Converting a 1967 Pontiac Safari Station wagon from an automatic to a 4-speed
Manual transmissions are a lot more fun than automatics, especially in a 60’s-era classic car. The 4-speed is the transmission of choice among muscle car owners. This tech article will describe how I converted my 67 “Grand Prix” Safari station wagon to a 4-speed.
A note beforehand: Beginning in 1964, GM started to consolidate their vehicle platforms. This means that most chassis and suspension pieces were interchangeable between makes (Chevy, Pontiac, Buick, Olds, etc.). Unfortunately for me, this did not apply to the full-size cars (B-body) until 1971. That means that there are major differences between my “GP” and, say, an Impala. This required me to either find (and pay for) the correct Pontiac components, or to make some modifications to the more readily available Chevy parts. I chose the less-expensive route, and this complicates the swap somewhat.
Some of the major components required for the swap: the transmission (note the long-tail Muncie), the bell housing and clutch, and the pedal assembly
The first thing I did was to rebuild the Muncie. This is a fairly simple process in concept; 4-speed transmissions aren’t very complex. The only special tool required is a sturdy pair of snap-ring pliers, and Second gear has a sleeve that must be pressed onto the shaft. Just get your hands on a service manual and follow the instructions. Getting all of those needle bearings to stay in place takes some patience!
As stated above, the pedal assembly I had was from a 65 Impala. The brake pedal is significantly different from the Pontiac, and would not have cleared the steering column, so instead of using the Chevy brake pedal, I took a spare automatic transmission brake pedal from a 67 Grand Prix (exactly the same as the original brake pedal in my car) and trimmed the face of the pedal down to match the Chevy clutch pedal (see photo below).
Here, you can see the modified Pontiac brake pedal, with the Chevy clutch pedal installed with it. The circle on the brake pedal was at the center of the pedal before modification. Note that the support brackets are the same; they just look different due to the angle of the photograph.
I did have to weld a piece of metal to the top edge of the pedal face, in order for the brake and clutch pedals to line up with each other. This allowed me to keep the original pedal ratio on the brake system. The automatic-transmission equipped Pontiacs use a 7/16” bolt as the pivot point of the pedal. There is a metal bushing inserted in the pivot hole of the pedal, and the bolt passes through this bushing. The Chevy manual transmission pedal assembly uses a shaft attached to the top of the clutch pedal as the pivot. In order to make this work, I had to remove the bushing from the modified Pontiac brake pedal (it is a simple slip fit, so it just falls right out), and I had to drill the pivot hole in the support bracket so that the Chevy pivot shaft would fit through. Without the bushing, the pivot hole in the top of the Pontiac brake pedal is the same size as the Chevy pivot hole. The Pontiac support bracket has a slot cut out of it for a clutch pedal stop. This did not line up correctly with the bracket on the Chevy pedal, so I had to remove the bracket, reposition it to fit the Pontiac slot, and re-weld it in place. I was able to do this and still keep the attachment hole for the pedal-to-Z-bar rod in the factory (Chevy) location (see photo below). Once the pedals were installed, they look factory and hang in the correct location.
This is the Chevy clutch pedal after the bracket was relocated and re-welded to fit the Pontiac support bracket
Obviously, the first thing that has to be done to the car is the removal of the automatic transmission and its related components. Simply follow service manual instructions to remove the transmission, the flexplate, the cooler lines, the vacuum modulator line (don’t forget to plug the port in the intake!), and the shift linkage.
Since I used modified Chevy pedals, and I had drilled the support bracket as explained above, I had to remove the original support bracket and install the modified one. This may not be necessary if you use factory Pontiac pedals. I have done a few other 4-speed conversions (On GM A-, G- and X-body vehicles, not full-size cars), and when I have used factory parts, I simply removed the pivot bolt and hung the pedals with no modifications. Removal of the support bracket required me to remove the A/C ductwork and drop the steering column down (when I dropped the column, I also removed the firewall plate that attaches to the column. Modification of this plate will be covered later). I then removed the 4 nuts that hold the support bracket to the firewall (these also hold the power brake booster to the other side of the firewall), and pulled the bracket and brake pedal assembly out of the car. While I was under the dash, I also removed the Turbo 400 kickdown switch that is attached to the accelerator pedal linkage.
Installing the flywheel, clutch assembly, bell housing and transmission is very straightforward. Again, factory service manual procedures can be followed. Remember that the bolts that hold the standard-transmission flywheel to the crank are longer than the flexplate bolts that were just removed. I bought grade 8 bolts from a local hardware store that were ¼-inch longer than the flexplate bolts. Also, don’t forget to install a clutch pilot bushing or bearing. (Note: I have been told that some Pontiac crankshafts are not machined for a pilot bushing. You should verify this before beginning the project. The only un-machined GM cranks I have personally seen have been Oldsmobile. Even Buick, who rarely installed manual transmissions, machined their cranks.) When installing the clutch, I like to use an old input shaft to align the disc and the pilot bearing rather than the plastic pilot tool provided with the clutch set. I have found that the plastic tools are not very accurate, and I have had trouble installing a transmission after aligning the clutch with such a tool. Also note that the transmission mount off of the TH400 may or may not fit the Muncie. I believe that the OE mounts are different (the TH400 mounting bolts are further apart than the Muncie), but all of the replacement parts I have seen have oval holes to fit either transmission. Such was the case with my car, so I didn’t have to replace the mount. This is also a good time to replace those 35-year-old U-joints. Don’t forget to fill the transmission with gear oil!
Once the transmission was bolted in, I turned my attention to the clutch linkage. In order to mount the Z-bar, there is a pivot ball that screws into the side of the block above the starter (OE full-size Pontiacs use a bracket bolted to the bell housing to support the pivot), and a bracket must be welded to the frame rail opposite this pivot to support the other end of the Z-bar. I had a bracket off of a 69 Roadrunner handy, so I simply welded that to the frame in the appropriate location (I did this previously, when I had the left front fender off of the car). Using the pivot in the block places the Z-bar very close to the steering box; this is probably why the factory used the bell housing-mounted pivot. I did not have any problems clearing the steering box, however.
As mentioned above, I removed the firewall plate that surrounds the steering column. From the factory, the manual-transmission cars used a different plate with a hole in it for the clutch rod to pass through. I simply cut the existing piece to provide that hole. There is a cutout on the firewall that can be used as a guide for where to trim the plate.
I am not familiar with the OE clutch linkage setup on a full-size Pontiac, but using the Chevy linkage presented a couple of problems. First, the arms on the Z-bar did not sit where I needed them. I had to cut off the lower arm and relocate it approximately 30 degrees to make it fit (see photo below). Second, the pedal-to-Z-bar rod on the Chevy was straight and would not clear the power brake booster on my Pontiac (probably another reason Pontiac located the Z-bar further back). I had to heat up the rod and arc it to pass underneath the booster. Once these modifications were made, the clutch linkage fit together nicely.
This is the Z-bar prior to modification. I cut of the lower arm (top of the photo) and relocated it to point almost exactly the opposite direction as the upper arm
The next objective was to cut the hole for the shifter. To do this, I simply located the shifter mounting holes in the tail housing of the transmission and drilled a hole in the floor at that location. I then cut a small hole, and gradually increased the size of the hole until the shifter body fit through it. I covered the hole and shifter with a factory floor plate off of a 69 GTO. It fit the full-size car transmission tunnel with some minor modifications. Then I mounted the shifter to the transmission using the provided bracket, and assembled the three shifter rods. This required some modification, as this was a “Universal GM” shifter kit (of course, I had long since lost the instructions). I had to heat and bend the 1-2 and the 3-4 rods, and the reverse rod didn’t fit at all. Fortunately, I had an OE reverse rod that I was able to use with this shifter.
Once all of the adjustments were made to the clutch and shifter linkage, it was time to take the car for a road test! Since the conversion, I have had to make some minor clutch linkage adjustments (see the notes below), but the station wagon drives like a totally different car!
I have not installed the finishing touches on this conversion yet. I need to install a shift boot, a firewall boot, and the pedal pads on the brake and clutch pedals. I also need to bypass the neutral safety switch and install a back-up light switch. I will probably just install an aftermarket back-up light switch, available through Hurst. I am going to use Chevy pedal pads, as I modified my Pontiac brake pedal to match the Chevy. Only the small (and lucky) group of factory stick shift full-size Pontiac owners will ever know the difference. I also need to locate a floor shift collar for my steering column, and I am going to remove the lens on the shift indicator in the dash and paint it black so you can’t see the “PRNDL” lettering from the automatic. Most of this will happen when I re-do the interior of the car (as you can see in the photos, it needs lots of help!)
This is a photo of the interior before I began the conversion. Note the automatic shift lever and brake pedal, as well as the indicator on the dash. The sticky note tells me how far off the speedo is at a given speed.
Here is the same view after the swap. Nothing is as cool as a Hurst shifter sticking through the floor, even in a station wagon! The 69 GTO floor plate can also be seen in this photo
A few notes: