 · August 3, 2004

There is not enough change there to even think about spending that kind of money on IMO..

4:10 at the very highest IMO.. 4:56 if you think you will ever get any bigger tires, or be towing alot.

oatey_ · August 3, 2004

go with at least the 4.10.........................but the better queston is y would u lift a 2wd trk...........................

Frank S · August 4, 2004

go with at least the 4.10.........................but the better queston is y would u lift a 2wd trk...........................

Better question yet is,Why not?

Some people like the look of 4wd without actually having a use for it so the answer is buy a 2wd and lift it.Some of the best looking lifted trucks I've seen are 2wd so it makes sense to me.