Getting the right gears to swap in a 12 bolt

[Jesse Jaymes]

I've just purchased a 1974 Blazer. I am wanting to build it fairly cheap. I am inquiring what the parameters are for swapping. I am interested in 4:56's. There are some occassionally on Ebay. I have the 12 bolt rear and the 44 front.

Can someone tell me which spline count I have ?

Also, what are the thick gear sets and such.
I currently have 3:73's. I am running 35's and don't think I'll go higher than that. With the TH350, it is kinda underpowered, so I was wanting a gear swap.

I also see many Gov locks or Eatons on Ebay cheap. Do I need to be very careful on which one I am ordering ? Are these real hunks of crap, or can the be pretty serviceable on the cheap. I would like to cut some corners where I can. For a part time off roader, I would rather put my cash into other places than a Detroit. Was thinking a cheap LockRite up front, but I am not smart enough to shop on Ebay, as I am nervous about buying something that will not work.

Can I get some guidence on what I need to look for ?

 

[pauly383]

1. 30 spline axles , 30 spline pinion . Buy truck 12 bolt gears , some car sets fit , but NEARLY ALL DON'T . Keep this in mind on Ebay .

2. Thick gears are for putting low gears on a carrier made for high gears . You already have 3.73's , so you want regular 12 bolt truck 4.56 NOT THICK .

3. Gov Locs go boooooom , very often . Eatons posi's are great for musclecars . What you want is to put a Lockright in both axles , which is perfect for 35's and 4.56 . A full Detroit is even better , but it ain't cheap .

Now , considering the tire size , thats a decent setup , and if driven without gobs of gas pedal in OHV areas it can last a long time .

Of course someone is going to come along soon and say put 8 lug rear on there and convert the front , which is fine for really large tires . But it means you need new rims , rebuild the brakes , get a conversion u-joint , get new u-bolts , find 8 lug front axle parts and replace bearings and grind calipers all before you even think about getting lockers and gears if the 8 lugs you find aren't 4.56 ( most are 3.73 or 4.10 ) .