My '04 FX4 has the tow package and the 3.55's. =( I always thought it had the 3.73's, then I had to go and get curious and check on it!

 

I'll be picking up my 07 FX4 on Friday (I hope - long story). I thought I had spec'd the 3.7's but it turns out I hadn't, fair enough... dealer showed me my email. My new baby has the 20 inch wheel. This is a special truck for me, I have ordered it with a Roush SC (plus, plus) so I'm sure power won't be a problem. I'm thinking I may actually be better off with the taller gears - maybe one fewer shift on the way to the legal limit.
Anyone else have experience with the 3.55 vs the 3.7's when making a bunch of extra power?

 

you should be quite happy with that set up....


post some dyno runs and some pics of that bad boy and congrads....it's going to be an awesome truck...

 

I got the smallest truck with a 4.2 and a 5 speed. I was only able to upgrade to a 3.55 and that was as low as ford would offer for my truck. It was cool with the stock tires, and they would spin without using the clutch, and have a nice chirp into second. Since I got the 275/55R20's the ratio was horrible, especially for the 4.2 which doesn't have the best low end and is better on top. With the sticky toyos I could barely spin in first when its dry, but when its wet I do second gear burnouts all day.

I was considering a swap to a 3.73 but have been told it would be to small of a change for the effort. Then I considered 4.10 and that would be for pure fun and excitement. With the very common 8.8" though I found more uncommon ratios like the 3.90 and the 4.00, and now I just don't know.

I live in a rural area, so most driving anywhere is going to be 45-60 most of the way. When I go on the freeway on the occation its usually up the sierra nevada and it is a steep climb for a long way, so 65-70 is the fastest I will ever go occationally for extended periods of time. I also do alot of city driving like 45mph.

The truck is used for transporting my quad to the OHV parks and some have gotten prety hairy where first was almost not low enough, and its almost a granny low, at a 3.90 first gear

Any suggestions?

 

mustang guys love the 3.90 ratio for automatics. with a stick you really don't need anything deeper than 3.73

3.90 and 4.10 are perfect for auto's because of the torque converter. with 4.10 in a stick, you really won't like 1st gear

 

thats true. Gear swaps in manuals usually make a bigger difference than autos. Im still a little unsure because of the 32" tires. Right now with 3.55 gears, I hate to say it but its guttless for my tastes, and the 4.2's have good potential.

 

My 01 with 4.2 had 17 inch aftermarket wheels and BFGs. It seemed to struggle even with 3.55. My current Scab with a 4.6 and 18 inch Lariat wheels and 3.55 seem a good match. Just right on accelleration. MPG seems as good as with the 4.2 so there must be less struggle getting to speed I would think.

 

can I or would I want to out a 3.73 in my 1998 4.2?

 

The rim size doesn't really matter. Its the diameter of the tire. You can get 17" rim on a 20" tall tire or a 44" tall tire. I have 275/55/R20, which is 20" rims on a 31.9" tall tire. Far from stock.

Not trying to be rude or anything just explaining my reason for considering an even lower gear, like a 3.90.

 

Go for the Heavy Duty Payload package, 4.10's are standard. The ride is way softer than an F250 and my cargo cap. is within 90lbs of my friends F250 4X4 psd.