2nd Gen Non-Engine/Transmission Changing rear gears

[Doc McGuiness]

I plan to change the rear gears in my '02 from 4.10 to 3.55. I was told by a shop that I would need to have the computer re-programmed, or change the speedo gear in the transmission. Is this true and which would be the easiest way to go?

 

[RustyJC]

I don't know why you would. Recalling our previous 2002 3500, the speedometer gets its signal from a toothed wheel mounted on the ring gear carrier (you can see the wiring going to the probe on the top side of the differential), and the ring gear carrier's speed is going to be the same as it is now at any given road speed. What will change is the pinion shaft speed and anything upstream from it (e.g., driveshaft, transmission output shaft, engine RPM, etc.).

Rusty

 

[Cummins12V98]

My question is why would you want to change? Not would want to go to 4:10's or 3:73's. On my 98 I went from 3:55 to 3:73's.

 

[Joseph Donnelly]

If Dana 80 (stick trans), iirc there is a carrier change between those ratios. Given the cost of changing gears, many owners elect to use taller tires instead.

 

[NIsaacs]

My question is why would you want to change? .

Because 4.10's are just too slow for a truck with only one overdrive. A taller tire is also not enough to help much. I do agree with your 3.73 choice, that's a perfect gear with 285's. I have the 3.55's with 285's so I use 5th a lot when I tow heavy.

Nick

 

[VolsFan]

I also want and need to change my gear ratio, I have 4.10 and at 65 I'm @ 2300 rpm and I avg 15.5 mpg. My old auto w 4.10 w 285/75/16 got 17-18 mpg easily. New truck has stock 235/85/16 and taller tire isn't an option because wouldn't be able to park it in garage, only have an inch or two to spare. Plus the bigger tires wears out hubs premature. What kind of $ can one expect to have a gear ratio swap done on a 4 wd? Weighing out a lockout hub conversion or gear ratio swap

 

[GAmes]

.....which would be the easiest way to go?

It isn't an either/or it is one or the other depending on if you have a '97 or earlier, or a '98 or newer. We can't read your mind, so a signature would help.

 

[Road Dog]

Well he said "in my '02" so that's a hint but he doesn't say whether it's a 2WD or 4WD or 2500 or 3500.

Rusty is correct --there's no change to the speedo. If the shop doesn't know that then they probably don't know it needs a carrier change too. If it's limited slip then that's more money too.

 

[GAmes]

I read that post three times and still missed it.

 

[Doc McGuiness]

Okay guys, the reason I want to change gears is because I don't tow much anymore, I'd like to reduce RPM's at highway speed, and of course I'd like to improve mileage. My truck, as I stated in my original post, is an '02. What i failed to mention was, it's a 2500, 2wd, with anti-spin differential. Another question comes to mind now; why would I need a different carrier?

 

[NIsaacs]

Like Joe said, if it is a standard transmission truck, it will have a Dana 80 rear axle. The carrier's are different between the 4.10 and 3.55. If your truck is auto, it will have the Dana 70 rear axle. They are the same for both gear sets. Since you have a 2 wheel drive the cost wont be bad at all.

Nick

 

[Road Dog]

Another question comes to mind now; why would I need a different carrier?

Changing the ratio (from 3.55:1 from 4.11:1) means changing the number of teeth on the pinion and ring. The pinion changes in diameter as you change the number of teeth so the ring gear has to be thicker or thinner to keep it meshing properly. A carrier will only fit a certain range of ratios. If you're going from 3.55 to 4.11 you can buy a thick ring gear that fits the 3.55 carrier.

It's called the "carrier break" and for Dana 70 it's 4.11 and down. For Dana 80 it's 3.73 and down. Maybe you're good to go.

 

[BigPapa]

Your savings in fuel will not be enough to pay for the change unless you keep the truck 20 years like Gary and I.

 

[Doc McGuiness]

Thanks guys, I appreciate all the responses. I'm not doing this because I want to save money, hell I know I'm not likely to recoup my costs. I'm doing it because I want to. Why do we do all these things to our vehicles anyways. This is my first diesel, I've had it about three years now. It had 41k on it when I got it, has a little over 77k now. I've owned a lot of vehicles over the past 50 years, and this one ranks high on my list of favorites. I really don't need a 3/4 ton truck anymore, much less a diesel, but I'm really hard pressed to get rid of it. Sure, I see all the new ones, and actually test drove the new Ram Ecodiesel. Now there's a truck I'd love to have. No doubt would be the last new vehicle of my life. Every time I get behind the wheel of my truck, it puts a smile on my face. My darling wife hates it, says it's too loud and it smells. The truck is going in the shop tomorrow for the gear change. We'll see how it all turns out.

 

[NIsaacs]

I'm doing it because I want to. Every time I get behind the wheel of my truck, it puts a smile on my face. .

I agree, the only way it can get any better is to have 3 of 'em

Nick

 

[Doc McGuiness]

Got the truck back from the shop today. New gear set installed and everything running fine. Speedometer spot on with no issues. Truck now revs about 1750 @65mph. About 250 rpm less. Still enough grunt from stand still to put a smile on my face. I swear, every time I get behind the wheel, I love this truck more and more! BTW, is anyone interested in buying the 4.10 set of gears I have left over?!

 

[JR]

Is it a Dana 70 or 80? What state are you in?

 

[Doc McGuiness]

Dana 70. I'm in central CA.

 

[SAndreasen]

Is it a Dana 70 or 80? What state are you in?

Not to be nosy or get in your business but why do you want 4.10 gears ?

 

[SnoKing]

Not to be nosy or get in your business but why do you want 4.10 gears ?

Didn't, he switched from 4.10's to 3.54's! SNOKING