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Whats your experience with 37's and factory 4.10's and an 8 speed

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Elevatorguy

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Title kinda says it. I can't decide between 35's and 37's and was wondering what people's experience is with the factory 4.10s while running 37's. I'm coming from Jeep world and a re-gear was almost mandatory if you wanted to see 8th on the highway. Mileage is not my main concern I'm more interested in what kind of performance hit did you notice? How is highway cruising, will it hold 8th or does it see a hill and downshift? If you've had a bad time what gears would you recommend? Thanks in advance
 
With larger tires you're generally running a "longer" gear ratio through all gears, so I wonder why downshifting seems to be an issue.
For the Jeeps, the re-gear is probably more about keeping a low gear ratio for crawling than staying in 8th gear on the highway.
I can't say anything about 37's, but with my 35's the truck does downshift into 7th when encountering a slight incline on the interstate at 75, and also on highways going 55, so I'd imagine it will be even more often with 37's.
 
I have 37" BFG K02s which are some of the smallest/lightest 37s out there. I have not noticed any real loss in power or changes in shifting behavior. I can still chirp the tires when I accelerate from a stop. My gas mileage may be slightly down. Overall the truck rides better and looks so, so much better with the 37s. I have not lift or level on either...truck is on stock suspension. Hope that helps.
 
Elevatorguy said:
Title kinda says it. I can't decide between 35's and 37's and was wondering what people's experience is with the factory 4.10s while running 37's. I'm coming from Jeep world and a re-gear was almost mandatory if you wanted to see 8th on the highway. Mileage is not my main concern I'm more interested in what kind of performance hit did you notice? How is highway cruising, will it hold 8th or does it see a hill and downshift? If you've had a bad time what gears would you recommend? Thanks in advance
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I'm currently running 37" Nitto Trail Grapplers on stock 4.10 gearing and stock suspension. I do have my speed-o adjusted to the new tire size.

For street driving at 50 mph or lower on relatively flat pavement, I haven't seen any difference in performance. It is mainly during a change in road grade, whether it is minor or significant, where I see a change in shift patterns.

For highway driving at 65 and up is where I do see a change in shift patterns. During long trips of 40+ miles on open freeways (early morning Los Angeles freeways are wide open) at 72+ mph, using active cruise control, I will see changes in shifting depending on road grade or if someone is in front and active cruise is adjusting to slow or catch up. A good example from today I was driving on a long stretch of the I-10 at 75 mph with no one in front of me. As I'm coming to an under pass and the road gets higher I lose a couple mph and the truck shifts from 8 to 7, then back to 8 as it gets back to 75.

At some point I should switch to 4.56 or 4.88 (leaning to 4.88) but I only travel far for wheeling and 95% of my work commute is on the street.

If you do a lot of far driving, I suggest re-gearing.
 
37s on 4.56 would put you nearly exactly the same as 33s on 4.10. Going to 4.88 would definitely help with power but I’d think it would put you revving a bit high for long distance highway use.
 
Elevatorguy said:
Title kinda says it. I can't decide between 35's and 37's and was wondering what people's experience is with the factory 4.10s while running 37's. I'm coming from Jeep world and a re-gear was almost mandatory if you wanted to see 8th on the highway. Mileage is not my main concern I'm more interested in what kind of performance hit did you notice? How is highway cruising, will it hold 8th or does it see a hill and downshift? If you've had a bad time what gears would you recommend? Thanks in advance.
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Responses are relative. I also came from the Jeep world. I spent the last 4 years driving a JKU on Fusion 60s and 40”s. So my non-power wagon tradesman with a 6.4 and 3.73s seems like a power house on 38”s. I live in the mountains of Colorado so goes without saying it needs a regear but honestly if I had 4.10s idk that I’d bother. It’s 10x better now than a pentacrap JKU.
 
I'm used to turds have an 06 LJ on 33's with 410's and got rid of a gladiator on 37's but was re geared with 4.88s but still couldn't get out of it's own way this 6.4 to me is a rocket for a daily. The reason I specifically asked about cruising is with the gladiator I could manually shift it to 8th and hold it there I don't believe there's a way to manually shift the PW. It seems like the safe bet is go 35's but 37's look so damn good. Would be nice if you could rent a set to try. Thanks everyone for the info and advice.
 
Elevatorguy said:
I'm used to turds have an 06 LJ on 33's with 410's and got rid of a gladiator on 37's but was re geared with 4.88s but still couldn't get out of it's own way this 6.4 to me is a rocket for a daily. The reason I specifically asked about cruising is with the gladiator I could manually shift it to 8th and hold it there I don't believe there's a way to manually shift the PW. It seems like the safe bet is go 35's but 37's look so damn good. Would be nice if you could rent a set to try. Thanks everyone for the info and advice.
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Ha, I had an LJR that was purchased with 38x15.50 TSL on stock 410s, hahahaha. I regeared that to 5.38s and dropped to 37s and had a built torque converter in it. Then I had another LJR but 6 speed, 35s and 410s, was liveable but still a dog. Built a gladiator with 37s and 488s and felt that combo was quite nice to drive. Nothing like the 6.4 but the 6.4 is nothing like the TRXs I had on 37s so it is all relative to what you're used to, what you EXPECT it to be realistically, and your intended use. I'll be skipping 35s and going to 37s, for the simple fact 35s still look too small and I'm not overly concerned about the gearing. I had a 2016 6.4 2500 with 373s and 37s on the 6-speed auto and that was more than manageable.
 
Enve46 said:
Ha, I had an LJR that was purchased with 38x15.50 TSL on stock 410s, hahahaha. I regeared that to 5.38s and dropped to 37s and had a built torque converter in it. Then I had another LJR but 6 speed, 35s and 410s, was liveable but still a dog. Built a gladiator with 37s and 488s and felt that combo was quite nice to drive. Nothing like the 6.4 but the 6.4 is nothing like the TRXs I had on 37s so it is all relative to what you're used to, what you EXPECT it to be realistically, and your intended use. I'll be skipping 35s and going to 37s, for the simple fact 35s still look too small and I'm not overly concerned about the gearing. I had a 2016 6.4 2500 with 373s and 37s on the 6-speed auto and that was more than manageable.
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Hehe. Hell 37s look small on these trucks. :) I put 37” KO2s on mine at first and 7,000 miles later I switched to 38” Pat XT’s.
The difference was negligible and the XTs are HUGE. Look more like 4dees on the truck.
 
I went with 35 inch duratracs and noticed a slight decrease in power and mpg. My speedometer is 4 miles per hour off at 80mph. ( actually going 84) I am sure I would notice a bigger power decrease if I went to 37s but since I do not plan on rock crawling I like the 36s.
 
To add on to my post, I want to point out that most of my freeway out of town driving is with active cruise control. The truck will automatically drop gear if your speed drops by 2 mph to get back to set speed or catch up with the vehicle in front of you. If I was driving normally my pedal control will keep me in 8th gear.
 
I also wanted to point out that you can squeeze a 35 inch tire into the Spare tire opening. That was a big factor for me as I did not want to put the spare in the bed or hanging off the back.
 
Got any pictures? What are Pat Xts?
5150RN said:
Hehe. Hell 37s look small on these trucks. :) I put 37” KO2s on mine at first and 7,000 miles later I switched to 38” Pat XT’s.
The difference was negligible and the XTs are HUGE. Look more like 4dees on the truck.
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Had a 16 6sp. Ran 37 Toyo RTs and 4.10s for a long time. Was mostly ok, but downshifts towing in the big hills was annoying. Manually shifting helped a lot.

Re-geared to 5.13 with AAM gears. Felt stress load while driving dropped a lot. Maybe picked up fractional mpg gains. Performed really really well towing after. Was a little buzzy over 85, but 80 has always been my usual speed.
 
5150RN said:
Responses are relative. I also came from the Jeep world. I spent the last 4 years driving a JKU on Fusion 60s and 40”s. So my non-power wagon tradesman with a 6.4 and 3.73s seems like a power house on 38”s. I live in the mountains of Colorado so goes without saying it needs a regear but honestly if I had 4.10s idk that I’d bother. It’s 10x better now than a pentacrap JKU.
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It's funny you mentioned your experience with the jeep. My wife has a gladiator on 35s with 4.10s and calibrated for the tires. I love how it performs off road, and it is fun to drive, but my 6.4 2500 on 37s with 3.73s is a rocket ship in comparison. I mentioned in a previous post that I had a rough quote of 5500 dollars to regear to 4.10s. I received the actual quote last week. It was 6800!!! Needless to say, I'll be waiting for the aftermarket to finally come out with some gears and install kits for our generation truck. Regardless, the truck is fine as is. I see 8th gear regularly on the road, even towing on the highway.
 
I had 37” Ridge Grapplers with the factory 4.10, non speedo corrected and didn’t care for the way it drove. Speedo corrected with a AEV procal and it is much better. Driving through (and offroading) in Colorado and towing my skid steer has been no problem.
 
Put 37s on my PW a week ago and it’s noticeable but not by much. The steering is the biggest noticeable difference in my opinion. I’m pretty sensitive to driving changes and I see no issue running this set up. Looking forward to adjusting Speedo to get shift points aligned howeverIMG_5341.jpeg
 
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