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I have a 05 screw with the 4.6 and 8.8 rear end with 3.55 gears. Now for my problem the truck is a dog when accelerating with my trailer 3800 lbs dry weight. Buying a new truck with a 5.4 and 3.73 gears is not an option. I would like to swap the gears but I have 8.8 and I might be able to find a 9.75 w/3.73 in the junk yard and swap them out myself. It would probally be comparable price to the gear swap. If I go this route how could I tell if something is wrong with the rear end before I buy and what else would be needed to complete this swap (U-joints, drive shaft ect.). Or I could get the gears done locally in Ft. Lauderdale but I don't trust anyone working on my truck down here to say that contractors in South Florida take short cuts is an understatement. By the way I had a Edge tuner and really didn't notice a huge differance in performance. If I get tunes next time they will be custom.
I'm not an expert by any means but I did research this topic extensively. I have a 2004 F150, 5.4, 3.55 rear gears (I feel your pain!), 4x4. I had it re-geared about a year ago. Paid about $1100. Was told that a 2wd would have run about $600-700. Regeared to a 4.10. Huge difference in towing and acceleration.
After researching, I'm glad I had it done at a driveline shop. Didn't want to use the Ford dealer. Didn't trust it to a regular mechanic. Sure didn't want to try it myself.
i'd say have it done on your truck, buy the parts new. gears/diff isn't where you wanna cheap out and get junkyard stuff. for an 8.8 you're looking at 300 bucks for a diff, 200 bucks for gears, and 100 for install kit as far as parts. should be about 300 bucks for install. The reason I put the diff on there is, if you have 3.55's you likely have an open differential; putting in 4.10s or 4.30s even will mean you're gonna boil one tire when you wanna take off fast w/ no load.
not sure what kinda splines are the axles in the 8.8/4.6s but if they're 31 spline, you can get by with an 03 cobra 8.8 diff, for about 250 bucks, and it has carbon fiber clutches, which are supposed to last a lot better than the traditional clutches...
First off i'm assuming you have a 2wd.....if thats the case, i'd go the route of swaping out to a 9.75 ....Close to the same cost by the end....and you'd get a stronger axle. Theres a great website. OEM Parts & OEM Wheels - Original Equipment Parts from NewTakeOff that has some good deals on brand new parts...I know theres a lady on here who did the same thing to her truck not too long ago...i'll try and find that post.