Can Change 3.55 Gears to 3.73?

hotpep1 wrote:
Without getting into all the specs. of my 2007 Ford F-150 King Ranch (we'll do that another day!), how big a deal (and how costly) is it to change the 3.55 gears out for 3.73's?

Thanks,
Carol

2007 Ford F-150 King Ranch Supercrew
2008 Coachmen Captiva 288FKS

When I had a Ford F-150 it had 3.42 gears in it an I changed out the rearend and 3.90 gears were installed. Definately woke up the truck and only changed the RPM's around 250 RPM's. Was really worth the money. Good Luck and Happy Camping. At the time, new gears and bearings were used and the cost was around $600 including labor.

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The most economical way to swap gear ratios is to buy an entire used axle assembly from a yard. Under 2 hours to install and doesn't require unusual skills, any decent shop can do it.

If replacing just gears, I've heard that factory gears are the highest quality for both steel and machining (noise free). They are also amongst the most expensive up front.

Wes
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I had a 1/2t gasser with 3.92 and they were a great compromise for mpg and towing. Craig

Skip 3.73 if you want to swap. Consider 4.10 or 4.56. But I highly recommend just replacing the truck with something new enough with a 6-spd trans. Take a look at this chart, Column E. 6-spd + 3.55 is waywaywaywayway better than 4-spd 4.56 even. 5 usable towing gears and that first gear ratio to get you moving and into peak torque engine speed.

Changed my 3.55 to 4.10 and it made a huge improvement. Previously it was always in the wrong gear and would downshift too easy. 4.30 would have been better, 4.56 probably a bit much. I also added Eaton TruTrac at the same time, both axles. Yes about $1,000 per axle and an extra $500 for the differential upgrade. No regrets. don't bother with 3.73 if spending money.

You could go with a 2" smaller diameter tire to get you near the 3.73 gear ratio your looking for.

JKaz

Probably not worth it for that small of a change. If you are going to do the change go 4.10 or even 4.30 depending on how much empty driving you do.

Have you already towed with it at 3.55. If you did what exactly about the experience did you dislike and want to fix with a change of gearing?

With my Dodge Dakota 4.7ltr V-8 going from 3.55 to 3.92's (factory tow option) I gained 2000lbs towing capacity so a rough guess you'd only gain about 1000lbs towing.

you will never notice the difference on that smidge of a change. Why not just give me 1/4 of the cost for the advice. :W

Agree with Tystevens, that's just a 5% change in final drive ratio. You won't be able to notice much difference. It's not worth the $ and effort unless you go to at least the 4.10 range.