gear ratio gm 14bolt upgrade
 

Ok, I have a custom built 87 Chevy heavy half with a mild 3-4 inch lift,np203 t-case, NV4500HD trans, dana 44 open front, locked gm 12 bolt rear with 3.73 gears currently on 32" tires. I have a gm 14 bolt that i have upgraded with disc brakes that I will be installing soon but I am stalled out at the moment. The 14 bolt needs a diff, the open carrier is shot and I am going to put in a locker I just cannot decide whether to upgrade to 4.10 gears or keep the 3.73 gears. I want to put 33" tires on in place of the worn out 32" tires so I know this will change things slightly. I am pushing more than 300hp and 420lb ft of tq out of the built 350V8 so the truck moves great even with a 5000lbs in the bed. I know that the 14 bolt is seriously heavyier than the 12 bolt even with the disc brakes and then throw in taller tires makes me think I should take this opportunity to throw in 4.10s. I built this truck for hauling and so it sees a lot more highway duty than trail duty and sometimes daily driver duty. That depends on the how my daily driver is doing. Any input would be great. I can get the locker and gears used but good here locally from a gears vendor for fairly cheap just dont know how good of an idea it would be to upgrade considering power has never been a problem before.

Re: gear ratio gm 14bolt upgrade
 

Go with 3.73s if you have the power. 4.10s make the motor scream with those tires at highway speeds. Truck nor you won't even notice the difference between the two axles....

Re: gear ratio gm 14bolt upgrade
 

I was kinda leaning that way. The only reason I was thinking of stepping upto the 4.10's besides the fact i could do the locker and gear for $200 is when I use overdrive at 50-55 mph the rpm drops to about 1500 which is just below my cams powerband that starts at 1600. So acceleration and maintaing speed in overdrive below 60 takes alot of throttle. Because of this I have learned not to use overdrive untill speeds of 60 or more. I was thinking that the few hundred rpm increase of the 4.10 might help that but its not a neccessary endeavor.

Re: gear ratio gm 14bolt upgrade
 

Keep the 3.73's if u ru upwards of s 35 and bigger then we'll talk 4.10's... Also if u go 4.10's u gotta change the front :/
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Re: gear ratio gm 14bolt upgrade
 

If you didn't have a trans with OD i'd say keep the 3.73. There really isn't a huge difference between 3.73s and 4.10s so If you're going to drop the coin I'd step up to 4.56s or otherwise stick with 3.73 and save the cost of changing the gears in the front to match. If you're anything like me you'll end up going bigger in the future anyways. I started out with 3.73s and 32s with a sm465 (no od) I went to 33s, 35s. and now I'm on 37s and use the granny gear to get the truck moving without wasting the clutch.

Re: gear ratio gm 14bolt upgrade
 

4.10s. I guess I missed the OD part....

Re: gear ratio gm 14bolt upgrade
 

A NP203 in and 87?

Yeah, go with the lower gears. 1500 rpm is too low for highway speeds.

Re: gear ratio gm 14bolt upgrade
 

Yeah and mounted on to the back of an nv4500 from a 93 one ton at that. Like i said custom built. I just love the looks on peoples faces when I accomplish something they tell me cant be done. The body and wiring is pretty much the only thing that is left from the 87. I dont think ill ever go to 35's and thats more of a money issue than anything. I dont really want to trim the front fenders to make sure they clear and cannot afford a lift so i think 33's are the biggest this truck will see. So i think the 4.56 gears would be a little overkill for what im doing with the truck. Need to keep it low enough for loading and unloading. As far as the front goes this guy has a loaded carrier with 4.10 gears for about $130. So it will not cost much at all to match the front.
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Re: gear ratio gm 14bolt upgrade
 

Ok, after doing some number crunching and some more research I have decided to keep the 3.73 gears for a few reasons, atleast for now. After taking in everyones comments and making a few calculations for tire size and gear ratio as well as looking at tire prices combined with my dana 44 front end's limitations, I have decided that overall I would be better off keeping the 3.73 gears and spending the coin on replacing the front driveshaft that is worn out. For what I do with the truck I have figured out that the majority of 33" tall tires will not handle the weight and abuse I put my truck through and the ones that do are to narrow to fit my wheels. Therefore I would have to either keep the 32's or go upto 35's. Going to a 35 brings up other issues like fitment, I think I would have to trim the fenders since my suspension flexes so much and the 32's almost contact now or I would have to invest in a taller lift which makes it harder to load and unload. Then I'm afraid I may stress the front axle in some situations to where I could break a shaft due to the weight I haul coupled with the power from my engine and my heavy right foot. I do not have the coin to upgrade the front axle to handle that yet. After using the calculation that was given to me by a local 4x4 shop (.12 x tire height) I am just barely outside of what would be best for my application. It was 3.84 and I have 3.73 so Im good. We will see what happens in the future. The wallet sort of won over on this one. If I ever stop using this truck for hauling then I will just turn it into a trail rig and probably go crazy. Thank you all for your input.