Changing 2018 from 3.31 to 3.73

[bchampion]

I bought my 2018 brand new off the lot back in December 2017 and it did not come with the heavy duty tow package. It's a 4x4 Platinum Max. According to the Ford factory towing specs, the max I can tow with this setup is 6000lbs. Well I would like to be able to tow at least 8000 lbs. The factory HD tow package includes 2-speed Automatic 4wd w/Neutral tow (4x4), Radiator upgrade, Pro Trailer b/u assist, 3.73 limited slip Diff, Trailer Brake controller, Trailer sway control which allows the 4x4 Max to tow 9000lbs. I recently added the trailer brake controller and I asked my dealership if they could change the ration in my rear end to 3.73. They said they couldn't do it and it would void my factory warranty. Well I'm not worried about the warranty and rear end ratios can be changed by any competent mechanic. The upgraded cooling is probably just a larger radiator which I'm sure I could order from Ford parts. The big thing for me is 3.73 rear, I'm not so concerned about the other items in the HD tow package and changing out the rear gears would sure be cheaper than buying a new Expedition.

 

[stamp11127]

May want to research the brakes before making any changes. You're wanting to increase the tow capacity by 50%.

 

[duneslider]

I can't see how changing gears would affect warranty. Anyway, any place that does gears could do a gear swap and probably cheaper. You will need a computer reprogram once the new gears go in and that probably has to be done by the dealer. It is possible that 5star or one of the other programmer companies may be able to make that change. Based on what happened in my Jeep the shift points were WAY off when I regeared. I have heard newer stuff isn't even driveable after a gear change due to errors.

I hate getting all "legal" but in most states DOT won't consider your tow rating higher just because you regeared it, if something were to happen, they would go back to what the factory says. I think in my state there is some process you can go through to get things reassigned but I haven't looked into it.

For me, I am like you, I would regear and see if the cooling needed anything. (Worst case, add a transmission cooler and upgrade the radiator) I haven't used the fancy backup thing at all and probably never will. The stickers don't really fit on my current trailer, if they did, I might try it just for fun but I don't have any issues with backing up trailers.

 

[shane_th_ee]

You're not going to like this. The 3.31 is an open differential. The 3.73 is an electronically controlled, hydraulically actuated limited slip differential, with locking mode. So the difference isn't just a ball of gears. It's a ball of gears, a couple of clutch plates, a hydraulic pump, a wiring harness to connect the pump to the truck's computers, a temperature sensor and some software to control it all. Oh, and the center differential is different, too. I think it'll be cheaper and easier to sell the one you have and buy one with the 3.73.

 

[bchampion]

Well that sucks

 

[Grey ghost]

See if you can locate two center sections from a junk yard but wiring them up would probably be a mess. Hate to say it but trading may be your best bet.
Why not call the guys at 5 star tuning?

 

[osteodoc08]

What are you towing exactly? If it’s a want to tow 8k vs a need to tow 8k.

depending on potential depreciation if selling, may consider buying a used HD to tow with.

 

[Deadman]

Trade it in. Theres 5X more involved than meets the eye.
There's new ABS reluctors needed for the gear change and all the internals of the rear end, a ton of programing that you probably can't get done and then all the headaches of when it doesn't work out and you have $5K stuck into a vehicle that isn't drivable.

 

[byathread]

I thought all the max expeditions have 3.73 rear ends, no?

 

[byathread]

I thought all the max expeditions have 3.73 rear ends, no?

Just looked it up, as you were... [emoji55]