Pros/Cons on gear swap/ GearVendors OD

[smketrfdny]

Good Afternoon. As i thought, I get better answers here than the usual social media. Anyway, I have the 07 MC 5.9 Cummins SRW with 4.10s. Would prefer better mpg with fuel costs, as I'm sure many would as well. With that being said, upon retirement I am looking into the RV scene. Nothing big like a 5th wheel (would prefer a dually for the 5th), and its just me for now, so prefer a smaller trailer. I do realize I can pull a house with the 4.10s, but also prefer better mpg. And yes, Im aware pulling anything no matter what the gear will lower the mpg.

With that being said, taller axles (3.55, maybe????) may make a difference when not pulling. While i may do a decent amount of traveling towing a camper, I still do a lot of driving without one (not buying the camper till after retirement in December), hence the post. The other option is the GV OD. Not towing, GV will lower the 4.10s to 3.20, which isnt bad, correct? Talking to GV, you cannot tow when using it, so it seems that keeping the 4.10s and adding the GV seems to be the best bet. FWIW, I may have 'answered my own question' and maybe so, but any opinion from those with extensive knowledge with either or would be appreciated. Many thanks in advance, safe travels.

 

[06 Dodge]

If its not a 4x4 you could swap to 3.73 gears... My self would not install the GV OD or swap gears, I have doubts either one would pay for its self any time soon, if you want to get better mpg you could always learn to hype mill or learn about other fuel saving ideas that have zero cost to you... BTW in my old 06 5.9 4x4 4 speed auto with 3.73 gears, empty could see 20+ mpg all by changing how I drove...

 

[smketrfdny]

If its not a 4x4 you could swap to 3.73 gears... My self would not install the GV OD or swap gears, I have doubts either one would pay for its self any time soon, if you want to get better mpg you could always learn to hype mill or learn about other fuel saving ideas that have zero cost to you... BTW in my old 06 5.9 4x4 4 speed auto with 3.73 gears, empty could see 20+ mpg all by changing how I drove...

Its a 4x4. I hit 2k rpm at 65 mph, so i keep it at about 62-63 and 18-1900 rpm, so i do try my best to HM. Even with that, im lucky to get 16 mpg. The 'Lie-o-meter' says 18-19, but i should be so lucky. At 150k, its hardly broken in, and $100k plus for a new truck, I'd prefer to keep this. If i got your mileage, id drive it cross country in a heartbeat and not my 50 mpg VW TDi. And as posted, i wont see 20 mpg with a trailer and 3.73s. I may have a gig doing a lot of travel with or without the trailer, so either the gear change or the GV would pay for itself. Thought of bigger tires as many have posted, but 3-4 sets of tires negates the cost of the adjustments mentioned. Thanks for the reply. Safe travels.

 

[MikeT]

I have an 06 CTD 2500 with a 545RFE trans 373 gears, unloaded I get an average around 21mpg, towing our toy hauler 15 - 16. The engine turns 1950rpm at 70 mph. Sorry I'm not positive about the gearing but pretty sure its 373. It's a 4X4 so all the front end is turning, the tires are slightly oversize from stock. As stated above I too am not sure that the gains made by a gear change will pay for themselves in any reasonable amount of time.

Mike

 

[TotallyHucked]

Honestly the cost of a gear swap or the GV either way will take a very long time to pay for itself in the fuel savings. I'd honestly be surprised if you saw a 2mpg increase. At 65+, aero is your biggest enemy. Personally, I'd go up a tire size the next time you need them and otherwise just drive it the way it is.

 

[HemiLonestar]

I have an 06 CTD 2500 with a 545RFE trans 373 gears, unloaded I get an average around 21mpg, towing our toy hauler 15 - 16. The engine turns 1950rpm at 70 mph. Sorry I'm not positive about the gearing but pretty sure its 373. It's a 4X4 so all the front end is turning, the tires are slightly oversize from stock. As stated above I too am not sure that the gains made by a gear change will pay for themselves in any reasonable amount of time.

Mike

If you have a Cummins in a 2006 you do not have an RFE unless you put it there. Should be a 48RE.

 

[mtnrider]

I would either re-gear, or live with it. You will never re-coupe the cost of the OD in fuel savings and you are adding another possible failure point to the system.

While not the same as re-gearing you could go a little taller tire to reduce your RPM when cruising? Obviously a larger tire has some down sides and will not give you the same mpg as just re-gearing but it's a cheap alternative to try?

.

 

[smketrfdny]

I have an 06 CTD 2500 with a 545RFE trans 373 gears, unloaded I get an average around 21mpg, towing our toy hauler 15 - 16. The engine turns 1950rpm at 70 mph. Sorry I'm not positive about the gearing but pretty sure its 373. It's a 4X4 so all the front end is turning, the tires are slightly oversize from stock. As stated above I too am not sure that the gains made by a gear change will pay for themselves in any reasonable amount of time.

Mike

Gotcha. thanks for the heads up. Even with a decent pension and investments, i do not plan on buying a new truck. So i may end up keeping it for another 2-300k, ill wager either mod will pay for itself. Only drawback to either is the truck will depreciate in value even more, so IMO that is the only advantage to buying new. So over time, any money put into the truck will be a loss should i wreck it or some clown totals it. But as posted, 150k on a 5.9 is not even broken in so at this point, its worth keeping, IMO. I realize with a ton of mods i wont get 50 mpg (lol), but even 4-5 mpg improvement is still 140-175 a tank, so with a decent amount of driving, mods may pay off. Again, a risk on a 17 year old truck, but at 100k plus for a new truck, may be worth the investment. Stay safe, stay well.

 

[tron67j]

Different things going on here. I had a 2500 03 5.7 2wd that I bought new and got rid of for a new 2018 6.4 4wd 2500.

The 03 pulled a really nice 5th, totally within specs, like a champ and never wished I had dual wheels. Your trailer wish seems like a diesel is overkill for your purpose. You could get a really nice gasser for well under your 100k mentioned above. Maybe the cost savings of cheaper fuel and cheaper gasser purchase price is worth it to consider converting to a gasser.

Good luck.

 

[smketrfdny]

I would either re-gear, or live with it. You will never re-coupe the cost of the OD in fuel savings and you are adding another possible failure point to the system.

While not the same as re-gearing you could go a little taller tire to reduce your RPM when cruising? Obviously a larger tire has some down sides and will not give you the same mpg as just re-gearing but it's a cheap alternative to try?

.

Tires have crossed my mind, agreed. But i plan on keeping this MC as long as i can. And once retired, ill be doing a lot of traveling, be it recreational or a small gig lined up after retirement, where ill need it. $100k is crazy for a new truck and as posted, 150k on the 5.9 is nothing (tho the rest of truck is a different story lol), and i will say it does ride nice. So while i dont expect 35 mpg, any decent increase in mpg i would drive cross country in a heartbeat. And for the cost of 2-3 tire replacements, i can just get it re-geared or the GV (and I know tires are gonna have to be replaced anyway). Any suggestions on a tire size on a stock truck with a leveling kit? Lots of knowledge here, so ill take 1 or 100 opinions. Thanks much.

 

[John Jensen]

I no longer need aggressive tires and I wanted to get a high rated road tire on my 2020 3500 HO thinking it will help mileage, have less noise and improve the ride. My tire dealer suggested
Continental TerrainContact H/T 275x70-18 E (Snow Flake)
33.2 x 11w x 14/32 td, 627 rpm, 52.1 lbs. I bought them and so far I like them. They replaced my Falken Wildpeak A/T3s

He said he has many 5th wheel haulers who are now using that tire and like it. Here are two tests that compare it to the popular Michelin.
Test 1
Test 2

 

[smketrfdny]

I no longer need aggressive tires and I wanted to get a high rated road tire on my 2020 3500 HO thinking it will help mileage, have less noise and improve the ride. My tire dealer suggested
Continental TerrainContact H/T 275x70-18 E (Snow Flake)
33.2 x 11w x 14/32 td, 627 rpm, 52.1 lbs. I bought them and so far I like them. They replaced my Falken Wildpeak A/T3s

He said he has many 5th wheel haulers who are now using that tire and like it. Here are two tests that compare it to the popular Michelin.
Test 1
Test 2

Im running Nitto Grapplers. Still live in NY and while we didnt get much snow this year, they earned their keep. I was running Pirellis but the infamous front end was killing them every 10-12k miles. A leveling kit was added with the Nittos and all has been well. If i move south or west as planned, i wont need an aggressive tread and may go with a high rated road tire. At this stage in life, im more mpg than mph, so some good options, opinions and advice posted so far. TY

 

[Smokeybear01]

I would look into why your Cummins isn't doing better on the mileage. I have the 410 gearing and with no load pull over 20MPG consistently unless my fuel filter needs bleeding. Drops to around 15MPG with 36' fiver in tow on mostly level roads at 60MPH. I have the Nitto Highwy Grapplers. Smooth and quiet. 48RE and dualies.

 

[smketrfdny]

I would look into why your Cummins isn't doing better on the mileage. I have the 410 gearing and with no load pull over 20MPG consistently unless my fuel filter needs bleeding. Drops to around 15MPG with 36' fiver in tow on mostly level roads at 60MPH. I have the Nitto Highwy Grapplers. Smooth and quiet. 48RE and dualies.

I'll be damned. I keep it under 2k rpm and its 65 mph. Im lucky for 17, maybe 18. The 'lie-o-meter' tells me 18-21 but filling up the gallons dont add up. On the long trips, i would top it off a few times, but in another post i asked about, was oblivious to the charcoal canister. And while i try to stick to name brand fuels and add howes and EDT to every tank, as we know the pressure varies at every pump, so I guess ill have to use the same pump a few times and average the mpg from the first click. 20 mpg with a dually? Nice, any suggestions aside from the fuel filter check? Thanks.

 

[smketrfdny]

Different things going on here. I had a 2500 03 5.7 2wd that I bought new and got rid of for a new 2018 6.4 4wd 2500.

The 03 pulled a really nice 5th, totally within specs, like a champ and never wished I had dual wheels. Your trailer wish seems like a diesel is overkill for your purpose. You could get a really nice gasser for well under your 100k mentioned above. Maybe the cost savings of cheaper fuel and cheaper gasser purchase price is worth it to consider converting to a gasser.

Good luck.

Love my diesels, own 3. Cant fix em but i love em, lol. Yes, ill agree a smaller trailer is overkill, but ive never RV'ed in my life, and to just go out and buy big and not like it doesnt sound good. Starting small, i can buy/sell the trailer and either sell with mimimal $$ invested, or trade up if i do, and have the right truck to pull it. Looked into the slide ins, but kind of tiny (even solo) and i would prefer an 8 foot bed and not the smaller bed with the MC. Thanks.

 

[06 Dodge]

I'll be damned. I keep it under 2k rpm and its 65 mph. Im lucky for 17, maybe 18. The 'lie-o-meter' tells me 18-21 but filling up the gallons dont add up. On the long trips, i would top it off a few times, but in another post i asked about, was oblivious to the charcoal canister. And while i try to stick to name brand fuels and add howes and EDT to every tank, as we know the pressure varies at every pump, so I guess ill have to use the same pump a few times and average the mpg from the first click. 20 mpg with a dually? Nice, any suggestions aside from the fuel filter check? Thanks.

IMHO when it comes to fuel mileage use the TQ not the HP, slow and steady is good for fuel mileage along with other driving adjustments. Have you ever tried Opti Lube? I used it in my 06 and now in my 2022, IMO its much better then Howes or Power Service ( don't know what EDT is but it sounds similar to the blue pill ) and you only need to use max of 1 oz per 10 gallons of fuel... https://opti-lube.com/opti-lube-boo...thout-accessories-treats-up-to-2-560-gallons/

If you want an additive that also keep water in check use the summer lube, both are good fuel additives: https://opti-lube.com/opti-lube-sum...thout-accessories-treats-up-to-2-560-gallons/

 

[smketrfdny]

IMHO when it comes to fuel mileage use the TQ not the HP, slow and steady is good for fuel mileage along with other driving adjustments. Have you ever tried Opti Lube? I used it in my 06 and now in my 2022, IMO its much better then Howes or Power Service ( don't know what EDT is but it sounds similar to the blue pill ) and you only need to use max of 1 oz per 10 gallons of fuel... https://opti-lube.com/opti-lube-boo...thout-accessories-treats-up-to-2-560-gallons/

If you want an additive that also keep water in check use the summer lube, both are good fuel additives: https://opti-lube.com/opti-lube-sum...thout-accessories-treats-up-to-2-560-gallons/

slow and steady is my schtick. No 'blue pill' lolol, Everyday Diesel Treatment from Hot Shots. Ill check out the opti lube and give it a shot. Thanks again

 

[Smokeybear01]

I'll be damned. I keep it under 2k rpm and its 65 mph. Im lucky for 17, maybe 18. The 'lie-o-meter' tells me 18-21 but filling up the gallons dont add up. On the long trips, i would top it off a few times, but in another post i asked about, was oblivious to the charcoal canister. And while i try to stick to name brand fuels and add howes and EDT to every tank, as we know the pressure varies at every pump, so I guess ill have to use the same pump a few times and average the mpg from the first click. 20 mpg with a dually? Nice, any suggestions aside from the fuel filter check? Thanks.

My lieometer gets all the way up to 24MPG on a long trip. Then I fill and do the math and I'm back to reality. I did fill one time and I noticed how quickly my fuel gauge came off the full mark. It was a local station and their fuel really foamed. Which I'm guessing caused me to stop filling before it was full. I run 60 in 55 zones and 70 in 65 zones using cruise control so I'm not constantly adjusting my speed which wastes fuel. I'm old, my foot gets heavy.
I should add that my engine is stock with 255K miles on it. Still tight (knock on wood)

 

[smketrfdny]

My lieometer gets all the way up to 24MPG on a long trip. Then I fill and do the math and I'm back to reality. I did fill one time and I noticed how quickly my fuel gauge came off the full mark. It was a local station and their fuel really foamed. Which I'm guessing caused me to stop filling before it was full. I run 60 in 55 zones and 70 in 65 zones using cruise control so I'm not constantly adjusting my speed which wastes fuel. I'm old, my foot gets heavy.
I should add that my engine is stock with 255K miles on it. Still tight (knock on wood)

Mine is at well. All stock. The 3-4 times i totally topped it off (long trip) i got about 130-140 before needle moved. Usually now about 100-110 rounding the $$ amount off after the first click. I usually keep it on cruise. Took it to work today in manhattan. Lie-o-meter went from 14.9 to 16.7. 50-55 mile ride. So im figuring 14- 14.5 with 99% NYS Thruway driving. ill hit the same pump tomorrow and see what i get for a round average

 

[06 Dodge]

One other thing that caused my old 2006 to lose fuel mileage was when I replaced the OEM Michelin tires to the newer Michelin LTX A/T2 and saw a lost of 1.5 mpg, also noticed I could keep air when empty at 60-65 front and 55-60 rear... IIRC my best mpg numbers was 55-57 MPH, as I recall the max TQ with the 3.73 was around 1500 rpm's once over 2050 rpm's MPG started to drop....