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can you get 2nd gear and pull away ok by slipping the clutch a little?
if so then the clutch is OK and the issue will either be with the transmission selector mechanism or its internal to the transmission
So if this is the case then I'd check the state of the gear selection cables and check the gear linkage for any worn bushes or pivots as any lost motion means reduced effort at the gearbox and replace as necessary. Ideally have your assistant move the gear lever with you watching the linkage and see if you can spot where there is any excessive play or lost motion.
As ts a cable type linkage check along the cable lengths for any damage or signs of heavy wear / fretting, if you find any replace the cable. There may be some adjustment on the cable tension at the gearbox end (depending on the year) and the cable should be tensioned so there is a minimum of slack but not so its taughtThen check gearbox oil levels and if its not been changed in the last 20K miles then drain it off and fill with fresh. I can strongly recommend the use of Castrol Syntrans 75W90 (was called SMX-S) as I've known it help with shift issues on many manual gearboxes
if this isn't effective then sorry to say that the transmission will have to come out for repair
do you still need help?
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