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

[mk216v]

I'm using the factory tire carrier. The Carli hitch is crazy expensive and only offers room for a 38" tire. I'm happy fitting the used 37" tire (close enough).

I really doubt there is any MPG increase with lower gears. I monitor the real time mpg and every time I bump RPM by downshifting the MPG drops. It wouldn't be worth switching from our 4.30 gears to 4.56 - way too small of a change. Maybe 4.88 but then I'd want 40s.

37s and 4.30 gears = 10-12mpg average with the camper loaded on trips in mtns and wherever. Best so far was 13.5mpg. 4WD off road exploring for days resulted in 9mpg. Rarely have driven empty but would be 14mpg or better depending. Trailer towing it is around 10mpg.

Just got the PSC hydro assist ram installed. More testing needed and will do update video. It basically reduces the stress and wear on the steering components (think gear box, drag link, pitman arm). Steering force comes from drag link and tie rod. It makes turning easy. PS pump appreciates it. Helps mute or reduce steering feedback from the large tires (nice side benefit). Complexity is really minimal... 2 hoses and steering ram. I can cap the gear box if anything failed. Loved it on the rock crawler Tacoma - complete game changer.

OX locker has been flawless so far. Once I got the proper compressor pressure switch. OX needs the ARB 180901 which operates 135-150psi. OX needs to update their website. Love the beefy diff cover and ability to manually lock in if air failed. It defaults to unlocked. Think the only bumper is the limited availability depending on application. Vastly superior design to ARB from a reliability and complexity standpoint. I've easily had 10 plus differentials with ARB lockers... The older ones were better as they used old school o rings on the air collar. The newer ones have a squared off o ring design with can roll and leak more easily. None of the issues I've had were installation related... They are amazing when functioning properly!! But they they will partly fail and do weird stuff like sucking gear oil back through the air line when locker released. Or slow internal leak that will pump diff full of air. Never had one break though! Selectable lockers incredible (when working).

Hope that helps!

With 37's I would go 4.88 all day long. I wish I would of gone 4.88 even with 35's and the load I was carrying. Remember you have a six speed. Charts online dont give acuratte info. You will not rev to high. Less work load on engine will save your truck. If 37s go 4.88. I get 14 without camper. Camper was 12, but I dont down shift and stay in 6 all day on the highway. PM for my number and will chat about it if you want.

Zach

Thanks to both of you.

Ah, it's a Carli hitch vs under-bed tire carrier. Well I'm really happy to hear that the factory tire cage can accept a shaved 37". Will save me from a custom rear-mounted tire swingout!

"-37s and 4.30 gears = 10-12mpg average with the camper loaded on trips in mtns and wherever. Best so far was 13.5mpg. 4WD off road exploring for days resulted in 9mpg. Rarely have driven empty but would be 14mpg or better depending. Trailer towing it is around 10mpg."
"-37s and 4.88 gears. I get 14 without camper. Camper was 12, but I dont down shift and stay in 6th all day on the highway."
What rpm's are you guys at in 6th at 55mph and 65mph?

Thanks for the PSC and OX info. How do you lock the OX manually if needed?

 

[montypower]

Thanks Zach -

I agree. If I was paying to regear... It would be 4.88 all day long! But 40s would be short behind that. I agree, it's not worth the money for small gearing changes. However, with the 4.30 gears and 37s it seems perfectly happy. Recalibrated the speedo with (free) Forscan software it is within 2% of GPS (sweet).

Keep in mind the 2017+ trucks have been dyno tested showing 10% more HP at the rear wheels compared in the earlier model trucks. Likely from the more efficient 6R100G 6 speed transmission. And possibly motor/programming changes. It is easy to downshift as needed on the hills for more power (higher RPM) but it does fine and the motor prefers lower REVs for mpg.

I'd be more likely to supercharge the 6.2L before dropping $2,500+ for regear. Plus, I may have to change the carrier(s) for the front/rear lockers which would add more $$. I typically drive under 3k RPM which is perfect for a supercharger. Loved my 3.4L 4runner with blower (great usable power in low RPM range).

It seems your MPG is the same as mine but I'm rolling 37s with lots of steel/armor. It's a hefty kid. I really don't find the motor lacking in power, ever. It can accelerate up any grade fully loaded. What more can you ask?

 

[montypower]

Thanks for the PSC and OX info. How do you lock the OX manually if needed?

You unthread the air fitting from the diff cover. Thread in the "drive away lock" which engages the locker as you bolt it in. Really simple. Like 5 minute deal.

 

[mk216v]

Thanks Zach -

I agree. If I was paying to regear... It would be 4.88 all day long! But 40s would be short behind that. I agree, it's not worth the money for small gearing changes. However, with the 4.30 gears and 37s it seems perfectly happy. Recalibrated the speedo with (free) Forscan software it is within 2% of GPS (sweet).

Keep in mind the 2017+ trucks have been dyno tested showing 10% more HP at the rear wheels compared in the earlier model trucks. Likely from the more efficient 6R100G 6 speed transmission. And possibly motor/programming changes. It is easy to downshift as needed on the hills for more power (higher RPM) but it does fine and the motor prefers lower REVs for mpg.

I'd be more likely to supercharge the 6.2L before dropping $2,500+ for regear. Plus, I may have to change the carrier(s) for the front/rear lockers which would add more $$. I typically drive under 3k RPM which is perfect for a supercharger. Loved my 3.4L 4runner with blower (great usable power in low RPM range).

It seems your MPG is the same as mine but I'm rolling 37s with lots of steel/armor. It's a hefty kid. I really don't find the motor lacking in power, ever. It can accelerate up any grade fully loaded. What more can you ask?

You unthread the air fitting from the diff cover. Thread in the "drive away lock" which engages the locker as you bolt it in. Really simple. Like 5 minute deal.

Peter, if you were paying for a re-gear for 37s, knowing you're happy with your 4.30's/37s, Zach likes his 4.88's/37s, why wouldn't you go with 4.56 as kind of a sweet spot(bit lower revs, maybe a bit better MPG, bit thicker/stronger gears)? Just curious is all.

'17+ F250's w/ the 6R100G dyno'ing higher?

Thx for the info on the OX--glad they thought of that.

Edit--
"-37s and 4.30 gears = 10-12mpg average with the camper loaded on trips in mtns and wherever. Best so far was 13.5mpg. 4WD off road exploring for days resulted in 9mpg. Rarely have driven empty but would be 14mpg or better depending. Trailer towing it is around 10mpg."
~1600 rpm @ 60mph.

"-37s and 4.56 gears. I get 14 without camper. Camper was 12, but I dont down shift and stay in 6th all day on the highway."
@ 60mph'ish, ~1700 maybe lower... it’s moves through gears way better. Down shifts less.

From Carl at JustDiffs, there's unfortunately no 4.56's for the '17+ Advantek M275 rear end, only 4.30 or 4.88.
2017+ Ford F250 Superduty with 14 Bolt rear cover
2017+ Ford F350 Superduty Single Rear Wheel (SRW)

 

[montypower]

True higher ratios are stronger. 4.30s are considered "thick cut" gears and sweet factory option! However, the strength difference between 4.56 and 4.88 is minimal (neither are thick cut). I wouldn't want to regear a 2nd time and having the flexibility for larger tires is great. MPG is really not going to change much either way and can be compensated by driving style and speed. 4.88 for the win (for me) if paying to regear. And then 40s!

6R100G is the transmission behind the 6.2L (2017+) in the F250 variety. In the 2017-2019 F350 had the 6R140. 2020+ F350 has the new 10 speed (same transmission for everything except F250 6.2L which has 6R100G).

Check out the dyno charts from 5 Star Tuning. They have one that shows stock 6.2L prior 2017 and post 2017. And tuned differences.

 

[Skinhyfish]

Thanks Zach -

I agree. If I was paying to regear... It would be 4.88 all day long! But 40s would be short behind that. I agree, it's not worth the money for small gearing changes. However, with the 4.30 gears and 37s it seems perfectly happy. Recalibrated the speedo with (free) Forscan software it is within 2% of GPS (sweet).

Keep in mind the 2017+ trucks have been dyno tested showing 10% more HP at the rear wheels compared in the earlier model trucks. Likely from the more efficient 6R100G 6 speed transmission. And possibly motor/programming changes. It is easy to downshift as needed on the hills for more power (higher RPM) but it does fine and the motor prefers lower REVs for mpg.

I'd be more likely to supercharge the 6.2L before dropping $2,500+ for regear. Plus, I may have to change the carrier(s) for the front/rear lockers which would add more $$. I typically drive under 3k RPM which is perfect for a supercharger. Loved my 3.4L 4runner with blower (great usable power in low RPM range).

It seems your MPG is the same as mine but I'm rolling 37s with lots of steel/armor. It's a hefty kid. I really don't find the motor lacking in power, ever. It can accelerate up any grade fully loaded. What more can you ask?

Better for slow starts on trails and your transmission. Don’t plan to tow you won’t have any power left.. $2500 gears for better driving experience is way better than a new transmission

 

[rruff]

Better for slow starts on trails and your transmission. Don’t plan to tow you won’t have any power left.. $2500 gears for better driving experience is way better than a new transmission

The truck is designed to tow and haul... that's really the only reason for 3/4+... and it comes stock with a 3.73 ratio. The 4.3 he has near perfectly compensates for the 37s. He's not even towing heavy, which is a much bigger strain on the transmission than carrying a camper, and people do that all the time with stock gears. So, I think he's good.

Plus, I've heard too many stories of mechanics screwing up gear installs and the aftermarket gears not lasting.

 

[Skinhyfish]

The truck is designed to tow and haul... that's really the only reason for 3/4+... and it comes stock with a 3.73 ratio. The 4.3 he has near perfectly compensates for the 37s. He's not even towing heavy, which is a much bigger strain on the transmission than carrying a camper, and people do that all the time with stock gears. So, I think he's good.

Plus, I've heard too many stories of mechanics screwing up gear installs and the aftermarket gears not lasting.

Well I’m a guy who had 3.73 gears in my truck and now have the correct gearing. I can vouch for the improvements and benefits over negatives from real world driving. Have you upgrade a vehicle the same way or have similar truck? If not my opinion might be more valid than yours.

i say this not for ego but want OP to get the right info rather than just an “opinion” with no real world knowledge and the OP get shorted on help.

3/4 ton is more weight carrying capacity. When you change the ratios and heights, it’s best to match what stock was supposed to compensate

these trucks have a 6 speed transmission, higher gearing is compensated by the over drive. The old ratios and most charts online are still thinking a truck has a 4 speed or 5 speed.

 

[rruff]

The old ratios and most charts online are still thinking a truck has a 4 speed or 5 speed.

You should talk to Ford about that. If you opt for the 10spd the stock gearing is only 3.55! They like the tall gears for some reason.

 

[Skinhyfish]

You should talk to Ford about that. If you opt for the 10spd the stock gearing is only 3.55! They like the tall gears for some reason.

Ya they are focused on mileage and taking strain of a transmission that’s why the number of gears in a transmission. My buddies 10 speed surely did not like 37’s until a regear. You want to talk about down shifting. That 10 speed was way happier to have less rolling friction than my 6. If you have a 10 speed than it’s a must.

 

[montypower]

Better for slow starts on trails and your transmission. Don’t plan to tow you won’t have any power left.. $2500 gears for better driving experience is way better than a new transmission

Appreciate the concern. I've build a dozen trucks or so over the past 18 years. I'm extremely familiar with gear ratios and their affects. Regeared many trucks. This build project was extremely thought through and planned.

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.

We do tow our enclosed double axle trailer with the camper which could add up to 7k lbs (max). Actually, with the camper blocking the wind it glides behind. 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!

 

[montypower]

The truck is designed to tow and haul... that's really the only reason for 3/4+... and it comes stock with a 3.73 ratio. The 4.3 he has near perfectly compensates for the 37s. He's not even towing heavy, which is a much bigger strain on the transmission than carrying a camper, and people do that all the time with stock gears. So, I think he's good.

Plus, I've heard too many stories of mechanics screwing up gear installs and the aftermarket gears not lasting.

Well stated. 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.

 

[montypower]

Well I’m a guy who had 3.73 gears in my truck and now have the correct gearing. I can vouch for the improvements and benefits over negatives from real world driving. Have you upgrade a vehicle the same way or have similar truck? If not my opinion might be more valid than yours.

i say this not for ego but want OP to get the right info rather than just an “opinion” with no real world knowledge and the OP get shorted on help.

3/4 ton is more weight carrying capacity. When you change the ratios and heights, it’s best to match what stock was supposed to compensate

these trucks have a 6 speed transmission, higher gearing is compensated by the over drive. The old ratios and most charts online are still thinking a truck has a 4 speed or 5 speed.

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.

 

[BajaSurfRig]

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!

 

[montypower]

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!)?

You won't notice 33s much with 3.73 gears. That is a standard factory size for the 2017+ trucks with that configuration. At least that would be my 2 cents. Have fun!!