Topic: 21 spline enough or 23 spline?

[navydood]

Alright...  I got a complete 1992 Jimmy 4x4 CPI 700r4 with rebuilt engine and tranny for $650.  Gonna do the 4.3 swap into my 85runner.

I will be using the AA adapter it looks like to mate to the toy t-case.  Since I am going this route, should I go ahead and change the t-case input to the 23-spline TS technology and get the AA adapter for the 23 spline?  Or will 21 spline be enough since I have no plans of competing?  After i get the swap done and make sure everything is running 100% I will  be going dual cases and most likley run a 4.7 gearset in the rear case.  I already have the donor spare toy t-case, that's why I am leaning towards changine everything out to 23 spline.  But then again i was under the assumption that with an auto, the auto kind of acts like a shock absorber to the drive train and 21 spline wouldn't be a problem.  I dunno.  Any input would be beneficial.

[bkg]

Opinion only, but I'd go 23... 

[FIREBALL]

23 spline. Do it once, and never have to worry about it again.

[navydood [OP]]

Well....

I was hoping more ppl would chime in.  From what I have read elsewhere if you don't run 4.7's in the front case then 21-spline is good enough.  Just make sure to use 23-spline in the rear case when going with 4.7's.  So that means I will need to be sure to order the MC-07 with the 23-spline coupler.

I can get the AA 50-5706 700r4 to 23-spline Toy T-Case for $435 shipped.  So I guess I will go 23-spline through out.  Go all out or don't go at all I guess.   

[LA_Fred]

I believe that Marlin only does dual 23 splines for V6 applications and there is probably a compelling reason to do so. I'd say do it now and not worry about it later.

[navydood [OP]]

Well heck.  I guess I shoulda read the V6 stuff here on teh website.

When building cases for vehicles with increased torque, such as a factory V6, or un upgraded V8, we highly recommend two 23-spline inputs to be used. 21-spline inputs may be substituted in the rear transfercase, however failure of the factory 21-spline input gear is certain. All applications built for a V6 or V8 setup will be built using 23-spline input shafts throughout.

[Volcom]

I don't really believe the need for 23 spline.  I've got a buddy that has run a 302 V-8 and dual toy cases with 4.7 gears in the rear and 21 splines.  He said was wasn't easy on them AT ALL and it lived no problems.  I'm going 21 and not worrring about it.

[navydood [OP]]

Well hell.

And still, none of the Marlin guys have chimed in.