ZF S5-42 & S5-47 Manual Transmission

ZF 5 Speed Transmission Specs & Ratios

The ZF 5 speed replaced the four speed BorgWarner T-19 in Ford diesel applications. The transmission can be found behind 6.9L/7.3L IDI and 7.3L Power Stroke diesels through the 1997 model year, although 6.9L applications are relatively rare and limited to the engine's final production year. The transmission is relatively reliable, although the hydraulic clutch system has been a common source of problems that include gear grinding and rough engagements. The ZF S5-42 was used on 1987 to 1994 model year pickups, while the stronger S5-47 was introduced for the 1995 model year. Both transmission models are extremely similar, with only subtle changes that gives the S5-47 a slightly higher input torque rating.

ZF 5 Speed Ratios & ID

Type

1st

2nd

3rd

4th

5th

R

S5-42 Close Ratio

4.14 : 1

2.37 : 1

1.42 : 1

1.00 : 1

0.77 : 1

3.79 : 1

S5-47 Close Ratio

5.08 : 1

2.60 : 1

1.53 : 1

1.00 : 1

0.77 : 1

4.66 : 1

S5-42/S5-47 Wide Ratio

5.72 : 1

2.94 : 1

1.61 : 1

1.00 : 1

0.76 : 1

5.24 : 1

 

Both the S5-42 and S5-47 transmissions have been offered in close and wide ratio variations. While the wide ratio versions of the S5-42 and S5-47 feature identical ratios, the close ratio S5-42 contains a much taller 1st and reverse gear ratio in addition to a slightly different spread in between. The S5-47 is a heavier duty version of the 42, but is otherwise interchangeable so long as the transmissions originate from a diesel application. However, it is not advised to replace a S5-47 with a weaker S5-42; replacing a S5-42 with a stronger S5-47 presents no such problems. The greater strength of the S5-47 is attributed in part by a refined case design (smoother transitions and therefore less stress concentration points) and revised synchronizers. Many, if not most part numbers for internal components are the same for both transmissions. It's worth noting that the wide ratio S5-42 and S5-47 were offered in gas engine applications and are not interchangeable with diesel engine versions of the transmission. Furthermore, all diesel applications utilize an external clutch slave cylinder configuration while all gas engine applications feature a concentric slave cylinder inside the bellhousing (no clutch fork).

In order to identify your transmission model and gear ratio type, locate the transmission identification tag on the driver's side of the transmission.

ZF 5 speed ID tag location

ZF 5 speed transmission identification tag

From the transmission ID tag, you will be able to distinguish the transmission model (S5-42/S5-47) and ratio spread, which will identify whether the transmission is a wide or close ratio model. The ID tag may appear different than that in the figure above depending on model year.

 

ZF 5 Speed Specs

Transmission:

ZF S5-42 & S5-47

Type:

5 speed manual transmission

Manufacturer:

ZF Friedrichshafen AG

Predecessor:

BorgWarner T-19

Model Years/Applications:

ZF S5-42

1987 - 1994 Ford diesel (6.9L/7.3L IDI, 7.3L Power Stroke)

ZF S5-47

1995 - 1997 Ford diesel (7.3L Power Stroke)

Synchronized:

Synchronized in all forward gears & reverse

Case Material:

Aluminum

Max Input Torque:

ZF S5-42

420 lb-ft

ZF S5-47

470 lb-ft

Max GCWR:

26,000 lbs

Weight:

~ 175 lbs

Oil Capacity:

3.2 liters, 3.38 quarts

Fluid Type/Spec:

Full synthetic MERCON automatic transmission fluid

Features:

• Dual PTO provisions, driver and passenger side of transmission

• S5-42 - Synchronized, 5 speed, 420 lb-ft maximum nominal input torque

• S5-47 - Synchronized, 5 speed, 470 lb-ft maximum nominal input torque

• ZF equipped vehicles utilize a dual mass flywheel in order to suppress engine harmonics (and the resulting noise) through the transmission.

Shift Pattern:

ZF 5 speed shift pattern

 

Common Problems & Troubleshooting

In all diesel applications, the ZF 5 speed utilizes a hydraulic clutch actuation system, which is comprised of a clutch master cylinder, clutch slave cylinder, and a hydraulic clutch line connecting the two components. Depressing the clutch actuates a piston in the clutch master cylinder which pressurizes fluid in the system. The pressurized fluid causes subsequent movement of the clutch slave cylinder pushrod, which extends against the clutch fork and disengages the clutch. The system is similar in principle to a typical hydraulic brake system, where depressing the brake pedal subsequently forces the brake caliper pistons to extend against the brake pad.

The hydraulic clutch system on Ford pickups is extremely fastidious and sensitive to wear. Transmission grinding, rough engagements, or other conditions in which it may feel as though the clutch is not disengaging completely are often associated with one of or a combination of the following problems:

• Excessive flexing of the firewall around the master cylinder when the clutch pedal is depressed (Ford offers a repair kit for such conditions which reinforces the firewall at the clutch master cylinder).

• Worn clutch pedal assembly and/or pedal bushings. This problem is most prominent on 1987 to 1991 model year Ford pickups, which feature an aluminum pedal assembly bracket and relatively small bushings. 1992+ model year pickups feature a steel pedal assembly bracket and much larger, more robust bushings. In extreme cases, the pedal bracket assembly (sometimes referred to as the pedal box) may crack or wear and need to be replaced in order to irradiate the problem.

• Worn clutch master cylinder pushrod eye bushing. This is the bushing that sits in the eye of the pushrod where the clutch pedal swing arm pin is installed. When the bushing wears, excessive play in this joint prevents full engagement of the clutch when the pedal is depressed.

• Master/Slave cylinder leaks and/or air in the hydraulic system. Even a slight amount of air present in the system will significantly reduce clutch throw. Prior to diagnosing possible transmission problems, ensure the system is bled completely (this can be difficult at times and takes persistence).

While these are not always the culprit in transmission problems, they account for a large percentage of rough engagement and gear grinding conditions. Before further diagnosis, we highly recommend these areas be thoroughly inspected and any worn parts replaced. The clutch slave cylinder requires a minimum 7/16" of travel for proper clutch actuation, which does not provide a great deal of room for error.

 

Problem/Condition

Possible Cause(s)

Transmission noise at idle/low engine speeds in neutral

This is called "rollover" noise and is common to experience with the transmission in neutral. The cause is engine harmonics transmitted through the transmission. Rollover noise should be minimal on engines equipped with a dual mass flywheel. For single mass flywheels (flywheel has been converted from DMF to SMF) some noise is completely normal and should disappear when driving in gear.

Difficult engagement and/or grinding with clutch fully depressed

Clutch not fully disengaging - inspect master/slave cylinder for proper actuation (minimum 7/16" slave cylinder travel), inspect pedal assembly bushings for wear, inspect master cylinder pushrod bushing and clutch pedal swing-arm for excessive wear, inspect firewall for excessive deflection when clutch pedal is depressed. If hydraulic system is functioning properly and the aforementioned components are in good condition, problem may be worn synchronizers.

Transmission jumping out of reverse

Worn reverse synchronizer - synchronizer is not fully engaging and therefore jumps out of gear once load is applied. Try double clutching when going into reverse in order to avoid false reverse engagement.

Notchy shifting (no grinding)

Clutch not fully disengaging - inspect master/slave cylinder for proper actuation (minimum 7/16" slave cylinder travel), inspect pedal assembly bushings for wear, inspect master cylinder pushrod bushing and clutch pedal swing-arm for excessive wear, inspect firewall for excessive deflection when clutch pedal is depressed. If transmission shifting is notchy only when transmission is cold, this is typically normal. Check master cylinder fluid reservoir level.

Growling or squealing noise when clutch is fully depressed

Throwout bearing likely worn and/or requires replacement.

Gear grind, rough engagements in cold weather

Rough engagements, slight grinding between gear shifts, and sluggish transmission shifting characteristics are normal and to be expected from both the S5-42 and S5-47 transmissions when cold. If condition irradiates itself once transmission is warm, it should not be cause for concern. If problem persists when transmission is warm, see conditions above.

Transmission noise in one particular gear

Worn, chipped, or otherwise faulty gear set.

Transmission exhibits rattle noise when taking off at low RPM

This is typically experienced when lugging the engine from a standstill - run engine at higher RPM while taking off.

Rough engagements, gear grinding after master/slave replacement

Air present in hydraulic clutch system - bleed system completely before troubleshooting further.

Transmission will not go into a particular gear or series of gears

Worn shift rail(s) and/or gear shift mechanism, worn synchronizers.