Ask for truck upgrade advice on a gun forum, what better place could there be?

[DDTSGM]

Hopefully the thread title hooked a couple of knowledgeable folks. Here's my quandary:

I have a 2003 Ram Quad Cab Short Bed 2WD with the 4.7L. I bought it new and do not want to get rid of it. I have motorcycles and cars to drive. My primary use for the truck is to go to and from the range and to tow my wife's travel trailer.

There is the rub, when she decided we needed to go camping we looked at trailers keeping in mind what Dodge and the owner's manual said about towing capacity. We ended up with a 6,000 pound trailer.

I had used the vehicle to tow a 16 foot trailer when we were go-kart racing and the truck spent many hours towing at 80 on the Kansas Turnpike and I-70. I figured it would do okay at a more sedate pace with a heavier trailer.

Nah.

Calm and level, no wind, 65 to 70 is possible if I ease it up. Up hills or into any appreciable wind 55 is about it unless I want it to over heat.

I know the 4.7 is a weak sister, but I don't want to spend the cash to shove a 5.7H engine and tranny in it.

What I'm contemplating is changing out the 3.55 rear-end for a 3.92.

Anyone have any experience with such a swap? I know from fiddling with ratios on race bikes and go-karts that I'll lose top end but generate more low end. Enough to make a difference?

Thanks.

[Welder]

Calm and level, no wind, 65 to 70 is possible if I ease it up. Up hills or into any appreciable wind 55 is about it unless I want it to over heat.

I know the 4.7 is a weak sister, but I don't want to spend the cash to shove a 5.7H engine and tranny in it.

What I'm contemplating is changing out the 3.55 rear-end for a 3.92.

Anyone have any experience with such a swap? I know from fiddling with ratios on race bikes and go-karts that I'll lose top end but generate more low end. Enough to make a difference?

Thanks.

I don't know much about those year Rams as I got out of the Dodge mechanic'ing in 01 before your body style came out. That said, you mentioned overheating and if that generation is anything like the previous one, you need to be most concerned about your transmission....get that heat down immediately; it's a killer. Look into the aftermarket cooling system solutions first; aluminum radiators, aftermarket trans coolers, approved synthetic transmission fluids, oversized trans pans, etc....whatever you can do to improve heat rejection. Unless there's a design problem with that engine's t-stat, putting one that opens at a lower temp isn't really going to solve anything although a lot of people misunderstand how they work and waste money on that.

Changing that axle ratio may or may not give you the extra power you're wanting. I've swapped gears from 3.73 to 4.10 before and it made a difference but it wasn't like adding another L of displacement. You can look at the HP/torque curves for your engine, use an RPM calculator plus your trans and rear ratios to figure out how much a ratio change would affect your usable HP and torque at certain road speeds. Then calculate the change as a percent of total engine output and decide if that % change is worth the money. I don't think a ratio change will solve your overheating problem. Sometimes when you've got limited power and an aerodynamic brick like a travel trailer, the only solution is to just gear down and be patient. That's certainly what we had to do in the old days with dump trucks that only had gas V8's in 'em. I've hauled a lot of silage, grain, and stone with GMC dump trucks powered by the old tall-deck big-block 366 V8's which had fractions of the available hp and torque that you do. That 55-60 mph range is where aerodynamics really start affecting fuel mileage and engine loads.

Finally, if your truck's rated to tow that GVW of trailer, I'm a little surprised you're having that much trouble. Mfgr's were supposed to take cooling capacity into account when figuring those ratings. I'd also just take a general look at your whole setup and make sure something else isn't going wrong, and I'd start preventative maintenance by changing the water pump and t-stat with OEM-quality parts, flushing the cooling system, and flushing the trans fluid as well since I know it's been hot. I'd check my brakes and be sure they weren't dragging (including trailer brakes), be sure my tires were properly inflated, be sure the truck / trailer combination didn't exceed weight ratings, etc. Also would get on the various Dodge forums and see if this type of problem is common, what the root causes and solutions were, and if in the end I didn't need to just either accept a slower top speed or switch tow vehicles.

[littlejerry]

RE tow ratings:

I'm looking at the same stuff currently as the wife has her eye on a travel trailer.

SAE tow ratings have changed in the last 15 years and IIRC not every manufacturer started using the newer standards immediately. I would not assume a X000lb rating from 2003 is the same as a X000lb rating today.

Have you weighed your trailer? The specs are notoriously bad, with the dry weight not including things like propane tanks, AC units, etc. Id recommend taking your trailer to get it weighed in your typical travel configuration if you haven't already.

The general recommendation on the various travel trailer forums is to keep your trailer weight well below your max tow rating. Certainly if you only do short, flat trips you can creep up on your max ratings. But if you plan on steep grades, high temps, or high elevation you are much better off staying around 50% of your tow rating. This is especially true if you plan to tow a lot. Keep in mind your GCWR (Payload+truck+trailer) is the other number you need to be keeping track of.

Getting the trailer moving is only part of the problem. You also have to keep it stable and bring it to a stop safely.

Were looking at a new trailer and truck combo. I'm trying to avoid a full size truck so I can keep it garaged. The Ranger has a 7500lb tow rating and 12500lb GCWR, which means we're looking at trailers that have a dry weight of 3500lbs max.

[RJ]

I have a fair bit of travel trailer + truck towing, full time (2 years+/50,000 mi), but not familiar with rear end axle ratios.

Paging @JRB?

[JRB]

What @TBone550 already said about ensuring good trans cooling, trailer setup, weight creep on trailer load, etc is all 100% true. The issue isn't just the trailer it's also the aerodynamics of the trailer, at speeds above 55-65mph the air starts to become a real jerk about things, and above 85+ it's a straight bastard. I also really can't overstate the importance of proper transmission cooling when towing at speed. If you haven't gone to an upgraded trans cooler yet, that is absolutely worth doing no matter what.

First things first - I'd take a Hemi swap right off the table, as it's the single worst financial decision you can make in this situation. Hemi swaps in general are an overcomplicated pain in the ass because of the way Dodge did so much of that stuff. The earlier years like yours aren't quite as bad, but still just not worth the expense or mess IMHO.

Years ago, a few companies offered supercharger kits for the 4.7L, but I can't think of any companies still making a bolt-in kit. Going Supercharged would 100% solve the power problem at the expense of fuel mileage, and a switch to 91+ octane premium would be almost mandatory - we could dive into pulley ratios to reduce boost pressure to an 86-octane friendly level, but generally that means a 120hp gain would be reduced to a 60-70hp gain. But locating a good used SC kit for the 4.7L, installing it, getting appropriate trans cooling upgrades and other supporting mods installed, and getting it dyno tuned is going to be a $6-9k problem if it's done right. Most of that expense will be in the SC kit itself which I'd ballpark at $3500-5k used and $6-8k new. Figure $1000 for most shops to install it properly if they have any business doing that kind of work, and whatever that same speed shop would charge for an SCT/Diablosport tuning solution and a dyno tune. Figure another $500-750 for the tuner/software, $500-700ish for tuning depending on how much time it takes to get the transmission mapping, etc sorted out.

As far as the easiest path forward - gearing down would help somewhat, but I don't think it'll completely solve your 55mph up hills dilemma. Ballpark it'd make it a 60-65mph thing at best. That generation of Dodge auto trans doesn't have the greatest reputation for taking the additional heat/load very well either. Getting the gearset, having it installed, and then getting a Diablosport or SCT tuner to uncork a little HP and correct the speedometer is going to run you $1500-$2k ish.

If I'm being 100% honest, having been down this road professionally with LS swaps, turbo setups, superchargers, you name it - unless that truck was a thank-you gift from Jessica Alba for letting her into your bed, best to clean it up, sell it, and buy a different/newer truck that's more suited to towing that kind of trailer.

[DDTSGM]

I don't know much about those year Rams as I got out of the Dodge mechanic'ing in 01 before your body style came out. That said, you mentioned overheating and if that generation is anything like the previous one, you need to be most concerned about your transmission....get that heat down immediately; it's a killer. Look into the aftermarket cooling system solutions first; aluminum radiators, aftermarket trans coolers, approved synthetic transmission fluids, oversized trans pans, etc....whatever you can do to improve heat rejection. Unless there's a design problem with that engine's t-stat, putting one that opens at a lower temp isn't really going to solve anything although a lot of people misunderstand how they work and waste money on that.

Changing that axle ratio may or may not give you the extra power you're wanting. I've swapped gears from 3.73 to 4.10 before and it made a difference but it wasn't like adding another L of displacement. You can look at the HP/torque curves for your engine, use an RPM calculator plus your trans and rear ratios to figure out how much a ratio change would affect your usable HP and torque at certain road speeds. Then calculate the change as a percent of total engine output and decide if that % change is worth the money. I don't think a ratio change will solve your overheating problem. Sometimes when you've got limited power and an aerodynamic brick like a travel trailer, the only solution is to just gear down and be patient. That's certainly what we had to do in the old days with dump trucks that only had gas V8's in 'em. I've hauled a lot of silage, grain, and stone with GMC dump trucks powered by the old tall-deck big-block 366 V8's which had fractions of the available hp and torque that you do. That 55-60 mph range is where aerodynamics really start affecting fuel mileage and engine loads.

Finally, if your truck's rated to tow that GVW of trailer, I'm a little surprised you're having that much trouble. Mfgr's were supposed to take cooling capacity into account when figuring those ratings. I'd also just take a general look at your whole setup and make sure something else isn't going wrong, and I'd start preventative maintenance by changing the water pump and t-stat with OEM-quality parts, flushing the cooling system, and flushing the trans fluid as well since I know it's been hot. I'd check my brakes and be sure they weren't dragging (including trailer brakes), be sure my tires were properly inflated, be sure the truck / trailer combination didn't exceed weight ratings, etc. Also would get on the various Dodge forums and see if this type of problem is common, what the root causes and solutions were, and if in the end I didn't need to just either accept a slower top speed or switch tow vehicles.

Thanks for the very informative reply. A little more about the truck:

Less than 25,000 miles ago the truck popped a head gasket. I had the top end redone. At the time I looked into getting a new engine or a used 5.7 installed but it was too expensive for my tastes.

Then a crazy lady got in front of me when I pulled out from a stop sign and I had a new front end put by insurance, it was my first wreck so WTF. My bed was starting to eat out around the fender wells so I had the bed redone. (I brain-farted and pulled away from the stop sign in front of her because I saw a buddy down the street getting out of his car, thank God no one was injured - I made/convinced her to take a ride to the hospital to get checked)

After the first problem towing I took it in and had the system flushed and t-stat replaced (same temp - not cooler) they recommended a water pump replacement in addition and I did that.

About 6 months later I had the rear-end and transmission serviced - tranny fluid replaced, not run through a machine.

Then about 6 months ago I had the front end rebuilt when it ruined two fairly new Michelins.

Last, I spent a grand to put a hard flip up bed cover on the truck so I could go a head and leave my metal targets in the back.

And, that my friends, is how to get upside down in an old truck.....let me tell you about my '91 Mustang GT convertible...LOL

Seriously, I just plan to tow from central Kansas to southern Nebraska, Oklahoma, Missouri and Texas for GSSF matches, plus three fairly close state lakes. My wife doesn't retire for a couple years and we will, no doubt get a new truck to travel more.

Again, thanks for your reply.

[Welder]

Getting the gearset, having it installed, and then getting a Diablosport or SCT tuner to uncork a little HP and correct the speedometer is going to run you $1500-$2k ish.

If I'm being 100% honest, having been down this road professionally with LS swaps, turbo setups, superchargers, you name it - unless that truck was a thank-you gift from Jessica Alba for letting her into your bed, best to clean it up, sell it, and buy a different/newer truck that's more suited to towing that kind of trailer.

Agree with JRB's whole post but clipped it for bandwidth.

Re: swapping gears, if 3.92 was a factory available ratio, on a vehicle of this age you might luck out and find a complete rear for a few hundred bucks in the junkyard or out of a wrecked truck on CL, which is the route I'd follow first and is what I did on my current F350 work truck...swapping a complete rear is actually pretty easy if you're mechanically inclined. SO much easier than swapping ring and pinions, which is into the realm of things most do-it-yourselfers won't attempt. With a complete rear swap you just need a roller jack, 4 jackstands (2 for the back of the truck, 2 for the rear itself), a flare nut wrench for your central brake line, impact / hand tools to remove the leaf spring u-bolts or trailing arms, and a small ratchet or wrench to remove the driveshaft u-joint. Drain the oil, drop the old rear, put the new one in, put new fluid in it, bleed the brakes, you're on the road. Get your truck's speedometer reset at a shop or with a reader. Resell your good, used rear for about what you bought the new one for.

Just an idea if you're reasonably handy with tools. It's not a difficult thing to do and although it's not ideal, you can do it completely by yourself with no help; I have several times. Just don't drop a rear on your toes.

[DDTSGM]

What @TBone550 already said about ensuring good trans cooling, trailer setup, weight creep on trailer load, etc is all 100% true. The issue isn't just the trailer it's also the aerodynamics of the trailer, at speeds above 55-65mph the air starts to become a real jerk about things, and above 85+ it's a straight bastard. I also really can't overstate the importance of proper transmission cooling when towing at speed. If you haven't gone to an upgraded trans cooler yet, that is absolutely worth doing no matter what.

As far as the easiest path forward - gearing down would help somewhat, but I don't think it'll completely solve your 55mph up hills dilemma. Ballpark it'd make it a 60-65mph thing at best. That generation of Dodge auto trans doesn't have the greatest reputation for taking the additional heat/load very well either. Getting the gearset, having it installed, and then getting a Diablosport or SCT tuner to uncork a little HP and correct the speedometer is going to run you $1500-$2k ish.

If I'm being 100% honest, having been down this road professionally with LS swaps, turbo setups, superchargers, you name it - unless that truck was a thank-you gift from Jessica Alba for letting her into your bed, best to clean it up, sell it, and buy a different/newer truck that's more suited to towing that kind of trailer.

I replying to to T-Bone when you posted. Thanks for the advice, I'll get a transmission cooler and temp gauge installed. Going to slowly pull the trailer to Lewisville, NE next weekend, I'll try to get it done before that trip

I'm keeping the truck regardless, I'm attached and I'll need something to pull a pontoon next year.

Thanks again.

[DDTSGM]

Agree with JRB's whole post but clipped it for bandwidth.

Re: swapping gears, if 3.92 was a factory available ratio, on a vehicle of this age you might luck out and find a complete rear for a few hundred bucks in the junkyard or out of a wrecked truck on CL, which is the route I'd follow first and is what I did on my current F350 work truck...swapping a complete rear is actually pretty easy if you're mechanically inclined. SO much easier than swapping ring and pinions, which is into the realm of things most do-it-yourselfers won't attempt. With a complete rear swap you just need a roller jack, 4 jackstands (2 for the back of the truck, 2 for the rear itself), a flare nut wrench for your central brake line, impact / hand tools to remove the leaf spring u-bolts or trailing arms, and a small ratchet or wrench to remove the driveshaft u-joint. Drain the oil, drop the old rear, put the new one in, put new fluid in it, bleed the brakes, you're on the road. Get your truck's speedometer reset at a shop or with a reader. Resell your good, used rear for about what you bought the new one for.

Just an idea if you're reasonably handy with tools. It's not a difficult thing to do and although it's not ideal, you can do it completely by yourself with no help; I have several times. Just don't drop a rear on your toes.

That is an idea. Thanks. I was actually considering doing the ring and pinion swap myself, but couldn't imagine that much time/work on my garage floor. Not a real mechanic, but I can do stuff that doesn't involve electronics or injection.

[JRB]

Agree with JRB's whole post but clipped it for bandwidth.

Re: swapping gears, if 3.92 was a factory available ratio, on a vehicle of this age you might luck out and find a complete rear for a few hundred bucks in the junkyard or out of a wrecked truck on CL...

There's merit to this idea, but Dodge did some funky stuff with ABS sensors through those years, so while the rest of the loaded axle might bolt in, the ABS sensors and rings may not match up exactly and it'll throw an ABS code. Assuming his truck has ABS, 03's may predate when it became standard.

The other problem is getting that 'good used axle' installed can be a fast way to discover it needs new axle seals, new bearings, or new pinion seal, and then you're tearing the whole thing down anyway, hence my recommendation for a new R&P kit in the ratio you want, and just having that installed in the axle you've got. Replace all those seals while you're in there and you won't have to worry about it for a long time.

Dropping the 3rd member/diff carrier/pumpkin/whatever you want to call it is pretty mechanically easy too, and you can take that to a 4wd shop and have them set it up with your R&P of choice for a pittance compared to paying for the whole job.

Speaking personally, if it were my truck and I were dead set on keeping it, I'd go to a 4.10. If that ends up being too much gear, you can go to a taller tire on the next set of tires and get to the equivalent of a 3.73 or 3.91 pretty easily.