2nd Gen Non-Engine/Transmission Changing the rear end ratio, your thoughts?

[rweis]

I have an 02 75k, 3. 54 (not POSI), ETC, DD2's, KSB1B, Scotty II, Smarty, tow heavy (high profile 13k 5er), and rarely go over 60 mph empty or towing, mainly southeast towing with some smokey mtns (ie low speed switchbacks). I am planning to have the ratio changed so I have better torque getting the 5er up to speed and rpm's ~ 2k with O/D (now run O/D out @ 2400).



Tentively looking at going to standard 4. 10, but are there other better options? or other better gear ratios? As I understand it the carrier has to be changed to get the 4. 10 ratio. As long as the carrier has to be changed (if that is correct) are 4. 10's the best choice?



Change takes place in 2 weeks by a local rear end rebuilder.



Your thoughts would be appreciated,



Bob Weis

 

[McCRam]

I want to switch to the 4. 10 as well. The only reason I haven't done it yet is I travel quite a few miles with it and don't want to take the mileage penalty since Im traveling at 70 and 75 most of the time. If the speed limits went back to 65 I would swap in a heartbeat.



I thought I heard you could get a 4. 10 gearset for either carrier.

 

[PRattenbury]

Good news. The carrier is the same for 4. 10 as it is for 3. 54. All you need is a ring/pinion set and whatever shims, bearings and seals get replaced out of routine.

 

[bkroupa]

The Dana 80 does use a different carrier for 4:10's



I switched the other way, 4:10's to 3. 54's & gained 2mpg @65 mph running empty on my weekly 800 mile commute. My trailer is lighter & not high profile, but the overall ratio in 4th is just slightly lower than it used to be in 5th so under ~55mph I cruise in 4th & still have OD for running empty. I'm also running 285's so that makes my gearing even taller. If I towed heavy most of the time, I'd either step back down to 245's or change gears to 3. 73's.

 

[rweis]

"The Dana 80 does use a different carrier for 4:10's"



NOPE unless you are going to a Dodge dealer. There are aftermarket ring gears that are extra thick that will bolt up on a carrier for a 3. 54 just fine.



I am going to have my 3. 54 changed to a 4. 10 and the installer is only changing the ring gear and pinion (pinion and carrier bearings etc of course) because he has found a ring gear and pinion that will bolt up to the 3. 54 carrier. No need to change the carrier.



IF you go to a dealer then they will change your carrier for the thinner ring gear.



Bob Weis



I am NOT differential savy, just repeating what the installer said. He rebuilds differentials and has done so for over 30 years and I am quite sure he is correct. I have to deliver just the housing to him and then he takes 3 days to install and rebuild. I have seen him work, and it is a real state of art.

 

[Silver_Ram]

I don't mind the 4. 10's with my 35" tires. If I would have stayed with smaller tires, I would have tried 3. 73 gears.

 

[Regcabguy]

3.73's

I don't mind the 4. 10's with my 35" tires. If I would have stayed with smaller tires, I would have tried 3. 73 gears.

I had mine changed to 3. 73's in order to "normalize" the gearing with my larger tires. Got a great deal with a local diff. guy and sold my 3. 54's in the classifieds. Not a whole lot of difference,just restored the stock gearing feel.

 

[MarkMiller]

Clarifying carrier "splits"- The carrier split for most Dana axles is 3. 73 (the dana 60 splits at 4. 09). That is point where the size of the pinion changes to the point where the strongest option is to move the mounting surface of the ring gear closer to the centerline of the pinion relief in the centersection.



So called "thick" gears are being produced and used in the aftermarket now. They add material to the backside of the ring gear to move it close enough to the pinion. They are a cost saving option for people wanting to move to the "higher" split. Strength of the thick gear is the arguing point(the extra material creates more of a chance for wear and movement in the tight tolerance friction fit). I will not offer and opinion either way. I will tell you that with 15 years of stupid sized Jeeps, Broncos, 500 cu in Cadillacs and now my high power Cummins I flat refuse to use thick gears in the rear axle. The peace of mind is worth more to me than the new carrier.

 

[SnoKing]

I have an 02 75k, 3. 54 (not POSI), ETC, DD2's, KSB1B, Scotty II, Smarty, tow heavy (high profile 13k 5er), and rarely go over 60 mph empty or towing, mainly southeast towing with some smokey mtns (ie low speed switchbacks). I am planning to have the ratio changed so I have better torque getting the 5er up to speed and rpm's ~ 2k with O/D (now run O/D out @ 2400).



Tentively looking at going to standard 4. 10, but are there other better options? or other better gear ratios? As I understand it the carrier has to be changed to get the 4. 10 ratio. As long as the carrier has to be changed (if that is correct) are 4. 10's the best choice?



Change takes place in 2 weeks by a local rear end rebuilder.



Your thoughts would be appreciated,



Bob Weis

Bob, I have 4:10 in my truck and like them most of the time. I did a 4200 mile RV trip in Sept at 12K on the 5er, combined at 19K.



With 4:10 I run 63 MPH at 2K and have all 4 gears to work with, not just 1-3. It pulls most normal freeway hills in OD just fine. I went from the HY35 to a PDR35 after the trip, becasue I found that I cound not use all the power available in the hot SW weather because of EGT restrictions.



55 is a tuff criuse speed for the 4:10's as you are out of OD and spinning a lot of RPM's. But pulling in the mounts you have a 40 to 60+ range in 3rd that will pull some pretty serious mountains.



Would I trade for 3:73 or 3:54's - never!



I averaged 12. 5 MPG for the trip. MS Streets and Trips said it was 3056 miles and we covered 4200 with side trips.



I also think that my exhaust brake works well with the lower gears. Long straight downhills at 6 percent in OD. Down to 3rd if it is 7 percent or windy. At 8 percent curvy I go down to 2nd (DTT locks TC in 2nd).



You will be happy with them. SNOKING

 

[WadePatton]

Have you considered or tried a smaller tire size? Don't see what you're running listed (assume 235/85), nor am I familiar with what else works for the DRT's, but it's another option when wanting to change your working RPM range.

 

[dodgeboy01]

I changed out my 3. 55's for 4. 10's and it made a world of difference. I pull an 11K toy hauler and my truck is running with 315 tires, so by changing out my gears was the only way to go for me. I get around 10. 5 to 12 mpg when towing.

 

[foolkiller]

bob



you will notice a HUGE difference. if you stay under 60mpg like you say, you'll love it and your truck WILL pull a lot better. if you're "just saying" you drive slow like i often say but don't really do, you'll feel like you're over revving all the time.



i base this on the difference between my dad's 4. 11 truck and my past 3. 54 truck.



3. 73 is an interesting idea but in my opinion would not make the impact i think you're looking for and i believe that just about covers all your options.



just a note, the 4. 11 with tires in the 33 inch range (285/75s) is a nice performing and nice looking combo and you have many options for the "E" rated tire still.



good luck, jeff

 

[Nate]

I put 4. 10s on my truck. 2000 rpm is ~72-73mph on the GPS.

 

[SnoKing]

I put 4. 10s on my truck. 2000 rpm is ~72-73mph on the GPS.

BIG TIRES!



SNOKING

 

[VIPERBLUELX]

I put 4. 10s on my truck. 2000 rpm is ~72-73mph on the GPS.

You got a stock transmission still with all those mods?

 

[rweis]

Thanks for the replies, tommorrow is take the axle off and get it to the differential rebuilder day. I really appreciate all the inputs.



I really do drive at 60 normally or at 51 1/2 if I am trying to get max mpg (with the 3. 54's). I just do not get all in a hurry ESPECIALLY towing (GCVW 21200, and I am getting hydraulic disc brakes for the RV (2 axle))



Again - TDR is THE PLACE TO BE when you have a question or need some input.



Thanks to ALL



Bob Weis

 

[Nate]

It's been rebuilt and "souped up" a bit before I bought it, though it's not anything that special. When it breaks... or I win the lottery, I'll put some $$ into it.

You got a stock transmission still with all those mods?

 

[Bart]

I did a weekend gear/housing swap. There's still lots of guys out there that would like to swap their 4. 10s for your 3/54s.

I did loose some mpg, but gained a tremendeous amount of torque/power. I can pull my 19K load in o. d. a lot longer than the older 3. 54s. Problem is that after the down shift into drive I had to settle in around 50 mph at about 2200-2300 rpms. Before I could settle in at 55 at 2000 rpms. EGTs are another issue. I still haven't got a handle on that so I don't want to go there.

One thing you should know is that GVWRs are higher with 4. 10s than 3. 54s. 16K vs 19K in my 3500 4x4.

On a side note, this last weekend I was coming home and loaded with my 19K when a high end pusher motor coach tried to pass me on the right from a signal and a merge lane loss on the other side of the intersection. I got on the skinny peddle and left him at the signal. He thought he was going to blow me off the road. Wrong!

 

[KLockliear]

For the money, you might also consider an underdrive unit, like a US Gear. Then you can keep the 3. 55's for normal driving, and have 20% underdrive when you want it. Pricing on those is around $2000, probably fairly comparable to front/rear gearset changes. Perhaps another option to explore.

 

[WTBurke]

NATE, I too see the same RPM 2k @ 70 Mph... I found that after the big tires went on the 3:54's didn't cut it. With 4:10's it feels the same coming out of the hole... . by doing the math it's too bad we can't get 4:18's for the exact ratio to tire size... . oh well close enough



William