OS giken 26 spline input shaft compatibility

[SiR_RB]

Hopeing someone can help me out here, 

so I have a 1-3 PAR straight cut synchro gearset, with standard input shaft/4th gear and standard 5th 

 

my question is, can the OS giken updated 26 spline input shaft be used with factory 4th gear ? Or specifically only for OS gearsets?

 

here’s a pic of the OEM item and OS item 

 

Edited February 10, 2021 by SiR_RB

[SiR_RB]

Never mind found a pic of my internals and it’s a PAR 4th helical and doesn’t look factory 

[BK]

No it won't, I'm sure they use a different tooth count and angle on the helical input with PAR and PPG synchro gearsets. It's all to do with the counter shaft gear which OS giken matches to the standard Nissan profile. You can use a stock Nissan input on an OS gearset, or an OS reinforced input on a stock box (not that you ever would).

Also be careful with ''reinforced input shaft", as OS giken do a reinforced input shaft in both standard Nissan 24 spline and GM 26 spline. PM me if you want to know more, but an OS giken uprated shaft even in 26 spline is still much smaller before the spline on the shaft area, than say a PPG or PAR 26 spline input shaft is.

You have a PAR gearset, you need a PAR 26 spline input shaft.

[SiR_RB]

Yep ur right 

confirmed that my input/4th is a par helical part and much more beefy then then the stock part

still a billet input but 24spline 

[BK]

So yeah in your case the 24 spline 25.4mm section itself is the weakest part as opposed to a stock or even OS giken uprated shaft having its weakest part before the spline.

So even your 24 spline input is still a pretty beefy shaft 👍

[SiR_RB]

I bit the bullet and got in contact with par and he sent the guys building my gearbox the 26 spline input shaft

 

may aswell do it all properly now that the box is out 

[Roy]

So digging  this thread up. Why would I do the GM 26 spline if doing  a full OS Giken gearset in an RB25 box?

I am pretty easy on gearboxes generally having never blown one. My current box has had gear on gear contact so now has very loud whining noise so need new gears

 

Not sure ro go 34 gtt box or rebuild with OS Giken gearset

https://youtu.be/N1N7eQEC1N0?feature=shared