i have a 99 silverado 4.8 reg cab and i went from 3.42 gear to 4.10 gear and im here to tell yall that this was the best mod for the money i have done. i wasnt sure at first after readin some forums but after first hand experience its great. and as long as you keep it between 45mph and 55mph gas mileage actually improves. before the the gear at 55mph it cruised at bout 1500-1600rpm's now with he gear at 45mph its at the same rpm. and shift points before the gear were about 43mph at 5200---85mph at around 5300 rpm's..after with a hypertech tune uping the shift rpm's are 40mph at 5900rpms--and 75mph at 5900rpms. parts and installation were under 159$$ for JEGS ring and pinion and like 25 bucks for oil and the gasket from autozone. and 40 bucks for a shim kit. installation i was told was spose to be 350 for trucks and 250 for cars but i payed the 250 ..got a real good deal. so EVERYTHING parts and labor was under 500 bucks. the only minor bad thing about everything is there is a barely noticable wine in the rear end..kinda sounds like drvin with mud tires. i ran a 14.8 @ 91 miles an hour thats with full bolt ons and the gear....

and for some one who knows about 4l60e transmissions..will it shift into overdrive under WOT? i've heard its not good for the transmission but i wanna be sure cuz u can only race up to about 115-120mph in 3rd ....assuming cuz my speedo only goes to 100.

 

I would agree with ya'- I did the same swap (from 3.42's) and it's a world of difference!

 

I think the factory tuning won't allow full throttle shifts into OD. If you let up on the throttle it will shift up, but it might downshift into third when you apply more pedal. If you get a custom tune, it can be done.

 

4.10s are a great mod dor the 4.8, wait until you add a torque converter, it will be 10X better