Problems With the 700R4 Transmissionsby Sam Kellenberg
The 700R4 transmission has been in use since the early 1980s, meaning a good market saturation for new, used and rebuilt transmissions and parts for this model. Many car problems can be mistaken for transmission problems, however, such as bad fuel filters, spark plug wires, catalytic converters, fan clutches and U-joints. To be sure you're identifying the correct issue, first check these common problems before turning to your transmission. Common problems in the 700R4 include: problems caused by improper TV cable hookup, overheating and valve bore wear.
Throttle Valve (TV) Cable Problems
At some point during installation, maintenance or driving, the geometry of TV cable linkage can become interrupted. This causes problems with proper shifting function, and will eventually go through the gears and will not properly regulate line rise and pressure. If these cables become disconnected, your vehicle will not be able to downshift.
Because of its reputation as a reliable transmission, the 700R4 transmission is occasionally installed on vehicles unsuitable for its class--such as trucks over a ton or vehicles used for heavy or extensive towing--which can quickly cause the transmission to overheat. Make sure that the transmission you're running is rated for your vehicle's weight, class and type of use to avoid potentially expensive and unnecessary repairs.
Valve Bore Wear
If your vehicle exhibits no lock-up, or locks up immediately after second gear, then you likely have excessive pump bore to valve clearance. This problem is caused by valve bore wear, a problem which allows oil to leak past the OEM spool and overwhelms the solenoid's exhausting capabilities. Valve bore wear may also restrict cooler flow, which can cause transmission parts to burn up.