If you're running 3,000 rpms at 70mph with 38" tires and 4.88 gears, your tranny isn't going into overdrive. If I run my truck with OD off at 70 mph, it hits around 2,900 - 3,000 rpms. With OD on, it runs at 2,200 - 2,250 rpms. I highly suspect that for some reason your tranny isn't going into OD.

 

So what gears would you go with if you were running 37's?? I've heard of guys running 38's with 4:56 gears and love it, I don't know is that pushing it??

 

no my trans is def def def going into overdrive, theres no doubt about that, its just the gearing man. i just took off a set of 40's and they run about 200 rpm's lower

 

So I should just stick with 4.56's then?

 

yeah i have 37s on mine and i have even more wheel space then the white ram picture up top. when i put my 39.5's on there a lil stuffed and i have a 5.5 inch lift and a 2 inch leveling kit.

 

the white ram picture on the first page of this thread i meant. and my sig pic isnt with the leveling kit and 37's that just mt 35s with the 5.5 inch lift haha

 

8.5 inchs of lift and 37" tires

My Sig is 8.5" of lift with 38.5" ground hawgs. I am going with 5.13's cause i want to makes sure i have the power to spin the hawgs in the mud, and there is a chart in the DIY section that says 5.13's are close to stock with 38's.

 

Heres that chart for you

http://www.4lo.com/calc/geartable.htm

 

your right as far as saying it will give you close to stock power back, but what is misunderstood by many is what it does at higher speeds.....your rpm's go through the roof at higher speeds

 

if the chart is true, its less then 100rpm difference.... just saying........ BUT when i had my 4.56's with my 35's it did seem a little low but nothing crazy and it had been awhile sence i drove it with stock tires when i had the 4.56's installed so its hard to say if it was close or not.