ZF stands for Zahnradfabrik Friedrichshafen

A quote from www.garbee.net/~cabell/transmission.htm

ZF S650: An extremely heavy-duty unit with 6 forward speeds. All gears are synchronized. This unit has an aluminum case with integral bell housing, a center support, and rear case. This unit is built in both 2 and 4WD versions. The S650 is found behind diesel engines of the 1998 and up Ford Super Duty, and stripped chassis up to a gross combined weight of 26,000lbs. The unit weighs in at 230lbs. A unique feature of this unit is an internal oil pump driven off the front of the countershaft that circulates the lube to a Transmission cooler. An easy way to identify this unit is by the cooling lines mounted to the case as found in automatic transmissions. Id tags are mounted on the left side of the main case. Only has a PTO port on the (passenger side).

Gear ratios...

1st = 5.79, 2nd = 3.31, 3rd = 2.10, 4th = 1.31, 5th = 1.00, 6th = 0.76 Reverse = 5.23

The companies site www.zf.com states...

2nd and 3rd gear feature dual-Cone Synchronizers.

TheDieselPage.com - ZF S6-650 Six-Speed Manual Transmissions says...

Key Features:
- Designed specifically for high torque pickup trucks.
- Synchronized in all gears.
- Dual-cone synchronizer in 2nd and 3rd gears.
- High helix angle gearsets provide high contact ratio and quiet operation.
- Lower shift forces w/ tight shift pattern.
- Lightweight integrated aluminum housing (front, center & rear)
- Center bearing suport for improved durability.
- Reverse & 1st gear location improve maneuvering ease.
- Overdrive 6th gear shift lever position located forward and away for improved passenger comfort.
- Gross Combined Vehicle Weight Rating up to 26,000lbs.
- Left & right ISO/SAE 6-bolt Power Take-Off ports.

and from the ZF Freidrichshafen AG - AZ North America website...

ZF 6-speed manual transmissions are designed for Ford and GM truck drivers who place a high premium on performance with flexibility, and responsiveness with control. With simple H-pattern shifting allowing for 3-up seating and easy "toggling" between 1st and reverse for increased maneuverability. ZF transmissions are easy and more comfortable to operate. With lightweight aluminum housings, they provide improved fuel efficiency with lower maintenance and repair costs while delivering a increased torque capacity for today's high powered pickup trucks.

ZF transmissions are true workhorses, designed and built for optimal flexibility during repetitive heavy-duty tasks and ideally suited for the harshest environments, while at the same time offering a rather engaging driving experience.

ZF 6-speed manual transmissions are available standard on GM trucks with 6600 Duramax, and 8100 Vortec engines, and Ford trucks with 5.4L V8, 6.8L V10 and PowerStroke 6.0L engines.

And from what I've read off of Fords web site, the ZF 6 speed manual will be offered standard behind their new '08 6.4L diesel putting out some 650lb ft of torque. Suffice it to say that tranny should last some time behind our V10s!

Now you know!
RustyFuryIII

 

I have seen a 4 door Long bed PSD ZF6 and 4.10:1 on stock tires hooked up with a logging chain to pull a Dodgem and a 38Foot goose neck trailer with hay bale rounds two high out of a bar ditch... the 4low and new dually tires that were aired down on the rear end, was getting enough traction to lift the front tires two feet off the ground before the stuck truck moved and eventually caught traction and climbed out of the ditch... I was passing by and had to stop to enjoy the stout FoMoCo iron assisting the Dodgem "tin n plastic" truck


BTW it was a 6.0L PSD on steroids billowing great goobs of sooty smoke...grin

 

The only down fall with the zf is the the stock clutch/pressure plate they put in front of it.To weak
And if you get one setup(endplay) wrong from the factory,their a bitch to work on

Been there worked on a few over the yrs
Rich

 

I see the reference to "dual cone" synchronizers for 2nd and 3rd. Must be something special, but does anyone know what this means?

 

In fact, why special treatment for just 2nd and 3rd?

 

2nd and 3rd usually have the highest upshift points and take the most abuse including down shifts...they are also centered on the shaft and in an area with the most side load

The "dual Cone" design allows for a more reliable engagement because it injects a slightly longer duration for the gear clusters to get to the same relative shaft speed...

When I can make this Damn site stop kicking my *** off and not responding I will edit in a gallery of the ZF internals..once you see the dual cone vs the single cone you will get the idea

 

Thanks Fred I appreciate the info. I discovered some time ago that shifting from 2nd straight to 4th above maybe 3,000 rpm would grind the gears unless it is done with just the right "feel" (or also double clutching works), whereas running sequentially through the gears never presents a problem. I never considered it a problem, just a quirk, but now I can see there's a reason for it...

 

Thanks for all the great info....I always enjoy learning more about my great truck...

 

help ,2nd synro is burnt out i am looking for the way to pull the trans down and install a new synro . I have been told there is a procedure to go through to get it apart. This trans is in a 2000 F-550 7.3 S6-650 ZF. thanks if anybody can help jim7777

 

By the title I thought this was going to be a post about how bad the trans is. I'm happy its good news.

My pto port is on the drivers side though not the passengers as stated.

 

Your best bet to get an answer is to make a new post in the SD forum.

Super Duty And Heavy Duty - Ford Truck Enthusiasts Forums

 

What great information on the ZF6!
Eventhough the 6-speed in my truck isn't dealing with the greater torque of the V10 or the PSD, I believe this transmission to be more than capable of handling all I can throw at it with a 5.4L. While it's not the fastest shifting transmission I've ever driven, it's great not having to worry about it off road. I love Low + 4wd Low Range!

 

Can this transmission be fitted to a 1995 F350 7.3 Power Stroke Auto to Manual conversion?

 

I would ask in the OBS 94-97 power stroke or the 87-97 truck section, you should get allot more help there.

 

How often and with what should the oil in the transmission be changed. With all this stuff about Mercron 5 I dont know where to go. You seem to know what is what with this gear box. Thanks Larry ;o)