no power down low...

hey guys,
i have a 99 silverado NBS with the 5.3/auto 3.73 rear gears..
i am soon to be running 20x9 wheels with 305/50R20 nitto terra grapplers...over the summer i had 20x9.5 wheels with 325/50R20 toyo proxes...i noticed the obvious better handling but poor brake performance and it seemed like my truck was a little slower but not too noticeable...
I wanted to know if i were to switch to 4.10 gears or so would that help my cause..
i plan on doing gears if necessary/ cam swap/ nelson tune/ and corsa exhaust in the near future...
also i was wondering i have a power dropoff in the low end and it doesnt seem like anything kicks in until @ 2500 RPM..its like a dead spot especially when im in overdrive on the highway i push the pedal a small amount and it just seems like nothing is there until i p[ress it hard to downshift the tranny...


any thoughts would be greatly appreciated... :thumb:

Hmmm...how many miles? No other mods? Installed a shift kit recently yourself? First and only owner?...lots of things could play in for down low performance loss. Doesn't sound like something a Nelson tune wouldn't make better...but need to hear the details of the trucks history. How long ago did you notice the change in performance?

The tires and gears....why are ya going from 325/9.5 to 305/9? I mean that's only like .79" or 3/4" of inch less in diameter. The braking performance is what bothers ya? I didn't notice any braking difference when I went fromstock 17"' to 20" (285/50). However I went ahead and put brembo's on anyway.

The 4.10's. I love mine. One of the greatest mods I did. Since you have 3.73's, in MY opinion it's a great jump. Damn fun in town.

Allen's tune, 4.10's,a stall, shift kit, cam, intake, and exhaust...I imagine you'll forget that it ever had a problem with low end perfromance...that's if it isn't some larger problem hiding in the background...waiting to rear it's ugly head after you do your mods. Sorry guys...my experience stills hurts. LOL

I am guessing if you haven't done any mods yet, you are just getting modification fever and are looking for reasons to update! j/k.

Quote:

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Originally posted by 99SilveradoSpeed@Jan 31 2005, 02:49 PM
hey guys,
i have a 99 silverado NBS with the 5.3/auto 3.73 rear gears..
i am soon to be running 20x9 wheels with 305/50R20 nitto terra grapplers...over the summer i had 20x9.5 wheels with 325/50R20 toyo proxes...i noticed the obvious better handling but poor brake performance and it seemed like my truck was a little slower but not too noticeable...
I wanted to know if i were to switch to 4.10 gears or so would that help my cause..
i plan on doing gears if necessary/ cam swap/ nelson tune/ and corsa exhaust in the near future...
also i was wondering i have a power dropoff in the low end and it doesnt seem like anything kicks in until @ 2500 RPM..its like a dead spot especially when im in overdrive on the highway i push the pedal a small amount and it just seems like nothing is there until i p[ress it hard to downshift the tranny...


any thoughts would be greatly appreciated... :thumb:

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You're running over a 32" tire now. Dependant on your truck it came with from a 245/75 to a 265/75 stock... ~30.5 to ~31.5. Both on 3.73:1 gears sucks. I'd do a min of a 4.10:1. A 4.56:1 would put you at ~2350rpm @ 70mph with the 32" tires, not too bad. A 4.10:1 will get you to only 2100rpm @ 70mph.

The biggest factor is the tune in the '99s... it's awful. They're worse than the '00+ trucks. I'd get that before you regear, they also are highly prone to false knock which pulls more power yet.

More than one person has gone to an '01 or '02 PCM and run WAY better with just that alone.

hey guys,
that was some fast feedback...
ok for starters..
1999 Silverado XTD cab...5.3L 4L60E 3.73's 4WD 265/65R16 stock tire size
i am going to 305/9 b/c i sold my 325/9.5
91,000 miles 2nd owner...

I noticed the change in performance after i installed and removed the wheels over the summer..it just seems like DEAD...also i changed my exhaust a few times trying different combos and it seemed to change a lot with that as well...

Current mods:
K&N series 77 intake
Dynomax Bullet muffler with custom piping
MSD wires with platinum plugs
nu image platinum gauge faces
Shift kit-not yet installed
5000K HID kit
Piaa P-3000 foglights
Clear bumper lights
WHELEN police strobe kit
Tinted windows

FUTURE MODS:
CORSA EXHAUST
THUNDER RACING CAM KIT
NELSON TUNE
4.10 GEARS
STALL CONVERTER
BREMBO PLUS-1 KIT

I didn't know you were 4x4, since you are... go straight to a 4.56:1. Don't waste your time with a 4.10:1. You have more mass to move and need the extra mechanical advantage to keep it going.

It's only about 200rpm more in OD over the 4.10:1. I messed up and have two sets of 4.56:1 IFS gears, so if ya want a set drop me a line. lol No need for 3 sets.

Start with a tune, 99s are mad slow stock. Then regear ASAP.

With that many miles, down on power and numerous performance mods over time, I would look at the cat convertors being plugged or damaged. I would replace them anyway just to get some high flow cats on there.