7.3 4:30 with 37's

[Craiger22]

For the ones running the 7.3 4:30 gears on 37's how does it handle the size? Im currently on 35 Toyo rt trail and thinking of going to a 37 AT.

 

[BFill85_KRTremor]

For the ones running the 7.3 4:30 gears on 37's how does it handle the size? Im currently on 35 Toyo rt trail and thinking of going to a 37 AT.

If you don’t mind me asking. Why the swap from rt trail to at3??

 

[Blade420Play🔪🏆]

For the ones running the 7.3 4:30 gears on 37's how does it handle the size? Im currently on 35 Toyo rt trail and thinking of going to a 37 AT.

I haven't noticed much difference. Just the full left lock rub and even that is minimal. Obviously my mph is off and so the fuel economy and actual mileage are off now, just haven't had the dedicated time to foreskin the thing yet

 

[McE]

With 4.30s and 38s, final drive is almost identical to a stock non-Tremor with 3.73s. I wouldn't hesitate for a second to put 37s on it, even if you tow heavy.

 

[Apples]

I did the "effective final drive" math - this considers the tire's overall diameter before and after.

Swapping my OE Goodyear Duratracs' 285/75-18 (an actual 35.1" when new) to a Nitto Recon Grappler 37 X 11.5 X 17 (36.5") acts AS IF I had kept the 35.1" tire then re-geared my Godzilla Tremor to 4.10s.

Normally, back in the day when 33s were the thing to have and 35s were HUGE, increasing your tire's overall diameter +/- 2" was a big deal to your final drive gearing.

But once we leave the 35" threshold (it seems), then the increase of 1.5" has much less effect because we already have a baseline of a large tire so the increase is less of a percentage change.

Before my swap to 37s, my RPM at a calibrated/verified 70 MPH was just over 2100 RPM. This was unnecessary.

The swap to 37s made 70MPH 1800-1850 RPM (guesstimate, since I'm not in the truck right now doing 70). It is PERFECT.

The only caveat I can offer is to watch your tire and wheel WEIGHT. A heavier wheel, a heavier tire will cost you a little more fuel to accelerate. My combo, a 71-lb tire and a 29-lb wheel totals 100 lbs. That right there is amazing. That's almost as light as the OE Goodyear/Tremor aluminum road wheel combo.

 

[Craiger22]

If you don’t mind me asking. Why the swap from rt trail to at3?

I was concerned that the bigger tire would have a negative affect on power. I looked up the weight of the rt trail and the AT3 and there is about a 3lb difference rt trail being heavier, not that big of a deal at 3lbs. The RT trail is a load F and the AT3 is a load E. I feel that maybe the load rating on the AT3 would be a bit smoother. Just thinking out loud at the moment I do run my rt trails at about 43-45 psi unloaded. With my Carli back country the 35"s look a bit small.

 

[BFill85_KRTremor]

I haven't noticed much difference. Just the full left lock rub and even that is minimal. Obviously my mph is off and so the fuel economy and actual mileage are off now, just haven't had the dedicated time to foreskin the thing yet

This far along in life I’d have thought you would have plenty of time with your foreskin…

 

[SuperCabF350]

I did the "effective final drive" math - this considers the tire's overall diameter before and after.

Swapping my OE Goodyear Duratracs' 285/75-18 (an actual 35.1" when new) to a Nitto Recon Grappler 37 X 11.5 X 17 (36.5") acts AS IF I had kept the 35.1" tire then re-geared my Godzilla Tremor to 4.10s.

Normally, back in the day when 33s were the thing to have and 35s were HUGE, increasing your tire's overall diameter +/- 2" was a big deal to your final drive gearing.

But once we leave the 35" threshold (it seems), then the increase of 1.5" has much less effect because we already have a baseline of a large tire so the increase is less of a percentage change.

Before my swap to 37s, my RPM at a calibrated/verified 70 MPH was just over 2100 RPM. This was unnecessary.

The swap to 37s made 70MPH 1800-1850 RPM (guesstimate, since I'm not in the truck right now doing 70). It is PERFECT.

The only caveat I can offer is to watch your tire and wheel WEIGHT. A heavier wheel, a heavier tire will cost you a little more fuel to accelerate. My combo, a 71-lb tire and a 29-lb wheel totals 100 lbs. That right there is amazing. That's almost as light as the OE Goodyear/Tremor aluminum road wheel combo.

29lb wheel? nice! mind sharing the details? guessing it's a forged wheel?

 

[Blade420Play🔪🏆]

I did the "effective final drive" math - this considers the tire's overall diameter before and after.

Swapping my OE Goodyear Duratracs' 285/75-18 (an actual 35.1" when new) to a Nitto Recon Grappler 37 X 11.5 X 17 (36.5") acts AS IF I had kept the 35.1" tire then re-geared my Godzilla Tremor to 4.10s.

Normally, back in the day when 33s were the thing to have and 35s were HUGE, increasing your tire's overall diameter +/- 2" was a big deal to your final drive gearing.

But once we leave the 35" threshold (it seems), then the increase of 1.5" has much less effect because we already have a baseline of a large tire so the increase is less of a percentage change.

Before my swap to 37s, my RPM at a calibrated/verified 70 MPH was just over 2100 RPM. This was unnecessary.

The swap to 37s made 70MPH 1800-1850 RPM (guesstimate, since I'm not in the truck right now doing 70). It is PERFECT.

The only caveat I can offer is to watch your tire and wheel WEIGHT. A heavier wheel, a heavier tire will cost you a little more fuel to accelerate. My combo, a 71-lb tire and a 29-lb wheel totals 100 lbs. That right there is amazing. That's almost as light as the OE Goodyear/Tremor aluminum road wheel combo.

Mine are 111 lbs per wheel/tire.

 

[JoeCO]

Curious what kind of mileage hit did you get going to 37’s?

I tow a 8k trailer so don’t think the larger tires will change the tow experience all that much??

Not sure if I want to get new wheels/tires and do 37’s or stick with factory wheels and stay 35’s.

 

[Blade420Play🔪🏆]

Curious what kind of mileage hit did you get going to 37’s?

I tow a 8k trailer so don’t think the larger tires will change the tow experience all that much??

Not sure if I want to get new wheels/tires and do 37’s or stick with factory wheels and stay 35’s.

So, without recalibration (forscan), I am maybe a mile per gallon less efficient. Was 11.2 lifetime, am getting 10.2 as is.
I can get up to 11.8 when on the interstate with the current set-up. Before (stock tires) I could get 12.6.
I wonder how it will change in my case when I do the recalibration, but @Apples probably has better data with his recalibrated. But his tires are 11 lbs lighter than mine too

Have not towed at all with the 37s so I have no data there.

 

[Apples]

29lb wheel? nice! mind sharing the details? guessing it's a forged wheel?

It's a relatively inexpensive cast wheel.

Vision Flow 351, 17 X 8.5, +18mm - correct load rating, hub bore diameter. Fits my F350 Tremor perfectly.

Curious what kind of mileage hit did you get going to 37’s?

None, really. My fuel economy seems to depend entirely on two things:

1. the distance my right foot moves the gas pedal

2. the amount of weight I have in the truck (when judging local errands' city driving fuel mileage - that being 7.5 - 8.5 because I like to shift manually most of the time and let my Godzilla spin up to 2500 just because*).



*or maybe it's because of the Borla S-Type exhaust system. Who knows!


Once up on the road, towing or not, how I drive is the greatest influence to my truck's fuel economy. As noted, my cruise RPM in 10th dropped from 2100 to about 1850, and on my last trip south out of Utah into southern Cal I saw an average! of 16.0, but then again it's primarily downhill.

But, seriously. I attribute this astonishing figure (I usually see 14.5 MPG across the open road when conditions are right) to my lighter throttle settings for two or three distinct climbs southbound out of Vegas across the Mojave desert on 1-15.

 

[Apples]

I wonder how it will change in my case when I do the recalibration

FORScan the 2799 or whatever the max number is for circumference.

Then verify your new speedo readout using a GPS app on your phone. I use SPEEDOMETER.

Also, how much ethanol does your state put in their gasoline?