Type 9 gear selecting issues

[PaulMK1]

For the last two events I have random difficulty in selecting 4th. On the highway it's fine but occasionally on the track when shifting up from 7000rpm in 3rd I just can't get into 4th.

This cost me a place in Albany RTH on the weeknd

Any ideas on what to look at first?

[Danny M]

I'd look at bellhousing alignment first

[PaulMK1]

Hi Danny - How do I check that? and why would that only effect 4th gear?

[Danny M]

I usually do it in a mill bolted to a block
If the alignment is out which can happen especially with aftermarket alloy bell housing it upsets the input shaft and synchro alignment and your input shaft is your 4th gear