Restoration
4-speed transmission

The name Hurst will forever be linked to the 4-speed transmission. Though in production prior to the 1964 introduction of the GTO, the coupling of the two validated the performance of one another. Today, the 4-speed transmission and Hurst shifter continue to dominate the drivetrains of musclecars.


Talk to any number of musclecar enthusiasts and most will recite moments of frustration with their 4-speed transmissions. At that all-important moment, running hard, side-by-side, a shift was missed and the other guy won. After being run hard for many years, it is not necessarily the transmission's fault—it is likely just an out-of-adjustment shifter, the mechanical one, not the one behind the wheel. We recently spent some time with fellow racer and "shifty character" Bill Baker to gain some insights into methods of keeping your 4-speed shifter on the mend. Baker has been rebuilding transmissions for decades.

Skill Level
Anyone with average mechanical skills utilizing normal hand tools can perform the checks, repairs and updates that we will demonstrate here. Welding may be required for some repair. The work is more easily performed with the transmission out of the car, but you can perform this Hurst 4-speed shifter tune-up with the transmission in your car. You may, however, need to remove the shifter and linkage as you make the necessary repairs.


Before any disassembly, take a good look at your shifter linkage as installed on the transmission. Give each of the shifter rods a jiggle and note the looseness of the rods. When reassembled, this rod shake will be nearly eliminated.

Shift Levers
One of the main wear items and one most overlooked are the shift levers that attach to the transmission. On hard 1-2 power shifts, wear occurs that diminishes the ability of the shift detent in the transmission to return to Neutral. To troubleshoot this problem, first place your shifter in Neutral then insert an alignment tool (1/4-inch rod or drill bit) at the base of the shifter, aligning the three shifter levers. With your transmission now in Neutral, remove the alignment tool. Shift your transmission up into 1st gear, down into 2nd gear then return to Neutral. Place your alignment tool back in place at the bottom of the shifter. If this does not go in without interference, the likely culprit is worn shift levers at the transmission.


The lever nearest the front of the transmission receives the most wear (that hard 1-2 power shift) and is usually the culprit. Its rectangular hole becomes widened top and bottom giving the appearance of a bow tie. This slop prohibits the internals from returning to the correct Neutral position resulting in missed shifts or hard engagement. The quick and easy fix is to just swap the two levers, as the rear lever receives the least amount of wear. But this quick fix is only a short-term fix. You'll be back to complete the repair later.


Both of the levers on Bill's transmission required fixing. Depending on the amount of wear, there are two fixes easily performed. In the worst case, you will need to braze or weld the worn areas then file fit each hole to fit back onto the transmission. If the lever is not worn too bad you can reshape the hole by using a hammer and center punch. Lay the lever on an anvil (the back of your vise) and make punches around the perimeter of the hole. This will swell the metal back into place. With these levers fixed, you can be assured of positive engagement and disengagement of the gears.

Continued on Page 2

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Photo Guide
muncie m-20 wide ratio 4-speed transmission
The Muncie M-20 wide ratio 4-speed transmission equipped with the Hurst Competition Plus shifter. The shift rods were loose. After inspecting the linkage, it was time for disassembly. Note that there are no shifter stops on this factory-installed shifter.

Here is the worn forward shift lever removed from the transmission. You can see the spread area caused by numerous hard 1-2 power shifts. This increased interior dimension can result in the transmission detents not returning to Neutral.
transmission repair
With the damaged area brazed to fill the spread/worn area, hand file the shift lever back to its original size. Take your time, file and test-fit the lever until you have it right and tight being careful to not remove too much of the material.
shift lever repair
File fit back to its original interior dimensions the shift lever is ready to be installed.
worn shift lever 4-speed trans
In some instances, where the shift lever is not too worn or elongated, the metal can be swelled back to size using a center punch and ball peen hammer.
competition plus shifter
The Competition Plus shifter has holes correctly located front and back on the shifter body, properly positioned and ready to be drilled and tapped for the installation of shifter stop bolts.
shifter repair and replacement
The final drill size for the 3/8x24 thread tap is 21/64. Securely clamp the shifter in a vise. First use a pilot drill and then the 21/64 drill. Go slow to ensure a clean circular hole for the thread tap.
4-speed transmission tech
Tap the drilled hole with the 3/8x24 thread tap making certain to lubricate the tap as you create the thread. After the hole is tapped, use some carb cleaner and compressed air to clean any remaining filing from the shifter before installing the stop bolts.
shifter stop bolts
The shifter stop bolts are 1-1/2-inch 3/8x24 thread bolts. A jam nut is utilized to lock the bolt in place after adjustment.
shifter stop bolts install
With the shifter stop bolts installed you have successfully upgraded your shifter. Time to reinstall the shifter, upgrade the fasteners and adjust thing right.

Here is the standard wave spring washer compared to the new heavier spring washer used in connecting the shift rods to the transmission shift levers. The new heavier wave spring washers eliminate the rod rattle.
transmission shift lever install
The transmission shift levers are first installed onto the side case with new, hardened washers and lock nuts. Next, the shift rods are attached to the levers utilizing the new wave spring washers and nuts.
shift lever in neutral
With the transmission in Neutral, the shifter is placed in Neutral with the alignment tool in place to assure position.
shift rods and shift lever
Secure the shift rods to the shifter levers. Adding hardened washers reduces the slop in the linkage. Make certain to bend up the end of each spring clip for good insurance.
set shifter bolt stops
With the linkage assembled, it's time to set the shifter bolt stops. The front bolt stop is for 2nd and 4th gears while the rear bolt stop is for 1st and 3rd gears. To adjust the stops, place the transmission firmly into gear. By hand, run the bolt up until it touches the shifter lever then back the bolt out one complete turn and tighten the jam nut. Repeat for the other stop.
shift rods attached to transmission levers
The shift rods are now firmly attached to the transmission levers and the shifter. With the shifter stop bolts adjusted you can be assured of minimal wear on the transmission shift levers. You're now officially a shifty character.



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