First when was the fluid changed last and what condition is your clutch in????
If you have never changed the fluid you have two choices a good 75W-90 or 10w-30 motor oil both can be used.
I use the 75W-90 Penzoil Syncrimesh and it shifts like butter. Some have used and have said the cheapest 10W-30 they could find and no issues.
If it is grinding it could be two things the worst being synchros worn out or the clutch sucks.
If it is a clutch problem start by looking at the master and make sure its full. Look for leaks in the cab eon the firewall where the peddle hooks to the master cylinder piston. Then if no leaks there look under at the bellhousing engine connection. Brake fluid used for the clutch has a distinct fell and smell.
If it is leaking you may not get full engagement of the clutch and thus the grinding. If it is not the hydraulics but a worn clutch plate or pressure plate time to do a clutch.
Don't jump to conclusions some of the fixes are easy and cheap.
89 2.5 TBI, 4" RC lift, 1" Booms, SYE, Adams Driveshafts front and rear, Ford 8.8 with 4:88s, BFG 33X12.50X15, and a ton of other stuff.
I'd put my money on the master cylinder, I had the same problem, just topped her off with some brake fluid and problem was solved til it leaked back down. I eventually just replaced it but forget where exactly it was leaking
I'm in the middle of a clutch replacement right now actually. I would suggest to make sure you know what is actually wrong before throwing parts at it. I have a '95 so my clutch madter/slave is set up a little different, but here's what I did: couldn't get into 4L bc of a broken link rod (tcase to lever connection) and had to climb a medium grade and of course lost the click on the way up. I first tried to replace master/slave (comes as one prefilled prebled unit) mine was under warranty but it is around $160-170 for that. That wasn't the issue (I knew deep down it wasn't, but was hopibg against hope that I didn't have to pull the trans) once I fot down and startes prepping to pull the trans I noticed a black fibrous material in all orifices (edge of starter, bottom of bellhousing) and knew then that I was In for a clutch job. The clutch kit which is disc, pressure plate, throwout bearing, and pilot bearing was only $124 w lifetime warranty from O'Reilly. Its not as bad as I was expecting, having never pulled the trans before-that is the most difficult part of it honestly. The actual clutch is easier to replace than a set of brakes
its not grinding it just wont go into gear like if im on the freeway going into 5th gear and then ill hit the clutch peddle like duoble bumping and it will shift smooth.... i havnt done a trans fluid change because i bought it like 6 months ago so ill do that soon, whats a good fluid to use? i was low on brake fluid for the clutch so i filled it up, is there a chance i need to bleed it? thanks for the help guys!!