Topic: Strength of 23 spline vs. 21 spline?

[Ghettofab88]

Looking to put a 4.3 4l60 motor trans in my 1994 4runner/truck.  I already have 21 spline stock dual cases in it.  I know the 23 spline is stronger than a 21 spline inputs, but I can't imagine its that much, maybe 10% stronger?  Does any one know?  Are there any numbers out there?  I'd like to do this once, but obviously don't want to spend a ton of cash and I  wheeled with a guy for many years that had a v8 in front of stock 21 spline duals.

Thanks,
Kevin

[OVRAROK]

Does the adapter to mate the trans to t case give you an option?

[Ghettofab88 [OP]]

Yes, hence the issue.  I can get either a 21 spline trans output shaft or a 23 spline.  Either way the adapter is $800.  If there was a huge increase in strength going to 23 spline it would be a no brainer, but I just can't see it being worth the extra $500+ dollars to do it.

Anyone broken a 21 spline input with a 4.3 auto combo?  I feel the auto should take a lot of the stress off the drivetrain.

Kevin

[mudmaster]

I only have 2 runs on my 21 spline single case (4.7), with a 4.3 and TH350. So far I've only broken the transmission case. The transfer case output has held up fine so far.

[85Buckett]

No Science in this reply but...

My Dual set up came out of a truck that was running a GM Automatic with 4.3. I tore the cases down and checked through all the bearing/gears and shafts. IT all seemed to hold up pretty well.  The only thing with a bit of wear and tear was the teeth on the 4:1 input gear in the rear case but i do not believe that to be from the V6 more so from improper shifting. Everything currently spins and seems to work fine.  I bought the set up used and relatively cheaply. In the future i may be going to a  229 Chevy V6 with a carburetor  and i think should be fine with the 21 spline dual cases as i don't use a lot of right foot.  If you are going  new and spending the money id say do it once and be done with it get the 23 spline you should never have an issues  .

[green200b]

My Toyota runs a 350 Chev and has done since 1994. It used to run a Turbo 700 auto with a Mark's 4wd Adapters transfer case adapter to a 21-spline transfer case. Whilst I can't speak for the car before I got it the transfer case had certainly not been removed for a while when I got it. Never heard of anyone breaking transfer cases out here, just G52s.