727 Splines On Input Shaft

Tech Question


terry leohr, seville OH, 1970 plymouth duster 383

I am currently installing a 383 in my 70 Duster. Everythingis going fine except I purchased a mild low stall converter from Summitracing and have had two different people try to install it. I even went backto Summit and exchanged it for another one, thinking there was somethingwrong with it. The trans I am using is a 1976 727. Is there a differentinput shaft on different year 727’s? I am kinda stuck and not sure where togo from here. Thank you, Terry.


Terry , there’s 3 different spline counts possible:

All A-727 transmissions from their inception until 1966 have 19 splines on the input shaft. Non-lockup 727 transmissions from 1967 onward (thru at least 1992) have 24 splines – this replaced the early, small-shaft version. Lockup 727 transmissions that debuted in 1978 had 23 splines. Virtually all the aftermarket converters are 24 spline and will fit all 67-77 727s (and the few later non-lockup ones, used mostly in trucks). So your tranny probably has 23 splines – but, count ’em!

If you do turn out to have a 23-spline tranny, several company do makenon-lockup converters to fit the lockup splines – you’re not dead, just on arespirator gasping for air!

Also, be sure you’ve spun it a bit while pushing inward to clear the pumpdrive tangs.

Just a bit of trivia: the good, hardened “Hemi” input shafts had yellowpaint on the end of the shaft.


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