Diesel - 4.56 Gears - 37 Inch Tires

[UTDieselRubi]

Throwing out another opinion data point for anyone doing their research in that search bar above like I was for some time.

Finally pulled the trigger on gears and traveled all the way to Cali to save 1500$, (why are utah shops so expensive!?). went to 4.56s and absolutely love them! The truck feels better than stock on 33s now. This ratio has my vote for 37s. No longer do I have to put my 33s back on for the daily drives and tow trips, feeling inadequate about my tire size I can now rock only 37s like a true jeep Baja Boss MTs for the trials and toyo at3s for the road, 24MPG at 75mph on Utah I15 average, with a 2" lift to boot. 100% would do again.

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[JTdiRtyD]

24mpg at 75mph? This hand calculated or vehicle indicated?

I really want 37s, but with the tent setup I wouldn't fit in the garage. Gotta build a new bed rack first.

 

[UTDieselRubi]

24mpg at 75mph? This hand calculated or vehicle indicated?

I really want 37s, but with the tent setup I wouldn't fit in the garage. Gotta build a new bed rack first.

That was my vehicles reading the entire way from SoCal to Utah on I15, which is mostly uphill. I also had the AT3s on and had 500lbs in the bed (8tires and 4wheels). I didn't calc it out exactly, but looking now, the journey was about 800 miles and it took two full tanks which puts me around 21. The truck would show 24-25mpg avg when it was completely stock as well which means I stayed just about at stock levels comparatively.

 

[ericw.]

Subbed for updates after you tow.

I'm really curious about towing capabilities with 4.56 and 37's. My trailer is roughly 2500 lbs fully loaded and towing long distance is the #1 reason why I wanted the diesel.

Mostly interested in maintaining highway speeds up hills, something I couldn't get close to doing with my 3.6.


I also got like 10-12MPG so I'd be very happy with 20.

 

[UTDieselRubi]

Subbed for updates after you tow.

I'm really curious about towing capabilities with 4.56 and 37's. My trailer is roughly 2500 lbs fully loaded and towing long distance is the #1 reason why I wanted the diesel.

Mostly interested in maintaining highway speeds up hills, something I couldn't get close to doing with my 3.6.


I also got like 10-12MPG so I'd be very happy with 20.

I'm going to take my travel trailer down south this weekend. The highway is mostly flat until I hit the mountains between me and Moab where Ill get some decent climbs in.
My trailer weighs 2600lbs empty and itll probably be about 3000lbs with gear and water this trip. Ill let you know how it goes. Ill be a happy camper if I don't constantly drop to 5th gear like before.

 

[kb5zcr]

I'm going to take my travel trailer down south this weekend. The highway is mostly flat until I hit the mountains between me and Moab where Ill get some decent climbs in.
My trailer weighs 2600lbs empty and itll probably be about 3000lbs with gear and water this trip. Ill let you know how it goes. Ill be a happy camper if I don't constantly drop to 5th gear like before.

When you do tow this weekend, please hand Calc your milage rather than relaying on the dash.
I'm assuming your speedo has been adjusted for your bigger tires.
Looking forward to your data.

Thanks,

 

[UTDieselRubi]

A quick update pre-towing. I grabbed my odometer reading at the pump the last two times. Starting was 36253, the next fill was 36601. I put in 15 gallons exactly to make the math clean, that puts me at 23.2 mpg avg. This is over the last 4 days of daily driving, mostly freeway 70-75mph with some city driving mix. My indicator showed 23.5 which was pretty accurate.

 

[Vtur]

Ensure that tire calibration is correct as well. Programming them too big/small will lead to false mpg.

I'm getting around 21-22 with 4.10s on 37s.

 

[UTDieselRubi]

Ensure that tire calibration is correct as well. Programming them too big/small will lead to false mpg.

I'm getting around 21-22 with 4.10s on 37s.

Tires are correct. I used to have to change tire size all the time. Now I can leave them be at 36.5 the overall dia. of these tires. Tazer makes it easy. Gears are correct as well. The mpg is correct.

 

[UTDieselRubi]

Post trip numbers are in. Overall happy with the performance. The truck stayed in 7th-8th gear 80% of the time, hitting 6th on steep inclines and once hit 5th on the worst incline. Much better than before. The mpgs are basically back to stock numbers, I saw a similar result towing with 33s on stock gears, so with the return to stock mpgs, 4.56s are a win in my book. Obviously tire choice and trailer type will play a big role. I may do the same test again on my ATs pulling my flat trailer and SxS (3500lbs).

Trailer weight was 3000lbs with maximum wind resistance lol.

Total payload approx. 1000lbs which includes rock sliders.

Tires 37x13.5R17 Mickey Thompson Baja Boss MTs
trailer has 31" MTs

Overall MPG calculation from Ogden to Moab was 12mpg average.
Leg 1: All I15, cruise control on 70mph, elevation 4,230' avg = 11mpg avg
Leg 2: canyon/mountain pass, 60 to 65mph, summit elevation 7,500' = 13mpg avg
Leg 3: desert/hills, 65mph, avg elevation 5,630' = 12mpg avg

 

[JTdiRtyD]

Assuming no derate or heat issues?

 

[UTDieselRubi]

Assuming no derate or heat issues?

My avg coolant temp stayed around 225 to 228. On the steepest climbes when it was in 6th it would climb to about 234 so I would slow down a little and it would cool. I didn't derate this time. I do have the bullet proof supp radiator mounted right in the bumper for better air. I tested it out a little while back and recorded the temps before and after it and my recorded data showed about 5-10 degrees cooler.

 

[ericw.]

That's great news. I'm happy with the report because it sounds like exactly what I'll be dealing with.

I could write an entire book of complaints about towing long distance with my 3.6 JKU.

 

[UTDieselRubi]

That's great news. I'm happy with the report because it sounds like exactly what I'll be dealing with.

I could write an entire book of complaints about towing long distance with my 3.6 JKU.

I'm glad I could help get some info out. I know even though these diesels like to get too hot, no way I'd like towing with the 3.6. Just a test drive in one, it felt incredibly underpowered.

 

[Chance575]

4.88s on 37s, I believe it weighs around 5000 loaded, I get 12 mpg and only have gotten the P00af code, I was at the top of hills and mountains and you could hear tye turbo singing , clear it and go with No more problems

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