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Discussion Starter · #1 ·
as stated many times, yes its silly, but its only money and in the end, i want it. so now that's out of the way... i've contacted a shop that is pretty highly recommended/reviewed, they only do differential type work and have been in business for sometime.

as several of you have helped me understand/learn, because i have 4x4 going from 3.55 to 3.92 isn't just the rear axle but there's work up front too... i get that. so waiting for a quote back.. now here's what i'd like to know (are you out there Dr. Honda, TC1500 and Ranger?) .... if going to 3.92, why not 4.10 ... just because i want to know the answer to "why can't i"? also, if i actually waste my money doing this (see what i did there?) what else do i have to ask/understand? is it pretty simple/straight forward or are there any other electronics/transmission changes needed? if i COULD go to 4.10, why not do it? or is there some limitation that 3.92 is the lowest we can go on the 1500? i know other trucks have 4.10 (like the honda ridgeline, the tundra, etc). i really don't know what i don't know so trying to just understand as much as i can.

for grins i'll post what i get for a quote. have to keep in mind the ED i ordered was going to have 3.92, the truck i ended up with has the 3.55's but was laramie with more options and essentially the same price as i was going to pay for the SLT with 3.92 and no air suspension, no nav, no leather... so even if its $2K (made up number) i'm still better off...

anyway thanks for the help and information.
 

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There is no reason that you cant. If they make it you can put them in. they probably make up to 4.56/4.88 for these. and yes, you are correct, they have to do front and rear. Odds are they will quote you in the 2k range for front and rear with parts/labor, etc. So you can choose whatever they make. what gear ratio to do is totally up to you. As far as needing the computer re-programmed. It shouldnt. At least with the 2500's it reads off the tone ring in the diff, so it has no clue what gear ratio is in there. It just knows when it turns once.

Hope that helps!
 

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Be careful on new vehicles it is not as easy as it was back in the 70's.
I had a national known shop try to change out 3:08 to 3:73, after installing six sets of gears a total of seven times the shop gave up. Couldn't get the new gears to run quiet. They had high pitch sound coming from them, finally gave up on changing the gears on the 2013 Tahoe and bought the 3D with the 3:92 gears and a few other extras.
 

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Discussion Starter · #4 ·
well local dealer can do the swap ... for $4650. uh yea...

local shop said not able to do '14 due to lack of parts. sigh. so that sort of sucks. going to be hard to explain to my wife that i need to order a '15 Ram when I just bought a '14 Ram... do i REALLY have to have a 3.92 lol... i think i've got to throw in the towel on this one. :)
 

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well local dealer can do the swap ... for $4650. uh yea...

local shop said not able to do '14 due to lack of parts. sigh. so that sort of sucks. going to be hard to explain to my wife that i need to order a '15 Ram when I just bought a '14 Ram... do i REALLY have to have a 3.92 lol... i think i've got to throw in the towel on this one. :)
Help me remember jeff - why the hunt for the 3.92s again? I realize "because that's how I ordered it" is a valid answer here, but what was the original "need" you had. I'm in the camp that thinks you don't "need" this, but I don't recall what got you to the 3.92 choice in the first place, so maybe I'm missing something. And for the love of all that's holy, talk to us about this before talking with your wife!!! ;)
 

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Discussion Starter · #6 ·
@sportsguy - i had a really logical reply justification reason explanation typed up and then my browser crashed and lost it....

ok the truth is - there is no reason. it was a flag planted in my head that i can't remove. there's nothing at all wrong with what i have. its a wonderful truck and i'm really happy with it. a lot of this is really me trying to educate myself in areas that i never really paid attention to before. so i like to ask 'what does it take, why, why not, what are my options'. and fortunately for me, there are people like yourself and others that humor me and take time to give some great information as well as give me an internet /facepalm /smackupsidethehead to help talk me down from the ledge.

i would like to see in time the aftermarket come up with some solutions to tweak a few things - maybe this becomes one of those things as parts become available, after all its not like the 3.92s are specific to the ED, they are available on the Hemi as well.

i'm at peace with where this ended up - i got the answers i wanted. if i run out of things to spend $4500 on and it simply must be spent, then i have an item on my 'truck bucket list' to spend it on. :)
 

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Is there a point (gear ratio) where the size of the ring and pinion gears wont fit in the housing?
Technically this can happen, but in reality it doesn't. Bigger is too big in terms of overall diameter of the gear. But, "bigger" in terms of the ratio is not a factor of the actual gear diameter...until a point. The ratio is determined by the number of teeth cut into a gear. So you can cut for 3.21, 3.55, 3.92, 4.10 and more all from the same diameter gear. But there are limits. The type of metal and it's preparation can play a role. Lower ratios (those which are numerically higher) require more material be removed (to cut more teeth). This can weaken the overall gear, but today's metallurgy generally still results in high enough strengths for most applications. Still, it pays to shop with reputable, established names when dabbling with ring and pinion gear sets.

The bigger issues are the trade offs. Going numerically higher (geared lower) lets you tow more, haul more and in some circumstances might be just the ticket...like when rock crawling off-road. This lower gearing lets you literally crawl up and over obstacles, provided there is traction and all other systems can handle the stresses.

The trade is...higher RPMs for the engine, increasing fuel economy...and a reduction in top speed.

Some military vehicles take this to an extreme. Off-road mobility is paramount, so "portal axles" are used. The added gear sets are often at much greater ratios than we're talking about here. Like 6.xx to 9.xx are seen in these applications. Ideal for moving your army over or around, we'll, anything, but when invading a neighbor, fuel economy and outright speed are secondary thoughts. It's ok if your troop transports can't top 45 mph, as neither can your tanks and fuel tankers. ;) no sense your troops outrunning their support and supplies.

@jeff - I like how your mind works, man. Explore ideas, learn new things, make decisions based on data and facts, as opposed to just a random internet thought. :)
 

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Is there a point (gear ratio) where the size of the ring and pinion gears wont fit in the housing?
Absolutely. BUT... it's not that they don't fit... it's that you need a new carrier, with a different offset. OK... think about this.....

As the ratio goes up... the pinion gets smaller. Since the pinion gets smaller, they have to make the ring gear thicker, to engage the pinion. Eventually... it's too think to be stable, and that will make noise, and they will wear premature. Since Ram got away from Dana axles, I'm not sure where that "Break" occurs. With the Dana 30/35/44... that happened around 3.73. So... if we still had Dana axles... it would require new carriers to go from 3.55 to 3.92.

The second situation with all of this is... it's not that the "ratio gets too big to fit"... it's that the pinion gets too small to work properly. The smaller the ring gear... the harder it is to make a set of gears over the "3.90" range.

Anyway... JEFF....

Personally... unless you are doing a lot of heavy towing... or are planning on doing a lift with large tires... I wouldn't spend the $$$ on a gear change. Also... even if you are doing a lot of towing... simply putting in the 3.92's doesn't LEGALLY raise your tow limit, or GVW. SO... even though the tow rating goes up by 1000 Lbs or so from the factory... if you get pulled over, and have your trailer weighed... you can still get fined for the combined weight.


As far as going up to 4.10 gears... sure... you can do it. But on the stock tires, your highway cruse RPM will hurt your MPG's. The diesel engine likes to have a load on it... and burns less fuel at lower RPM's. So... putting in 4.10's, at 70 mph will make you turn over 2000 rpm's. That would be the equivalent of just keeping it in 7th gear all the time. And hear again... it's not legally going to allow you to tow more. With that said... Back in the day... trucks would NEED 4.10's to be good tow vehicles. But... they also only had 3 speed transmissions. Then... once the 5 and 6 speeds came out... 4.10's were hardly used... and 3.92's were king. (my last truck had them) But, that partly because first gear was only 2.70:1. So, the high ratio rear was needed to help get things rolling. (in the 70's and earlier, you would hear the term granny gear, because people would get a trans with a VERY low first) BUT... now... our 8 speed as a CRAZY low first gear. (4:1) and even our second gear is lower than the first gear of the 5/6 speed trans. Because of that... we don't need high ratio rear-ends to compensate.

As you can see... choosing a rear-end ratio isn't just pulling a number out of the air, based on "What other trucks use." You have to consider the ratio of your first gear... the ratio of your final drive (and if your O-drive is strong enough to tow in)... the tire size (or "Roll out ratio)... and what your target cruse RPM should be. (based on engine efficiency)

And finally... as suggested above... it's not as easy as finding the gears anymore. I remember swapping gears, and just accepting that the speedo may be off. But now... the entire truck uses the speed info to know what's going on. Everything from shift points, to the ABS... to the air bags need to know the proper speed to work. AND.... you may not be able to get a flash to fix it. (if 4.10's aren't available from the factory) It was nice when Ram was using the New Venture Gear T-cases. They were set up with an adjustable speed sensor. All you had to do is calculate the change... then swap the gear on the end of the speed sender. ($17)





So... in conclusion... I wouldn't spend the $$$ unless I was doing a lift, and needed to compensate for the bigger tires. After the truck is built... it's not even worth the $$$ for towing since it doesn't legally allow you to tow more, and our 8 speed already has a huge ratio range.
 

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Absolutely. BUT... it's not that they don't fit... it's that you need a new carrier, with a different offset. OK... think about this.....

As the ratio goes up... the pinion gets smaller. Since the pinion gets smaller, they have to make the ring gear thicker, to engage the pinion. Eventually... it's too think to be stable, and that will make noise, and they will wear premature. Since Ram got away from Dana axles, I'm not sure where that "Break" occurs. With the Dana 30/35/44... that happened around 3.73. So... if we still had Dana axles... it would require new carriers to go from 3.55 to 3.92.

The second situation with all of this is... it's not that the "ratio gets too big to fit"... it's that the pinion gets too small to work properly. The smaller the ring gear... the harder it is to make a set of gears over the "3.90" range.

Anyway... JEFF....

Personally... unless you are doing a lot of heavy towing... or are planning on doing a lift with large tires... I wouldn't spend the $$$ on a gear change. Also... even if you are doing a lot of towing... simply putting in the 3.92's doesn't LEGALLY raise your tow limit, or GVW. SO... even though the tow rating goes up by 1000 Lbs or so from the factory... if you get pulled over, and have your trailer weighed... you can still get fined for the combined weight.


As far as going up to 4.10 gears... sure... you can do it. But on the stock tires, your highway cruse RPM will hurt your MPG's. The diesel engine likes to have a load on it... and burns less fuel at lower RPM's. So... putting in 4.10's, at 70 mph will make you turn over 2000 rpm's. That would be the equivalent of just keeping it in 7th gear all the time. And hear again... it's not legally going to allow you to tow more. With that said... Back in the day... trucks would NEED 4.10's to be good tow vehicles. But... they also only had 3 speed transmissions. Then... once the 5 and 6 speeds came out... 4.10's were hardly used... and 3.92's were king. (my last truck had them) But, that partly because first gear was only 2.70:1. So, the high ratio rear was needed to help get things rolling. (in the 70's and earlier, you would hear the term granny gear, because people would get a trans with a VERY low first) BUT... now... our 8 speed as a CRAZY low first gear. (4:1) and even our second gear is lower than the first gear of the 5/6 speed trans. Because of that... we don't need high ratio rear-ends to compensate.

As you can see... choosing a rear-end ratio isn't just pulling a number out of the air, based on "What other trucks use." You have to consider the ratio of your first gear... the ratio of your final drive (and if your O-drive is strong enough to tow in)... the tire size (or "Roll out ratio)... and what your target cruse RPM should be. (based on engine efficiency)

And finally... as suggested above... it's not as easy as finding the gears anymore. I remember swapping gears, and just accepting that the speedo may be off. But now... the entire truck uses the speed info to know what's going on. Everything from shift points, to the ABS... to the air bags need to know the proper speed to work. AND.... you may not be able to get a flash to fix it. (if 4.10's aren't available from the factory) It was nice when Ram was using the New Venture Gear T-cases. They were set up with an adjustable speed sensor. All you had to do is calculate the change... then swap the gear on the end of the speed sender. ($17)





So... in conclusion... I wouldn't spend the $$$ unless I was doing a lift, and needed to compensate for the bigger tires. After the truck is built... it's not even worth the $$$ for towing since it doesn't legally allow you to tow more, and our 8 speed already has a huge ratio range.
Seriously. One of the best responses ever posted. Awesome Tony!
 

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