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Discussion Starter · #1 ·
I am starting to put together parts for my next 4bt swap. My 1989 f150 2wd is treating me great but now I need a 4x4 with lower gears and a 5 speed.

The pickup is a 1976 f250 "Highboy" 4x4 4speed with divorced transfer case and 4.1 gears. (this truck has a mechanical clutch)

I am going to need a 5 speed transmission. I would like to go with the ZF tranny.

Should I:
1. Use the ZF tranny with a small block bell and add a hydraulic clutch to my pickup.

2. Somehow convert the ZF too accept my f250s mechanical clutch

3. Use the m5od tranny out of a f150 which also has a hydraulic clutchbut at least its external and would probabally work with my mechanical clutch.

4. anything else that I hadn't thought of?

I am assuming that a 2wd tranny is what i'll need since my transfer case is divorced?

Thanks for your help

Mark
 

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I am starting to put together parts for my next 4bt swap. My 1989 f150 2wd is treating me great but now I need a 4x4 with lower gears and a 5 speed.

The pickup is a 1976 f250 "Highboy" 4x4 4speed with divorced transfer case and 4.1 gears. (this truck has a mechanical clutch)

I am going to need a 5 speed transmission. I would like to go with the ZF tranny.

Should I:
1. Use the ZF tranny with a small block bell and add a hydraulic clutch to my pickup.

2. Somehow convert the ZF too accept my f250s mechanical clutch

3. Use the m5od tranny out of a f150 which also has a hydraulic clutchbut at least its external and would probabally work with my mechanical clutch.
I say #1, go with a factory setup where factory parts are available in case of breakdown. Obviously I'm not referrring to the clutch master cylinder.
There are aftermarket clutch Masters which may work. Also 1999+ Ford F-series Superduty pickups have a clutch pedal assembly that may be worth looking at for adapability to a hydraulic conversion since they have both the assist spring, and unlike 84-97 trucks, the clutch pedal assembly is separate of the brake pedal.

#2 isn't very feasable surely it could be done, but there'd be very customized parts to wear out or fail inside the bellhousing.

#3 the M5OD is internal slave just like the Windsor pattern ZF transmissions, so my answer for #2 applies the same.
 

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You should lose the divorced case if you want to run a Ford 5 speed. They're too long.

The hydraulic clutch is very simple to add to your truck using factory 80's/90's parts.
 

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Discussion Starter · #4 ·
Are the 2wd M5od and the Zf5 both about the same length? The borg warner tranny that is in the truck now measures 24" from bell to the base of the yolk. I read in another post that the ZF measures 26" but I presume that this is for a 4x4 version.

Dustin, did you use a married transfer case on your 1971 f250?

Thanks for your help

Mark
 

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Are the 2wd M5od and the Zf5 both about the same length?
The comparison is hard to make for 2wd versions, since all 2wd M5ODs are reverse slip yoke, but most(virtually all) 2wd ZF transmissions are fixed yoke output. There is a reverse slip version 2wd ZF, but they are very very very rare. I've only read about them being available and seen one on eBay awhile ago.

4x4 versions are the same length though.
 

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No, 4x4 versions are not the same length. The 4x4 M5R2 is about 3" longer than the 4x4 ZF.

For a 2wd M5R2 from bellhousing to the center of the U-joint yoke is 34"

Don't have a 2wd ZF to measure, but you'd probably get a couple inches shorter there.

Guys run all kinds of trannies in highboys that are too long, but they don't care and are perfectly happy replacing U-joints every 5K miles.

With a 435 the center U-joint angles in a highboy are 3 degrees. With a factory short shaft C-6 auto they are 4 degrees. With the custom NV4500 with a fixed 1350 yoke I had in my '70 I had 4 degree U-joint angles.

The shorter your driveline gets the greater the U-joint angles unless you completely re-engineer the mounting points and drop the crank centerline.

I went mated case on my 71 with a BW 1356. Don't get me wrong, I really do like the divorced setup for it's simplicity and ease of working on everything, excellent U-joint angles, etc, but they do have some inherant issues. The biggest of which is their tendancy to buck under heavy loading. Not sure what your experience is with towing heavy stuff with a highboy, but put 400+ lb/ft through the stock drivetrain and 20K in tow and you will see that transfercase try to get the hell out from under the truck. Even with new poly mounts and an NP205 with the factory strut rod with poly mounts as well they buck.

Going to a mated case is simple, but it's also necessary to go to a HP front axle. a highboy with a mated case, 4" lift and low pinion front end would mean about 30 degree front U-joint angles, not even possible with standard joints.
 

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Discussion Starter · #7 ·
Thank you for your help. I'm glad I didn't have to find that out the hard way. I won't do much heavy towing, I have a peterbilt for that.

This might be a stupid idea but what if I move the engine ahead to make up for the longer transmission? I have at least 10" of space in my f150 between the front of the engine and the radiator.

I just got this f250 and everything is really tight the prevoius owner put a bunch of money into it about 5 years ago including new drive lines. I would like to use what I have but I also want it to last.
Maybe it would be easier to buy a 1990 f250 and strip it down to the frame and mount my 1976 cab onto it. I plan on building a flatbed anyway. How are the transfer cases on the 1988-1994s.

averagef250: Thank you for your patience on all these questions. Your help was second to none on my last build.

Mark
 
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