Standard Ignition TM-23 Automatic Transmission Vacuum Modulator

Automatic Transmission Vacuum Modulator TM-23

Standard Ignition TM-23 is an automatic transmission vacuum modulator built to help match shift timing to engine load. It is a direct-fit service part for select Cadillac, Buick, Oldsmobile, Pontiac, and Chevrolet applications from the 1970s and early 1980s.

• Performance-calibrated to help align transmission shift points with engine load
• Nylon-reinforced diaphragm for durable, tear-resistant operation
• High-temperature oil seals for a secure fit and leak-resistant sealing
• 100% end-of-line tested for functional verification before release
• Cross-reference part numbers include 7R1003 and VM401

Fitment Details

• Fits 1981-1983 Cadillac Fleetwood, N/A
• Fits 1976-1978 Cadillac Fleetwood, N/A
• Fits 1977-1981 Oldsmobile 98, N/A
• Fits 1980 Buick Riviera, N/A, w/ Brown Dot; Screw Type Cap
• Fits 1980 Cadillac Commercial Chassis, N/A, From VIN 188506; w/ Calif. Emissions
• Fits 1980 Cadillac DeVille, N/A, Automatic Transmission Vacuum Modulator for use with vehicles with 2.56 or 2.73 Axle Ratio.
• Fits 1980 Cadillac Fleetwood, N/A, Automatic Transmission Vacuum Modulator for use with vehicles with 2.56 or 2.73 Axle Ratio.
• Fits 1979-1980 Oldsmobile Toronado, N/A, w/ Brown Dot
• Fits 1980 Pontiac Firebird, N/A
• Fits 1977 Pontiac Firebird, N/A
• Fits 1979 Cadillac DeVille, N/A, Automatic Transmission Vacuum Modulator fits with 2.28, 2.73 or 3.08 Axle Ratio.
• Fits 1979 Cadillac Fleetwood, N/A, Automatic Transmission Vacuum Modulator fits with 2.28, 2.73 or 3.08 Axle Ratio.
• Fits 1977-1978 Buick LeSabre, N/A
• Fits 1975 Buick LeSabre, N/A
• Fits 1977-1978 Buick Riviera, N/A
• Fits 1977-1978 Buick Riviera, N/A, Compatible with vehicles equipped with Federal Emissions.
• Fits 1977-1978 Cadillac DeVille, N/A
• Fits 1977-1978 Cadillac Eldorado, N/A, OE Style Tire Pressure Monitoring System Sensor Clip
• Fits 1977 Buick Century, N/A
• Fits 1975 Buick Century, N/A
• Fits 1977 Buick Regal, N/A
• Fits 1975 Buick Regal, N/A
• Fits 1977 Oldsmobile Custom Cruiser, N/A
• Fits 1977 Pontiac Grand LeMans, N/A
• Fits 1977 Pontiac Grand Prix, N/A
• Fits 1977 Pontiac LeMans, N/A
• Fits 1976 Cadillac Seville, N/A
• Fits 1976 Oldsmobile Toronado, N/A
• Fits 1975 Buick Skylark, N/A
• Fits 1975 Oldsmobile Cutlass, N/A
• Fits 1975 Oldsmobile Cutlass Supreme, N/A
• Fits 1975 Oldsmobile Omega, N/A
• Fits 1973 Chevrolet Monte Carlo, N/A

What This Part Helps Address

• Delayed or inconsistent automatic transmission shift timing
• Shift behavior that does not match engine vacuum or load
• Vacuum modulator leakage at the transmission
• Rough or poorly timed gear changes on older GM vehicles
• Service replacement needs for Cadillac Fleetwood, Buick Riviera, and Oldsmobile Toronado applications

Installation Notes

Verify the axle ratio, emissions package, and any listed build notes before ordering, especially on Cadillac DeVille, Cadillac Fleetwood, Buick Riviera, and Oldsmobile Toronado applications. Confirm the existing modulator style and cap type against the vehicle notes, and inspect the vacuum line and transmission case sealing surface during installation.

Quality Assurance

Standard Ignition TM-23 is built with a reinforced diaphragm, high-temperature oil seals, and end-of-line testing to confirm performance before shipment. This part cross-references Monroe Shocks & Struts (e.g., 172286, 182286) for the same application.