ZF5 Transmission
Official ZF5 workshop & troubleshooting manuals, parts catalogs, specifications, gear ratios, etc. In addition, how to install a ZF5 transmission behind a 351M or 400.
Here are some of ZF's documents on the ZF transmissions:
Service Manual: Contains a diagnostic & testing section, exploded views and parts lists, removal & repair procedures, and clutch specifications.
Troubleshooting Guide: Includes description of operation, power flow diagrams, diagnostics, exploded views and parts lists.
This document provides lists of remanufactured transmissions, spare parts, and kits.
Gear Tooth counts for the S5-42, S5-47, S5-47M, S6-650 and 6S-750 transmissions.
Unfortunately the Bullnosed trucks (1980 - 86) didn't have a robust overdrive transmission option. Yes, there were some transmissions with overdrive gears, like the SROD for a manual and the AOD for an auto. But, neither of those was available for the 351M or 400. However, a few years later the ZF5 tranny came out behind 460, among other engines, and the 460 shares a bell-housing pattern with the 351M/400's. But, the flywheel on the 460 is ~1/2" further aft than that of the M-block pair, so while the transmission will bolt up the input shaft doesn't properly engage the pilot bearing and the clutch doesn't fully engage the splines.
To solve that problem I designed a flywheel spacer. But, that just kicked the can down the road as I then realized that ZF clutches have a larger spline than smaller transmissions used on the M-blocks. And, most clutches available for the 460 wouldn't fit under the 351M's 11" pressure plate. (The 400 had a 12" pressure plate that might work.) Then there was the question of what throw-out bearing to use as the one for the ZF was eaten quickly by the pressure plate that came on Dad's truck. And, there was the issue of what starter to use.
Fortunately Tim Meyer is now selling a kit that solves those problems. The kit includes the needed spacer and longer flywheel bolts. And, he will drill your M-Block flywheel to accept a 460 clutch and pressure plate. But, there are still some things to consider in this swap:
To solve that problem I designed a flywheel spacer. But, that just kicked the can down the road as I then realized that ZF clutches have a larger spline than smaller transmissions used on the M-blocks. And, most clutches available for the 460 wouldn't fit under the 351M's 11" pressure plate. (The 400 had a 12" pressure plate that might work.) Then there was the question of what throw-out bearing to use as the one for the ZF was eaten quickly by the pressure plate that came on Dad's truck. And, there was the issue of what starter to use.
Fortunately Tim Meyer is now selling a kit that solves those problems. The kit includes the needed spacer and longer flywheel bolts. And, he will drill your M-Block flywheel to accept a 460 clutch and pressure plate. But, there are still some things to consider in this swap:
- Starter: The 351M & 400 flywheels are the same diameter and have the same ring gear tooth count as a 460's flywheel. So if you space the flywheel back it'll be in exactly the same spot as a 460's. And, since the starter bolts to the transmission and not the engine, a 460's starter fits perfectly. I suggest a Permanent Magnet Gear Reduction (PMGR) unit as it is smaller in diameter and therefore provides more clearance. In addition, it uses less current and/or gives greater torque. See the page on PMGR Starter Wiring for how to connect it.
- Clutch Release Arm: The ZF5 came out after Ford went to a hydraulic linkage for all manual transmissions. So, there's no mechanical release arm available for it, and there is significant difference between mechanical and hydraulic release arms - leverage. As I describe on my page re Clutch Release Levers, you can use a release lever for a mechanical clutch mechanism, but your leg will not like it. Instead, you may want to create a hybrid release lever, as described on the Release Lever page.
- Rear Support Bracket: There is a bracket from the transmission crossmember to the upper flange of the frame, as shown in the illustration to the right. (Click on the image to enlarge it.) The ones for a ZF5 are different than those for other transmissions, so when you get your tranny also get the brackets. But, what if you, like me, didn't get them? Then you will have to drill new holes in the upper part of the frame, as shown here on my thread in FTE.
- Transmission Flange: The large flange of the ZF5 prevents getting to the inside bolt of the passenger's side exhaust manifold in order to tighten it. The solution I found was to grind a "U" in the flange, as shown in this post on FTE.
- Transfer Case Linkage: Apparently part of the extra length of the ZF over the other transmissions is between the mounting point on the transmission for the transfer case's shift mechanism and the rear flange of the transmission. That causes the transfer case to be further back and the linkage needs to be lengthened about 1" in order to put the shift lever where it needs to be in the truck. I'm sure there are many ways to lengthen the linkage and provide adjustment to get it right where you want it, but I've used the method shown in the picture to the right in a few cases and it works.
These tips come from a gentleman who formerly worked for ZF:
That transmission is actually a S5-42, 47, etc.
The S is for fully synchronized. Even the reverse gear was synchronized. The 5 is for 5 speed. The 42, 47 etc. is for foot pounds of input torque rating. Example: 42 represents 420 foot pounds of input torque.
That transmission was my technical responsibility as a service engineer at ZF.
This series of transmission was installed in most if not all HD and Super Duty Ford trucks.
The achilles heel was the "pocket bearing" and noise. The pocket bearing is the bearing located between the input shaft and main shaft of the transmission. The noise is from the gears rattling in the aluminum casing. This is caused by the expansion of the aluminum casing.
A small amount of play of the input shaft does not necessarily indicate that there is a problem.
These transmissions were notoriously noisy and you would swear that it was going to fall out but would operate just fine.
The trouble shooting procedures were set up for the transmission to be tested while in the truck or on a test stand.
With the correct tools from ZF, it is not difficult to repair.
That transmission is actually a S5-42, 47, etc.
The S is for fully synchronized. Even the reverse gear was synchronized. The 5 is for 5 speed. The 42, 47 etc. is for foot pounds of input torque rating. Example: 42 represents 420 foot pounds of input torque.
That transmission was my technical responsibility as a service engineer at ZF.
This series of transmission was installed in most if not all HD and Super Duty Ford trucks.
The achilles heel was the "pocket bearing" and noise. The pocket bearing is the bearing located between the input shaft and main shaft of the transmission. The noise is from the gears rattling in the aluminum casing. This is caused by the expansion of the aluminum casing.
A small amount of play of the input shaft does not necessarily indicate that there is a problem.
These transmissions were notoriously noisy and you would swear that it was going to fall out but would operate just fine.
The trouble shooting procedures were set up for the transmission to be tested while in the truck or on a test stand.
With the correct tools from ZF, it is not difficult to repair.