When i take my car for a drive it shifts Great.
Until I have been driving for a while at highway speeds.

Then I cannot for the life of me get it to down shift.
The only way it will work is if I come to a stop then shift it to first gear.

I pulled the clutch because I thought the clutch was gone but it looked fine.looked like it had been replaced not 2 long ago.
It
I replaced seals,throw out bearing,and made sure clutch and flywheel were not glazed on surface,and bushing on throw out fork.

Any suggestions would be great.
I will change the tranny fluid since I dont know what was put into it.
But dont know what else to do?????

Thanks.

I changed the fluid to Mystic GL-5 80/90 weight fluid.
Car shifts great,might have been original fluid in car???.

Went for a 50 mile drive,car run and shifted Great.
If your 914 is not shifting good,might be worth swapping fluids.

Could have certainly been the fluid.
914 Synchro rely upon certain friction additives to work and many of the newer synthetic fluids don't have them, so it gets harder to shift

There are no "additives", really. That tends to make one look for friction enhancers or other things. Any fresh GL5 80-90 should do just fine. A cool read on it here.
http://www.widman.biz/uploads/Transaxle_oil.pdf

i use strait 90w ford tractor oil from tractor supply. works fine