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NP231 SYE Issues


NAXJA Member
NAXJA Member
San Jose, CA
I’ve looked this over and messed with it for way too long, either I’m missing something stupid or I’m unaware of some additional steps.

1990 NP231 from behind an auto
G2 Gear SYE part # 37-231SYE (fits 87-01)

I’m running into two issues

1. Main shaft seems to sit too deep into the planetary side roller bearing. The upper larger shift fork in its highest position is still grabbing the synchro. Meaning the shaft is never in neutral. With the chain on it also binds/rubs on the larger shift fork collar slider piece. I’ve flipped it both ways, chain won’t fit period one way and rubs the other way.
Grabbing the main shaft and pulling up (towards rear axle) about 1/4” allows for neutral spinning and the chain to stop binding.
Was there some sort of button at the end that I lost or something? Or is a c-clip supposed to be holding it in a different position?

2. Shift fork shaft is too long with the new G2 housing. The new G2 housing won’t get anywhere near sitting in the correct spot. Pics are without the second case half but notice where the riding surface is on the shaft for the tail housing bearing - nowhere close. It’s sitting on the splines in the pic.





I have not installed an early 231 SYE, but I do know that with some brands of SYE the mode fork rod might need to be trimmed. I also think I remember reading that the output yoke installation influences the location of the shaft in the housing.

I would do a thorough job of research before any cutting.

Here are the directions from JB Conversions.
Step #11 reads:

11) Verify the length of your mode fork shift rod as shown (Fig.11). If your shift rod measures 10.2", it will need to be cut down to a length of 9.380".
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