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Discussion Starter #1
Hi there, I have a 98 ram 1500 sport with the 5.9 that came stock with 3.50 gears and a limited slip in the rear end. I was wondering how practical it would be to change the ratio to 3.73 or 3.90? Which would give me the biggest bang for my buck and will my transmission hold up?
 

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Are you pulling something heavy or do you just want a quicker launch?
 

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Hi there, I have a 98 ram 1500 sport with the 5.9 that came stock with 3.50 gears and a limited slip in the rear end. I was wondering how practical it would be to change the ratio to 3.73 or 3.90? Which would give me the biggest bang for my buck and will my transmission hold up?
The practicality of it is relative to what you want out of it. Also what size tires you're running/want to run. It's relatively simple to change a ring/pinion setup in an open diff; not entirely sure about the LSD. If you're going through the trouble of changing things anyways, you might consider getting an Eaton Truetrac carrier which is a Torsen style LSD that doesn't have clutches and is a little more durable and forgiving in snow/ice because you don't get a full 100% lockup and it's a gradual progression.

As far as your transmission is concerned, it will have less stress on it with a higher gear ratio. The only place where stress increases is from the diff out to the wheel. So principally, your axles. The Off-road edition has 4.10 gears and taller tires, so you shouldn't have any problem unless you're putting down far more than stock power.

Getting some used tires that are smaller than your current tires by an amount proportional to the change in gear ratio is a relatively cheap way to experiment with how the truck will behave before you commit to a gear ratio.
 

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Discussion Starter #4 (Edited)
Right now the only thing ive done to the motor is throw in some e3 spark plugs but I have more performance mods planned in the future, also I don't do a lot of towing I am just looking for a quicker launch and more passing power, and I am running a little bit larger than stock tires, but nothing massive.
 

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It doesn't take much on tires. Going from 31's to 33's as I did, means that the equivalent observed axle ratio goes from 3.5 to 3.28. Which was very noticeable.

I think 3.90 or even 4.10 would help a lot with what you want to do.

But... if you're not going off road, or specifically need the bigger tires, smaller tires would be cheaper than gearing.
 

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Discussion Starter #6
What do you think I would be looking at cost wise in your opinion? Also the tires I got on are on the stock 16' rim but they are bigger than factory specs but nothing crazy big.
 

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4.10 for sure would be the right choice. As far as cost it can rack up in total. It takes a special kind of set up so it requires a guy that has done this before. DO NOT LET YOUR BUDDY DO IT FOR A CASE OF BEER! lol

Look for a good deal but most important be sure they can set up a rear.
 

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Discussion Starter #9
so with the 4.10 It will have more punch off the line as well as greater passing power on the highway, also will my transmission suffer
 

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so with the 4.10 It will have more punch off the line as well as greater passing power on the highway, also will my transmission suffer
Yes, Yes, No. Stress on transmission is lower. It will spin 17% more revs than before, but given that there is 17% less stress on it, the wear should be a wash.
 

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Discussion Starter #11
the thing that I never understood about gear ratios is that I always thought a higher gear ratio meant essentially a higher top speed and slower acceleration and a lower gear ratio meant greater acceleration lower top speed and was good off road can someone please explain?
 

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Strictly speaking the lower/higher terminology is a bit misleading and frankly, I'm not sure I even know what the correct terminology is.

In any case, trust in the numbers.

With a 4.10 gear ratio, the pinion gear (drive shaft) has 10 teeth on it. The ring gear (wheels) has 41 teeth. For every 1 revolution of your tires, your drive shaft has to spin 4.10 times.

With 3.50's, your driveshaft spins 3.5 times to make the wheel go around 1 time.

So for a given engine/driveshaft RPM, a 3.50 rear end will go farther than a 4.10 rear end. Meaning that a 3.50 is like being in a "higher" gear even though the number 3.50 is lower than 4.10.

So with that in mind, think of riding a mountain bike. In a low gear, you have to pedal many times to make the tire go around, but you have a lot of torque. You get this when your chain is on the small sprocket at the pedals and the big sprocket at the wheel. When you change up, the opposite happens.
 

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Interesting analogy. Basically a higher gear(lower number) is going to give you more top end and better fuel economy while a lower gear(higher number) will give you more low end torque, faster acceleration, and more frequent trips to the fillin station. I swapped out my stock 392's for a set of 456's while running 35" tires. That gave me exactly what I wanted as far as more low end but fuel mileage suffered pretty good. Went from 18 to 13.5 mpg.
 

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Interesting analogy. Basically a higher gear(lower number) is going to give you more top end and better fuel economy while a lower gear(higher number) will give you more low end torque, faster acceleration, and more frequent trips to the fillin station. I swapped out my stock 392's for a set of 456's while running 35" tires. That gave me exactly what I wanted as far as more low end but fuel mileage suffered pretty good. Went from 18 to 13.5 mpg.
That isn't necessarily the case. Every engine has an optimal power/fuel consumption point that depends on a whole bunch of variables. Given your average driving speed, driving style, elevation, tire size, etc.etc.etc., will dictate your best gear ratio for fuel economy. Go too far in either direction and your economy will suffer.

My 1500 5.9 w/ Overdrive auto 3.50's and 33" tires, gets its best mileage (13.7) at between 65 and 70 mph, but I don't spend any real time on the interstate, so I'm typically down around 55-60, and when off-road, like 35-40. So if I go to 3.90 or 4.10, I believe I will actually get an increase in mileage given the speeds I normally drive at.
 
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