Gears

[Country Boy K10]

I apologize in advance if I missed a thread talking bout this but I just bought a set of 38's and want to change my gears frt and rear any ideas for me. I have stock 308's and thats just not gonna cut it. Thanks and again sorry if this has already been talked about.

 

[HotRodPC]

I'd be taking it all the way to do 4.56's with 38's. What trans are you running?

 

[crazy4offroad]

Also depends on what you plan to do with the truck. Mostly offroad, or daily driver? I went with 5.13s in mine but it is dedicated offroader that I drive to the trail. It seems to top out around 60 mph at 2500-3000 rpms though. Also what axles do you have, and engine matters. Stock 1/2 ton axles and 305/350 would want to use 4.56 where if you have a big block and heavier duty axles you could go with 4.11.

 

[HotRodPC]

I'd say the transmission matters more than the axles type. I know where you're going, about the axles being strong enough, but I'd just about say being a half ton and 305 motor, that he's got a 700r4, and that trans isn't going to like those 38's for one second. Could be a SM465 though.

 

[Country Boy K10]

I actully removed the 700 and put a 350 turbo in and its a 305 with a mild cam and long tubes. The plan was playing in the mud and a driver as well just not daily but you know how it is to like to drive and just show your truck off a lil

 

[crazy4offroad]

OK as long as you don't have long highway commutes. I like to run mine around too but I stay on the 2-lanes and stay away from highways and it does fine. Are you running a stall converter in the TH350? Mine with 38s, TH350 and stock stall is a dog, I'll be looking into about 2400 stall before long and that's with 5.13s. I agree with HR, trans was the primary concern but other factors weigh in as well. You may want to play with this gear ratio calculator and figure out what your optimum top speed will be, and what target rpm you want it to run at....
http://www.grimmjeeper.com/gears.html
You have 2 columns to compare 2 different setups. If you don't have an under drive you can leave it blank (think 203/205 doubler). Only thing I don't like about that calculator is you cant copy the URL and share the numbers you have done, you have to take screenshots and the whole thing wont fit in one screenshot. And if the feet per minute figure for low range confuses you, you can convert it to miles per hour by multiplying the returned number in a particular column by 5,280 (feet in a mile) then divide by 60 (minutes in an hour) and you'll have miles per hour.

 

[Country Boy K10]

No stall but did think about it

 

[DoubleDingo]

Best way to figure out which gears to get is by using the following formula:

mph x gear ratio x 336/tire diameter

So, you figure out your desired miles per hour, multiply that by rear end gear ratio, multiply that by 336, and divide by actual tire diameter. I always try to get the engine rpm at my desired miles per hour to be as close to stock as possible. Works every time! Grab a piece of paper and write down a variety of configurations using the formula and then figure out which setup you really want.

 

[Country Boy K10]

Oh I know how to get the gear size and all that ...I just wanted to hear some ideas of what everyone else runs and how they like them. I do appreciate all the input

 

[HotRodPC]

With 4.56's you'd be about 3000rpm @ 70mph, 4:10s would put you about 2800 @70. With Th350, you can probably get by with 4.10's just bog down a bit as expected with biggo tires. I'd also consider carrier ratio size breaks in your decision depending on your axles. Example being, If I was running a 14 FF, and I was on the fence of 4.56 or 4.10's, the carrier break is 4.56 on down to lower gears, or 4.10's up to higher gears. If I thought there was a chance I might want to go a deeper gear in the future with even taller tires, I'd just go the 4.56's now so I wouldn't have to buy carriers again in the future. If I thought, I might be a bit afraid of the high rpms, I'd just go with 4.10s now and I did decide the 4.10's were to much, then I could always step taller to 3.73's without replacing carriers.

Another thing to consider is future axle upgrades. I was currently running 10bolts, I'd go with 4.10's instead of 4.56's. Reason being, I know 14b Full Floats from the factory are fairly common. I also know it's hard to kill a 14b FF. So if I go 4.10's now, I find a 14b FF with 4.10's in the future that are pretty common, then all I have to do is swap my front 10b to 8 lug hubs. And the chances I was to find a 4.56 14b Full Float is because I purchased a set of axles from a CUCV having a Dana 60 front and 14B FF w Detroit Locker in the rear and I'd just have to move spring perches and shock brackets and bolt it in.

 

[Country Boy K10]

Im thinking 38's will be my ride height, i have no need to go higher..I had talk to another friend that builds rock crawlers and he had metioned 5.38. I think that might be a bit much

 

[HotRodPC]

Im thinking 38's will be my ride height, i have no need to go higher..I had talk to another friend that builds rock crawlers and he had metioned 5.38. I think that might be a bit much

Yeah, it might be. You might want to drive it to the store and get a beer in the truck someday. I mean, the school zones are 25mph, you wouldn't want to hold anyone up.

 

[nvrenuf]

I'd say 4.56 or 5.13's.

Are you setting the gears up or paying to have it done? What axles?

Weigh the cost of gears / carriers / labor against a set of military 1 tons already equipped with 4.56's and a rear Detroit.

 

[Country Boy K10]

LOL yeah might need a beer sometime and deff dont wanna anger anyone staring at my axles

 

[Country Boy K10]

A friend of mine and myself will be doing the work John...military axles...didnt even think that way..kudos