[535banshee]

i just put a 4.5 lift on my truck with 35's
i want to change the gear to make up for the power lose when towing. i can go with 4.10 or 4.56. has anyone done this to thier truck and what gears did you use?

 

[535banshee]

i have a 6.7 3500 with a bully dog pmt. i towed my 11000lb fifth wheel stock and now with the 35's and its a night and day differance. the truck will still pull it but not like before. i called the gear company today and talked to them and came up with 4.56 to get me back to stock. it will raise rpm's about 70 more then stock but 4.11 will still be lower so i went with 4.56

 

[535banshee]

i really didnt want to go threw all the work of changing gears and still have the rpm's lower than stock. every gear company that i have talked to said the same thing go with the 4.56. its ony going to be 70rpms over stock. i just want to get that bottom end back i had when its was stock.

 

[535banshee]

i see you have a 5.9 i have 6.7 with a six speed. the gear ratio is way different. the 68re is 1:1 in forth gear and .81 for fifth and .62 in sixth. all tire to gear charts are for 1:1 at 65mph. my tire size with 4.56 is 2852rpm's @1:1
then take 2852 x .81= 2310 in fifth
2310 x .62=1432rpm's in sixth at 65mph

stock is [email protected] 1:1 @65mph
2715 x .81= 2199rpm fifth gear
2199 x .62= 1363rpm in fifth @65mph

69rpm diff

 

[535banshee]

Isn't stock tire size 265/70-17? That's roughly 31.6" diameter. If stock gearing is 3.73, you need 4.10 to get you close to stock. Here's the formula:

3.73/31.6 = x/35 where x = new gear ratio.

i checked my stock tires and where right at 30''
you can also take your new tire size divide by your old tire size and then x's that by your old gear ratio.

34.5 divide by 30= 1.15 x 3.73= 4.29 gear ratio to get back to stock. they dont make a 4.29 so its 4.11 or 4.56

 

[535banshee]

power is not a problem with 35's and a my bully dog but it is when you have 11000lbs behind it. its just not like it was when you are tring to take off. its a big differance that i thought there was something wrong with the truck at first. changing the gears should get me back to where it was before.

 

[535banshee]

good point. you might be right? i will check and see.