Rb25det S15 swap gearbox mount help

[Haden]

Hello,

Im currently part way through a rb25det neo swap into my S15 silvia.

Car was factory sr20de auto but was manual converted previously.

I am using r33 front subframe and engine mounts and am using the stock sr20de gearbox with a rb20de bellhousing to make the box the same as a factory rb20det small box.

My issue is the gearbox is sitting around 1.5inchs further back than factory location so the mount doesnt fit and the driveshaft is too long.

Everything I read online said using this small box means I can retain factory driveshaft without mods. Was this wrong? 

Is there a different crossmember I could use? How can I use factory driveshaft??

 

Thanks

[GTSBoy]

Is it sitting on the engine mounts correctly? If it is, then that is the position and that will determine the length of the tailshaft.

However the position ends up as a function of the above mounts, you then can usually choose between the 3 different Nissan S & R chassis gearbox mounts (marked A, B & C) to get one that will line up with both the gearbox and the chassis holes. But this does not affect the tailshaft length.

If you haven't got the engine sitting on the mounts in the engine bay properly, start there. That may then lead to you being able to use the stock tailshaft. If not......

I don't know if this is true or not, but it quite possible that the front half of the auto tailshaft is a different length to the manual tailshaft, and maybe something dodgy was done when the car was manual converted previously.

[Haden]

I think i have puzzled it out. I found info online stating that the sr20 and rb20 det shared same back side of gearbox and just had different bellhousing so I assumed I could swap a rb20det bellhousing onto my gearbox and it would be same as rb20det gearbox but it looks like the tail side is different too and the rb20 tailside is shorter by just over an inch which would explain my issues.
Will buy a rb20det box and go from there

Edited August 24, 2019 by Haden

[GTSBoy]

No. Now that you have to buy a gearbox, buy one that won't shit itself behind an RB25. Buy an R33 gearbox. Spend more money, yes gasp, more money, on the box, and a little extra on getting the tailshaft cut and shut.