2020 Ford F250 on 37s - Expedition Truck Camper Build!

[yfarm]

I went from that tire size to 315/70 17 with 430 gears. No lift. Speedo is off by 5 mph. Engine rpm dropped by couple hundred at same speed. With new tires running 75 mph at around 2100 rpm. Hand calculated known distance mpg is 12.5 at 75-80 mph interstate driving empty. Towed a 13000 lb triple axle boat last week 8 miles for repair, no issues but 5-6 mpg.

 

[greengreer]

I'm on 32's with 4.30's and my speedo reads fast by a little bit. 33's would probably be perfect. That being said I think we'll go 285/75/17 (34") when we need tires next.

I feel like there's no lack of power with the camper or towing my dump trailer here in the mountains. Best mpg is 13, average is closer to 11. Pass everything but a gas station...

 

[mk216v]

Here's what you need to know:
+ 3.73 gears are "standard" with 33" tires for this truck.
+ 4.30 gears with 37" tires are exactly the same overall ratio as the "standard" gears. A deeper gear couldn't hurt to help offset the tire weight increase. However, this is a HD truck not a Toyota. They are not affected nearly as much. Everything is beefy included the dedicated transmission cooler.
+ I monitor the truck with a scangauge 2 for exact transmission temp, coolant temp, engine load, fuel consumption. It has stayed far from any sort of "overheat" situation. Trans fluid temp will drastically shorten a transmission life.
+ We run with "tow/haul" when loaded. Slight improvement is shift speed and higher rev shifts. It is far from feeling bogged down or overloaded or overworked. It pulls great. And happily chugs along at low revs generally.

Our recent 3hr tow resulted in 11.5mpg fully loaded with the camper and trailer. So definitely don't think we are risking damaging anything. It has margin to spare!

I've had multiple sets of gear sets fail on previous Toyotas. Partly because the low ratios significantly reduce gear strength and material. But I totally prefer the factory thick cut 4.30 gears. 4.56 would be a downgrade in many ways. 4.88 is enough ratio change to possibly be worth while but only if I wanted to further increase tire size - really don't think we will at this point.

Don't forget. We also owned essentially the same exact truck but 2019 Crew Cab model. It had the 3.73 gears with 33" tires. And we hauled the Laredo SC camper on it. So I'm very familiar with how either setup feels.
4.30s with 37s is not much different. And our speedometer is nearly dead on (within 2%). It's an ideal truck to build as you can factory option the gears and rear locker for CHEAP. Love factory stuff that works.

Minor correction; 4.30/37"s are the same as 3.73/32.1"s(275/65/18), but if someone has the optional OEM 275/70/18's(33.2") with 3.73 and they wanted to upgrade to 37"s, they'd need a new ratio of 4.16 gears to be equivalent to "stock." Of course the 4.30 would cover that easily. https://tiresize.com/gear-ratio-calculator/

Why do you say the 4.56 would be a downgrade (if they were offered for the Advantek 275 rear end, which they aren't--only 4.30 and 4.88; https://www.justdifferentials.com/Ford-Super-Duty-Gear-Package-p/gpsd17-select-275.htm; 2017+ Ford F250 Superduty with 14 Bolt rear cover, 2017+ Ford F350 Superduty Single Rear Wheel (SRW))?

You did it right by ordering your truck new with the factory 4.30's ($390 option). In my experience it's VERY difficult to find a pickup with 4.30 vs 3.73. I was lucky to find my chassis cab with 4.30's, but the issue now is that I need a backseat in it for furry kids, hence selling the ReCab chassis cab for the CrewCab pickup.
Cost to add high quality 4.30's(or 4.88's) after the fact? ~$3700 parts/labor!

 

[Grassland]

If you don't mind a quick hi-jack I have a question for the folks here that have more experience with gearing and tires than I do.

I have a 2014 6.2 with 3.73's and stock my truck came with 245/75r17's (31.5's) FWIW.

The PO put on 275/65r18's (32.1's).

I am looking into up sizing to a 275/70r18 (33.2's), and my truck hauls around a built out Grandby FWC full time (~2k #'s).

Will bumping tire size 1.7" above stock be noticeable (I wish my truck came with the 4.30 gears!)?

@montypower amazing truck. Rad to see how far you are able to push an F250 with a hardside off road!

Not an apples to apples comparison but on my 3.73 geared 3.7 V6 F150 stock size was 235/75R17 (30.9) and went to BFG KO2S in 34x10.5R17 (they measure small so call them a 33) and that's about the max it can handle without a regear. I've tuned the truck and calibrated speedo/shifting etc with new tire size.
This is towing 2500-3000# with 800-1000# in/on the truck.

The Super Duty is weird in that the exact same engine and gearing comes with tires ranging from 31.5 to 33" depending on trim.
So if 3.73 is just fine to run as large as 33" tires stock, then running a 35-37 on 4.30 is essentially the equivalent.

As well, F150 raptor on 35s has 4.10 gears yet ask anyone what to re gear to with 35s on any other F150 and they will say 4.56 or 4.88. ?

 

[montypower]

Why do you say the 4.56 would be a downgrade (if they were offered for the Advantek 275 rear end, which they aren't--only 4.30 and 4.88; https://www.justdifferentials.com/Ford-Super-Duty-Gear-Package-p/gpsd17-select-275.htm; 2017+ Ford F250 Superduty with 14 Bolt rear cover, 2017+ Ford F350 Superduty Single Rear Wheel (SRW))?

You did it right by ordering your truck new with the factory 4.30's ($390 option). In my experience it's VERY difficult to find a pickup with 4.30 vs 3.73. I was lucky to find my chassis cab with 4.30's, but the issue now is that I need a backseat in it for furry kids, hence selling the ReCab chassis cab for the CrewCab pickup.
Cost to add high quality 4.30's(or 4.88's) after the fact? ~$3700 parts/labor!

4.56 gears are so similar to 4.30 that you'd be hard pressed to notice much if any difference. And they are thinner than the 4.30 gears (less strong). And the cost. So I'd consider it a downgrade. Would keep the 4.30s or go to 4.88s.

We actually paid closer to ~ $200 for the 4.30 gearing option (got fleet pricing). I agree. There was nothing searching the entire country on the ground. Ordering is fantastic option! Totally worth the wait to get the good options and all the stuff we selected was cheap!

 

[montypower]

The Super Duty is weird in that the exact same engine and gearing comes with tires ranging from 31.5 to 33" depending on trim.
So if 3.73 is just fine to run as large as 33" tires stock, then running a 35-37 on 4.30 is essentially the equivalent.

As well, F150 raptor on 35s has 4.10 gears yet ask anyone what to re gear to with 35s on any other F150 and they will say 4.56 or 4.88. ?

Exactly. 4.30s are near perfect match for 37s. Thanks @mk216v for doing the math again. Technically it's slightly too low of gearing for the 37s. If you want to bolt on 37s stock... order 4.30s. It's the cheapest route to big tires on any stock pickup with proper factory gears. Plus, rear selectable locker!

This was the cheapest truck I've built so far. So many great factory options. Aux switches, vinyl seat, vinyl floor, locker, gears, power inverter, gas skid, 240amp alternator... and it's an XL yet I can remote start/lock the truck on my phone (free). Ford doesn't advertise this for the base trucks but totally works! Love the beefy axles, massive transmission cooler, huge power steering cooler.

 

[mk216v]

4.56 gears are so similar to 4.30 that you'd be hard pressed to notice much if any difference. And they are thinner than the 4.30 gears (less strong). And the cost. So I'd consider it a downgrade. Would keep the 4.30s or go to 4.88s.

We actually paid closer to ~ $200 for the 4.30 gearing option (got fleet pricing). I agree. There was nothing searching the entire country on the ground. Ordering is fantastic option! Totally worth the wait to get the good options and all the stuff we selected was cheap!

Exactly. 4.30s are near perfect match for 37s. Thanks @mk216v for doing the math again. Technically it's slightly too low of gearing for the 37s. If you want to bolt on 37s stock... order 4.30s. It's the cheapest route to big tires on any stock pickup with proper factory gears. Plus, rear selectable locker!

This was the cheapest truck I've built so far. So many great factory options. Aux switches, vinyl seat, vinyl floor, locker, gears, power inverter, gas skid, 240amp alternator... and it's an XL yet I can remote start/lock the truck on my phone (free). Ford doesn't advertise this for the base trucks but totally works! Love the beefy axles, massive transmission cooler, huge power steering cooler.

Well, we have a few details of importance here, hehe;
--4.56's not available for 2017+ Ford F250 Superduty with 14 Bolt rear cover, 2017+ Ford F350 Superduty Single Rear Wheel (SRW) with the Advantek M275 rear end. 4.30 or 4.88 are from Nitro. 3 of you are saying go to 4.88, I'm still thinking 4.30 for a bit better MPG.
--Regarding cost, most of us aren't building/buying new Ford's, so the cost savings by going with factory Ford 4.30 vs aftermarket 4.30 isn't an option <cry>. BUT, if someone is wanting to spec a new truck, and go 37s, then factory 4.30 e-locker rear for sure!
--Awesome! You spec'd yours very well, nearly identical to my used '19 F350 4x4 CrewCab Lariat SWB pickup (upfitter switches, LED clearance lights, 110V/400W inverter, 240A alt, HD battery, heated/cooled seats, leather, 3.73 e-locker...but missing vinyl floor option, 4.30, skids(will code in Hill Descent with Forscan), 360deg camera). Did you order the heavy duty battery on yours?

 

[montypower]

@mk216v Well summarized...

I'm plenty happy with the 4.30 gears and 37s. But think 40s!!

Think we have the standard battery (at least no upgrade charge). Figured I'd try to kill it and replace in the next year or two. It has handled some high load winching (pulling trees).

 

[mk216v]

@mk216v Well summarized...

I'm plenty happy with the 4.30 gears and 37s. But think 40s!!

Think we have the standard battery (at least no upgrade charge). Figured I'd try to kill it and replace in the next year or two. It has handled some high load winching (pulling trees).

Ok, 40s look cool, but let's be practical(shock!). You already have a hard-sided camper and I will too, we'll both be at the same lift height (Carli 3.5"--'19s are already 1" taller than the '20s, which is why a '19 specs at only 2.5" lift but the '20 specs at 3.5" lift); do we need to go even taller in the air with 40s? Plus, I was asking Dan at Carli if he has any customers with 40s on their susp; check out hoopdeez on IG. Dan says 40s will most likely need fiberglass fenders (McNeil are nice yes), which look cool and all, but just more $$$. And despite some people asking for it, Carli doesn't have any current plans to offer a 4.5/5.5" lift to help clear 40s better.
I'll give it more thought as to what gears I go to with 37s, but while the majority are suggesting 4.88s with the 6.2L gasser, I'm thinking 4.30s will be just fine for me. I appreciate your feedback.

Good to hear on your battery.

Looking forward to the next video...

 

[montypower]

There are those ugly Fab Four fender flares to cut/fit 40s at stock height. Nothing should be required in the rear. Front may require dropping the bump stop 1" more and cut/roll/weld front fender. So it wouldn't require fiberglass but some fabrication (to keep height lower).

But I think I'll keep with 37s. It's clean and fits well. Axles are plenty strong asis. 40s would require further modifications like RCV axles. Probably not worth it... other than the cool factor.

Doubt there is anywhere with skilled driving this truck on 37s won't go that 40s would enable it to go. And getting to remote places is what it's all about!

 

[mk216v]

Doubt there is anywhere with skilled driving this truck on 37s won't go that 40s would enable it to go. And getting to remote places is what it's all about!

That's what we like to hear! Thanks for pushing your truck and documenting it through video for us to follow along. <beers>

 

[montypower]

As with any truck build project… there is always more to do! Here’s the latest changes we made to the Ford Super Duty:

- Fox 2.5 Resi DSC Rear Shocks (tuned by Accutune) – Icon Shock Boots
- Rear shock mounts chopped for 2” increase in ground clearance
- UCF (Under Cover Fabworks) Sterling 10.5” Differential Cover
- Crown Performance SS Rear Brake Lines (custom length)
- Interior Bike Rack (moved over from 2019 Crew Cab)
- Carli Rear Bump Stop Drop
- Deaver Leaf Springs
- Sway Bar Delete
- Fox ATS Steering Stabilizer
- Carli SS Front Brake Lines
- PSC Hydro Assist Steering
- ScanGuage II (monitoring)
- RAM mounts for camera and tablet
- ForScan computer programing changes (tire size, tire pressure and more)

So far… The truck has been working great! It’s fun putting it through the paces on/off road and making changes as needed. Performance has been excellent. There are several additional modifications in the works but nothing that will keep us from adventures!

 

[Ninelitetrip]

Nice build, making great progress. Nice to see a current production truck getting modified with documented upgrades, and not turned into a rolling advertisement. All the fabrication work looks top notch. My bad if I missed it. Are you using factory fluids, or will you change out to something different in say the rear diff.? I read the post on YT asking for a spreadsheet. Maybe change your original post with rolling updates on changes? Or somewhere. Does make keeping track easier for some us.

 

[montypower]

Nice build, making great progress. Nice to see a current production truck getting modified with documented upgrades, and not turned into a rolling advertisement. All the fabrication work looks top notch. My bad if I missed it. Are you using factory fluids, or will you change out to something different in say the rear diff.? I read the post on YT asking for a spreadsheet. Maybe change your original post with rolling updates on changes? Or somewhere. Does make keeping track easier for some us.

Yes, will do! I'll edit the first post with current details. Still running factory equivalent fluids... front/rear differentials were changed with Mobil 1. Power steering system is running Swepco fluid (for PSC hydro assist).

 

[Ninelitetrip]

Peter,

Did you manage to get any video of the fab work on the rear mounts? Would certainly like to see whatever you put together on the PSC. Now that you have the FOX shocks, can you expand on the choice vs say the KING shocks from Carli? What was end goal with the shock tuning?


Thanks.