GM TH700-R4 Transmission Rebuild - The 700 Club
Monster 700-R4 Rebuild
From the March, 2011 issue of Chevy High Performance
By Sean Haggai
Photography by Sean Haggai
Getting the best out of something usually means taking something else out of the equation to get it; a little give and take, if you will. For instance, in order to get a small-block to create big-block-like grunt would require a camshaft spec so big, it would be nearly impossible to drive on a daily basis. Adding steeper rearend gears will help accelerate your car harder at the lights, but it wouldn’t make for an ideal cruiser during sustained freeway hauls. Traditionally, the same adage went with automatic transmissions too; they were either great at the track or on the street, but never both.
Purchasing a new performance...
Purchasing a new performance transmission can be an expensive endeavor. In our case, this 700-R4 core was pulled out of a vehicle, making it the perfect overhaul project and a way to get a performance four-speed without spending a ton of cash. Through the identifying casting numbers, we determined it was an early ’90s 700-R4 with an electronic lockup and ordered a master overhaul kit from Monster.
Automatic transmissions, namely the GM TH700-R4, were widely used and often found in LT-1powered Corvettes to work trucks. Unfortunately, these were never known for their strength and would tend to self destruct with any significant amount of horsepower. On the other hand, their First and Second gear (3.06:1, 1.63:1) ratios are lower than the gears found in the more common TH350 and TH400. This made First and Second gear shifts much quicker, ultimately helping to accelerate the vehicle. Added features included lighter internal components, which created less drag on the engine, and add in the overdriven Fourth gear with a 0.70:1 ratio and the 700-R4 had the great potential for increased fuel economy.
If you’re looking to install one for yourself, but worried about its inherent weaknesses you’ll be happy to know that Monster Transmissions has the solution. These days, it’s possible to have a smooth, durable, and strong four-speed transmission that can handle the added power, all the while providing lightning quick and positive shifts at the track. To do this, Monster Transmissions packs some serious gear when it comes to retrofitting these four-speeds. Monster’s Monster-In-a-Box kit came with everything we needed to rebuild our 700, including the five-pin front and rear planetary gear sets, a Corvette Second gear servo, Teflon pump bushings, superior shift reprogramming kit, heavy-duty sprag, and a chrome pan. It even came with all the incidentals like the gaskets, seal, and O-rings. Should you need a converter, Monster can supply that too. In our case, we added a 2,600-2,800 stall torque converter.
To get it all done correctly, we headed over to Reb’s Specialites in Reseda, California, where Brian Kardell tore the transmission down to the case, cleaned all the reusable components and installed the entire Monster kit.
The SS Mega Monster rebuild kit includes:
-Rear heavy-duty five-pinion planetary
-Front heavy-duty five-pinion planetary
- Chrome transmission pan with drain plug
-700-R4 Corvette Second gear servo
-700-R4 billet servo Fourth gear and cover
-0.500 boost valve
-Alto Kolene steel kit
-Alto Red Eagle clutch kit
-700-R4 Alto wide high-performance band
-Teflon pump bushing
-Delco front seal retainer clip
-700-R4 Superior shift reprogramming kit
-Hardened pump rings
-700-R4 10 Vane rotor gear
-700-R4 10 Vane rotor guide
-700-R4 high-rev Vanes
-700-R4 heavy-duty throttle valvespring
-Heavy-duty Beast sun shell
-Heavy-duty 28 element Sprag
We started at the rear of...
We started at the rear of the transmission by removing the governor and the speedometer gears.
Releasing the clip, we pulled...
Releasing the clip, we pulled out the factory servos. Monster’s kit provides a Corvette Second gear servo as well as a billet Fourth gear servo and all new seals.
To gain access to the rest...
To gain access to the rest of the components inside the transmission, we removed the seven bolts on the front pump assembly from inside the bellhousing. The converter splines into this pump and creates oil pressure for the transmission. Once that was removed, we flipped the transmission over and removed the pan with the old gasket. Monster supplied a custom oil pan with gasket so the old one can be tossed out.
With the bottom of the transmission...
With the bottom of the transmission uncovered, we removed the transmission filter, filler tube, lockup solenoid, and valve body (10mm bolts). The filler tube softens the gear change; it’s what differentiates the early and late-model 700 transmissions.
We then removed the clutch...
We then removed the clutch assembly, along with all of the friction and steel plates. If you look closely, you’ll notice the black coloring on this friction plate, which shows excessive heat.
A quick rinse in the parts...
A quick rinse in the parts cleaner removed all of the old fluid and dirt from the components as well as the transmission case. Cleaned parts are essential and will keep contaminants and materials out of the transmission.
Five-pin Front & Rear Planetary Gear
Both the front and rear planetary gears are substantially larger and stronger than the factory 700-R4 units from GM. While the factory units only had four pinions, the Monster units have five. The additional pinion allows for a greater load capacity and increases its strength.
Rear Planetary Gears New(left)...
Rear Planetary Gears New(left) and Old(right)
Front Planetary Gears New(left)...
Front Planetary Gears New(left) and Old(right)
In the transmission, servos serve as a direct link between increasing pressure to hold power and to reduce slippage. Monster supplies two servos, one for Second gear and another for Fourth, and they both apply the band onto the direct drum. Both supplied servos have larger piston diameters than the factory, which allow for more clamping force for the band to the drum.
Working from the outside in,...
Working from the outside in, Brian started by installing the shift linkage first; once we install the park rod actuator, the transmission can be placed in park and will prevent the transmission from trying to spin. The piston shown here actuates Reverse and First gear. Monster also supplied fresh seals for the clutch pack.
The small springs inside the...
The small springs inside the sprag can wear out over time and Monster’s kit includes them for replacement. The sprag itself fits into the roller clutch while the inner race fits inside the sprag. Make note that the sprag will only rotate one way depending on how you hold it.
Alto Red race friction clutch...
Alto Red race friction clutch plates as well as Alto Koleen (heat-treated) steels are supplied with the rebuild kit. Since the friction clutches only work when they are exposed to transmission fluid, they need to be soaked in fluid prior to installation; this will prevent any damage occurring to the friction clutches before fluid reaches them. It’s also important to mention that, for every friction plate, a steel one is added.
Monster’s kit also replaces...
Monster’s kit also replaces the factory sun shell with its own proprietary design. It features additional teeth to engage the clutch pack and is able to transmit more power to the sun gear. The shell’s also thicker and has smaller windows to allow for less deflection.
The shift kit from Monster...
The shift kit from Monster is a major portion of the rebuild. It requires specific placement of check balls, springs, and pistons in the valve body, along with drilling several holes into the valve body spacer. This allows increased oil flow to create higher line pressure for firmer shifts. As noted earlier, Monster’s supplies the correct valve body gaskets and they’re appropriately labeled “V” and “C’ for its proper location.
The Alto heavy-duty band is...
The Alto heavy-duty band is a new unit that’s wider to provide greater torque capacity and more positive First-Second shifts. The anchor area on these bands is extra thick and heat treated to eliminate stretching or breaking.
To finish off the rebuild,...
To finish off the rebuild, we installed the new oil pan gasket as well as the new custom-engraved Monster oil pan. Then, we lined up the 2,600- to 2,800-rpm torque converter to complete the package.
19370 Oliver St.