Re: [Chevelle-List] Tranny Talk; spline counts

[Michael Pell]

The spline count is the number of splines on the input or output shaft.  Typically, GM transmissions have 10 or 26 splines on the input shaft (if memory serves).  When comparing 2 side by side, it's quite an obvious difference.  The 10 spline is considered a "course" spline, and the 26 spline is considered a "fine" spline. In general, the more splines, the stronger it is.   For example, you can go up to 40 splines on an axle shaft for a pure race application.  Street applications don't require that much strength (usually).  The 10 spline is considerably weaker than the 26 spline input shafts.  After a certain year (1970?) GM quit using the 10 spline input shafts. As for your car, you'll likely have to look at the input shaft to determine if you have the fine spline or the course spline.   I'm not sure if you can look at the tranny numbers and know.  Someone else will have to address this. The diameter of the GM input shafts are typically 1 1/8". The only part affected by the input shaft spline count is the clutch disk.  If you're buying a new clutch with your trans, then all you need to do is to get the clutch with the same spline count as the input shaft on the trans. The same basic info holds true of the output shaft, although I don't remember the spline counts on the Muncies.  The 5sp Tremec TKO has a 31 spline output shaft, which is the same as the Ford C6. Also in general, the larger the output shaft is, the stronger it is.  Unless you're running tons of hp and torque with slicks, you probably don't need to be too concerned about output shaft sizes.   I believe the M18/M20/M21 all share the same output shaft as the TH350.  And the M22 shares the same larger output shaft as the TH400.  So, you will be concerned to the point that your existing driveshaft's slip yoke will fit into the transmission. The Tremec 5sp TKO ships with a C6 slip yoke.  You'd either need a new driveshaft, or have this slip yoke installed onto your driveshaft. Hope that helps!   Lojac wrote: Can anyone explain to me the "spline" of a tranny.  I have a 69 Chevelle with a borrowed Muncie in it.  How can I tell the "input spline" and whether I need a larger or small output shaft.  I am totally confused.  I need to buy a tranny for my 69 Chevelle, but I have no idea what I am looking for.  Can I compare the numbers on the tranny I have now to find out all of this information??? Thanks,Lojac --   Check out my webpage at http://www.ProStreetCar.com   and my For Sale page at http://www.ProStreetCar.com/classifieds.html   Tremec Distributor at http://www.tremectransmissions.com/   Team Chevelle membership #178 (Gold)