TH400 rebuild tech
(→Main case bushing replacement) |
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You must also modify the 1-2 shift valve as listed below for FULL manual shift conversion: | You must also modify the 1-2 shift valve as listed below for FULL manual shift conversion: | ||
| − | The | + | The T-400 has a over-ride shift that will shift out of low gear even if you have manually selected low. It was designed to prevent engine damage. |
You can eliminate this feature by performing the following modifications to the valve body. | You can eliminate this feature by performing the following modifications to the valve body. | ||
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==Valve body mods, automatic shifts== | ==Valve body mods, automatic shifts== | ||
| − | The | + | The T-400 has a over-ride shift that will shift out of low gear even if you have manually selected low. It was designed to prevent engine damage. |
You can eliminate this feature by performing the following modifications to the valve body. | You can eliminate this feature by performing the following modifications to the valve body. | ||
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===Drum installation=== | ===Drum installation=== | ||
| − | Then the intermediate clutch stack is assembled into the case on top of the center support. There is a snap ring that goes in the case above the pressure plate pictured. The splined case lugs here in the case are one of the weak points of a | + | Then the intermediate clutch stack is assembled into the case on top of the center support. There is a snap ring that goes in the case above the pressure plate pictured. The splined case lugs here in the case are one of the weak points of a T-400. High line pressure, harsh shift calibration, and fatigue cause the lugs to break here. TransGo kits contain a heavy snap ring to help this, I use a center support snap ring from a 200-4R. Some performance vendors sell a brace that helps prevent case lug breakage. One of the keys is to keep the T-400 line pressure under 250 psi if possible. |
This is the direct drum sitting in the case. The sprag race engages the intermediate clutches. If using a valve body with engine braking, be sure you install the intermediate band. | This is the direct drum sitting in the case. The sprag race engages the intermediate clutches. If using a valve body with engine braking, be sure you install the intermediate band. | ||
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===Governor=== | ===Governor=== | ||
| − | Photo of the | + | Photo of the T-400 governor and cover. Note the direction the plastic drive gear teeth. The plastic drive gear can wear out or break. This result in no upshifts since the governor is not rotating. |
| − | [[File:T-400_governor.jpg|thumb|300px|left| | + | [[File:T-400_governor.jpg|thumb|300px|left|T-400 governor with cover]] <br style="clear:both"/> |
==Vacuum modulator== | ==Vacuum modulator== | ||
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;Output shaft lengths (from the back of the case to the end of the shaft): | ;Output shaft lengths (from the back of the case to the end of the shaft): | ||
Output shaft lengths (from the back of the case to the end of the shaft)... | Output shaft lengths (from the back of the case to the end of the shaft)... | ||
| − | * | + | *T-400 to NP203 = 1-3/8" (1.1" adapter) |
| − | * | + | *T-400 to late NP205/NP208 = 2-1/2" |
| − | * | + | *T-400 to early NP205 = 4-1/2" (same as short 2WD output) |
[[Category:Transmission]] | [[Category:Transmission]] | ||
[[Category:GM]] | [[Category:GM]] | ||
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