Best gear ratio for towing

[garyp4951]

I have a 03 2500 cummins srw quad cab with 3.73 gears, and wondering about changing to 4.10. I know it would tow better, but probably get less fuel mileage. Has anyone towed with these ratios.
Thanks, Gary

[Huntindog]

USMA Dad wrote:
While were on the subject (yet don't want to take over the OP), let me ask y'all this: I'm in a similar situation. I have an '04 2500 5.9 CTD, 48RE tranny, and 3.73s 2WD. Stock tires are 265-70-R17. I'm towing about 16,000 (loaded) with a pin weight of about 3,800.

I added two springs on each side to compensate for the pin weight and increased my tire size to the Michelin XZE 245-70R19.5 (33") for increased tire rating (best I could find in a 17 was 3750). Since I increased the tire size, I've taken my 3.73s to somewhere around 3.5x. The engine also runs around 208* when towing. I have a Bulldog Juice with Attitude and tow in the tow mode.

All of that for this, would I benefit by moving to the 4.10s? If I do make the change, I think I'm back closer to the 3.7x area. My main concern is I have a long trip to NY coming up in May and will have a some sections of grade to contend with. What say all???

BTW, this is a "gearing" question, not a "weight" question! :B

Look at the ratings for your MY with your "new" effective gear ratio. Probably the closest offered was 3.42. IIRC It had a dismal 8800# rating. With your tires, you probably should be in the 4.30 area for max towing.

[USMA_Dad]

john&bet wrote:
I am very happy with my '04.5 cdt with 3.73s towing at a gcw of 19,800# in all kinds of terrain from Baltimore,Md to Moab,Ut.,from Charleston,S.C. to Great Falls,Mt.

Do you have the stock 17" tires? My GCW is 23,540 (truck by itself is 7100)

[john_bet]

I am very happy with my '04.5 cdt with 3.73s towing at a gcw of 19,800# in all kinds of terrain from Baltimore,Md to Moab,Ut.,from Charleston,S.C. to Great Falls,Mt.

[USMA_Dad]

While were on the subject (yet don't want to take over the OP), let me ask y'all this: I'm in a similar situation. I have an '04 2500 5.9 CTD, 48RE tranny, and 3.73s 2WD. Stock tires are 265-70-R17. I'm towing about 16,000 (loaded) with a pin weight of about 3,800.

I added two springs on each side to compensate for the pin weight and increased my tire size to the Michelin XZE 245-70R19.5 (33") for increased tire rating (best I could find in a 17 was 3750). Since I increased the tire size, I've taken my 3.73s to somewhere around 3.5x. The engine also runs around 208* when towing. I have a Bulldog Juice with Attitude and tow in the tow mode.

All of that for this, would I benefit by moving to the 4.10s? If I do make the change, I think I'm back closer to the 3.7x area. My main concern is I have a long trip to NY coming up in May and will have a some sections of grade to contend with. What say all???

BTW, this is a "gearing" question, not a "weight" question! :B

[Huntindog]

Dodge has had different ratings for the different ratios.
They also have had a rep for weak trannys, especially in the OPs MY truck.
A lower ratio will be easier on the tranny.

As for whether it is worth it or not.. That all depends on how often/heavy one tows, and the terrain coupled with ones performance expectations... Everyone will have a different opinion on this.

[Me_Again]

JIMNLIN wrote:

bmanning wrote:
Lots of factors need to be considered when debating a gear ratio swap.

True and especially in the OP '03 Dodge/Cummins which had three engine hp/torque options (235/460 or 250/460 or 305/555 HO) and the 47RE and 48RE along with a NV4500 or the NV5600 manual trannies.
Any gear recommendation for anything other than a '03/'04 Cummins doesn't apply in this case.

Not knowing what engine/tranny combo he has makes it impossible for a good recommendation.
I'm not a fan of taller diameter tires which drop rpms. I tow up to 16k with the '03 305/555 HO 3.73 and the NV5600. I added a Edge for towing when they hit the streets in '04. It bumps the power 50 hp or so and 80-100 ft lbs. Very mild and really woke the Cummins up in the 1800-2100 rpm range.
If the OP has the 47 or 48RE tranny with the tall .69 OD gear then it kills rpm and power in a HPCR engine.

I often wonder about those that get the highest gears available, then install larger tires and finally complain of lack of towing power!

:S:S:S

Chris

[Shepherd]

My previous ram 07 6.7 with manual tranny with 3.73 was great but my 12 ram with auto and 4.10 is so much more.:C

[transamz9]

JIMNLIN wrote:

bmanning wrote:
Lots of factors need to be considered when debating a gear ratio swap.

True and especially in the OP '03 Dodge/Cummins which had three engine hp/torque options (235/460 or 250/460 or 305/555 HO) and the 47RE and 48RE along with a NV4500 or the NV5600 manual trannies.
Any gear recommendation for anything other than a '03/'04 Cummins doesn't apply in this case.

Not knowing what engine/tranny combo he has makes it impossible for a good recommendation.
I'm not a fan of taller diameter tires which drop rpms. I tow up to 16k with the '03 305/555 HO 3.73 and the NV5600. I added a Edge for towing when they hit the streets in '04. It bumps the power 50 hp or so and 80-100 ft lbs. Very mild and really woke the Cummins up in the 1800-2100 rpm range.
If the OP has the 47 or 48RE tranny with the tall .69 OD gear then it kills rpm and power in a HPCR engine.

Depends on the speed that you like to tow at.

[JIMNLIN]

bmanning wrote:
Lots of factors need to be considered when debating a gear ratio swap.

True and especially in the OP '03 Dodge/Cummins which had three engine hp/torque options (235/460 or 250/460 or 305/555 HO) and the 47RE and 48RE along with a NV4500 or the NV5600 manual trannies.
Any gear recommendation for anything other than a '03/'04 Cummins doesn't apply in this case.

Not knowing what engine/tranny combo he has makes it impossible for a good recommendation.
I'm not a fan of taller diameter tires which drop rpms. I tow up to 16k with the '03 305/555 HO 3.73 and the NV5600. I added a Edge for towing when they hit the streets in '04. It bumps the power 50 hp or so and 80-100 ft lbs. Very mild and really woke the Cummins up in the 1800-2100 rpm range.
If the OP has the 47 or 48RE tranny with the tall .69 OD gear then it kills rpm and power in a HPCR engine.

[transamz9]

garyp4951 wrote:
This forum is great, and I appreciate all the info.
Goducks, I looked at my door panel when I got home, and it came with 265-70r17 tires 31.7", and now has 285-70r17 32.5".
Don't get me wrong, the 170k miles truck does great, but what really bugs me is like I said, the 47re tranny feels like the torque is not getting to the wheels until it locks up at 45mph, and then its on. I envy those of you with a manual that have full torque in every gear.

I also run the same size tire as you on my 05 with a 48 auto. The difference is I lock the TC in 3rd and I don't think you can. I also tow 18,000# with mine. I will tell you that if your truck is stock that you would benefit greatly by going back to the stock tire size. My truck ran 70 @ 2000 rpm with stock tires and now 74 with the 285's.

[garyp4951]

This forum is great, and I appreciate all the info.
Goducks, I looked at my door panel when I got home, and it came with 265-70r17 tires 31.7", and now has 285-70r17 32.5".
Don't get me wrong, the 170k miles truck does great, but what really bugs me is like I said, the 47re tranny feels like the torque is not getting to the wheels until it locks up at 45mph, and then its on. I envy those of you with a manual that have full torque in every gear.

[bmanning]

Gearing is interesting and IMO very drivetrain-specific.

By that I mean this:

My 2008 F250 had the 5.4L with 3.73s; I went to 4.30s to get the RPM up to tap into the 5.4Ls powerband. I perceive a healthy benefit in power with only a (very) small loss of MPG, with no MPG loss in city driving. To me the 5.4L in the heavy F250 (crew cab 4x4 to boot) benefits greatly from the 4.30s.

Other engines, like the CTD in question, produce their power at much, much lower RPM, so even though math dictates that deeper gears add torque at the wheel, it would likely be a waste of money to make the swap, or a minimal benefit.

Lots of factors need to be considered when debating a gear ratio swap.

[goducks10]

The 2007 6sp has a final drive of .79
The 2003 47RE is .69
Running 3.73 with 31.5" tires the 47RE is turning 1647 rpms at 60mph
The 6sp is turning 1886rpm
The 47Re with 4.10 would turn 1811rpms. Close to your 6sp manual. He would have the same or so pulling power up those 6% grades.

[mr__ed]

3:73 rear in my 2007 Cummins 3500, 6-speed manual, towing fiver weighing around 12k. Never a problem with power. I can pull mild grades in 6th gear without lugging the engine. The only positive factor for 4:10 I can think of, at least in my case, is when backing my fiver into a spot needing a lot of maneuvering. It may be easier on the clutch, but the difference wouldn't be much.