swapping gear ratio in the 14 bolt??

[75k20]

i’ve been daily driving with the sm465 and 4.56 gears for a while now and i need something more suitable for everyday use. my mileage came back at 8.3mpg and i need to get my rpms a little lower while cruising. not to mention how slow i am speeding up..

right now i don’t use 4wd as it’s missing a right axle shaft entirely. so for budget reasons i’d probably want to just swap the rear for now.

what’re some good options on a budget? and what’s a good gear ratio to go for? let me know if you have any other ideas to help with mileage as well

 

[nvrenuf]

Tire size?

Just fyi, with no inner axle at all in the front water / dirt / debris can freely get in to both the diff area and the locking hub / wheel bearings.

 

[75k20]

Tire size?

Just fyi, with no inner axle at all in the front water / dirt / debris can freely get in to both the diff area and the locking hub / wheel bearings.

33x12.50 tires 17 wheels

it’s next up on the long list of fixing stuff, but i don’t know if there’s any difference between the dana 44 axle shafts, or what seals i need.

 

[crpntr78]

There's a guy on here from Australia, posted the other day with pretty much the same set up as you and he's going with a 3:21 ratio.

 

[75k20]

There's a guy on here from Australia, posted the other day with pretty much the same set up as you and he's going with a 3:21 ratio.

is there a good company that i should go with? i’m not looking to gain more speed, fastest i’d want to go would probably be 55 or 60, feels like i’m pushing the truck just to get up to 50

 

[nvrenuf]

I don’t think anyone makes a front ratio that would work with the 3.21’s.

 

[75k20]

I don’t think anyone makes a front ratio that would work with the 3.21’s.

would something like 3.73s be suitable? that would put me at 55mph and 2000rpm

 

[Turbo4whl]

I don’t think anyone makes a front ratio that would work with the 3.21’s.

Correct!

Some common GM ratios:
GQ1 -- AXLE REAR, STD RATIO
GT4 -- AXLE REAR, 3.73 RATIO
GT5 -- AXLE REAR, 4.10 RATIO
GU4 -- AXLE REAR, 3.08 RATIO (3.07:1)
GU5 -- AXLE REAR, 3.23 RATIO
GU6 -- AXLE REAR, 3.42 RATIO
G80 -- AXLE REAR, LIMITED SLIP

would something like 3.73s be suitable? that would put me at 55mph and 2000rpm

Yes, better choice.

Remember your 1975 Square was designed/ engineered when fuel was $.30 a gallon. Good daily fuel mileage is not something you will get from your truck.

 

[Shorty81]

I'm running 3.73 in K20. 496/sm465, 32" tires. 2000 rpm at 55. 11 mpg. Truck is very happy with this setup.

 

[77 K20]

If I remember right you can't just put higher gears in your 14 bolt without changing out the carrier. The break was between 4.10 and 4.56

 

[nvrenuf]

On a full floater 14 bolt, the carrier break is up to 4.10 and 4.56+. His 4.56 carrier will not work for higher ratios.

 

[77 K20]

You must be registered for see images attach

 

[75k20]

Correct!

Some common GM ratios:
GQ1 -- AXLE REAR, STD RATIO
GT4 -- AXLE REAR, 3.73 RATIO
GT5 -- AXLE REAR, 4.10 RATIO
GU4 -- AXLE REAR, 3.08 RATIO (3.07:1)
GU5 -- AXLE REAR, 3.23 RATIO
GU6 -- AXLE REAR, 3.42 RATIO
G80 -- AXLE REAR, LIMITED SLIP



Yes, better choice.

Remember your 1975 Square was designed/ engineered when fuel was $.30 a gallon. Good daily fuel mileage is not something you will get from your truck.

i measured out the gears and it turned out to be 4.10s instead of 4.56s

can’t complain but still not the best for a daily driver.
350/465/205/4.10 33” should be a decent enough setup for now. thanks for the responses