It’s a SD33 T engineWhat engine do you have. That will help the resident MQ-MK train spotters assist with your query.
I believe 5 speed and 4 speed diesel boxes arent necessarily a straight swap. If it's an L28 or P40 things are different again. I only did some light reading on these things because I looked at buying one some time back.
FS5W81A for 5 spdIf you check your compliance plate - the gearbox type will be stamped there. Once you have the gearbox type, keep your original bellhousing and chase a replacement. Input shafts can be different lengths though.
These boxes last forever - unless your synchros are shot you're probably better off replacing the gearbox bearings as a cheap rebuild for under $120 for the 4x gearbox main bearings.
Easy done mate. Let us know how you go.Will do, thank you for your help!