I'm knee-deep in opinions regarding my desire to swap out the 3.73 rear diff on my '12 E-350 (V10), and I'm getting nowhere fast.

Some people say "you gotta swap the entire axle assembly." Others say "you can swap out just the ring and pinion in the housing."

Some people say "I had my Ford dealer change out my diff for a couple thousand dollars." I've spoken with actual Ford dealer service managers who say "You're crazy. It's gonna be around $5k. We've never done stuff like this before."

Some people say "Install a 4.30 or 4.56." Others (like a Ford Srv Guy I spoke to) say "You can't install a 4.30 or 4.56 on the E-350."

Some people say "You can sell your old axle to offset the cost of the swap." Others say "Any price you get from your Ford Dealer includes the dealer keeping your old axle."

I've scoured this site to try and get a handle on reality, but I haven't found it yet.

Plus, when I visited Randy's Ring & Pinion site, I found out that 4 different axles were available for my truck -- and I have no idea which one I should specify.

All I know is, I need to put either the 4.30 or 4.56 LS on my truck because it's incapable of towing a 9,700 lb travel trailer up a slight grade while meeting my performance expectations.

Here's what the build sheet says it currently has:
EGAJB - 3.73 Final Drive Ratio / EGJAB - Non-Limited Slip Rear Axle

It's a 2012 E-350 Extended with the 6.8L and 5-spd auto.

I'll send $20 via PayPal to the first guy who can send me an itemized parts list to swap out my diff to a 4.30 LS... something that I can hand over to my mechanic (or ignorant Ford Service Guy) and get the job done.

Any takers?

 

It can be done both ways.

Wow.. run the hell away from that dealer ASAP because they're about to violate you with a large pole. At this point you have shopped online and know what a R&P costs, add some new axle bearings and an LS diff to that and then labor to install it and you might spend $1000 to $1500 at a reputable shop that knows what they are doing.

You can install any gear ratio that is available for the axle.

Forget the Ford dealer.

You want performance while towing 10k with a non turbo gas engine? Seriously? You do realize this gear change will further tank fuel milage even when not towing. Why don't you just get over this irrational expectation and put the money you would spend to better use.

You need the ring and pinion, axle bearings, and an LS diff for your axle. I know the older vans used to have Dana axles but I don't know if that's still the case. Take your VIN and axle code(drivers door pillar) to the Ford parts counter and ask them if they can help you positively ID what axle you have.

 

So Joe Rankin at RRP wins my $20. I pulled the axle tag number off my E-350 and he responded with the parts i need.

Now the only issue i have is: my trusted and very talented mechanic says that he had a customer that did something similar to his truck. It fouled his ABS and traction control and he was unable to get the computer re-programmed to fix the condition.

He is strongly and persistently trying to talk me out of swapping my diff.

Would a 5-Star Tune post diff swap solve this problem? Or does 5-Star simply tweak engine performance (and not the speedo, sensor feeds, etc...)?

 

I think, based on my experience with my Excursion V10 and a 4.10 pulling the same RV trailer, that a 4.30 on my '12 E-350 V10 will positively smoke my old Excursion.

It probably won't be as supernaturally awesome as the 2005 Excursion with the PSD I also used to own (with a 3.73, I think, before the engine blew up on me). That truck pulled a similarly weighted RV trailer up Tennessee's 6% grades like a bat on speed and Red Bull flying outta hell!

As far as gas mileage... folks around here say that fuel economy will most likely improve towing the trailer or putzing around town. I can expect fuel economy to drop if I drive it sans the trailer on long-distance highway trips. I'll see and report back.

Love this forum, guys. Thanks again for all your insights, advice and snarky comments!

 

Is that the same guy from your post above at the Ford dealer? If so your trust is misplaced because clearly he doesn't know what he is doing. Vehicle speed and ABS input is obtained from a tone ring that is attached to the ring gear in the rear axle, and since this tone ring doesn't change there is no reason ABS or indicated vehicle speed should change when swapping gears... unless the mechanic doesn't reinstall the tone ring on the new gearset for some reason. The only thing that will require tuning is a change in tire size.