Changing Axle Ratio from 3.73 to 4.10 and GCWR

[scottkeen]

I'm looking to get a used 2004-2007 Dodge Ram 3500 truck.
The specs I've found for 2004-2007 Ram 3500 Quad Cab 4WD LB DRW:

3.73 axle ratio = 21,000 (GCWR) 13,350 (max trailer)
4.10 axle ratio = 23,000 (GCWR) 15,350 (max trailer)

Pretty much all I can find on the used market are ones with 3.73 axle ratio.

My questions:
1) How costly is it to change out the gears to 4.10?
2) How can I get the truck re-rated/re-certified to 23,000 GCWR after the gear change?
3) If I have 4.10 gears but my truck sticker says my GCWR is still 21,000, will I have a legal problem if I'm made to weigh my rig and my trailer is 14,500 lbs (truck is 7,500)?

I'm new to all this, so maybe I don't understand. I read about people pulling trailers in excess of their rating. I don't want to do that without changing the gears so that it's safe. But how do people pull trailers around the country with trailers in excess of their truck's rating? Aren't they made to weigh their trailers at weigh stations? Does highway patrol make people weigh their rigs and verify GCWR compliance?

[transamz9]

Me Again wrote:

mtofell1 wrote:
If you do re-gear there are many options other than just the 4.10s. I have the 3.73 and if/when I do it I will likely go to 4.44 or 4.56.

I towed for 11 years with a 47RE/4:10's, same ratios, and would NOT wanted lower gears. Chris

I agree with you. My 2005 has 3.73 and really does great with a 4 speed auto. 2000 RPM with the factory tires is 70 MPH on the button. When I replaced the tires @ 75,000 I stepped up a size and now @ 2000 RPM it is 74 MPH on the button. I believe 4.10's would put it back close to factory gearing. It pulls my 20,000# fine now but at factory gearing 70@2000 it would be great. I do have a little added power that makes a difference also but at the OP's weights I beleive 3.73 would be great.

[Me_Again]

mtofell1 wrote:
If you do re-gear there are many options other than just the 4.10s. I have the 3.73 and if/when I do it I will likely go to 4.44 or 4.56.

I towed for 11 years with a 47RE/4:10's, same ratios, and would NOT wanted lower gears. Chris

[mtofell1]

If you do re-gear there are many options other than just the 4.10s. I have the 3.73 and if/when I do it I will likely go to 4.44 or 4.56.

[JIMNLIN]

My main concern was that it's a 3.73 axle gear ratio and if I load the 347THT 5'er toy hauler to the max GVWR, then I'd be over the max trailer weight specification for the truck by +900 lbs over.

Don't worry about that size trailer with a 3500 DRW truck with the diesel.
Dodge gave that truck a 9350 rawr so its good for around 5800 lbs payload in the bed.

The '07.5 Cummins is the 6.7 engine with the 68RE so it sure won't have any problems pulling a 14k gvwr trailer.

Trucks don't carry a GCWR/max trailer weight placard nor are they certified at a GCWR or for a certain trailer weight.

When the new '07.5 6.7 Cummins hit the streets lots of folks pulling commercially had to have one pulling heavy GN trailers. My neighbor lady came up with one for his and her hotshot company. She had it tagged for 38k gross combined which is a commercial requirement. You sure won't have any problem with a 14k gvwr rv trailer that may weigh closer to 12k-13k lbs gross.

[jaycocamprs]

scottkeen wrote:
The trailer I'm planning to get is a Mountaineer 347THT 5'er toy hauler. Dry weight is 10,700 and GVWR is 14,200

I'm going to look at a 2007.5 Dodge Ram 3500 on Tuesday (2 hours away). It's a Crew Cab, Dually, 4X4, Long Bed with only 82,000 miles and it has the 6.7L Cummins motor (has the diesel exhaust brake). It's being sold by an individual so the price doesn't have the dealer markup putting it within striking distance of my budget. He said he used it tow his boat in and out of the lake a couple of times a year and as a grocery-getter, never used as a plow. It's a Pennsylvania truck so rust may be an issue.

My main concern was that it's a 3.73 axle gear ratio and if I load the 347THT 5'er toy hauler to the max GVWR, then I'd be over the max trailer weight specification for the truck by +900 lbs over.

You should be all right with 3:73 gears in a truck of that vintage. Our 05 Duramax has the 3:73 gears, and we have a similar size Mountaineer. You may slow on the grades, but it should do ok You will want a DRW truck if you stay with a truck of that age.

[Durb]

scottkeen wrote:
Thanks for the replies. Sorry for my misunderstanding of "safety", I figured the "max trailer weight" specification was about what is safe to tow depending on the gear ratio. I guess it's more about capability(?) than safety.

OK, so couple questions answered -- glad to hear that as a RV'er, not commercial trucker, that I don't have to pull into weigh stations. I thought I read somewhere about someone with a trailer whose weight exceeded the truck spec, so they were not allowed to tow the trailer and had to unhitch and have a tow truck move their trailer for them or have it impounded.

I don't have the truck and trailer yet. My strict budget limit for the truck is $20K and I want the Cummins diesel motor, which puts me in the 1998-2007 range of used Dodge Ram 3500 trucks. The trailer I'm planning to get is a Mountaineer 347THT 5'er toy hauler. Dry weight is 10,700 and GVWR is 14,20

I'm going to look at a 2007.5 Dodge Ram 3500 on Tuesday (2 hours away). It's a Crew Cab, Dually, 4X4, Long Bed with only 82,000 miles and it has the 6.7L Cummins motor (has the diesel exhaust brake). It's being sold by an individual so the price doesn't have the dealer markup putting it within striking distance of my budget. He said he used it tow his boat in and out of the lake a couple of times a year and as a grocery-getter, never used as a plow. It's a Pennsylvania truck so rust may be an issue.

My main concern was that it's a 3.73 axle gear ratio and if I load the 347THT 5'er toy hauler to the max GVWR, then I'd be over the max trailer weight specification for the truck by +900 lbs over.

My son bought pretty much the same truck new (2500, quad cab SRW). At the outset he wasn't real happy with the fuel economy emission related check engine lights. At 100k he did an emissions delete with chip and the engine came alive. 50% better fuel economy and better power. You couldn't pry the truck from him now. good luck.

[scottkeen]

Thanks for the replies. Sorry for my misunderstanding of "safety", I figured the "max trailer weight" specification was about what is safe to tow depending on the gear ratio. I guess it's more about capability(?) than safety.

OK, so couple questions answered -- glad to hear that as a RV'er, not commercial trucker, that I don't have to pull into weigh stations. I thought I read somewhere about someone with a trailer whose weight exceeded the truck spec, so they were not allowed to tow the trailer and had to unhitch and have a tow truck move their trailer for them or have it impounded.

I don't have the truck and trailer yet. My strict budget limit for the truck is $20K and I want the Cummins diesel motor, which puts me in the 1998-2007 range of used Dodge Ram 3500 trucks. The trailer I'm planning to get is a Mountaineer 347THT 5'er toy hauler. Dry weight is 10,700 and GVWR is 14,200

I'm going to look at a 2007.5 Dodge Ram 3500 on Tuesday (2 hours away). It's a Crew Cab, Dually, 4X4, Long Bed with only 82,000 miles and it has the 6.7L Cummins motor (has the diesel exhaust brake). It's being sold by an individual so the price doesn't have the dealer markup putting it within striking distance of my budget. He said he used it tow his boat in and out of the lake a couple of times a year and as a grocery-getter, never used as a plow. It's a Pennsylvania truck so rust may be an issue.

My main concern was that it's a 3.73 axle gear ratio and if I load the 347THT 5'er toy hauler to the max GVWR, then I'd be over the max trailer weight specification for the truck by +900 lbs over.

[Durb]

I have the truck you are considering except 2WD but with 3.73 axle. When towing on the flats the sweet spot of the engine and tranny is 62-65 mph. There is an awkward area below 62 where the torque converter is locked in OD and the engine lugs and fuel economy goes down. When in hills I travel in Tow Haul which locks out OD and reduces exhaust gas temperatures which have a tendency to spike. A little noisy but commendable performance.

I tow a 10k trailer which is fine behind the truck.. If you want the 4.10 axle to tow 15k trailer then maybe look at a next generation truck. This isn't based on experience just a gut feel

[Grit_dog]

What are you pulling with now, that the trucks you're looking at would be a downgrade capacity wise? Or is that a theoretical trailer weight?

Away from gcvw ratings and speaking to the trucks you're looking at in particular.
As said the deeper gears will only provide more "power" not more safety in an apples to apples comparison.
Shopping for old vehicles/machines, my theory is looking for the best condtion/lowest miles, NOT the exact preferred combo. If happen to find all 3 that is a bonus.
Speaking to the particular trucks you're looking at. My strong preference would be 6 speed manual regardless of gears. If you need more power, any cheap programmer will make up the gear ratio difference just on its economy setting for far less than gears.
If you need more power than that you'll have to make sure the rest of the truck is up to it (transmission or clutch), in which case then it's a debate, spend the money on an older rig or buy newer with mo power.

[stickdog]

scottkeen wrote:
I'm looking to get a used 2004-2007 Dodge Ram 3500 truck.
The specs I've found for 2004-2007 Ram 3500 Quad Cab 4WD LB DRW:

3.73 axle ratio = 21,000 (GCWR) 13,350 (max trailer)
4.10 axle ratio = 23,000 (GCWR) 15,350 (max trailer)

I'm new to all this, so maybe I don't understand. I read about people pulling trailers in excess of their rating. I don't want to do that without changing the gears so that it's safe. But how do people pull trailers around the country with trailers in excess of their truck's rating? Aren't they made to weigh their trailers at weigh stations? Does highway patrol make people weigh their rigs and verify GCWR compliance?

Changing gears won't make you safer. If you are under capasity for all axles and tires you are legal. I'm under all axle and tire capasity pulling a 5er the truck is rated for and still over GCWR. In fact the truck is not even at its GVW.

[Tiger02]

Scott,

I would get the truck you want with the 3.73, and wait to see how it tows for you. You may find it just right for your needs. 4.10s are nice, but not a necessity for sure. If after some time towing you still feel the need then it may be worth the $1000 to $2000 for you.

Don't worry about the weights other than your F/RAWR and the GVWR along with your tire capacities. People re-gear vehicle all the time, and it's no big deal.

Good luck in your search.

[Me_Again]

You would be much better to invest in a newer truck with a 6 speed automatic, preferably a DEF model. A 2004-2007 5.9 will have the 4 speed 48RE tranny. I towed with a similar tranny for 11 years and found it very gear bond to do a really good job like my new RAM with the Aisin tranny.

So you will spend 1-2K for gears and mostly 3-6K for a tranny rebuild/upgrade with a 2004-2007. Put that money on a newer truck.

Chris

[Tyler0215]

Changing the rear axle gears will probably cost 1K to 1.5K. It will not affect the GCWR on the truck. State weigh stations only weigh commercial vehicles.

[carringb]

1) Gear changes run about $700-$900 per axle depending on your local labor rates.

2) Your owner's manual will tell you the maximum recommended combined weight for an available gear ratio. Note that you may install gears outside of those charts, but you may not be able to easily calibrate the truck's computers if you go beyond factory options. Keep in mind, these are only recommendation, mostly pertaining to performance and longevity.

3) You can print your own sticker if it makes you feel better. Seriously. You don't have a sticker now, and there are no laws pertaining to Combined Weight ratings, other than your combined weight can't exceed the truck's GVWR + trailer's GVWR. You could legally pull 23,000 pounds with a F150 as long as the driver and truck were properly licensed for the load being hauled, and federal bridge limits are not exceeded.

That all said..... going from 3.73 to 4.10 is a pretty minor change. I wouldn't do it for the cost. If 3.73s aren't cutting it for you, even lower gears might be worth considering.