The Toploader’s top cover and side-mounted shifter shafts distinguish it from all other American 4-speed designs. Although there were some 3-speed transmissions manufactured, the Toploader 4-speed loaded the geartrain from the top. The T10, Muncie, Saginaw, and Chrysler A833 all used a side cover.
It is also interesting to note that this transmission used a 3-shift rail design. The shift rails kept the shift forks moving in the exact same plane as the synchronizers. All other transmissions were designed with the forks moving in an arc, and these side-cover designs allowed for more shift-fork play. The Toploader design maintains a better shift-fork geometry, reducing wear and contributing to a better shift feel.
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Ford, just like GM, used a T10 4-speed. The Toploader was introduced in Ford cars in 1964. There are several years in which both the T10 and Toploader were actually used within the same platform. The passenger- car Toploader came in three different case lengths and several spline configurations. Output shafts in early 1964–1965 cars had weak 25-spline output shafts. Later, these were revised to 28-spline output shafts.
Engines with 200 to 390 ci got 11/16-inch-diameter, 10-spline input shafts whereas the 427-, 428-, and 429-ci engines came with a huge 1 3/8-inch-diameter, 10-spline input shaft. In fact, this is the largestdiameter input shaft ever used in a passenger car manual transmission. The “big input” mainshafts also had 31-spline “big-output” transmissions.
There are many variations of main cases and extension housings sporting individual and multiple bolt patterns for shifter and engine mounting. By the mid 1970s, Tremec took over manufacturing this transmission for Ford. Overdrive versions appeared as early as 1977 in the Ford Granada and Mercury Monarch. Overdrive versions with shifters mounted on side turrets as well as top covers were made with alloy cases.
Identification of Toploader models can be confusing. After all these years, few transmissions actually have remained untouched. Most units I find have been built from bits and pieces, making it harder to distinguish what was or was not original. The Toploader had more than 100 different models based on engine, vehicle, and year. Two basic ratios were offered. The wide-ratio features a 2.78 first, 1.93 second, 1.36 third, and direct fourth. The other was the close-ratio with a 2.32 first, 1.69 second, 1.29 third, and direct fourth. The close ratio was the only ratio offered with the large-style input and output shafts. Today, you can purchase aftermarket wide-ratio input shafts in the larger style.
Tags fastened to the passenger side of the transmission tell what make and model the transmission was used in. Tags starting with the letters HEH- followed by two additional letters are typical of early 1964–1966 Models. The RUG designator was introduced in 1967 and continued into 1986. All RUG models from 1977-up are overdrive models. Top cover versions used in Bronco have the RTS designator.
Common Mainshaft Failure
Here is a common 25-spline mainshaft (right) and one with a failure (left). Often, these early 25-spline designs did not survive the shock loads of power shifts nor startingline clutch dumps. The 28- and 31-spline mainshafts were a big improvement.
Step 1: Remove Top Cover
The bearing retainer and top cover are removed. The front bearing had exploded in this transmission, and all that was left of it was the inner race. This ruined the front bearing bore of the case.
Step 2: Remove Detent Spring
With the top cover off, some units have the 1-2 detent spring exposed. Sometimes it is held down with a screw. Remove the spring and fish out the detent with a magnet.
Step 3: Remove Set Screws
Remove both set screws for the 1-2 and 3-4 forks.
Step 4: Remove 3-4 Detent Bolt
Remove the 3-4 detent bolt, spring, and detent. Again, fish them out with a magnet.
Step 5: Remove Tailhousing
Remove the four tailhousing bolts and slide the tailhousing off. Be careful not to damage the plastic speedo drive gear.
Step 6: Take Off Speedometer Gear
Remove the speedometer gear snap ring, and slide the gear off. Use a magnet and remove the anti-rotation check ball that is under the gear.
Step 7: Remove Snap Ring
Remove the rear bearing mainshaft snap ring.
Step 8: Pull 1-2 Shift Rail from Case
Once the set screw and detent have been removed from the 1-2 shift rail, slide the rail out of the back of the case.
Step 9: Punch Countershaft Out of Case
Punch the countershaft out of the case from front to rear.
Step 10: Remove Countergear Shaft from Case (Professional Mechanic Tip)
Flip the transmission over so it is lying top down. This takes the load off the countergear and allows the shaft to be easily removed. Don’t be concerned about needle bearings falling out of the case. New ones are in the rebuild kits. If you are reusing them, you may want to lay the whole assembly in a flat pan.
Step 11: Pull Input Shaft Out of Case
Flip the transmission back over. The countergear will drop down, allowing the input shaft to be pulled out of the front. Tilting the whole transmission front face downward may help keep the maindrive needle bearings from falling out of the input shaft.
Step 12: Tap Mainshaft Out of Case
Use a soft hammer to push the mainshaft out of the rear bearing. With the countergear dropped, you can almost get the rear bearing completely removed.
Step 13: Push Main Bearing Out of Case
Use a bearing clamp to support the rear bearing. This allows you to push the mainshaft out of the rear bearing completely.
Step 14: Pry Rear Bearing Out of Case
Pry the rear bearing out of the case using screwdrivers or pry bars.
Step 15: Remove 1-2 Shift Fork
Once the rear bearing and front input have been taken out of the case, you have the necessary clearance to remove the 1-2 shift fork.
Step 16: Remove 3-4 Shift Rail
Remove the 3-4 shift rail by tapping it from the rear and pulling it out from the front. Once the rail has been removed, remove the 3-4 fork as well.
Step 17: Retain Interlock Pin (Professional Mechanic Tip)
The 3-4 rail has an interlock pin. Make sure you don’t lose this pin. The interlocks that sit above and below this rail may fall out as well. If you don’t want to remove them at this time, stuff the center rail support with a paper towel.
Step 18: Remove Geartrain
With both forks and rails removed, it is now possible to remove the entire geartrain. Be careful not to catch your fingers in the case these parts are very heavy.
Step 19: Remove Countergear
Now that the geartrain is removed, the countergear can be removed as well.
Step 20: Remove Detents
Spraying the detent/interlock bores with WD40 may allow you to remove the detents more easily. Oil deposits and sludge usually can make them difficult to remove.
Step 21: Remove Rail Set Screw
Unless the reverse idler gear is damaged, rarely does this assembly need to be removed during a rebuild. To start, remove the rail set screw.
Step 22: Pull Reverse Rail from Case
Remove the reverse rail by rotating it 90-degrees clockwise to dislodge it from its own detent. Pull the rail and fork out of the case. Remove the reverse detent and spring.
Step 23: Remove Shifter Shaft
Since all the rails have been removed, it is now possible to remove all the shifter shafts. Be sure to mark which ones go in which places.
Step 24: Remove Reverse Idler Shaft
Remove the reverse idler shaft by tapping it from the front and then by pulling it out from the back. When removing this last component from the case, notice the orientation of the sliding idler gear in relation to the main idler.
Step 25: Note Orientation of Parts (Documentation Required)
Putting parts back in the wrong place causes most building errors. Notice the difference between the 3-4 fork on the left and the 1-2 fork on the right.
Step 26: Remove First Gear from Main Shaft (Documentation Required)
Pull the first gear and first-gear thrust washer off the mainshaft. Notice the direction of the 1-2 slider.
Step 27: Remove 3-4 Synchro and Parts (Critical Inspection)
Remove the 3-4 synchro snap ring, 3-4 synchronizer, and third gear. Also inspect the tip of the mainshaft for galling and wear.
Step 28: Remove Second Gear and Parts
Remove the second-gear snap ring, snap-ring spacer, and second gear.
Step 29: Remove 1-2 Synchro and Parts
Remove the 1-2 synchro snap ring and 1-2 synchro assembly. Notice the orientation of the 1-2 synchro hub. The thin edge faces towards second gear.
Step 30: Install Strut Synchro Keys (Important!)
The most common mistake in Toploader rebuilds is mixing up the synchro strut keys or dogs. The longer key on the right is the 1-2 key; the one on the left is the 3-4 key. New 1-2 keys are notched to distinguish them from 3-4 keys. Putting the long key on the 3-4 synchro will cause the unit to lock up on final assembly.
Step 31: Inspect Components (Critical Inspection)
Another overlooked wear point is the key slots. Over time, keys pound out of the slots. The pounded-out key allows the synchro ring to rotate farther than it should, and this causes a block-out shift condition. The unit requires a completely new assembly on both 3-4 and 1-2 because of this.
Both second and third gears have badly worn and broken engagement teeth. This is very common in the Toploader design. The new, modern gears have longer teeth with torque-locking angles.
This input shaft front bearing has badly damaged the gear teeth, and this gear is just too rusty.
Assembling the Toploader is basically a reversal of the disassembly techniques. I have noticed that some units have different-shape detents with a flat edge rather than conicalshape interlock pins. Other units have the same-size conical-shape interlocks and detents and still others may have different lengths. It is best to lay everything out on a flat surface and pre-fit the rail system to make sure it works properly. I find it is better to test the rail system first without anything in the way so that it is quite easy to make corrections, rather than have to remove gears and start over.
Step 1: A)Deburr and Polish Shift Rails (Professional Mechanic Tip)
Deburr and polish the shift rails. Most interlocks and detents groove and burr the shafts, so deburr and polish each rail and make sure they glide smoothly in the case.
B) Use of Aftermarket Case
We are using a new David Kee case. Be sure to prefit all polished and deburred shift rails in the case.
C) Interlock System Components and Tools
This is basically how the interlock system works: When any one rail is moved, the interlock pin is raised, preventing any other rail from moving.
You can see that the detent pin is longer than the interlock pin. If you mix them up, the unit will not shift.
Use a long screwdriver with a flattened tip as a tool to install detents and interlocks.
Step 2: A)Drill and Tap Case
Some cases have a 1-2 detent spring that is held in place by the cover. I drill and tap the case and make my own detent hold-down. I like this method better because I can fully test the transmission with the top cover off.
B) Toploader Rebuild Kit
Many companies sell a typical small-parts kit. Never throw out your old small parts. This kit had no front bearing snap ring, and the countergear needle spacers were the wrong size. The new thrust washers are nylon instead of bronze. Fortunately, these are actually what the newer units use, so they will be fine.
Step 3: Install Reverse Idler
Insert the new needles and spacers in the reverse idler assembly. Place the rear thrust washer in the case first and keep it in place with grease. It is easy to place the forward thrust washer in last after the idler shaft is supporting the idler assembly and rear washer.
Step 4: Install Shifter Shafts
After installing the reverse idler assembly, you can install the three shifter shafts with their new O-rings. Notice that the longer reverse shifter shaft faces down.
Step 5: Install Reverse Springs
Install the reverse spring and move the detent into place with your “tool.”
Step 6: Install Reverse Fork and Rail
From the top, compress the detent down and install the reverse fork and rail into place. Once in place, reinstall the reverse fork set screw.
Step 7: Install 3-4/Reverse Pin
Before installing any other gears, it is easier to install the 3-4/reverse interlock pin. Use your special tool to get it into the bore.
Step 8: Place Countergear in Case
Install the needles and spacers in the countergear and install the thrust washers as well. Drop the countergear in the case, making sure the washers stay aligned properly with the countershaft bore while the gear is sitting as low as possible.
Step 9: Position Strut Springs (Important!)
Both strut springs’ “hump” needs to be located on the same strut key in every synchro assembly. For complete synchro ring assembly instructions, refer to page 26.
Step 10: Install 1-2 Synchro Assembly
Install the 1-2 synchro assembly and snap ring, second gear, second-gear snap-ring spacer, and second gear snap ring on the main shaft.
Step 11: Install Third Gear
Now install the third gear, third-gear synchro ring, the 3-4 synchro assembly, and 3-4 synchro snap ring. Some transmissions have tighter fits than others when it comes to installing synchro assemblies.
Step 12: Install First Gear Snap Ring and Parts
Flip the whole mainshaft assembly over and install the first-gear snap ring, first gear, and first-gear thrust washer.
Step 13: Install Mainshaft into Case
The new case as well as old cases have a relief for the 1-2 slider to clear. My thumb is keeping first gear in place.
Step 14: Install 3-4 Rail Interlock
Hold the 3-4 rail interlock in place with grease.
Step 15: Slide 3-4 Rail into Position (Important!)
Locate the 3-4 fork on the shifter shaft and slide the 3-4 rail into place. Make sure to keep the rail positioned with the set-screw hole facing up.
Step 16: Install Forks and Position 1-2 Shifter Shaft
Drop the interlock in that sits between the 3-4 rail and the 1-2 rail. Position the 1-2 fork on its shifter shaft, and slide the 1-2 rail in from the back. With both forks in place, lock them in place with the set screws. Factory screws had nylon locking inserts, which may be worn. You can use blue liquid threadlocker instead.
Step 17: Reposition Case
Flip the case on its front. Use something to keep the upper geartrain in place, such as an older pinion gear.
Step 18: Press Bearing into Case
You can use a punch or pipe to press the rear bearing in place. Install both inner and outer snap rings.
Step 19: Install Steel Gear (Performance Tip)
Because the plastic gear strips out all the time, Auto Gear has reproduced the common seven-tooth gear in steel, which is similar to the black-nylon gear. It saves you the headache of pulling a transmission for a $25 part.
Step 20: Install Check Ball on Main Case
Install the check ball on the mainshaft. Slide the speedometer gear in place and secure it with a snap ring.
Step 21: Install Fourth-Gear Synchro Ring
Install the fourthgear synchro ring from the front. Apply assembly lube on the ring and stick it in place.
Step 22: Install Input Shaft (Professional Mechanic Tip)
The input shaft has some clutch teeth removed, so it can be installed from the front and clear the countergear. Position it so that the flat spot is facing the countergear.
Lay the transmission on its cover side. It makes installing the countershaft simple and fast. I’m using my left index finder to hold and feel that the countergear is in place.
Step 23: Use Sealant for 3-4 Detent Bolt
My finger points to the 3-4 detent, and the screwdriver is on the 1-2 detent. Use sealant on the 3-4 detent bolt.
Step 24: Place Sealant on Housing Bolts (Torque Fasteners)
My finger points to the 3-4 detent, and the screwdriver is on the 1-2 detent. Use sealant on the 3-4 detent bolt.
Step 25: Install Front Retaining Bolts (Performance Tip, Torque Fasteners)
The factory front retainer bolts have a serrated locking thread. These ruin the case threads, so regular grade-8 bolts were used with blue liquid threadlocker. Torque these bolts to 18 ft-lbs. Don’t forget to install the 11/16-inch case plug.
Step 26: Install Top Cover
The top cover has bolts of two different lengths. The two longer bolts are placed in their correct positions.
Here is the completed unit. Notice the special filtered vent I installed in the tail. The factory vent is that little bulged pinhole in the top cover.
Written by Paul Cangialosi and Posted with Permission of CarTechBooks