2008 ram 3.7 going from 3.55 to 4.56 gear

[nathantc]

Well, my "little ram" as i call it, is getting what i think will be the best mod possible for the lil v6 truck with its 33" tires and 20" wheels.
Today i just bought an entire rear axle assembly that was fully rebuilt with 4.56 gears in it. gear set has less than 2000 miles on it due to the doner truck having a fire. (never touched the rear axle)
So i've got the 12 hole injectors, my 10" android radio. I love the truck but it just cannot hold overdrive at 65 mph or above if there is any hill or head wind. This will cure that issue. Not building a race truck or trying to make it special. i just want a comfortable daily that is cheap to maintain. Im installing it in the morning and will report back my feelings on the swap from a 3.55 to a 4.56 with a mostly stock set up.

next major mod will be modding a 4th gen rear bumper and dual exhaust. (keeping it quiet) just for looks.

by the way i got the entire rear axle for only $200 and can do the work myself. so add the cost of fresh gear lube, and that is a damn cheap gear swap. Oh and it's got new rotors, calipers, and pads.

 

[nathantc]

crunching the numbers. i find my truck seems happy at 2k rpm. this is why i wanted 4.56 over 4.11 gears. i'm no speed demon and pretty much normally cruise at 65 mph.

 

[Quyonmob]

This will really wake a 3.7 truck up. Great find for $200 and a driveway swap!

 

[Quyonmob]

I’m desperately looking to swap my 3.6 with 3.21 to 3.92.

 

[nathantc]

ok so results are in. I LOVE IT.
truck is completely different. not just holds overdrive at 65 and 75 MPH, but it can actually accelerate uphill in OD at these speeds. keep in mind im running a 33" tire. 275/60R20

65 MPH is 2100 RPM on the tach
75 MPH is 2400 RPM on the tach
80 MPH is 2550 RPM on the tach.

truck is twice as fast from 30 mph to 80 mph as it was with the 3.55

these rpm's might sound high but with the 3.7 v6, you dont make any power or torque until you are above 2k.

transmission shudder (rumble strip feeling) at 30-35 is gone
kicking out of OD any time the wind blows or a hill is present, is gone.
truck actually feels like it should have came like this from the factory.

 

[Snake15eyes1998]

I have the 5.7. When I'm in O/D off, so 3rd gear. Doing 70 ( 60 mph on my speedo), my RPMs are at 2600. I have 3.55 gears in mine, I want 4.56, but thats not in the budget right now. Glad you like them. If I don't put it in O/D off. 4th and 5th are to low and she hunts like a ****. 3rd is perfect. It works for now. Thanks for sharing man. Maybe one day.

 

[nathantc]

I have the 5.7. When I'm in O/D off, so 3rd gear. Doing 70 ( 60 mph on my speedo), my RPMs are at 2600. I have 3.55 gears in mine, I want 4.56, but thats not in the budget right now. Glad you like them. If I don't put it in O/D off. 4th and 5th are to low and she hunts like a ****. 3rd is perfect. It works for now. Thanks for sharing man. Maybe one day.

keep watching FB marketplace, go search (your year) ram 1500 rear end. each morning before you leave for work. that is what i did. found a complete rear end with a new 4.56 gearset, and all new bearings and seals for only $200. so after opening it up to inspect, buying mobil 1 75/80 full synthetic, and about 6 hours total time with run around and all. ive got just under $300 invested in this swap. you can do a full rear axle swap without disconnecting and having to bleed the brakes.

 

[kmrtnsn]

The problem I see is that sure your RPMs are down but the 3.6 develops most of its power and torque above 3,000 RPM. 90% of your maximum torque is developed in the band between 1900-6300RPM.

 

[nathantc]

The problem I see is that sure your RPMs are down but the 3.6 develops most of its power and torque above 3,000 RPM. 90% of your maximum torque is developed in the band between 1900-6300RPM.

that was exactly the case, before the gear swap.

 

[kmrtnsn]

that was exactly the case, before the gear swap.

Ii have the 3.6l in my JKU with 373s and the 5.7l Hemi with 321s in my SLT. Wife has the 392s in her 1500. Day and night between them and how they drive.

 

[nathantc]

pretty sure the 3.6 and the 3.7 are different, though im sure the power to rev range is probably pretty close. keep in mind tire size and vehicle weight will play a factor in what gear will work best. i just know my 3.7 is a total dog at 1500 or less rpm