Hydra-Matic Transmission (MD8) General Motors

Considering overhauling your Chevrolet transmission or just need GM 700R4 parts? We provide a large inventory selection for 700R4 automatic transmission overhaul kits, parts including steels, kits, solenoids, filters, solenoids. This wide selection of parts are used in the GM 700R4 automatic transmission in GM model years 1982 to 1993 Chevy light duty trucks and passenger cars. In addition to these kits we also supply torque converters, fluids, problem prevention kits and in most cases we can supply good take out hard parts and save you some money.

Free information is provided on parts illustrations, maintenance tips, overhaul tips and assistance in identifying just what automatic transmission you have in your vehicle. In addition a factory description and ratio information is available. 

Torque Converter ---------- Torque Converter Problem & Information For this series transmission there are MANY different possible torque converters (not all listed here). When rebuilding your transmission it is always recommended that you change the torque converter. When ordering the torque converter you must supply the four digit code off of the existing unit (located on a sticker). Some of the possibilities are:						Torque Converter Installation/Preparation
Code	Order Part Number		Application	Price
C33	NATC33C		Small Bowl 10" Code: HD, HJ, HE, SJ 1980-96: 2.8L, 3.1L and 3.4L low stall	$20123
C35	NATC35		Small Bowl 10" Code: HA, HB, HK, HZ, SZ 1980-1996 2.5L, 2.8L high stall	$156.33
The following modifications are also available for above converters: HD Heavy Duty Designed for heavy duty applications with stock stall speeds. Caged Allison bearing to resist heat & fully brazed to resist loads. Dummy Dummy Stock converter with the lockup function removed. Remember to install the non-lockup conversion valve part number 37921-TG
C21	NATC21		Large Bowl 12" Code: CG, CF, CK low stall 1980-84E, 5.oL, 5.7L Non-turbo, pads may be round or square	$219.10
C24	NATC24		Large Bowl 12" Code: CB, CE high stall 1980-1984E 4.3L, 5.0L turbo, pads may be round or square, use C24HP in Corvette	$145.76
C40	NATC40		Large Bowl 12" Code: DG,DF, DK, low stall, 1984L-1992 5.0L, 5.7L: Use C40HDT in trucks 1984L-1994 pads may be round or square	$203.25
C48	NATC48		Large Bowl 12" Code: DB, DE, high stall, 1984L-1994 4.3L, 5.0L, Turbo, Use C48HP in Corvette, pads may be round or square	$156.33		Be sure to use our transmission cooling line flush in order to remove debris. Your cost is $11.88 order Kooler Kleen.
C40HDT			Large Bowl 12" Code: DG, DF, DK, low stall 1992-1994: 5.0L, 5.7L, Trucks 1987-1994: will retro to 1984L Heavy duty bearing and turbine hub	$203.25
C48HDT			Large Bowl 12" Code: DB, DE 1992-1994: 4.3L, 5.0L Turbo; use C48HDTHP in Corvette: will retro to 1984L Heavy duty bearing and turbine hub	$202.74
C37			Large Bowl 12" Code: 1980-E84; 6.2L Diesel May us C21SQ (square pad) design as an upgrade	$156.33
C39			Large Bowl 12" Code: 1984L-86 6.2L Diesel May us C21SQ (square pad) design as an upgrade	$156.33
The following modifications are also available for above converters: HD Heavy Duty Designed for heavy duty applications with stock stall speeds. Caged Allison bearing to resist heat & fully brazed to resist loads. RV Low Stall Reprogrammed for towing applications & fuel economy. Caged Allison bearing to resist heat & fully brazed to resist loads. HDT Heavy Duty Turbine Designed for heavy duty applications with stock stall speeds. HD+Flanged turbine hub to prevent twisting. HP High Performance Factory performance stator. Designed for the Corvette and Buick Grand National. Caged Allison bearing and fully brazed vanes. Dummy Non-lockup Stock converter with the lockup function removed. Remember to install the non-lockup conversion valve part number 37921-TG We supply only high quality remanufactured torque converters, cost + $50.00 core deposit (some may be higher

These manuals are typically 50 to 85 pages and contain both troubleshooting information and data to support overhaul, such as electronic data, illustrations and specific procedures and specifications. These are professional shop manuals which will give you the capability to diagnose problems, and evaluate repair options. If you decide to have your transmission overhauled at a local shop you will be armed with detailed knowledge of problems and potential fixes. This information should allow you to get the best deal, Always compare pricing for labor. If you supply the parts and ask for warranty in the end you will save money. 

Fluid Recommendation:

 Red Line high-Temp ATF

Our Red Line high-Temp ATF --is a synthetic GL-4 gear oil for use

where Dexron III is recommended. A higher viscosity allows optimal operation at 70 degrees higher temperature, providing better torque converter efficiency. Perfect for heavily-loaded vehicles. Superior stability allows high-temperature operation without varnishing valves and clutches.


Recommended for use after overhaul, mixing with existing fluid is not recommended!

Our LubeGard "automatic transmission protectant" is recommended as an additive to improve transmission life and maintenance.

Typically contains gaskets and rubber kit, sealing rings, metal/rubber clad seals, friction plates, steel plates* , front and rear bushings, filter and where applicable Band* and/or Modulator*.

*not included if listed separately

Maintenance Tips

Regular maintenance cycles and continued checking of fluid levels is critical to the life of your transmission. Operating temperature is the single most critical parameter effecting the life of the transmission. Keep the temperature down and fluid fresh helps the units typically last a very long time under normal driving conditions (no teenagers involved). We can supply a couple of aftermarket products to help you get the most out of your transmission:

Auxiliary Transmission Oil Cooler.

The Truco part number LPD4451 is an excellent auxiliary oil cooler to provide additional cooling capacity. The kit includes all parts required to mount the unit and connect to existing cooling lines. This is a typical do it yourself project. The unit typically mounts in front of the radiator. Your cost on this transmission life saving product is $54.94 plus shipping and handling.

Fluid Additive

Generally we don't recommend additives but we have found that the Lubegard "Automatic Transmission Protectant" at only $13.93 + S&H can:

Always consult and follow owners manual for maintenance intervals and requirements.

Overhaul Tips
Before you tear into the transmission, we suggest you first study the troubleshooting/overhaul manual, add a bottle of our "Automatic Transmission Protectant" and put a few miles on the vehicle. This just might free valves and governors that are possible stuck in valve bodies. Be sure to get computer trouble code(s), see owners manual for technique to acquire malfunction codes. This will be a great assistance in diagnosing possible problems.

Twenty-One Steps to Successful Transmission Repair:

1) Do your research locate any technical bulletins pertaining to your transmission, ask your dealers parts department for bulletins.

2) Clean the entire transmission, including the valve body.

3) Check pump, valve body and case for warpage.

4) Flat file pumps, valve bodies, and cases. Just a few strokes with the file to knock off high spots and handling burrs.

5) Check all pump gear clearances.

6) Check planet pinion end play and side to side motion.

7) Soak all planet assemblies.

8) Soak all friction materials for 15 - 30 minutes.

9) Make sure all steels are in usable condition or replace. Do not sand or tumble steels when used against High Energy friction materials.

10) Inspect all surfaces upon which a band will ride.

11) Replace all rotating oil control rings.

12) Check all oil control rings and rubber products in the bores for proper fit.

13) Check all major support bushings and bushings that control lub oil.

14) Pre-lubricate all bushings and thrust washers.

15) Pre-lub pumps.

16) Pre-fill torque converter.

17) Use available manuals to ensure proper specifications and clearances.

18) Set correct clutch and band clearances.

19) Take the time to set the total end play.

20) Use a torque wrench on all pumps and valve bodies.

21) Always double flush the cooling and cooling return lines to the radiator to remove particles trapped there.

Take your time, take your time, take you time!

Torque Converter Information

Failure modes for torque converters manifest themselves in different ways, slow Failure, i.e. loss of power over time, instant failure, i.e. input shaft spline failure. Following is a short list of problems, possible causes:  

The difference between stator design, look inside the converter at the larges set of spline's (stator shaft spline's). If the spline's are split then the unit has a dual element stator. Do not interchange single element and dual element converters.

Torque Converter Installation/Preparation

Many torque converter problems can be avoided with proper preparation:

1) Pre-thread converter bolts by hand to make sure there is no sign of stripped threads.

2) Check and clean crankshaft thoroughly. Change crank spacer (if applicable).

3) Use 320 grit sandpaper or Emory cloth to remove any metal shavings on crankshaft.

4) Check converter for any damage that may have occurred during shipping.

5) Pre-fill converter with a minimum of (1) quart of transmission fluid.

6) Clean all paint off the pilot using 320 grit emory cloth.

7) Apply grease, not transmission gel, on the pilot.

8) Check flexplate for cracks and be sure there is no more than .006" run out.

9) Make sure all engine dowel pins are in place and clean.

10) Make sure all electrical ground straps are properly connected.

11) Never, Never use an impact gun to install torque converter bolts. Driving a bolt into the converter cover will create a dimple on the lockup apply surface. Lockup clutch failure will occur when the lockup piston applies against and uneven surface. Grinding off on thread length from all lockup converter bolts is recommended to avert this type of failure.

Parts Illustration

  Click to enlarge Illustration