4.10 to 3.73 Swap

[RobG]

I've pretty much concluded that the 4. 10s in my truck have to go. They're killing my mileage, and before I take a $5000 hit to get rid of the truck, I should try doing a gear swap first.



Who has the best deal on the parts? The ring and pinon and whatever else is needed? Will the carrier have to be changed too since it's a 4. x carrier? I'm thinking not, but I'm not that familiar with these new American Axles. I have the limited slip option on this truck, so that may be affected too.



Setting up gears is one thing I've never done, and don't think I'm quite ready to try... so once I can get the best deal on parts, I can find somebody to install 'em.



Also... are there any major computer software changes that I'll have to get the dealer to do? Or is it just a matter of a reflash for the speedo?



Thanks!



Rob

 

[EEngel]

Swap

Rob,



There always people looking for 4:10's on here. See if someone is willing to swap the 3. 73's with you.



A good # of people want the lower gears to offset larger tires.

 

[DPelletier]

Nice looking truck. I'd try the swap thing too.



Dave

 

[Bertram65]

I think the biggest things causing bad mileage on your truck are the 4X4 and automatic. Lowering your rpm by going to 3. 73s will not make that big of a difference. You can try it yourself by just lowering your highway speed for a tank full to what the 3. 73s will run at, I would guess about 150-200 rpm. The city driving should not really be effected.

 

[XcumminsX]

Put on some 35's... . I have 4. 10's on my truck when i get it back im going to put on 3. 73 gears... i hate the 4. 10's even with 35's. .



Nick

 

[Johnstra]

Slightly off-topic question. Anybody know if the speedo calibration and the mileage computer are based on the same inputs? Are they both based on crank position (RPM) or something else? Just curious.

 

[thejeepdude]

Originally posted by RobG

Who has the best deal on the parts? The ring and pinon and whatever else is needed? Will the carrier have to be changed too since it's a 4. x carrier? I'm thinking not, but I'm not that familiar with these new American Axles.

I've had good luck with www.ring-pinion.com . Their installation kit included everything thing I needed to do the gears in my Jeep's D44. They don't show a Dodge 11. 5" application, but there's one listed for GM... not sure if the R&P will work in both, I'd give them a call. As for the carrier, I don't think it needs to be changed, but maybe someone else can confirm. The nice thing is, from what I've read, the carrier bearing preload adjustment is threaded... that should make it a lot easier to set up that the Dana axles and their shims. If you do find someone local that wants to swap ratios with you, you might find it a lot easier to swap entire axles rather than just gearsets.

 

[Johnstra]

Slightly off-topic question. Anybody know if the speedo calibration and the mileage computer are based on the same inputs? Are they both based on crank position (RPM) or something else? Just curious.

 

[John - K5AWO]

I would prefer to go the GearVendors route. In double over-drive you get some decent improvements, AND, you can still pull stumps when you need to. I have 4. 10s also with 235R85 x 16 tires. Currently the speedo is 4. 5 mpg slow at 70 mph per my GPS, so 70=74. 5 true. Now add in the GearVendors 27% reduction and the RPMs will drop by 27% for the same mph. Gives you the best of both worlds. I expect to see 20-21 mpg at 65-70 mph with this setup. I currently get 16. 0 average over 6,000 miles of city driving w/25% of that freeway.



3. 73 gears are a waste of money IMO. The fuel savings, even at the $2. 37 price I saw this morning, will take a lot of miles just to break even. They are a nice all around gear, providing they were there before you bought the truck.



If you get 3. 08 gears, you can put yourself in the 23-25 mpg range, but then you would loose stump pulling power.



The last two tanks of fuel I averaged 28 mpg of diesel fuel 'purchased'. I have started running clean, filtered crankcase oil at about 40% oil to 60% diesel. Be sure it is cleaned down to 2 microns or so... .

 

[klenger]

I agree that the gear swap won't make that much difference in milage. I had an 01. 5 with 4. 10's that got better milage than my 04. 5 with 3. 73's. If you can do a no cost swap, then go for it, if not, then save your money and buy the fuel.



Even with a gear swap, you have the worst combo for milage: 3500, DRW, auto, 4WD.

 

[RAMINSPEED]

Hey RobG I live in Northern Nevada also and would be interested in swaping my 3. 73's with your 4:10's saving you the cost for parts. PM me and I will call you and then we can talk.

 

[bulabula]

Originally posted by RobG

I've pretty much concluded that the 4. 10s in my truck have to go. They're killing my mileage, and before I take a $5000 hit to get rid of the truck, I should try doing a gear swap first.

What are you getting for mileage? I calculated 19 after my round trip from MD to MI. 19+ doing 65; dropping down to 17+mpg @ 70-75 mph.



I'd say its your driving style thats killing your mileage rather than the gears.



I think an even-steven gear swap would be the only thing remotely related to helping you save some money; if you pay for the gears and to swap them, you'd have to drive a couple hundred thousand just to have the fuel savings "possibly" pay for the swap.



I second the motion for bigger tires.

 

[RobG]

Thanks to all the responses. I'll respond to PM's shortly.



My current mileage is awful. 11,800 miles on truck and combined average is 11. 98 mpg. That's normal driving, not leadfoot. That's calcuated too. The computer shows . 1 mpg worse than actual.



I had 4. 10s in my 01 6sp HO truck and put a US Gear Overdrive in it for better cruising RPMs and better fuel mileage. It never happened. The thing got worse mileage than my current truck until 27k, when combined went up into the 15 range.



I'm pretty disappointed with the whole deal. If I can find a way to do a low-cost or no-cost swap, I will. If not, I'll stomach it for another year until I can ditch this thing.



Thanks!



Rob

 

[BMancin]

I just completed a 500+ mile trip. My computer avg 18. 2 mpg. This was mostly hiway 62 - 68 mph @ 1900 - 2100 rpm. Considering the duelly weight and 4. 10's, I am pretty satisfied.

 

[CumminsBu]

I did a 500+ mile trip same speeds as BMancin. I avg 20 mpg over head, hand calc to 23 mpg. I would go with intake and exhaust upgrades, before gears.

 

[XJSuperman]

Rob... I looked at the pics in your signature... looks like you are still on stock tires... meaning the engine RPM's you are running may be higher than they need to be ... not that that will hurt anything but usually a little lower RPM will mean better MPG... . so have you considered putting on a little taller tire to compensate??

 

[RobG]

Maybe my photos aren't right, I'll have to check that later. I'm actually running Rickson 225/70-19. 5 wheels and tires. This is the third Dodge I've had 'em on (they were on my '96 first, then my '01, now this one). Been on it since about 500 miles.



Diameter is about the same, within 1/4" anyway. I don't really want a taller tire because I carry a camper and don't want to screwup my center of gravity. Besides, there aren't many choices for dually owners on stock wheels anyway because of the 17" wheels.



If I was made of money, I'd get a set of Rickson's new alloy wheels and run the 245/70-19. 5 setup. I can't on these wheels because they're 6" wide instead of 6. 75" which is required for the wider tires.



Rob

 

[Rockcrawler]

If you search, you'll find about a yr old thread- I traded entire axles with another TDR member, funny thing was he ended up living 25 miles from me.



The expense of setting R&P up in two axles + parts is considerable. We had two people working for 8 or so hrs, had to pay for an alignment when done. I'm experienced at R&P work and was too lazy to do it myself. If it were a 2x4 I may have considered the R&P option,



it's 250 rpm's at highway speeds, about the same as going to 315's (not an option for you, I realize). I bought my truck with 4. 10's and it was just too good a deal to pass up with my trade in etc. Even with the 315's the rpm drove me nuts.

 

[Bertram65]

Did you notice any change it mileage changeing to the 3. 73s.

I have 315s with the auto and 4. 10s and I lock out OD when towing unless I am really flying.