dumb noob question about rear end gears

i have a dumb noob question. I have a 2006 ram 1500 qcsb 2wd laramie and when i got the truck the dealer said it has 3.55 gears but with out jacking the truck up and rotating tires or pulling cover how can i tell ?

You can check the build list posted in the glove box.

did not know it was there ill check it in a bit thanx

What size are your tires and what is your RPMs at 70 mph, a simple calculation and I'll tell you what you have.

My '07 still has the sticker on the rear axle.

It's on the passenger side, facing the front.

I thought they always paired the 20" wheels with 3.92 gears, but I could be wrong

mine specifies 3.92 on the decal in the glovebox.

ok theres no sticker in glovebox,center console,or under hood but i did find the sticker on the rear end where ron said its a 3.92 rear end yaaaaaaa no gas mileage lol

Originally Posted by catman113

ok theres no sticker in glovebox,center console,or under hood but i did find the sticker on the rear end where ron said its a 3.92 rear end yaaaaaaa no gas mileage lol

Before you say that, you need to remember you're driving a heavy truck with the aerodynamics of a cargo parachute. Give this a read ...
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AIR_RAM

This subject has been beaten to death, I know I personally have beaten it to death alone... so I will make this as short as possible.

-RPM's alone do NOT dictate fuel economy.
-The load on the engine at ANY given RPM has more of an effect on fuel economy then the RPM's alone.

At steady highway speeds at 2000RPMs your fuel economy will very depending on the terrain. UP Hills will cause increased load so even though your RPM's stay at 2000, your engine burns more fuel. On DOWN hills its just the opposite and at the same 2000RPMs your engine burns less fuel... this backs up the fact that RPM's do NOT control your fuel economy and the load on the engine does.

With that said, if we can decrease the load on the engine then the fuel economy will increase... This is what gears do. They decrease the load on the transmission/engine at the cost of increase RPM's. But the only way to know for sure if the increase RPM's will help or not is to do the math. I will not argue that a 1500RPM increase will have a negative effect on MPG. BUT on the flip side, a 300-400RPM increase teamed up with a DRASTIC decrease of the load on the engine at any RPM will only increase efficiency.

To find out what to expect with your particular application just do the math... its simple, and math only has ONE correct answer. Its not an opinion so you cant argue it.

1) Find your overall gear ratio.
TRANSMISSION GEAR x REAR GEAR = OVERALL GEAR RATIO

2) Find your RPM's at any speed.
SPEED X OVERALL GEAR RATIO x 336 / TIRE HEIGHT = RPM'S

You need to keep in mind that the OLD SCHOOL thinking does NOT apply hear.

Back in the 60's/70's they did NOT have dual overdrive transmissions. They did NOT have 31"+ tall tires... as a matter in fact the tallest tire was like 26" tall... So a 4.56's with NO over drive and a 26" tall tire would have you whipping your crank around at 3535 RPM's...

While 4.56's in your Ram with short 31" tires .67 OD at 60MPH would have you at 1983 RPM'S.

So as you can see 4.56's in today's overdriven overdrive vehicles does NOT instantly mean poor fuel economy... In my opinion these overdrives ADD to the load of the engine because they are way to overdriven.

If you're planning on driving with the shorter tires, I would suggest the 4.10's if you're UNDER 30". I never had a problem when I ran 29.5" tall tires and 4.56's... but I don't feel it was ideal. In my opinion, 31-32" tall tires would be a good candidate for 4.56's... 30" you could go both way's but under 30" I would have to lean towards the 4.10's.

Ohh yeahh... we still have the best prices with free shipping!

SPEED SAFE, AIR RAM
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Be thankful for 3.92's instead of 3.55's

Originally Posted by 05Ramhendrix

Be thankful for 3.92's instead of 3.55's

X2...if you really ant to throw away your gas mileage, go with 4.56's