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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

Size clutch

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Old Oct 24, 2006 | 06:38 AM
  #1  
j_boehler04's Avatar
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Size clutch

i just bought a 81 f 150 and trying to figure out what size clutch it is before i take it apart 10 or 11 inch. Any knowledge is helpful.
 
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Old Oct 24, 2006 | 08:47 AM
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We need more info on the truck. What engine does it have? Is it 4 wheel drive?
 
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Old Oct 24, 2006 | 10:07 AM
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i have an 82, it's 2wd with a straight 6 and a 4 speed manual, it has a 10 inch clutch
 
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Old Oct 24, 2006 | 12:10 PM
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There is honestly no way to tell without taking it all apart first. You'll hear people say 4x2 trucks got 10", some will say 4x2's with 3 speeds got 10" but the 4 speeds got 11", others say all 4x4's got 11". . . really no way to know, especially since the clutch has probably been changed at least once in the truck's life and who knows if the flywheel was changed.

The '80 4x4 parts truck i used for the conversion on my truck had a 300 and a 4 speed but only a 10" clutch while the clutch that was in my 85 4x2 4 speed was an 11 inch behind a 300.

Besides, there's no point in putting a clutch in without getting the flywheel resurfaced. While the flywheel is at the machine shop, just measure the disk or take the old pressure plate with you to match up at the parts house. (The pressure plate is the important part, it's what needs to match the bolt pattern in your flywheel)

Justin
 
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Old Oct 24, 2006 | 08:10 PM
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it has a 300 inline six 4 spd 2wd. I talked to one parts place and they said something about having a hydralic clutch or mechanical cluthc could also tell me the size. and yeah i planned on doing the flywheel and ring gear. thanks
 
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Old Oct 25, 2006 | 10:29 AM
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hydro clutch vs. mechanical is just a year difference, 1982 is when it went hydro IIRC. You really are just better off taking apart and measuring. Either that or if you were intending to ::replace:: the flywheel, just buy an 11" flywheel and clutch.

Justin
 
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Old Oct 25, 2006 | 10:43 AM
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I believe the flywheel is drilled for both the 10 and the 11 inch clutches.. If so doesnt matter what one you use just that you will have to change the bolts when going from the smaller to the larger one..
 
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Old Oct 25, 2006 | 11:01 AM
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Some flywheels are double drilled, but not all. my 10" flywheel was single drilled and my 11" was double drilled.

All replacement wheels i've seen have both patterns, but factory ya just don't know.

Justin
 
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Old Oct 25, 2006 | 11:16 AM
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so what difference does it make between an 11 or 10 inch clutch. Ive never really delt that much with clutches.
 
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Old Oct 25, 2006 | 12:09 PM
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It's a matter of grip. the 11" disk has more friction area than the 10", so it grabs better, proportional to the increase in surface area. The 11" pressure plate also uses a heavier spring, so it clamps harder.

The 11" has about 18% more torque capacity based solely on the area and about a 7% increase from increased clamping forces. Therefore, a stock 11" clutch can handle about 25% more power than a stock 10" clutch.

Justin
 

Last edited by hoxiii; Oct 25, 2006 at 12:14 PM.
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Old Oct 25, 2006 | 07:07 PM
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Would you recommend changing from a 10 to an 11 inch. im gonna be using the truck to get wood and stuff like that. also do you know if the tranny from the 300 i6 will work with a 400 big block. im thinkin bout doing a conversion.
 
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Old Oct 25, 2006 | 07:15 PM
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Originally Posted by hoxiii
hydro clutch vs. mechanical is just a year difference, 1982 is when it went hydro IIRC.
My 83 F100 was mechanical. 300-6 and SROD, 8.8 rear with 2.47 gears 4th was totally useless... Don't know the clutch size...

As for the trany swap behind the 400 it depends on the trany. Some are junk (or will be) behind a bigger motor. SROD comes to mind.
 
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Old Oct 25, 2006 | 07:31 PM
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Originally Posted by f100beatertruck
My 83 F100 was mechanical. 300-6 and SROD, 8.8 rear with 2.47 gears 4th was totally useless... Don't know the clutch size...

As for the trany swap behind the 400 it depends on the trany. Some are junk (or will be) behind a bigger motor. SROD comes to mind.





My 83 4x4 has a mechanical clutch also, and originally came with a 300.
 
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Old Oct 25, 2006 | 08:43 PM
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If it's dual drilled, get the 11" since they're the same price. if single drilled, get whichever fits UNLESS, you need to change flywheel. If the flywheel needs replaced anyway, go 11.

If the flywheel is a 10" and is still good, might as well just stay with the 10" setup.

With a 300 and 3.0 gears I've overpowered an older stock 10" clutch, when i changed it i went to 11 and haven't had an issue.

as for 300-400, it does depend on the transmission. If you have a granny low 4 speed it'll be fine. All it takes is the 400/351M/429/early 460 bellhousing and the frame perches for the motor mounts. I'm sure there are all kinds of hookup details like with the radiator and all, but motor into frame and to transmission is pretty straight forward.
 
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Old Oct 25, 2006 | 08:56 PM
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nice thanks alot with all your help.
 
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