Does a Turbo 400 have a kick down cable?

When the Turbo 400 began reaching production models in the late ’60s, its kickdown switch was mounted on or near the carburetor. It was, however, relocated to the passenger compartment and mounted on the throttle pedal in later years.

What should I do about my TH400 transmission?

Replace the filter and fill the transmission with new ATF (the TH400 requires six quarts). Do not put the bolts back on too tightly, as the gasket can become damaged.

Why does my TH400 downshift when under load?

When the engine is under load and vac is low, the line pressure in the trans will go up. This increases the holding power of the clutch packs, increases oil flow to the torque converter, and delays the shift. If you disconnect the vacuum to the modulator the pressure in the trans will go to max and the trans will shift later and harsher.

What are the signs of a transmission problem?

Some signs of issues include slipping while shifting or accelerating, loud noises, slushy shifting or difficulty putting the vehicle into gear. Check the fluid level. The first thing to check if you suspect that the transmission is acting up is the automatic transmission fluid (ATF) level in the transmission itself.

How to troubleshoot a Turbo Hydramatic 400 transmission?

Check the linkages. The linkages that are connected to the shift lever can get out of alignment at times, causing sloppy or difficult shifter response. Look for abnormalities such as bent or broken parts, loose attachment points, or blockages that would prevent smooth shifting. Change the filter.

What’s the gear ratio on a GM TH400?

Aluminum and iron construction. Weighs 135 pounds without fluid. Bell housing integrated into the transmission. First gear: 2.48:1, Reverse gear: 2.08:1, and third gear is an even 1 to 1. Came with three tail shaft lengths. The Turbo 400 transmission can be identified in the following ways:

What causes a Turbo 350 trans to not shift out of first gear?

Turbo 350 trans won’t upshift from first gear. Discussion in ‘ The Hokey Ass Message Board ‘ started by todd_a, Apr 28, 2010 . What would cause a turbo 350 to not shift out of 1st gear? It has plenty of fluid. It has vacuum to the hose to the vacuum modulator. That vacuum hose is brand new so not cracked or anything. It does reverse and 1st fine.

When did GM change the name of the TH400 transmission?

The naming of the TH400 was changed to 3L80 (3-speeds, Longitudinally positioned, 8000 lbs. GVW or Gross Vehicle Weight) in 1990 to make it easier for buyers to identify the transmission. The change in naming does not come as surprise since some GM transmissions were also renamed (for example the 700R4 to 4L60).

Is the GM TH400 transmission compatible with Buick engines?

The TH400 is compatible in Buick engines especially when you use a Buick V8 or V6 version of the transmission. The TH400 may have offered improved performance over its predecessor, the ST300, but it still came with its own problems.