I recently bought an 06 f150 with a 6 inch Fabtech lift and Toyo 35's. I have had a roush i/c supercharger installed and am not impressed as I thought I would be. I have already ordered custom tunes from Mike Troyer and eventually plan on adding more mods. I have been told by everyone that regearing my truck will make a huge difference in low end HP. I have stock 3.55's in right now and I am guessing that is why I am not feeling the potential acceleration that I could with the supercharger. First, will regearing make a noticable difference, second what size and brand would you recommend and will I still be able to cruise on the interstate at 80/90 mph without running at too high of a RPM. Finally, what should I expect to pay for gears and labor. My pick-up is 4wd. Thanks for all of the help. Dave

 

4.56's. Expect to pay from $1500 to $2000 parts and labor for both axles. Your RPM's in OD at 90 mph will be 2750.

 

To start off, I'm not a mechanic or anything, but have been reading the powertrain threads for a while now. What you will hear is very knowledgable people recommending 4.56's to 4.88's for your truck. 4.10' will not be enough gear for your tires. There are no 4.30 gears for your front diff, so that rules that out. 4.56's will be your probable first choice, since you are concerned about rpm's. I have some 4.56's waiting in my garage to go into my truck, just waiting on my tru-trac diff to arrive. Go to ringpinion.com for all the info you need about re-gearing. There are calculators there to figure out your rpm's with whatever gear choice you are considering. Your not going to get your supercharger to perform to your expectations without the means to get the power to the ground efficiently. Gears won't improve your horsepower, but will get you into the horsepower curve faster. Some may even recommend 4.88's, especially if you tow anything with those big tires. You aren't going to get VW TDI efficiency with our trucks. You'll have to be happy with 10-15 mpg depending how you drive with your supercharger and your speeds. Cruising at 80-90 mph is not going to get you anywhere near good mpg numbers. You can't have performance AND mpg without compromising either.

 

Thanks for the help. I realize that my mpg will not be that great. I live in MT and cruising at 80/90 mph on the interstate is the norm. Does anyone have any preference or dislike for any particular brand of ring/pinion or will most of them do the job. I have looked into motive/yukon/ford racing/richmond?? Any Suggestions???

 

Hmm - then why did I get stopped for doing 81 in a 75 on I-94 in the middle of nowhere?

 

Probably because they saw your out of state plates. I am a pharma rep who drives about 70k miles a year covering the whole state and have never been stopped by a cop for driving 81 mph. Must be bad luck. It was only $20 anyways and doesn't go on your record. Right.

 

Most people seem to really like Yukon gears. I have Ford Racing and I have no complaints or problems yet. I really dont know anything about Richmond at all..

 

2 Grand....Ouch, I was planning on doing this in the fall. What is the average shop time to do the swap?

 

I got away with a written warning - no fine.

 

It's easy to calculate the rpm your engine will turn with any combination. Just use this formula.

New rpm at certain speed= (current rpm at same speed)X(4.56/3.55)

 

Or use this calculator:

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

 

Thanks for all of the help. Does anyone have any experience with motive gears. I was able to find them for about $125 less per axle compared to Yukon and others. Is there a reason or truly just a good price. Dave

 

I believe that Motive makes the Ford Motorsports Gears the last few years.

The Mustang Speed Shop on Long Island told my son that he got one of the last sets of Ford Motorsports 4.10 gears made by Motion for his 04 Mustang and that Motive was the new supplier. The implication was that the Motion were better. I know my son's Mustang 4.10s have no noise at all.