WTB 4.30 or 4.33 12 Bolt passenger car gears any date

[jbtech]

Update 10/31 4.33 GM gears found. They sold them over the counter for performance applications. Learned something new!


Update 10/30 Looks like GM did not make 4.30 or 4.33's. So any aftermarket good used gears will be ok.

Looking for a good used GM gearset for my car.
I want to swap out my 3.55's.
Not particular on dates just looking for a reasonably priced original GM set if there is such a thing.

Jose

[Lynn]

Freddie will correct me if I am wrong, but I think your options for a correct GM set of gears for a 12 bolt are going to be 3.73, 4.10, 4.56 and 4.88.

Aftermarket makes 4.30 and 4.33 gears. While they were available from the factory in Pontiacs in the late 60s, I think the BOP rear was different from the Chevy 12 bolt.

[jbtech]

Originally Posted by Lynn

Freddie will correct me if I am wrong, but I think your options for a correct GM set of gears for a 12 bolt are going to be 3.73, 4.10, 4.56 and 4.88.

Aftermarket makes 4.30 and 4.33 gears. While they were available from the factory in Pontiacs in the late 60s, I think the BOP rear was different from the Chevy 12 bolt.

Thanks for the info looks like aftermarket is my only option.

Anyone have some good used gears I won't need to break in?

Thanks!

[lbnaz]

I have a NOS set of GM 433's (9/39) in the box if interested. There dated 75. Contact me for more info. Larry 5203492337

[jbtech]

Originally Posted by lbnaz

I have a NOS set of GM 433's (9/39) in the box if interested. There dated 75. Contact me for more info. Larry 5203492337

Perfect I'll take em.

Thanks Larry!
Jose

[lbnaz]

Just for a sanity check there is no part number on the box but the pinion is 3936481 and the ring is 3936482 and both have 9/39. Can someone verify there chevy 12 bolt. I bought them on this site a year or two ago represented as chevy 12 bolt along with other GM gears. Thanks, Larry

I found in the revised special parts book dated 3-9-72 they list part number 3961430 as ring and pinion 4.33:1 ratio