42/14 = 300 gear ratio ?

[454 blazer]

I posted earlier today regarding a diff i have of a 78 Blazer i did the teeth counting and the ratio counter came up with 300 this must mean i have 308 rear gears right ?I also did a post a few weeks ago saying my big blocked blazer was slugish of the line , i supose this all makes sense now right ? Am i calculating this correctly ? 42 divided by 14 ?

 

[Blue85]

The calculation is fine, but I wonder if you counted right. If you have the diff cover off, the numbers are almost always stamped on the side of the ring gear, so you can just read them instead of counting.

Assuming it is 3.08, that is an economy ratio, even with 29" tires. Post up your tire size, your drivetrain specs and what you use the truck for and the brotherhood will suggest the perfect ratio. A gear swap will certainly much the truck much more enjoyable.

 

[Greg Ducato]

That sounds correct, 42 ring gear teeth divided by 14 pinion teeth.

 

[454 blazer]

No wonder its takes a while to get going ha ha ! 454 / th350 / np205 / 33x12.5x15 tyres ive always thought there was something not right , ive bought so much to upgrade the HP/torque ect..but have neglected the running gear , kinda feel sorry for my tranny now ha ha! This really makes sense , no wonder it goes like a raped ape when its in 4lo (hubs unlocked).Think it could do with 4:10s what do yall think ?
I only do sand dunes and street here.

 

[Greg Ducato]

I think a 3.73 would be a good all around ratio for your use and would not only give you a real boost in bottom end performance but will still keep your rpms somewhat low on the hwy.

 

[djtejas]

3.08 = 40/13
3.42 = 41/12
3.73 = 41/11

 

[454 blazer]

3.08 = 40/13
3.42 = 41/12
3.73 = 41/11

Ok ,now im confused

 

[imiceman44]

Ok ,now im confused

He showed you the ratios available and it mean you counted 14 where it was 13

 

[Blue85]

If you need great freeway economy you might choose 3.73 since you don't have overdrive, but with a 33" tire, I would really like the 4.10s.

 

[6.2Blazer]

It all depends on what your perspective is regarding performance, but a healthy 454 and only 33" tires should run pretty good even with 3.08 gears. It's not really any different than 4.10's and 42's (a LOT more rolling mass) and I've had two friends run this combo (one was a 460/C6 and one was 454/th400) with milder low-end torque builds. Both were heavy trucks but could still spin 42" tires on pavement, and I'm sure they would destroy a set of 33's.