I went searching to find what ratio my X was equipped with. I couldnt make out the tag on the rear diff, but the front has a tag that says 3.73 Which is what I figured it had. I just happened to come across a vin check website and ran a report on my X and it says it has 4.10's. I would assume if the axle has a tag that that is what it'd be. But why does the VIN read different?

 

The 4.10 gears only came on V-8 5.4 EXs I think, your V-10 either has the more common standard 3.73s or the factory option and desirable 4.30s. Do you have stock sized tires? If so, what RPM does it turn at 65 MPH?

 

I have stock tires for now. I'll check the rpms when i head out in a bit. Having 4.30's would he great for when I add the 35's. Not ideal but better than the 3.73's.

 

Stock tires, cruising at 65mph i'm at 2000rpms.

 

I've been thinking about regearing my 5.4 4r100 Expedition from 3.55 to 4.10. I was worried 4.10 might be too much but 3.73 isn't a big enough change to worry about. My current tires are (and the new ones will be) bigger than stock Excursion tires.

So learning this makes me feel better.

 

I'm pretty sure the rule of thumb is that 3.73s will be under 2K RPMs and 4.30s will spin over 2K. My rig with an effective ratio of 4.39 (4.88 and 35" tires) and it turns about 2250 RPMS at 65 MPH.

 

I am at 1800-1900 RPMs at 65 MPH with my 3.73 gears. Not sure if it makes a difference with the engines?

 

Does anyone know what is the best ratio for the Ex's? Maybe a nice list showing best ratios for the different engines (Diesels and V10) and uses (towing, offroad, street queen). I know the info is out there, but having it all in one spot would be a great addition to the tech folder.

 

All of the diesels came with 3.73 gears, all years. They do fine even towing with those gears and only really need to go with deeper 4.10s if towing heavy and running 35" tires, some have gone with the 4.30/37" combo also. The PSDs will run out of RPMs too quickly if geared too deeply.
The 5.4 gassers came with 4.10 gears, and while not the best option for towing the V-8 will benefit fron deeper 4.30/4.56 gears for that work.
The mighty V-10 makes better power at higher revolutions than the standard 3.73 gears allow at cruising speed in OD, that's why the factory optioned 4.30 gears do a better job in both performance and towing modes. For heavy towing and still retaining somewhat acceptable solo mileage the 6.8 does great with an effective ratio between 4.30 and 4.56. I ran 4.88s with nearly stock sized tires and it pulled like a locomotive but the unloaded mileage dropped to 12 or below on the highway. With my current combo of 35"s and 4.88 gears it has an effective 4.39 ratio and tows our 11,000lb TT very well with the ability to hold OD on most highway grades and we typically see between 8 and 9.5 MPG on our mostly highway towing trips. Unloaded it gets 12.5 MPG on the highway with the cruise set at 65 MPH. My EX does have the Bank headers and 5Star tunes which both help with the towing work and efficiency.

 

My plan was to lift and throw on 35's. See how the performance feels and then decide on whether it needs 4.30/4.56 gears.

 

It will still drive OK with 3.73/35"s but it will be a bit slower to get up to speed and if you tow it will be a dog.
If you are looking for a "sporty" feel or are looking to do a decent amount of heavy towing then 4.88 (or even 5.13s) will get you there. My rig with the 4.88s and 32" tires was a Hotrod around town unloaded.
We have stayed on Grand Island a couple of times, most recently this past July at the Branches of Niagara campground, will most likely be back up there for a few days this coming May.

 

My 2001 V10 4:30s is over 2000 rpm at 65. Also, my vin does NOT reflect the 4:30s but the door tag code on drivers side does. C1 is 3.73 and C3 is 4:30.

 

WE3ZS,

I currently run a basically stock 2004 X w/ 6.0 and factory 16's (265/75/16) and 3.73's. I am planning a X/C mod and installing 18's with a 275/70R18's. My current travel trailer weighs in around 7500 lbs, but I plan on getting a new unit that will weigh closer to 10K including our gear. Will I notice a significant decrease in performance that would require re-gearing, or would it be negligible, in your opinion?

 

Those tires are about 33.2" tall vs the stock 31.6", so not a huge change from the tires. And the 6.0, even stock has plenty of HP/TQ, I think you should be fine with some way of monitoring your 6.0's vitals. Going with a deeper gears might be counterproductive as they could have you running out of RPMs on the highway.

 

Thanks, I appreciate the feedback. I know many members run larger tire and rim configurations, but I wanted to make sure I would not lose too much. I have a CTS that I use to monitor the vitals.

Now I just need to pull the trigger and get things done. I want to get the springs and wheels done before our first camping trip. That doesn't leave me much time!