I have an 08 Screw 5.4 that came stock with 3.55's. I am looking at getting a 33-34" tire here soon which now also has me thinking about tearing into the axles to upgrade the gearing. I do plan on towing my 05 Mustang to and from races and I haven't gotten a trailer yet but I would guess around 5,000lbs combined trailer and car weight. With that information, what gearing would you suggest? I was thinking 4.10?

Also while I am in there I figure I might as well upgrade the differentials. I've had tons of luck with the Detriot Tru-Trac in my Mustang. It's always been smooth and planted the power when I need it. Anyone use them in their F150? Any downside to installing one in the front axle, or similar limited slip/locker for that matter?

Thanks in advance.

 

so, I assume your 4x4 ?

I would suggest, since you plan on towing, maybe looking into the 4.56:1 gears. They will give you additional "umph" and get you going with that trailer. Also, it would put you in the stock power curve, if you had the original 3.73's (like what comes in the towing package). I also would suggest the lower gear ratio, because I can assume you don't have the towing package, which means you have the smaller transmission cooler. The lower gears would make the trans work less, reducing some heat, making it live a little longer.

detroit tru-trak. Decent option. I personally will be running the detroit locker in the rear. Tire wear is about the same as the tru-trak, plus its locked 100% and breakage is un-heard of. So, either way is a good route. I wouldn't suggest putting one up front. You have IFS, which = plenty of weak spots. I can't imagine putting these new trucks in a situation where you need a front locked. If your there, your breaking things. That being said, you can run one. Guys on here do. One guy runs the selectable locker, when "off" it works as a LS diff, and then "engaged" its fully locked. I wouldn't abuse that little front diff too much though. I would suggest leaving the front open.