Transfer Case and Clutch questions

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Atmus
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Transfer Case and Clutch questions

Post #1 by Atmus » Mon Nov 27, 2017 8:12 pm

I'm in the parts-gathering phase for my F-250 project, and I need some advice. My goal is to convert a 1986 F-250HD 4wd from a 460/C6 to a turbocharged 300/NP435. The current transfer case is a NP208 that was freshly rebuilt, the differentials are 4.10, limited slip rear, no slip front. I don't expect to go more than a couple inches over stock tire diameter.

While I currently have and am familiar with the NP208, I have a couple NP205's that came with the NP435's I bought last weekend (a guy was storing them at his mom's house and she decided 20 years was long enough, so I got a good deal on the lot). I'm not building a rock crawler, but I'd like it to hold up to mild/moderate established trails. The gearing advantage of the NP208 doesn't seem to matter too much given transmission's low 1st gear, but it might be nice to have? I don't know which transfer case is better for me, if either is substantially better, or if the NP205 is 'better' enough to justify digging up the shift linkage, speedometer cable end, and (possibly?) driveshafts to make that work. Thoughts?

My other question is to do with the clutch. I learned to drive on an 82 F-150 with a 300, NP435, and a mechanical clutch between them. I've always liked how 'alive' the mechanical one felt compared to the hydraulic one I've used in a 90's truck, but they probably switched to hydraulic for a reason? As far as the clutch itself, are there any considerations I should be aware of? I assumed that the largest one that fit would be 'best', but I've come to realize that this area is a big gap in my automotive knowledge.

I'm not rich, but I'm not dumb enough to cheap out on something that I expect to take me camping, get me through a blizzard, and tow a small trailer. Any advice? Or am I overthinking this?
1967 Galaxie 500 hardtop, no drivetrain
1982 F-150, 300I6, NP435 manual, single cab longbed
1984 F-250, 420 Diesel, C6d Auto, limited slip rear, standard cab longbed
1986 F-250HD, 460v8, C6 Auto, NP208, limited slip rear, no slip front 4wd, extended cab longbed
2013 Focus ST

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bubba22349
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Re: Transfer Case and Clutch questions

Post #2 by bubba22349 » Tue Nov 28, 2017 4:23 pm

The gear driven NP205 is a much stronger unit than the chain driven aluminum case NP208. About the only advantage of the 208 is its lower gearing you could also get that back if you needed to have that with a married together combo of a NP205 and NP203. Most of my trucks have been older and had mechanical clutch linkage its usally pretty bullet proof even if the parts are starting to wear. The advantage with the Hydrolic linkage and I think the biggest reason they probally switched is it's easier operation or pedal effort. Yes usally a bigger clutch is needed as the power level goes up. Good luck on your build :thumbup: :nod:
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

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B RON CO
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Re: Transfer Case and Clutch questions

Post #3 by B RON CO » Wed Nov 29, 2017 8:49 am

Hi, X2 on the durability of the cast iron gear box, but since your 208 is fresh, and installed with all the other parts you need I would probably stick with it for now. If it can't take what you dish out you can go with the 205 later. I got over 250,000 miles out of a 208 with a lot of beach driving, trail riding and snow plowing. Good luck
B RON CO. Still workin' on it!

1933 Ford Pickup - 59A Flathead V8
1966 Ford Bronco - U14 - 170/200 Straight 6
1966 Ford Mustang - 289 V8

Atmus
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Re: Transfer Case and Clutch questions

Post #4 by Atmus » Thu Nov 30, 2017 4:25 pm

Okay, while I'll probably stick with the 208 for now due to it already being set up, I'll look harder at the 205 transfer case (with and without the 203 option). It would be amusing to have like 4 shift levers, which would render the truck entirely 'unborrowable'. I was probably overthinking it with the 208's lower gears, as my 82 F150 with a stock 300 has highway gears and never failed in towing/hauling anything, and my plans (if successful) would produce sufficient power to counteract the increased weight and torque losses from the larger diameter tires anyway. It's a shame you can't reverse the 203 and make it an overdrive (unless you can?), but not everything needs to do 100mph.
1967 Galaxie 500 hardtop, no drivetrain
1982 F-150, 300I6, NP435 manual, single cab longbed
1984 F-250, 420 Diesel, C6d Auto, limited slip rear, standard cab longbed
1986 F-250HD, 460v8, C6 Auto, NP208, limited slip rear, no slip front 4wd, extended cab longbed
2013 Focus ST

Atmus
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Posts: 12
Joined: Tue Jan 15, 2008 1:36 am
Location: Aurora, Colorado

Re: Transfer Case and Clutch questions

Post #5 by Atmus » Thu Dec 14, 2017 9:53 pm

Another question, how does the PTO actually work? Is it a neutral only thing? Or is that dependent on the construction of the PTO unit? I had an idea on how to use a jammed up PTO unit to function as a parking brake, but I want to find out how terrible an idea that is.
1967 Galaxie 500 hardtop, no drivetrain
1982 F-150, 300I6, NP435 manual, single cab longbed
1984 F-250, 420 Diesel, C6d Auto, limited slip rear, standard cab longbed
1986 F-250HD, 460v8, C6 Auto, NP208, limited slip rear, no slip front 4wd, extended cab longbed
2013 Focus ST

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bubba22349
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Location: Flagstaff, Az. 86005 near the old Route 66

Re: Transfer Case and Clutch questions

Post #6 by bubba22349 » Fri Dec 15, 2017 1:55 pm

Atmus wrote:Another question, how does the PTO actually work? Is it a neutral only thing? Or is that dependent on the construction of the PTO unit? I had an idea on how to use a jammed up PTO unit to function as a parking brake, but I want to find out how terrible an idea that is.


The PTO's that I have used on a T18 and NP435 were to operate a hydrolic pump to raise a hoist (dump bed) in that case its usally only operated in neutral. But I would think they would also work when the trans is in gear too as long as the operating RPM's (the PTO Shaft speed) isn't to high. So your idea may work. Good luck :nod: Edited
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

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Shorty
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Re: Transfer Case and Clutch questions

Post #7 by Shorty » Sat Jan 13, 2018 9:30 am

the 205 case can be easily modified for twin stick allowing you to operate the front and rear output independent of each other and putting another shifter in the cab. The hydraulic clutch also does not require freeplay adjustment just bleed and run.
85 F150 on 78 bronco frame C6 np205 welded dana44 front, trussed posi nine inch rear. EFI exhaust manifolds into one 2 1/2" rolls on 35x12.5x15 Maxxis Trepador.

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