I spent a bunch of time researching the gear swap on my 3.7. Most of my time was looking over reviews and information on these forums so I figured I would do my part and share my results.

I have had the new gears in for about two months now and I would definately say that it was worth every penny. I think most of my freinds would tell you I am very frugal (aka cheap) and I would do this upgrade again in a heartbeat. I opted for Yukon gears and an Auburn limited slip differential which cost me just over $1200.

It may sound expensive but I have put a few minor mods on the truck and this one is by far the most impressive. I would highly recommend it to anyone with our 3.7.

I have the 20" wheels which really made the stock 3.21 gears just unbearable. I also have the 6 speed which was essentially a 5 speed with the old gears unless you wanted to travel over 80MPH all the time.

I do not have enough good information to share about the gas mileage difference but the best I can tell so far is that it has not changed much. My guess is that it improved slightly in the city (which is about 80% of my driving). I plan on updating this posting when I get more concrete numbers.

 

what year's your truck? stock 3.21? stock is 3.55.

i have 4.56 in mine, they're sweet. what made you not wanna make the bump up to 456? our overdrive is so ridiculously awesome, that i'm cruising at 70 and still just over 2000rpm.

edit: ah, i see you had a manual tranny. maybe that made the difference.

 

With the stock 6 speed and 3:21 gears I turnning 2000 RPM'S at 70 MPH It has a .78 OD ratio.

The way I figured it out I should be turnning 2500 RPM'S with 4:10 and 3000 RPM'S with 4:56 I dont know about you 3000 is a lot ofRPM'S to be turnning all the time I do 90% HWY driving this is with stock O/D tires 30.5 tall.

If I go with oversize tires say 33 inch tall tires 4:56 is the way to go then once again I dont want to dump a lot of cash in to this Truck not knowing if I will keep it after it's payed off, Like the Truck but hate beening so under powered.

It's very hardto swicth fromV-8 and Diesel trucks to this 3.7 V-6 it's killing me.

 

I am in the same boat as marv02, who by the way stopped sending pics of nice ladies on bombs. I dont know if I'll keep the truck. If I keep it, I would go to 4.10 too. Just thinking about shifting quicker, makes my knees hurt. Maybe Auto would be nice a 4.56.

 

I 2nd what eltupac next truck will be Auto most likely a Diesel still not a real fast truck be it's nice not to be undered powered and get ok MPG at the same time.

The 4.7 gets the same or better MPG on the HWY as our 3.7 but I want the big motor once again thats me.

I f I was smart I would get a compact car that get 70 MPG I hate driving small cars as you can see I not that Smart keep on buying full size trucks Ha Ha.

 

My truck is an '05. I run about 2500 or so RPM at 70 with my 33" tires. It is just about enough where you no longer lose speed on the hills. I decided to get the 4.11s over the 4.56s because I drive very fast on the highway (particularly in the 70 MPH zones) and did not want to take the hit on gas mileage.

 

same. I have 4.56's like derricksmash. They are a great addition and gave the truck a nice boost in power

 

http://youtube.com/watch?v=tzjU5ZBPKCw

^^ keep in mind, my 55mph reading is actually 60mph. my speedometer reads 8.2% slower cause of the bigger wheels.