Hi everyone,
hopefully someone can shed some light on this topic for me. My truck currently has the 3.55 open axle and I'm interested in swapping to the 3.73 LS as I do a fair amount of towing with the truck.

My concerns are as follows.

- if the front differential is 3.55 and I swap the rear to 3.73 will that screw up my 4x4 when engaged? do I need the matching front diff as well??

- I may have read wrong but the 3.73 LS is an electronic locking diff, does anyone know what electronics and wiring I'd need to add in order for the swapped axle to function?

FYI my truck is a 2009 supercab xlt

Thank you

 

You need to do both front and rear the same if you are 4x4. Also LS stands for limited slip which is automatic and not a locker.

 

^thanks for the quick response. noted about the LS. so I have the non LS /non elock 3.55..
So if I found a LS e/locking 3.55 what electronics would I need?

 

You wouldn't find it because it doesn't exist. It would just be a locking diff not LS and locking.

You'd be much better off going aftermarket of a locker. Automatic locker would be cheaper but selectable would be best but more expensive.

Parts wise $400-1000 then factor in labor.

 

for those wondering, I did some searching and found what you need to install the elock

#AL3Z-7E453-DC Motorcraft #TM-233 which is the tccm (transfer case control module) & part #AL3Z-14B166-BA which is the 4x4 control switch located on your dash board, both together should run you about $150 from tascapart.com.. both parts are plug and play with f-150's from 2009 up to 2011 with the electronic locking differential(all fx4's not sure on other trim types).

read http://www.f150online.com/forums/200...ff-trucks.html for further clarification.

 

Don't take this the wrong way,but if you're asking about what you need to do this, I will assume you will be paying someone to do it for you. Yes?
If so, you are looking at I'd guess $2000 (minimum) even maybe $3k or more, parts & labour to;
get new gears (front n back) then installed (front n back) and then the switch and wiring installed and working.

Another option would be to run the 3.55 gears as they are, and get the electronics & locker only installed. What benefit are you expectjng from the higher gears? Unless you are looking to tow heavier things, the 3.73's won't be that big of a dif from what you have. And it won't change what your truck is "allowed" to tow legally (door sticker limits)