For concours detailing of the 71 429 Mustang/Cougar C6, click this link: C6 Concours Detail Page

The 429 CJ/SCJ C6 Transmission

This is the special C6 transmission used on the 71 429 Mustang/Cougar. It had a special planetary, extra clutch packs and a more powerful servo (see "R" Servo at right) than normal passenger car C6 transmissions.
 

Important!

 429 CJ/SCJ Crankshaft Pilot Diameter Difference effects Torque Converter Selection

The 71 429 CJ/SCJ used two different diameter crankshaft torque converter pilot diameters throughout the 71 model year. The small diameter version was 1.375" and the large diameter was 1.848". This information is important to know when selecting the correct torque converter. If you aren't aware of this pilot diameter difference, and install a new torque converter with a mismatched pilot, you'll be in trouble either way. A small diameter converter pilot into the large diameter crankshaft pilot will bolt together just fine, but will result in a horrible powertrain vibration that you will never find (unless you're really lucky). The large diameter pilot converter, when mismatched with a small pilot crank, cannot insert far enough and will prevent the torque converter bolts from coming through the holes in the flexplate far enough to get the nuts on. However, you will probably only discover this when you're lying on your back under your car wondering why things won't bolt up. The photos above will show you where to measure to avoid this nightmare that two of us have experienced ;-)

C6 Flexplate

The 429 CJ/SCJ C6 flexplate (D1VP-6375-AA)  is shown above left. The Flexplate Reinforcement Ring is at right.

Transmission Mounting

The C6 cross member (D1ZZ-6A023-A) is shown above along with a diagram showing assembly. Below are photos of the correct 429 CJ C6 mount - part number D1ZZ-6068-B (service number) and D1ZA-6068-BA (engineering part number).

Shifter     

The shifter Bezel for the C6 is shown at left and center. An installed view of the bezel and shifter are at right. A view of the shifter mounting location from underneath the car is shown below left. The shifter lever pointer, is  shown below right. This piece slips onto the shifter lever and provides the pointer for the P-R-N-D-2-1 dial. It also provides the housing for the illumination bulb;

429 C6 Tail Shaft Length

The 71 429 CJ/SCJ Mustang/Cougar also came with a "short" (14") tailshaft (as indicated by the Ford Master Parts Catalog). Other Ford applications (ex; some Lincoln) came with the longer 17.5" tailshaft. Also, note the mount is in a different location on the long version.
 

        

429 Bellhousing/Related Components

Comparison of the 429 (left) to the 351C (right)  C6 transmission bell housing. As can be seen from this photo - if you want to drop a 429 into your 351 C equipped car, you will have to change the trans as well. The C6 Inspection Plate is shown at center and the block plate (which fits between trans and engine) is at right. The C6 used a C8VE-7007-A block plate which was replaced by D1AZ-7007-A.

To Paint or Not to Paint?

Did Ford paint the block plate Ford blue? We have some clues in the photo above from this original 1971 Boss 351 block/4 speed plate. Blue paint is visible (under the grease) on this plate on the portion facing forward in car (starter side). No blue paint was evident on the transmission side. This suggests the plate was installed on the engine with the 4 speed bellhousing bolted on when the engine was painted. In addition, the bellhousing from this same car had Ford Blue overspray all around the portion of the bellhousing which bolts to the engine, with all of the bellhousing rearward natural, unpainted metal. We have yet to find an untouched 71 429 Mustang/Cougar version, but this at least shows what process Ford used on the 71 Boss 351.
 

Cast Iron Tailshaft

The 71 429 CJ/SCJ Mustang/Cougar C6 came with a cast iron tail housing as shown above.
 

Correct C6 trans Shifter and Kick down rod Links

The photos above show the correct shifter and trans kick down links for the 71 429 CJ/SCJ Mustang C6.

C6 Dipstick

The correct dipstick for the 71 429 CJ/SCJ C6 is part # D1OP-7A020-AB. Note the yellow paint code dot on the dipstick tube (reproduced at left, original at center and right).
 

Vacuum Modulator Line              

C5AZ for CJ with Quadrajet

The CJ w/C6 trans used a unique kickdown rod return spring which was connected as shown to the rod itself. The other end of the spring hooked into an eyelet on the throttle bracket (see below).

D1AZ for 429 SCJ with Holley

The SCJ's return spring was located in the normal location, along the side of the Holley's throttle lever as shown above.

Kickdown Rods for C6

There were two C6 kickdown rods - one for the CJ with the Rochestor carburetor, D1ZZ-7A187-H (above left)  and one for the SCJ with the Holley carburetor, D1ZZ-7A187-K (above right). The two rods are similar in that they each have a bend to avoid the carb secondary linkage. However, they are in fact, different designs. The CJ rod has a small hole in it to hook up a return spring which attached to the rear of the throttle bracket as shown in the photo above center. The SCJ rod did not have this hole. Also, based on a side by side comparision of an original CJ and SCJ rod, several other minor differences are noted: 1) There is a  slight difference in the offset between end points, 2) there is a small difference in length in the area that dives down from the intake to the trans and 3) the bends at the trans end occur at slightly different points. Note the SCJ kickdown rod is coded with a green paint marking and CJ with a pink paint marking. 

Comparison photos of the 429 CJ/SCJ Mustang kickdown rods are shown below. The photo below left shows a repro CJ (made identically from an original 71 429 CJ Mustang sample) compared to an original 71 429 SCJ Mustang sample. At center, the same two rods from another angle. Photo at right shows a comparision of a CJ and SCJ rod on original cars;

Megasite friend John Van Heertum has  worked with members of our group to borrow their original CJ and SCJ rods to be able to make us correct reproductions. We really appreciate John doing this! Anyone interested in obtaining one of these rods, please contact John at this e-mail address; jovahe@verizon.net  

Detailing notes: Although not necessarily shown in all the photos on this page, the correct detailing for the 4 speed is as follows;

• The shifter rods were phosphate & oil.
• The levers that bolt to the case were painted black.
•  The bell housing should be Ford blue.
• The transmission case a natural cast color.
  

The Toploader

In the photo at left is the correct Hurst Shifter for the 71 429 CJ/SCJ Mustang. At center are two detail shots of the toploader. Below is an exploded view showing the components of the clutch mechanism and how it assembles. 4 Speed Blockplate lower right - part #C9AZ-7007-B, and an undercarriage view of the sheet metal the shifter mounts to.

Bellhousing

429 Z-Bar and Clutch Mechanism

These two photos above are of the '71 429 SCJ Mustang Z-bar bracket. Note the third photo from the left shows how a  repro (that was once available) looks somewhat different from the original. Note that the 429 Mustang Z -Bar bracket (Part #D1ZZ-7A572B) is different than the version used on the 351 Cleveland and is a very hard piece to find. At far right is the 71 429 Mustang clutch fork. Other photos above and below show the Z-Bar bracket installed and other views of the 429 Mustang clutch mechanism.

4 Speed T-Handle

The 71 429 4 speed  Mustang/Cougar came with a Hurst Shifter T Handle. Above left is an original T-Handle and an installed view is at center. At right is a comparison between a repro and an NOS handle. At top is shown the repro T - Handle and at bottom an NOS. Note the NOS has a more polished look and sharper numbers than the repro.

Update 2013 -  Pat Whalen (Thank you!) has created this tutorial on how to determine if a Hurst T-Handle is an original or a reproduction: Tutorial on Determining an Original Hurst T Handle

4 Speed Linkage

Below are photos from below showing the shifter linkage hookup;

Shifter Boot

The correct shift boot for the '71 4 speed Mustang is shown above. After years of use, many car's boots have split or torn along the bellows parting line from movement of the shifter. Unfortunately, this correct version with the correct rounded edge (as shown above), is not in reproduction. If you can find an NOS one, they are very expensive. The part number is D1ZZ -7277-B.  Note that the 72 - 73 boot looks very similar to the 71, but it has a round hole for the shifter to come through instead of the rectangular slot used on the 71. Additional photos of the correct '71 boot are shown below;

Backup Switch for 4 Speed Toploader

Part number D0ZZ-15520-A.

Flywheel

This is the Flywheel used for the 429 CJ/SCJ. It is part number C9AE-6375-C. The outer diameter measurement is shown at right.
 

4 Speed VIN Location

The VIN is usually stamped on the front rail of the trans case, but  may have been located anywhere along the front rail and not necessarily to the left hand side as seen here. The numbers on this case are 1F136578 indicating a 1971 Dearborn built Mustang. The body style and engine code are not stamped. This lack of body and engine code numbers is typical of 95 percent of all transmissions. The case shown is most likely from a 429 SCJ since it still had the Speedo gear reducer in place when purchased. 

Trans ID Tag

This is the 4 speed trans ID tag located on the trans case. The 71 429 Mustang had either a RUG-AZ or RUG-AZ-1 ID code on this tag.

Lower Dust Boot

Shown above is an original lower dust boot for the 71 429 Mustang/Boss 351 factory Hurst shifter. The one shown below is a '70 repro, but is somewhat similar to the '71 and expanded so you can better see what the shape looks like. The 71 Mustang used one with a D1ZA part number. 

Hurst Adapter Plate

The Hurst adapter plate was used with the 1971 CJ and SCJ  4 Speed transmissions. This plate bolts to the tail housing and the Hurst shifter is then bolted to it. These are unique to the 71 Big Block Mustangs and are extremely rare. 

 4 Speed Shifter Bezel Filler Plate

4 Speed Cross Member

The 4 speed cross member (D1ZZ-6A023-B) is a different design from the version used on the C6. The diagram above shows the difference between the two and the installation with mount.

71 429 Mustang Clutch/Brake Pedal Assembly

Clutch Fork Boot

This boot covers the clutch fork and prevents contamination from road spray.

Speedometer Gear Reducer

This small gear box is the (Drag Pak) Speedo Gear Reducer that was used on all SCJ's. It was fitted on the trans, on the end of the speedo cable. The one shown at left  is the C6 trans version (C8ZZ-17294-A). The 4-Speed version (C9ZZ-17294-A), shown at right, was made at a 90 degree angle (L shaped) for a better fit, as opposed to the straight body for the C6. These gear boxes allowed the speedometer to read correctly with the low rear end gears of the SCJ, (3.91 or 4.11). The gear box required a special "Drag Pak" speedo cable that had a screw-on end which screwed onto the threaded portion of the gear box. The regular non-Drag Pak cable had the standard press into the side of the trans fit. The C6 reducer is shown below in an installed view in an original 71 429 SCJ Mustang C6. 

Speedometer Cable

This is the special speedometer cable used with 429 SCJ Drag Pack Speedo adaptor. Note the special threaded fitting (at red arrow) that attaches to the Speedo adaptor. The D1ZF-17260-DA, EA or EB were used with the C6 and D1ZF-17260-EA, FA or FB were used on the 4 speed. A view of a non-drag pack speedo installed in a C6 housing is shown below.