Ordering exhuast, what do you guys think of this...Pacesetter y-pipe and gibson single side exit cat back...

Do i need to replace the factory cats?

Any recommandations on electronic dump companies?

Will 4:54 gearsand posi increasethe hp to the rear...

Thanks guys.

 

come on guys...

 

i'm not sure on exhaust but gibson exhaust is a good brand, pace setter headers are damn good as well. The 4.56's and posi will not increase HP but it will utilize what you have better. You will scream off the line. Your mileag ewill go down if you highway drive though.

 

thanks moto...

 

No problem, maybe some other guys who may know better the me will chime in soon.

 

Gibson and Pace Setter are good brands, but I don't have any personal experience (use Magnaflow myself). As far as the 4.56's, my opinion is these trucks shouldn't even come with less than 3.92's or 4.10's because they are so big and heavy. I put on a bit larger tires (factory were about 31", new are about 34") and had 3.73....totaly sucked. Gas mileage went down city and highway was always gear hunting. Had some Yukon 4.56's installed and mileage around town is back, highway is same as before bigger tires, and the biggest difference is "normal" driving the truck isn't working nearly as hard. If I nail it off the line the poor torque mgmt. has a hell of a time dealin'

 

What happens with bigger gears is your truck or car will hit higher RPMs earlier. In other words lets says you are taking off and running in1st @15 MPH, with the old gears you may be turning 3800 RPM, but with the new gears you will be turning 4200 RPM. (These are not actual numbers, just made up for a explination)

Why does this feel like more HP? Well your max power and torque is made at higher RPMs, usually around 3500-4000RPM, since you get up to those RPMs faster with bigger gears it makes it seem like that truck has more power, when in actaulity is the same power, just applied sooner.

This will lower top end speed. It will also cause you to turn more RPMs while cruising on the hgihway, resulting in slightly lower gas milage.

Another thing to consider, if you put a bigger diameter tire on your truck, then bigger gear the effect will be a wash as the larger diameter tire will eat up the gearing change.

 

Ok, now that the pseudo-science is out of the way, here's the real reason gears make your truck feel stronger:

It's gear multiplication. Leverage, pure and simple.

In first gear, you've got a 3:1 ratio. Say you have 370 ft-lbs of torque.

With 3.73 gears you have a gear ratio of 11.19:1. That gives you (not counting drivetrain losses) 4140.3 ft-lbs of torque turning the rear wheels.

With 4.10 gears you have a gear ratio of 12.3:1 Now you have 4551 ft-lbs of torque turning the rear wheels. (9% more)

With 4.56 gears you've got 13.68:1, which makes for 5061.1 ft-lbs of torque at the tires. (22% more)

Torque moves things, especially big, heavy trucks.

As for the gas milage and lower top speed, well... My power wagon turns about 2100 rpm at around 70 mph. I've had my truck up to scary fast (for a big, tall truck) 110 MPH, and I wasn't in 5th, and still had more left. How fast to you really want to push a truck?

 

I did not say it was a bad idea to change, just mentioning everything that will happen. Fact is your top end is lower and your gas milage will be slightly less. Better to know all the facts when making a decision.

 

Gibson was a very bad choice for me. Extreem drone in the cab at 2000 rpm. Poor fit on my HEMI SPORT. Wound up putting a Walker Dynomax and it sounds perfect. Same as my Dakota RT did.