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3.73 vs 4.10???

11K views 18 replies 7 participants last post by  devinferg 
#1 ·
i have a lifted truck with 38's and the thing is pretty much helpless taking off and in high gear, really notice it pulling my boat and my boat isnt that heavy.

my question is would 4.10's be a good idea? also will it help my fuel mileage? i currently get 10-12 mpg so i dont even drive the thing. im not concerned with how 38's wont get me fuel mileage....thats a no brainer i just want a sharp truck with decent mpgs...i used to get 20+ years ago and now thats all i can help to think it should be. will 4.10 gears fit properly in my rearends and what all is needed to do so. i dont know an awful lot about rears but i have done a couple over the years, never a swap though. i do like to go fast but with that big of a tires thats not a good idea and that truck is more a leisure truck/boat hauler so a little slower wont hurt my feelings.

i always start out in 1st not low. and with the boat it takes alot to get the thing moving off the line. its the truck in my sig. 6 speed weighs over 8000# on its own...no matter how i drive it i can barely get 300 miles on a tank.
 
#2 ·
4.10 will deffinetly help with bottom end power and take off. Should fit in your rear end just fine. You'll need to buy new axle seals and possibly shims. I would recommend taking it to a shop and have them do it or if ya know someone that's good with differentials have them help ya. A differential is not something that you wanna mess up. Hope this helps a little man
 
#4 ·
yea my old votec teacher does them when he not teaching mayb ill give him a call too.

i jacked the truck up and moved each wheel to check for brake drag, and made sure 4 wheel drive is unlocking and hubs are unlocking cant seem to find anything dragging.
 
#7 ·
Id go with 4;30 that what I did also if you dont have the right tools take it somewhere I did mine but It cost me a lot more then I wanted it to. and I had to buy and make some tools also my truck ended up being down 3 weeks lucky I still have my f150 to drive, hope this helps:ford:
 
#9 ·
thanks for all the input guys, glad for some helpful info instead of people just wanting to bash a thread.

we farm and have about 10 big trucks that i do alot of the work on, i dont however know alot about rears and honestly i couldnt explain a 4.10 from a 4.33 or anything. i would almost say if i had one in my hands to look at i could figure it out but i really have no idea of what the numbers all mean.

i can work on about anything and prefer to do all my own work but as zmann said i would hate to mess something up as they run a very tight tolerance.

i said about my votec teacher, he teaches ag mechanics and really is very intelligent with engines and really anything mechanical and he does rearends on the side so i plan to call him when i get a chance and see what he says and if he can help me out or show me how its done. his knowledge ofcourse comes from experience, which is how i like to operate, if i havnt done something myself then im not satisfied and i love to save a dollar haha

sorry for the life story, but im always ready to learn is what im saying.
 
#10 ·
The numbers such as 4.10 ratio means the driveshaft will spin 4.10 times to 1 turn of the axle. The higher the ratio the more high rpms you will see and the more bottom end power you'll have, but also means your top end power is gonna be brought down some. To find a gear ratio by just looking at a ring and pinion you take the number of teeth on a ring gear and divide by the number of teeth on pinion. Example being 41 teeth on ring gear divided by 10 teeth on pinion means you have a 4.10 ratio
 
#12 ·
ohh ok i thought it to be that simple just didnt consider it correct till i was told so.

so with that being said why run the 4.30 instead of a 4.10? i dont want it to be too slow or run too high of rpms just need to make up what seems to be lack of horsepower....not being smart just asking. im thinking 4.10's will be a big upgrade from 3.73 but am not sure of the reason of a 4.33....
 
#13 ·
Ideally, you want the same engine speed/actual speed ratio to be the same as with stock sized tires. It is much more important with an automatic trasmission because shifting is engine speed based, and bad things happen when using the wrong gear for too long.
 
#14 ·
well i have a 6 speed manual tranny
 
#16 ·
yea it was there. so you think 4.10's would be good then? i get what you mean with an automatic as they tend to see more wear and tc slipping
 
#17 ·
Go 4.10 that will be more than low enough for your truck
 
#18 ·
i delivered a tri-axle load of mulch to my votec school the other day and talked to my shop teacher, he said i wouldnt notice much difference with a 4.10 and had a guy he put 4.56 in and he loved it. also he said he normally get $250 for rear and $350 to do fronts that all labor....is that good or bad? also im related(cousins) to a ford dealership and my cousin says we can do the gears, so im not sure what im gonna do or how soon, would like to put a tower on my boat this winter.

would i be better off to just buy a set of geared axles or trade mine? im not real sure what to do, and where would be a good place to buy gears?

alot of questions for you guys this time haha
 
#19 ·
The 250 and 350 prices are a steal for install! I know I had 4.10s in my obs with a zf5 tranny and it was low enough I didn't even need first gear unless takin off with a heavy trailer
 
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