I recently became the owner of a 92 F150 4.9L straight six with a 5-speed. Everything runs perfect except the previous owner informed me the clutch slave cylinder has a slow leak and needs to be replaced eventually. I've called around to a few shops and gotten a few quotes but a few have asked me if I have the Heavy Duty clutch or non-heavy duty clutch. I asked them how I could tell which I have and since most of the service departments I've called just have a secretary clicking on a computer, they have no idea either. What is the difference between the two and how would I be able to figure out which I have. Thanks for the help!

 

honestly i dont know the difference between the two...maybe one is more heavy duty??
either way i have a 95 f150 with the 4.9 and mazda tranny as well and i just did a standard one from napa when i did my slave cylinder. oem replacement; if it was good enough rolling out of the factory then its fine for me now.

 

There's a 10" and an 11" one. The flywheel has the bolt pattern for both though, so long as you buy the kit and the proper bolts either one will work but it sounds like you just want to do the slave cylinder and not the clutch?. I don't see why they need to know before you bring the truck in, once they get it apart they can just measure to see which one it is and order that one. The P/O either upgraded mine when it was replaced or it came with an 11".

When I ordered the slave cylinder there was only one part number though.

 

they might need to know so in case they get everything apart, and find out that it does need a clutch(i would do regardless while apart) to make sure that the parts house has one in stock so your truck isnt stuck on some lift at a shop waiting on a part to be shipped in.

 

A few of the shops I've called have quoted me a higher price if the clutch is 'heavy duty' to change out the slave cylinder.

 

If they're quoting you a higher price then they are trying to screw you. You don't even need to touch the clutch to change the slave cylinder.

 

If that slave is leaking then you may as well change the clutch while you're in there. It's a lot of work to pull the tranny twice. unless you're broke or lucky I'd change it all and resurface the flywheel.

 

I installed a heavy duty clutch back when I had my 85. The smaller clutch wouldn't last. On that truck it didn't matter what slave it had.
I really hate the type of clutch slave these trucks have where you have to remove the transmission to replace the slave. What were they thinking when they designed it?

 

They were thinking "save $$$ in original build". I hate the damn design, too. OTOH, having had old-style mechanical linkage fail, welds broke on cross-shaft from frame, throw-out fork cracked, pivot block rivetted to inside of bell housing broke off, well,..........

Got the damn inside slave on both current vehicles, '96 F-150 and '99 Explorer. Lesson learned, replaced clutch F-150, slave bone-dry, left it alone, it started leaking a month later! Pissed-off City!

 

I prefer an external clutch slave design. I've seen my share of failed slaves and replacing them, external slaves are the easiest to service.
I know what you mean about mechanical systems. My last mechanical clutch was in my 63 F100. I miss the truck but not the clutch. They're prone to breakage (though mine never did) and need regular adjustment.

 

When they say heavy duty, they might be refering to the transmission itself. Or maybe only the hd 11" clutch came with the hd transmission from the factory. Light duty 5 speed being the M5OD, Heavy duty 5 speed being the ZF 5 speed. I believe the ZF was available in an F150 as an option. The mazda and ZF have different slave cylinders

 

My ZF and the M5OD it replaced used the same clutch slaves. In fact I used the M5's slave in my ZF because it was almost new.

 

I think I will take your advice and put in a new clutch + machine the flywheel while everything is apart. That said, will a 11" clutch fit in the madza transmission (which I assume is what I have). Either way, what type of clutch would you guys recommend? I don't do much hauling, just maybe a light motorcycle trailer to the track 4-5 times a year so I don't need anything crazy expensive. Just a good balance of reliability, strength, and price.

 

Yes the 11" clutch will fit if you get the clutch kit with the flexplate. But if your truck has the 10" in it now you need to get 6 grade 8 3/8"-16x1" bolts with lock washers. The flywheel is tapped for both clutch sets but the 11" set uses these bolts. When I was pricing them out the 11" actually didn't cost much more at all.

I can't say if it drives better than a 10" since my truck with the m50d had a 11" previously installed. I know it sure felt better than a worn out 11 incher though,lol.

 

Centerline performance clutches.