Got 89 mustang lx 5sp can push in clutch pedal and put in gear when car is off no problem. Turn it on and it wont go in gear with a lot of force it still wont. While doing this if i have my foot off the brake and try to push it into gear the car will start to move forward. Anyone know why this is?

Well guess that i will try changing the clutch and flywheel. Gonna cost a lot but got to start somewhere.

Do you have a hydraulic clutch?
If no, then the cable may have stretch and need adjustment or replacement.
If yes, does the clutch work if you pump the pedal? Have you lost any fluid? Have you checked for fluid leaks.
If you are going to change the clutch, check the clutch fork for oblong pivot points.

No i have a clutch manual clutch not hydro i took the cable out a while ago and put it next to a new one it was the same length. I would check the fork but i have no clue where it is.

Try this website. It explains how the clutch works. You also need to check the pedal assembly to make sure none of the pivot points are enlongated.

http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/19/65/e6/0900823d801965e6.jsp

yean thanks but it really does answer my question. He car wont go into gear and when you pust the clutch and put it in gear it wont go but as i pusth the car willstart to roll forwaard.

The clutch is not releasing. Is it adjusted properly? Is the bearing release lever moving enough?

Like I just replaced the quadrent to some poeple the cable adjuster. But I put that in but even before that it was getting harder to put the car in gear. Cluth in at a stop would be hard to go in.No it wont at all. with clutch all the way in. Now i can have clutch pedel to the floor and wont go in gear inless car is off. While car on and trying to pust into 1st the car will start to roll forward a bit. I read in the post name 88 mustang tranny problem its like three posts below same problem as him. But I have yet to take anything apart.

I have not idea how to tell if it is adjusted. and i dont even know where the bearing realse lever is. One person thinks clutch cause same problem i have he took clutch out and the plate was cracked and spring was out. Then one guy says adjustible clutch cable. Then another clutch fork. This sucks.