Sm465 - 6 Vs 10 Spline Question

Working on a 4.3/SM465/D18 build and would value some feedback on the two output shaft options. Talking here about the transmission output shaft which ends up being the transfer case input/gear.

Novak has two different options for the SM465/D18 adapter kit: 6 spline and 10 spline. Generally speaking, the 6 spline is found with the transmissions originally mated to the 4cyl whereas the 6cyl (primarily T14) had the 10 spline. Also in general terms, more splines means stronger (likely the change for the V6).

Either kit from Novak is the same price, so no issue there. I do have a really nice 6 spline gear, but would likely have to buy a better 10 spline (either NOS or reproduction), so an additional $70-100.

On to the question: Is there a appreciable difference between the 6 and 10 spline? Anyone ever broken either one...or is this just splitting hairs?

 

Must match your gears in the transfer case. Bull gears are not all interchangeable.

 

If you plan on installing an overdrive, be sure the spline count matches.

 

Good point, thanks Chris. I actually have a full set of D18 gears for both 6 and 10 spline, my 10 spline input gear just has a few chipped teeth.

Good point #2. Have a set of 3.73 axles for this project, so likely will not employ an overdrive.

 

Is there an overdrive you would have to fit my 70cj, v6, T14 / T18 with 10 spline? I have 4.88 and would like to keep highway rpm Dow.

 

Advance Adapters now owns he rights to the Warn/Saturn OD and still sells them new. Not cheap, but if you click the "Configure and add to Cart" button, it will list all the various options...

Saturn & Warn-OD : Saturn & Warn Overdrive for Dana 18 Transfer Cases | Advance Adapters

 

I never could get the overdrive to work. Not sure if the Novak Main shaft has something to do with it. I could only get it to work for a few months, then it would pop out of direct drive.