I finished my 300 to 351 swap the summer/fall of 2018. Before mating the M5OD gearbox, I installed a new flywheel, disc, pressure plate, and throw-out bearing/slave cylinder. Here’s my problem, this past summer I started having problems shifting gears. I’ve tried bleeding the clutch and even tried reverse bleeding. It’ll shift great and then after a while the same hard to shift problem. I replaced the master cylinder a few weeks ago and it worked great that day and the next day, same problem. So I’m guessing that I need to replace the throw-out bearing/slave cylinder. Mind you, when I replaced the slave cylinder the first time around, I used a new unit for a 302 v8 from Car Quest. On their website, the slave cylinder unit for an F250 with a 351 5 speed has a different part number compared to the slave cylinder unit for an F150 wIth a 302 5 speed. I am thinking that if I have to go through to all this trouble again I want to at least use the best slave cylinder unit. You guys have any advice or suggestions?

 

What, exactly? Loose shifter? Tight shifter? Can't find the gears? Won't go into gear(s)? Goes in w/engine OFF, but not running? Shifts hot, but not cold? Be specific & detailed.

 

When first started, I’ll step on the clutch pedal and from the top to about mid clutch travel, I can feel very little pressure from the pedal and it is hard to get into first gear or go into reverse(it grinds badly unless I first shift into second gear and do a quick u-turn into reverse). I have to pump up the clutch several times, shift into second and then shift quickly into first. Once underway it’s okay for the most part....when coasting, I’ll put it in neutral and just pump the clutch and actually feel it buildIng pressure from the top.

 

Sounds like there is still air in the system.

 

I’ve tried bleeding it by gravity, reverse bleeding, and pump several times then bleed. The clutch will feel nice and firm and works great until the thing sits for a few hours and then I get that same light feel from the top of the clutch arc through middle of the way. That’s why I’m thinking that my slave cylinder is on the fritz....

 

Read the captions in this photo album:

(phone app link)

 

Thanks Steve! I will give my clutch pedal a look...

 

The problem is you will not be able to see if the most likely to fail bushing (the one behind the cross lever) has worn out because the cross lever is in the way, blocking its view. Removal of the cross lever is very difficult while the whole pedal box is in the vehicle and will likely require installation of a new one if you remove it.
If the clutch pedal is sitting low, has slop in it where you can lift it up a great deal, chances are the bushings are worn out and you will have to pull the whole pedal box to service it.

 

The clutch lever height is fine. When I try to pull it up, there is no play or slop and it is at the top of its travel. When I push it down with my hand, it feels light from the top to about middle of the way...then it takes more effort to push down, obviously no problem if you are using your foot. That's why I was thinking that maybe my slave cylinder might be on the fritz. If I pump it up a number of times, it'll build pressure, especially if it's warm outside. If I drive in stop and go traffic, it's fine as well.





I even thought about replacing my master and slave cylinder with the units from an F350...which are definitely different from the units from an F150 (the top two pics.)

 

But the lever is solidly attached to the shaft that's in the bushing. So if the bushing lets the shaft wobble, the lever will wobble in exactly the same way, and it will be apparent by observing the lever's movement when applying & releasing the pedal (even over a tiny distance).Ford describes doing it that way to replace the lever, but it's so easy to pull the whole box down that I've only pulled it in-cab once. Never again.Again: that's what Ford specifies. But when the ONLY problem is the worn bushing, I've simply reinstalled the old lever back onto the same splines on my 2 trucks with total success.You said "lever", but it seems like you're talking about the PEDAL. You can't observe the lever-end bushing wear in the motion of the pedal because it's too slight, and not in the direction you're talking about. You must put eyes (or fingertips) on the lever end of the pedal shaft to know what's happening at the high-wear end.That's why you shouldn't try that. The slave is specific to the transmission bellhousing & clutch stack that it fits - you can't necessarily mix from a 1/2-ton trans with a heavier (different model) trans from a heavier truck.