What driveshaft length

Hi guys i need your help again
i have just replaced the two speed with a three speed lenco, now i need another driveshaft and couplers, 32 spline, i need to know what is the best lenght driveshaft for a gap of 21.5" from rear of output shaft to nut on rear axle
cheers
gaz

 

I fit my drive shafts from the rear to the trans tail shaft (plus 5/16" cross bolt in front coupler) to the end of the spline area on the 32 spline rear coupler - to make sure that you are using all of the 32 spline area on the rear coupler....no need to extend past the splined area to the front of the pinion nut.....did I mention that I have a nice used 32 spline drive shaft that measures 19.375" for $100.00? Might be the correct length....depends on your rear coupler inside spline length as they vary a little.....then there is the discussion about how much drive shaft end clearance....I like about .100" to keep the rear outer 10 spline male coupler fully engaged with the pinion female 10 spline, but there are some teams that run a ton of drive shaft end clearance...that's probably for another thread....

 

All drive shaft manufacturers will build you a shaft off these measurements, Just call them.