A couple nights ago I was driving home when a new Chevy Siverado extended cab pulled up next to me. Im not sure if it was a Z71 or not. We were going about 40mph and then both gunned it. Well he was definitely faster. The reason why I special ordered the 5.4 regular cab was so this type of thing wouldnt happen. Now i want some good mods.
I already had a 3" catback with a flowmaster at the time. A week after the encounter with the Chevy I installed an airintake system like the Airaid. Then I ordered a Jet chip and found this awesome site for my first time later on that night. I realized I just ordered the wrong chip. The next day I cancelled the order on the Jet and put an order in for a Superchip, which should be here soon
I think those Chevys have 285-305hp. Should these three modifications put me over the Chevy? Part of the problem may have been my 6" suspension lift with 285/16 BFG tires. Are my tires too big for my stock 3:55 limited slip gear ratio? I want a gear ratio that will put me back to stock. But I also have to drive 35 miles too school, so i dont think i want too low of gears. Yet i love more and more power.

2000 5.4 Regular cab XLT 3:55ls
3"catback w/flowmaster
Jet air intake system
Superchip(on its way)
Billet Grille
6"suspension lift, Blistein shocks, Eibach coils. 285/16 BFG all terrain tires.
Weld Racing Rims
Tinted windows

 

Ryshark5, I think you answered your own question. The 285's are quite tall for your 3.55 gears.

I've made an assumption that your stock tire size was 255/70-16 for the following:
Stock Diameter - 30.05"
Current Diameter - 32.8"
Stock Circumf. - 94.4"
Current Circumf. - 103.1"
Stock Rev/Mile - 671
Current Rev/Mile - 614

This represents a 9.2% change. If you want to spank the Chevies you're going to have to do something with the gearing or reduce your tire height. The Superchip will definately help - but you're gearing sure sounds like the problem.

Tom in Tacoma

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1998 F150 XLT S/C 4.6L Auto, 3.55LS, 4X2, Moonlight Blue, all the factory bells & whistles except for leather seats.

• Lund Deflector
• Lund Premier Tonneau Cover
• K&N Filter
• Body-color painted Throttle Cover
• Blue wire-looms
• Pentaliner S/R
• Window tint
• Ford side-steps
• Infiniti component speakers - front
• Polk Audio speakers - back
• Superchip (OH YEAH!!)
• Flowmaster 50 Series 'Delta-Flow' w/ 3" pipe
• Clear turn signal lenses

Tom in Tacoma

(Washington not Toyota)
Go check out http://communities.msn.com/SS97FordsPics for the second best website for F150's

 

Ya know, I have read a a lot of posts on this web site (across different forums) about wanting to race (or being afraid to race) a Z-71 Chevy.

Now please correct me if Im wrong - and I know you will - isnt the Z-71 package an off-road package?

Off-road, as in 4 wheel drive, low gears, locking diff, gas shocks, skid plates, big tires, etc.

None of which equates to any 'on street' performance gain. Now I can see that GM has a better selection of engines, and maybe most of the folks getting the Z-71 package are also getting the better engine (I would), but unless your racing up a mountain on a rain-soaked fire access road, the 'Z-71' means nothing.

I just dont get it.


sorry .... off topic



------------------
01 SUPERcrew XLT 4x4
*rare* amazon green

 

I was thinking the same thing about those Z-71, heavy off road vehicles which my regular cab 2wd shouldnt have a problem with. But dont under estimate them. By the way Tom my stock tires were actually 235/ R16 And now i have 285/75-16, so i guess my gears are even more off then you thought. Ill have to call a differential shop and find out if i should use 3:73 or the 4:10s. Has anybody tried the underdrive pulleys or hearders yet? I heard the pulleys make your truck run hotter and the a/c doesnt work as good. And i also heard the headers take away from bottom end torque.

2000 5.4 3:55ls(will be changed soon)
catback exhaust
air intake
superchip(on its way)
tint
alarm
suspension lift etc etc etc

 

I was thinking the same thing about those Z-71, heavy off road vehicles which my regular cab 2wd shouldnt have a problem with. But dont under estimate them. By the way Tom my stock tires were actually 235/ R16 And now i have 285/75-16, so i guess my gears are even more off then you thought. Ill have to call a differential shop and find out if i should use 3:73 or the 4:10s. Has anybody tried the underdrive pulleys or hearders yet? I heard the pulleys make your truck run hotter and the a/c doesnt work as good. And i also heard the headers take away from bottom end torque.

2000 5.4 3:55ls(will be changed soon)
catback exhaust
air intake
superchip(on its way)
tint
alarm
suspension lift etc etc etc

 

Right again Ryshark5 - Here's the numbers comparing the 235/70-16 to 285/756-16's:

Stock Diameter - 28.95"
Current Diameter - 32.8"
Stock Circumf. - 90.95"
Current Circumf. - 103.1"
Stock Rev/Mile - 697
Current Rev/Mile - 614

This represents a 13.4% change.

Gears, gears, gears, gears....

Tom in Tacoma

 

FYI- I've had good success racing from a dead stop or slight roll. The wide ratio of 1st & 2nd gear in the 4R70W provides a good pull. 0-85mph seems to be it's sweet spot with the truck style and mods I have.

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2000 F-150 XL,RC,LB,5.4,4R70W,3.55LS,
Class III tow/Payload #3/Convenience pkgs.,
4-wheel disc/ABS,Chestnut/Parchment 40/60,
Ford bedliner & gas/wheel/spare locks,
3" cold air box modification,Superchip,
Dynomax ultra-flow welded 3" cat-back.

 

I have never had a problem outrunning a Z-71 ...

------------------
99 Black Lightning
Superchip
13.429@101.14

 

Aw thanks Blacklight - I'd imagine it's a rare Corvette that you couldn't outrun....

By the way - you ever head south toward Tacoma? Interested in hooking up with the Washington Chapter of F150online? Drop me a note at TColegrove@excite.com.

Tom in Tacoma

 

Hi Ryshark5,

Welcome to F-150 Online, we're delighted you decided to join us here!

Tom did some excellent work there for you, and he is right on the money. The stock tire height on these F-150's, regardless of which *factory* wheel & tire combo you have, is always somewhere between 29.5 & 30.5 inches. You have increased the tire height by almost 3 inches, which is quite a bit of difference. What you want to do is a gear change that will restore the engine back to turning the same rpm's in Overdrive at a given speed that it did before the tire size change, that is the ultimate goal. If that is done *properly*, it will also restore your speedo & odometer accuracy as well, or at least get it much closer than it is now. With larger tires, you are indicating a slower speed than you are actually going, and you are also putting a little bit less mileage on the odometer too. That can get you a speeding ticket if you're not careful, or if you don't know how far your speedo is off.

This is also further compounded with that 6" lift you have, which has tremendously increased your aerodynamic drag, so starting at about 40 mph and from there on up, your engine is having to work much harder just to overcome the increased aerodynamic drag alone, not even taking into consideration the added load from the larger tires. This is very typical of what we see here when a gear change is not included as part of the larger tires & lift kit "conversions", so you're not alone!

You're also right about those new Chevy's having as much as 305 hp stock in those new LS1-variant motors they're putting in those 2000 trucks, pretty stout, those rascals!

There are any number of ways of calculating what your new gear ratio should be, we always prefer to do it by rpms, trying to match the original rpm's for a given speed the motor was turning, as that seems the most accurate. There are many different "conversion engines" all over the Internet, wher you can plug in tire size etc. and get that calculated, but you have to be very careful as some of them are not accurate, and can cause a mistake to be made in this regard. Which is why we prefer to do the gear ratio selection by determining how may rpm's we want the engine to turn in Overdrive at a given speed.

As far as other modifications you can do, you now have basically the top 3 best bang-for-the-buck mods with the Superchip, the opened intake & opened exhaust. From there you can do headers, underdrive pulleys, etc., but I'd probably want to do the gear change next, to take care of he "basic problem" at hand, and then see if your performance is where you want it.

Good luck!

------------------
Mike Troyer
Performance Products, Inc.
National Distributor of Superchips
(540) 862-9515
Email: mtroyer@compuserve.com
Performance Products F150Online Superchip ordering system: F150Online Superchip Ordering System
First National F-150 Online Rally Info:https://www.f150online.com/rally2000/index.html

 

Ryshark5-

You know one thing...the Chevy could have had 4.10 gears already on smaller tires. I know my chevy 2500 silverado has 4.10 gears on 235-70 tires (its my towing vehicle) and I can beat the pants off my friends in their 5.4 fords...hey i gotta have something that can beat'em cause this 4.2 aint gonna do it. But chevy has 4.10 s an option whereas fords can only get up to 3.73..and thats on the 4x4

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1999 4.2l 2wd super cab F-150 3.55 gears LS Mods: 3in body lift, 285/75 R16 BFG AT, suglid tonuea cover (white) 10 disk changer K&N Air Filter Tow package 6000 Lbs GVWR

Things to come: 4.10 gears, Flowmaster 40 series Delta, Superchip, Grill

 

Hey Ilmagil, What kind of gas mileage do you get with the 235s and 4:10s?

 

That i don't know...mostly because its used by someone else during the week and I only use it for towing or just putting some friends in their place...but probably not very good.

------------------
1999 4.2l 2wd super cab F-150 3.55 gears LS Mods: 3in body lift, 285/75 R16 BFG AT, suglid tonuea cover (white) 10 disk changer K&N Air Filter Tow package 6000 Lbs GVWR

Things to come: 4.10 gears, Flowmaster 40 series Delta, Superchip, Grill