I wanted to change my gears...

[15 Handicap]

From 392 to 373. My son said go down an inch or a little more on the tire size and accomplish the same thing. What say you?

 

[Brandon-w]

It would work yupp. Just use a tire size calculator and it'll tell you relatively how much your speedo will be out. I have a truck with 455 gears and I did the opposite as you. Dropped 300 rpm at cruising and have better clearance. 1st gear is almost useful now.

 

[RLJ10X]

You're only the second guy I can ever remember that wanted to gear UP. The other guy ended up leaving his truck alone.

Can I ask Why?

 

[JoeCo]

You're only the second guy I can ever remember that wanted to gear UP. The other guy ended up leaving his truck alone.

Can I ask Why?

I was thinking that, and usually don't hear of someone wanting to do a gear change that minimal. For the cost of doing it, hardly seems worth it. I could see changing the tire size though, since you'd need new tires eventually anyways.

 

[Quyonmob]

Wait, if you want your 3.92 to feel like 3.73, you need tires an inch or two bigger, not smaller.

Going smaller will make them feel like 4.10

 

[mtofell]

Can't imagine going to all that work and expense for such a small change. If you're looking to gain MPGs you would probably need to drive to the moon and back to get your money back on the cost to swap.

 

[Pull Ya]

The difference in those gear ratio's will be negligible. You will not be able to tell the difference. I don't think that the 1500 has a factory gear ratio of 3.73 available. I think your choices are 3.21, 3.55 and 3.92.
Jay

 

[RoadRamblerNJ]

Wait, if you want your 3.92 to feel like 3.73, you need tires an inch or two bigger, not smaller.

Going smaller will make them feel like 4.10

Correct. My '09 Ram had 3.92s. I also spent some time driving a buddies truck with 3.73s. Personally, I couldn't tell the difference, it was so slight. Put a taller tire on it and call it a day.

 

[RoadRamblerNJ]

The difference in those gear ratio's will be negligible. You will not be able to tell the difference. I don't think that the 1500 has a factory gear ratio of 3.73 available. I think your choices are 3.21, 3.55 and 3.92.
Jay

Correct Jay. 3.73s are only in the HD trucks.

 

[O.R.T.]

*How is anyone getting upsize +1 or 2 to gear-up? IMHO Skip the tire size calculator for simple things. Just use high school algebra math, Means and Extremes. Free calculator via https://www.wyzant.com/resources/lessons/math/algebra/calculators/proportion

Say for example on my 1500 w 3.55’s, the factory tire size is basically a 33”. If I wanted to calculate for tire size change to gear-down to a 3.92 I do the following...

3

 

[O.R.T.]

I’m still not seeing the solution being a +2, I’m seeing -2?? O/P wants to gear-up to 3.73’s, not gear-down. *Assuming you have a tire ratio w a p-metric conversion equaling 33’s. Here’s using OP’s ratio numbers with an assumed tire size and even then it shows as a downsize even if I switch the tire size to a 35”.

Assuming 33’s equates to dropping to 31’s.



Assuming 35’s equates to dropping to 33’s.

 

[tidefan1967]

The OP shows the 3.6 as his engine size......were 3.92's even an option on 6 cylinder trucks? I thought they all came with 3.21s and 3.55s. I was under the impression you had to have the Ecodiesel or the HEMI to get those.

Anyway if you go up an inch in height that should get you pretty close to that 3:73 you're looking for. I changed tire sizes on my 2015 RAM and I used a Hypertech speedometer recalibrator to correct for tires. This product also allows you to change the gear ratio also. There are other products that do the same thing available. You DON'T need an unlocked PCM for this to work either.

 

[15 Handicap]

My bad you are correct 3.21 is what I have, want to haul a little more comfortably.

 

[Dantra]

Gear change is a huge expense.. to have it done right anyway. I took my Jeep from 3:73 to 4:88 and the end result was amazing but not cheap. I'd recommend driving a truck with 3:92s to see if you like it emough for $2k. 3:92 and 3:73 are close enough together to be able to tell..

 

[Quyonmob]

My bad you are correct 3.21 is what I have, want to haul a little more comfortably.

Then you will need to find some 27” tall tires.

3.21 sucks. I have them too.

 

[Hemi450hp]

If your truck is 2wd, then swapping to a 3.92 gear is easy and not too expensive. Looking at about $500 in parts for OEM rear gears and an install kit with new bearings.

If 4wd, then it gets a little more complicated as you would also need to replace the complete front housing with 1 that already has 3.92's in it. Can get expensive if buying new on that font housing.

 

[O.R.T.]

^That too. AFAIK you cannot regear the front differential cases on IFS at this time due to casting and a couple other differences.

That said it’s pretty easy to get a used front diff from places like LKQ.

 

[768mph]

And also something to consider, if you go to a bigger tire it will increase rotation mass weight. More weight, more fuel consumption. Usually.
Provided you may just want a 3.73 for drivability.

Rule of thumb:
Every 1lb of spinning weight = 8lbs If unsprung weight.

Every 100lbs is a .10 slower in the 1/4.

Old racing guides but still apply.


Sent from my iPhone using Tapatalk

 

[kurek]

If you have 3.21's now and want to feel a bit more torque to the road your choices are to regear to higher numerical ratio (3.55 or 3.92) or you could put smaller tires on if that fits your cosmetic/functional needs (i.e. if it's a full time street truck) or you could work on engine power which... really just means that Sprintex supercharger
- it's expensive but it's a massive change in power with supposedly minimal change in fuel efficiency so the cost-to-benefit ratio is pretty good.

For tire sizing it's a matter of percents, you decrease tire size by 6% (going from 33s to 31s) you get the effect of having 6% more torque to the ground which in your case means something similar to what would happen if your engine made ~15 more ft-lbs. Up to you what that's worth...

3.92 rear axles seem like they're going for around $1300.. plus of course you would need a programmer but if you're 2wd and able to do the work yourself that might not be a bad deal. I mean swapping the whole rear axle as a unit, which can be done with a couple floor jacks, jack stands and hand tools. The difference between 3.21 and 3.92 is about 22% so that would mean ~22% more torque to the ground. That's a pretty big difference.. but it also means that if your normal highway cruise engine RPM is 1800 it would now be ~2200. (My other 4wd cruises at ~3100rpm on the freeway and I do cross country road trips in that thing so the RPM difference wouldn't bother me one bit)

The down side of that is if you're 4wd the cost and complexity double so you're getting pretty close to that supercharger money.. I'd just go with the supercharger at that point.

 

[Marshall]

Just buy a newer truck with better gears in it , simple .