1994 mazda navajo manual transmission gears are grinding and hard to shift.any idea what is causing this? it has a 5 speed .

Go for the manual they are easier ti repair.

99 00 01 02 03 FORD F150 MANUAL TRANSMISSION 5 SPEED MAZDA-TOYO KOGYO 4X2 8 CYL

will it shift if you double clutch ?

might be a shift linkage adjustment
internal shift fork has broken a scroll pin

clutch fork movement ok ?

If the shift lever is what is hard & sticky, get some grease & lube the handle at the joint at the trans. ( Maint. anyway) . The right gear oil? Was it doing it before the oil chg ? How's the clutch feel? Clutch, Pressure plate & throw out bearing poss. Smell any burning smells? One step at a time. Good luck

Transmission Is the Cause of this. INTERNAL

Transmission

don't shift into 1st until stopped and 10mph or less is your down shift range to 2nd gear from 3rd

I suspect it's time for a new clutch.

You need to check the clutch hydraulics i.e. the clutch master cylinder and the slave cylinder for their function, even if its cable operated try to adjust it so as it opens the clutch fork a little more to allow the clutch plate to be free,thus easy selection of gears.
If this fails thn you will have to replace the pro-kit i.e. clutch plate, pressure plate and release bearing.
Hope this helps!

First thing to do,try to pump your clutch before you shift into 1st gear then if you feel makes better, most probably you have problem with your hydraulic clutch system, check the clutch line if there is an evidence of fluid leaking or it could be internal leak.

Second thing to do, check your transmission oil, may be it' s too old or you use a thick oil thats why when cold its hard to shift then when the engine rich the normal temperature(warm) the oil become thin and the shifting will smooth. Remember the very old oil become thicken and the purity is gone and can cause of hard shifting. in this regards i suggest you to change the transmission oil and check the used oil if there is small peace of metals, then you are in big trouble,