I have a 2wd with the 33/12.5/17 on them. I have 355's right now. I notice that when I get up to 75 mph it has a hard time not dropping out of overdrive to keep up the power. I had 275/60/17 on before and it did not do this. I have a friend that will sell me 373's for it. Will that be enough? I also have a superchip in my truck. I have heard of some problems when changing gears and having the superchip. Will I have to have it reprogrammed? I know 4.10 will make a big change, but I don’t want overkill. I want my truck to run like it did when it was stock. I don’t want the rpm's to be higher then they were before because I don’t want to lose MPG. If you think 4.10's will put me back or close to the same then that is what I will do. The 3.73's are close to 3.55's.and I know the rpm difference is about 118 between the two. I can get knew gears for about $135 in Tucson at the Desert Rat. I have done a lot of gear changes in the past so I won’t pay for install. Takes me about 5 hrs to do. I posted this in the Tires and wheels forum. Everyone said I should get 4.10’s so that’s what I will probably do. Will this cause a problem with the superchip and shifting points? Mike, jump in here please. If so I guess I will be sending it back to you for the fix. Man, I will hate to be without my chip. How long will it take to get it back if I have to send it to you? Thanks

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2000 F-150 sport 4.2 v6
Jacobs Ignition
K&N
Superchip
Throttle body spacer
cat back exaust
Custom Seat Covers
Dash Mat
Ford Floor Mats
Cd player
pioneer Speakers
Rockford Amp
Truck Box
Rhino Liner
Grill Gaurd
Nerf Bars
custom graphics
tail light covers
tinted windows
Fabtech Lift spindle lift
33/12.5/17 Procomp A/T

 

Hi TucsonTruck!

OK, 3.73's are not enough, you actually need about a 4.30 gear or so to compensate for those 33's, and I actually like to see a little bit more gear put in, say like maybe a 4.56, just to compensate for the additional unsprung weight load on the motor as well.

However, you probably don't want to go 4.56 with your concerns, and that's OK, and 4.30's are hard to find, so you'll most likely end up going 4.10's. Sorry, 3.73's just aren't going to be near enough and aren't worth doing over your 3.55's in this situation, in my humble opinion.

Yes, we'll need to change some things in your Superchip program most likely, and when we do that, you keep the module until the new program is ready, so you're only without it for a few days or we can do it overnight, too, whatever you need.

Because there are a number of issues here, I would suggest giving us a quick call so we're both on the same wavelength on everything up front before you do anything, leave us a voicemail if you call over the weekend and we'll return the call, otherwise we can talk on Monday if you like.

------------------
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 Event Organizer

 

Thanks Mike. I will be puting in 4.10 here shortly. I will see how it runs. I will then record all the rpm shift points. I'll give you a call after that so we will have more to go on for the fix for the chip. Thanks again.

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2000 F-150 sport 4.2 v6
Jacobs Ignition
K&N
Superchip
Throttle body spacer
cat back exaust
Custom Seat Covers
Dash Mat
Ford Floor Mats
Cd player
pioneer Speakers
Rockford Amp
Truck Box
Rhino Liner
Grill Gaurd
Nerf Bars
custom graphics
tail light covers
tinted windows
Fabtech Lift spindle lift
33/12.5/17 Procomp A/T

 

Hi TucsonTruck,

OK sounds good, have fun & talk to you soon!

------------------
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 Event Organizer

 

Hey Mike,

Would a 98 need a new program for gear or tire changes? I put on a set of BFG 255/85R16s (33.3") and naturally noticed the lost power, but other than that it's running fine (I haven't swapped the speedo gear yet, either). I'm planning on swapping gears up 4.56s later this year.

Thanks,

Jay

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1998 F150 Lariat 4x4 Extended Cab. 4.6L Auto
Mods: Superchip
Airforce One
BFG 255/85R16 M/Ts
Planned: Ravin Z-55

 

Hi Jay,

Because the 1998 & earlier F-150's still use a standard reduction gear, you can restore speedometer & odometer accuracy just by installing the correct reduction gear, and that will automatically bring shift points, etc. back into line with no further adjustments needed in the program.

The ECU will first look at MPH, and then if the speedo is off, it will usually default to engine rpms to determine it's upshift points, so those are normally OK, though you may have downshift point issues, etc. As long as you're happy with how it's behaving, then there is no need to change it.

I'm very glad to hear you're going to do the gear swap so you can get the engine back into it's power band; for your tire size it would require something along the lines of about a 4.33 or so ratio, but doing the 4.56's like you mentioned I like even better, as you'll have just a little bit of extra gear, so to speak, to make up for the additional weight load on the motor from the tires increased weight, so that will work out very nicely indeed.

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 Event Organizer

 

Thanks Mike,

I was wondering if the reprogram was just for the speedo or there were other issues involved.

The other reason I'm going up to 4.56s is that I'd like to get a travel trailer later this year or early next. According to the gear calc web page, 4.56s with my tires yields an effective 3.93, which ought to do pretty well towing < 5000 lbs, I think.

Thanks again,

Jay

 

Here is the site that I use for tire size/rpm/gear change calculations.

www.ring-pinion.com.

I hope this helps you out!

------------------
Boss™

Ordered June 29th, 2000; took delivery Nov 28th, 2000: 2001 F-150 Lariat, Oxford White/Silver Supercab 4x4, Styleside, 5.4L, 7700# payload, Class III Tow, 3.73LS, Skids, Leather Captains, 4W disc ABS, shift-on-fly, keyless, HD everything
Modifications:
"Protected by the Owner with his 2 friends, Smith & Wesson" sticker, Westin Chromed Stainless Nerf Bars, ARE LS II bed cover, Bedrug™, Gibson Swept Side Cat Back, K&N filter w/airbox mods, Pacesetter ceramic coated headers, Hyper-White bulbs, Pioneer DEH-8200R, Ventshades(not on back doors), Hood deflector.
Future Modifications
Superchip, 3" body lift with at least 33's, alarm/pager/auto start system, stereo system

 

Hi jayf,

Yes, an effective ratio of 3.93 should do a very nice job for towing.

Say, if you wouldn't mind, could you post the URL of that gear calc web page, so others will have it handy? Thanks!

------------------
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 Event Organizer

 

Well, I misspoke, I used a spreadsheet I got off of a web page . Here's the url: http://members.home.net/mjbobbitt/f150/tirecalc.html

Another useful site for calculating speedo gears is:
http://www.finer.com/internet/pages/speedo.htm

Jay

 

OK, thanks to both of you for posting those URL's, that should help out a number of people. I couldn't remember the ring-pinion.com, I thought it was something like ringandpinion.com, I just couldn't remember correctly to tell others, so thanks for posting!

------------------
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 Event Organizer