4.88 or 5.13 - pulling camper, heavy 37s and steelie wheels

[Trlr8tdd]

I think a lot of us miss the mark on the 8th gear. It’s a Second Overdrive. There’s a lot of factors involved in when and why it comes out of 8th. If your geared to stay in 8th going up a hill, your deleting the overdrives. No big deal if that’s what you want but my JTR is more of a mall crawler than my JKR. I Like that it stays in 8th on flats and mild hills for gas mileage but drops to 7/6 on a steep hill, heck with 35’s she’d drop to 5th. I’m certain at some point I’ll re-gear but I’m happier with 4.10’s and 37’s than I was with 35’s. That said, I do Plan on cylinder pressurization in the future but doubt financially it will ever happen. A little more tq would be a complete game changer but I knew what to expect going into the JTR.

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[KurtP]

If you want to defeat the overdrive gearing, you’ll need 5.38

 

[Rummie]

Just an update - I ended up going with 5.13s. Should be picking it up tomorrow. We have a trip to Moab in a few weeks. That will be the real test since we'll be pulling the camper, have highway driving with elevation changes, and wheeling. Now I have about a week and a half to get the break-in done and checked before we head out.

 

[WK2JT]

If you want to defeat the overdrive gearing, you’ll need 5.38

37’s and 5.13’s here and it definitely kicks down on anything more than a mild grade. Of course I’m starting at ~5,500’ too. Climbing the passes here in CO, I spend a lot of time in 5th and 6th. I think 5.38’s would be slightly better for my location due to the loss of power, but agree 5.13’s are fine for most who are not at elevation.

Watching your testing with a very keen eye to regain some power and extra efficiency. I’m right there with you on drivability vs MPG. I bought my diesel GC for the exact same reason. It made hauling that thing around a lot of fun. I knew I would never make up the extra cost in fuel savings.

 

[KurtP]

37’s and 5.13’s here and it definitely kicks down on anything more than a mild grade. Of course I’m starting at ~5,500’ too. Climbing the passes here in CO, I spend a lot of time in 5th and 6th. I think 5.38’s would be slightly better for my location due to the loss of power, but agree 5.13’s are fine for most who are not at elevation.

Watching your testing with a very keen eye to regain some power and extra efficiency. I’m right there with you on drivability vs MPG. I bought my diesel GC for the exact same reason. It made hauling that thing around a lot of fun. I knew I would never make up the extra cost in fuel savings.

5.38 would help the hills but you pay the price everywhere else.

Its hard to overcome elevation without boost. Id put a blower on it. Seriously. Dont waste a dime on my method until youre supercharged. Nothing will counter elevation better than boost. Not gears, not tuning, nothing.

 

[Jaydebe]

I was completely 100% set on 488s.

About 90% of the time, I think they'll be great for driving around and short trips.

That said, we're looking at smaller RV campers for longer XC trips and I'm thinking the 5.13s might be better for it.

What's tough is, we have 6-12 weeks a year to travel, so while that is a small % time wise, the traveling is likely be closer to 60-70% (10-12k mile) of of yearly mileage.

 

[MoparToYou]

Just an update - I ended up going with 5.13s. Should be picking it up tomorrow. We have a trip to Moab in a few weeks. That will be the real test since we'll be pulling the camper, have highway driving with elevation changes, and wheeling. Now I have about a week and a half to get the break-in done and checked before we head out.

Keep us posted on how you like it with the new gears Rummie. I have 37s with the stock 4.10 gears, and all I can say is I'm glad I don't have to tow with this set up. I have a 2019 Ram 3500 with a Cummins that I normally tow with, but yesterday I decided to tow a small utility trailer (1000 lbs), with a UTV on it (1500 lbs), that weighed just 2500 lbs total. Our round trip was just 150 miles, and since the Ram was already hooked to our 40' fifth wheel toy hauler, I just hooked up the small utility trailer and UTV to my Mojave. I was very disappointed in how it did the job. Maybe it was just the particular day, because it was very very windy (40+ mph wind gust). The Mojave is sprung way too soft, and with the 37" MTs and their tall tread blocks and squishy soft rubber, the truck gets pushed around a lot. Either by the wind, or the trailer, or both, but it was a real challenge just to keep it in my lane. I tried moving the UTV to a different place on the trailer, and it was marginally better about not getting moved around so much with the UTV moved back about 4". I think I had too much tongue weight initially. Towing power is horrible with this V6 engine as well. On the way home we had to come directly into the wind for the last 30 miles on the interstate. The speed limit is 80 mph, and I tried several different speeds to find the speed that felt the best, and finally settled on setting the cruise at 67 mph. At 67 mph the transmission had downshifted several gears and engine RPM was right at 4800 RPM. And it just stayed there, and stayed there, and stayed there, for thirty miles. I tried shifting the auto manually, and it would just go back to that gear and RPM. The engine will run at that RPM, and not feel like it is getting shaken apart, but it gets real thirsty for fuel. My gas gauge dropped from 1/2 tank to 1/8 tank with the low fuel light on, in just thirty miles. Today I checked engine oil, and it was half way between the full and add mark on the dipstick. So I think the sustained high RPM use burned some oil through the engine, which is not good. Like I said, I am sure glad I don't have to tow with this set up. Next time I'll take the extra few minutes to hook up the Cummins, even if it is just for 2500 lbs. I think this truck is pretty close to the worst tow vehicle I've owned in a long time.

My question to you is, ... does the re-gear make a significant difference, not in power, or getting up to speed, but in towing RPM? Lets say I was in 4th gear at 4800 RPM. If I had 5.13 gears would I still be at 4800 RPM to get the power needed to tow into that wind, but instead of 4th gear I would be in 5th or 6th gear. If I'm just in a gear or two higher, but need the same RPM, then what is the point?

 

[WK2JT]

Keep us posted on how you like it with the new gears Rummie. I have 37s with the stock 4.10 gears, and all I can say is I'm glad I don't have to tow with this set up. I have a 2019 Ram 3500 with a Cummins that I normally tow with, but yesterday I decided to tow a small utility trailer (1000 lbs), with a UTV on it (1500 lbs), that weighed just 2500 lbs total. Our round trip was just 150 miles, and since the Ram was already hooked to our 40' fifth wheel toy hauler, I just hooked up the small utility trailer and UTV to my Mojave. I was very disappointed in how it did the job. Maybe it was just the particular day, because it was very very windy (40+ mph wind gust). The Mojave is sprung way too soft, and with the 37" MTs and their tall tread blocks and squishy soft rubber, the truck gets pushed around a lot. Either by the wind, or the trailer, or both, but it was a real challenge just to keep it in my lane. I tried moving the UTV to a different place on the trailer, and it was marginally better about not getting moved around so much with the UTV moved back about 4". I think I had too much tongue weight initially. Towing power is horrible with this V6 engine as well. On the way home we had to come directly into the wind for the last 30 miles on the interstate. The speed limit is 80 mph, and I tried several different speeds to find the speed that felt the best, and finally settled on setting the cruise at 67 mph. At 67 mph the transmission had downshifted several gears and engine RPM was right at 4800 RPM. And it just stayed there, and stayed there, and stayed there, for thirty miles. I tried shifting the auto manually, and it would just go back to that gear and RPM. The engine will run at that RPM, and not feel like it is getting shaken apart, but it gets real thirsty for fuel. My gas gauge dropped from 1/2 tank to 1/8 tank with the low fuel light on, in just thirty miles. Today I checked engine oil, and it was half way between the full and add mark on the dipstick. So I think the sustained high RPM use burned some oil through the engine, which is not good. Like I said, I am sure glad I don't have to tow with this set up. Next time I'll take the extra few minutes to hook up the Cummins, even if it is just for 2500 lbs. I think this truck is pretty close to the worst tow vehicle I've owned in a long time.

My question to you is, ... does the re-gear make a significant difference, not in power, or getting up to speed, but in towing RPM? Lets say I was in 4th gear at 4800 RPM. If I had 5.13 gears would I still be at 4800 RPM to get the power needed to tow into that wind, but instead of 4th gear I would be in 5th or 6th gear. If I'm just in a gear or two higher, but need the same RPM, then what is the point?

I towed from Atlanta to Denver with about the same type of trailer and weight with 5.13’s. My subjective experience is it was a little better, but a tow rig this will never be. Even solo, the 37’s are just a lot of weight for our rigs, but you’ve got towing covered with your 3500.

 

[Trippin01]

Yup, I use my 33's for towing my 4k lb trailer. But when I have my ultra light RTT and/or do trails, I drive to where I'm going, (Moab - Ouray from Idaho) then thro the 37's on. 5.13's No regrets, on the trails or for towing.

 

[Muddzy]

Just an update - I ended up going with 5.13s. Should be picking it up tomorrow. We have a trip to Moab in a few weeks. That will be the real test since we'll be pulling the camper, have highway driving with elevation changes, and wheeling. Now I have about a week and a half to get the break-in done and checked before we head out.

Interesting thread. It's been a year - any updates?

 

[Rummie]

Interesting thread. It's been a year - any updates?

5.13s were the right choice for me. We have done three cross country trips in the past year. Moab, Colorado, Death Valley, Sand Hollow, and a few other places. Have pulled the camper. Have used the roof top tent. The 5.13s can handle it all. They also give great pick up around town.

I haven't really paid much attention to gas mileage differences. Pulling a camper is going to get you bad gas mileage when driving a lifted brick no matter what you do.

 

[shrinkhead]

6.4L V8 and keep gears

 

[FLUndertaker]

5.13s were the right choice for me. We have done three cross country trips in the past year. Moab, Colorado, Death Valley, Sand Hollow, and a few other places. Have pulled the camper. Have used the roof top tent. The 5.13s can handle it all. They also give great pick up around town.

I haven't really paid much attention to gas mileage differences. Pulling a camper is going to get you bad gas mileage when driving a lifted brick no matter what you do.

Glad it’s worked out well for you. I have 5.13 in my JT with. 37s and it empty unloaded 98% of the time and on flat roads in the Great Plains states. I just love it for the snappy acceleration especially paired with the pedal commander. So glad I went 5.13 vs 4.88.

 

[Panthers65]

There's only a 5% difference between the too. IMO people give too much though to these small changes on gears. 95% of the drivers out there wouldn't know the difference between running 2500RPMs and 2625 RPM on the highway, you'll quickly adapt.

I would almost always error to the side of deeper (numerically higher number) gear ratio. Unless you know you are going to spend a lot of time on the interstate and like running 10+ over the speed limit, the benefits you get from a deeper gear are apparent.

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