The Ford Transit 5 speed RWD gearbox ( later cable change type) has very common issues including , Jumping out of fourth gear , guide tube working loose, wear on the forks also causing gear selection problems , synchro’s can and do wear out or can completely bottom out ( whether they be 3 part or single part). The main shaft can wear out on its journal , the lay gear bearings fail and any loss of oil can cause the gearbox to burn out.
Typical costs for an exchange reconditioned gearbox are £ 550 – £650 + Vat if supply only
Recommended oil: ATF / DEXTRON II
Image 5 speed RWD Ford Transit gearbox ( cable change) prior to strip down ( The above unit was burnt out )
Complete loss of fourth gear is normally caused by the dogs breaking away from the gear ( The weld breaks)
You can see the separated dogs versus the brand new input shaft on the left