You got some very bad information there.

Knew was being in general slightly inaccurate. I couldn't find the original sources because the links wouldn't load, but I was trying to get to the truth because had read somewhere there is a lot more to this. Thanks for all the great info. Maybe this should go in the stickies. :beer:

In general the S in the ZF S5-42 model name is short for synchronized, the 5 designates the number of speeds (not counting reverse), and the 42 stands for the ZF's torque capacity of 420 lb-ft. An external slave cylinder was used on early '87 ZF models. Since it is on the outside of the bellhousing, it can be replaced without removing the transmission.

Here's some data I found:

http://www.high-impact.net/transmission_and_gear/zf_5&6spd.htm
They distinguish between the "Big Block, Windsor, Diesel, and FE" blocks.

ZF Transmission Data Summary

S5-42 Gas Units

• Model Year 1987 - 1995

• 1992 and newer applications have the electronic speedo.

• On all 4 x 4 and Superduty applications, the speedo cable connects to either the parking brake or the transfer case.

• 1987-1991 4 x 2 applications have a 7 or 8 tooth speedo that connects via the transmission.

• 4 x 4 units are used in 4 x 2 superduty applications.

• If a 4 x 2 vehicle is equipped with electronic speedo, use O.E. speedo plug number F2UZ 7H183A.

• 1307 050 064ZW only used in UPS vehicles.

• S5-42 units are not interchangeable with S5-47 units.

• Gas units must use ZF recommended Dexron Il/MERCON® XT-2 QDX or DDX equivalent.

• Available in 4.9/5.8 engine as well as 7.5 Gas

• 5.72-.076 ratio

• 4WD: 31 spl output

• 2WD trans 619mm OAL to Flange

S5-42 Diesel Units

• Ratios avail 5.72-0.76 4.14-0.77

• 6.9 / 7/3 engines

• Model Year 1987 – 1994-1/2

• 1992 and newer applications have the electronic speedo.

• On all 4 x 4 and Superduty applications, the speedo cable connects to either the parking brake or the transfer case.

• 1987-1991 4 x 2 applications have a 7 or 8 tooth speedo that connects via the transmission.

• 4 x 4 units are used in 4 x 2 Superduty applications.

• If a 4 x 2 vehicle is equipped with electronic speedo, use O.E. speedo plug number F2UZ 7H183A.

• 1307 050 103ZW only used in UPS vehicles.

• S5-42 units are not interchangeable with S5-47 units.

• Diesel units must use ZF recommended Dexron Il/MERCON® XT-2 QDX or DDX equivalent

• 4WD: 31 spl output.

• 2WD trans 619mm OAL to Flange

S5-47 Gas Units

• Model Year 1996 - 1997

• 1317 050 007 and 1317 050 013 [7.5 Gas Units] are 100% interchangeable.

(What is different about the 1317 050 006 7.5 unit?)

• S5-47 units are not interchangeable with S5-42 units.

• Gas units must use ZF recommended Dexron Il/MERCON® XT-2 QDX or DDX equivalent.

• Gas Units are shown for 4.9/5.8 engine, as well as 7.5 engine

• all show 5.72-0.76 ratio

• 4WD: 31 spl output

• 684mm OAL 2WD to ctr of u-joint in yoke

S5-47 Diesel Units

Ratio 5.08 1st; .77 reverse

S5-47M Gas Units

• S5-47M Model Year 1999 - current

• S5-47M units are not interchangeable with S5-47 units.

• Gas units must use Ford Synthetic Mercon E6AZ 19582-B or Castrol Transmax-S.

• Gas units used with 5.4 and 6.8 engines

• All show 5.72-0.76 ratio

• 4WD: 31 spl output

• 684mm OAL 2WD to ctr of u-joint in yoke

Ford S6-650 Diesel

• Model Year 1999 – 2000

• Application 7.3L Diesel

• S6-650 standard torque transmissions may be replaced with the S6-650 High Torque transmissions.

• Diesel units must use ZF recommended Dexron II/MERCON® XT-2 QDX or DDX equivalent.

• 5.79-0.72 ratio

• Internal oil pump for lubrication and cooling

• Rated to 500 ft-lbs input torque

• Wt: 235 lbs

• 4WD: 24 spl output

S6-650 High Torque Diesel

• Model Year 2001 – current

• S6-650 standard torque transmissions may be replaced with the S6-650 High Torque transmissions.

• S6-650 High Torque transmissions may not be substituted with the standard torque transmissions.

• Diesel units must use ZF recommended Dexron II/MERCON® XT-2 QDX or DDX equivalent.

• Application 7.3L Diesel

• 5.79-0.72 ratios

• Internal oil pump for lubrication and cooling

• Rated to 520 ft-lbs input torque

• GCW 26,000 lbs.

• Wt: 235 lbs

• 4WD: 24 spl output

Ford S6-650 Gas

• Model Year 2002

• Application 6.8/5.4 Gas

• Gas units must use ZF recommended Dexron II/MERCON® XT-2 QDX or DDX equivalent.

• 5.79-0.72 ratio

• 4WD: 24 spl output

• OAL 842mm to flange 2WD

Ford S6-750

• Model Year 03-?

• 6S-750 Transmissions may not be substituted with the S6-650 transmissions.

• 6S-750 OAL 2wd 766.3mm

• 6S-750 ratios 5.79,3.30, 2.10,1.31,1,.72,5.23

• 6S-750 ratios dry wt 235lbs, oil cap 6.0L GCW 30,000lbs

• Rated to 560 ft lbs input torque

• Wt: 235 lbs

• Oil Capacity 6.0L

• Internal oil pump for lubrication and cooling

• 4WD: 34 spl output