TH350 rebuild tech

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==Variations of the T-350 family==
 
==Variations of the T-350 family==
There was also a T-350C & T-250C version that has a lockup torque converter (TCC). Look for the end of the input shaft to have a smooth polished end with O-ring on it. The case has a "C" cast into it, and there will be an electrical plug adjacent to the shifter shaft on the driver side of the tranny.  
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There was also a T-350C and T-250C version that has a lockup torque converter (TCC). Look for the end of the input shaft to have a smooth polished end with O-ring on it. The case has a "C" cast into it, and there will be an electrical plug adjacent to the shifter shaft on the driver side of the tranny.  
  
Don't confuse the TH350C with a TH350 non-lockup tranny with a screwed-in electrical connector on the ''passenger'' side of the case. This is a pressure switch that was used ~1972-'73 for the Transmission Controlled Spark (TCS) system. This disabled the distributor vacuum advance in all gears except high gear, and is a single wire switch threaded into a pressure port near where the cooler lines are located. In the case of this switch, you can either leave it in place, unused- or remove it and plug the port.  
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Don't confuse the T-350C with a T-350 non-lockup tranny with a screwed-in electrical connector on the ''passenger'' side of the case. This is a pressure switch that was used ~1972-'73 for the Transmission Controlled Spark (TCS) system. This disabled the distributor vacuum advance in all gears except high gear, and is a single wire switch threaded into a pressure port near where the cooler lines are located. In the case of this switch, you can either leave it in place, unused- or remove it and plug the port.  
  
 
Only the larger transmission/converter companies build high stall torque converters for the T-350C because of the low demand for them.
 
Only the larger transmission/converter companies build high stall torque converters for the T-350C because of the low demand for them.
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The HD applications should also get a heat treated intermediate sprag race. It is darker colored than a stock piece. The intermediate sprag race and intermediate sprag (actually roller clutch) take a brutal amount of force on a 1-2 shift at high rpm. Even more so with harsher shift calibrations. It is the single weakest part of a T-350. This is not to say a T-350 is not tough; they are under-rated and can reliably handle in the 600 HP or lb/ft range based on my experience.
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The HD applications should also get a heat treated intermediate sprag race. It is darker colored than a stock piece. The intermediate sprag race and intermediate sprag (actually roller clutch) take a brutal amount of force on a 1-2 shift at high rpm. Even more so with harsher shift calibrations. It is the single weakest part of a T-350. This is not to say a T-350 is not tough; they are under-rated and can reliably handle in the 600 HP or lb/ft range based on experience.
  
 
[[file:TH350intspragraces.jpg]]
 
[[file:TH350intspragraces.jpg]]
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An even heavier duty direct drum/sprag assembly is available. It uses a 36 element sprag and a machined drum, it will withstand more torque than a stock unit or one w/just a hardened race. These units can cost upwards of $300.00.
 
An even heavier duty direct drum/sprag assembly is available. It uses a 36 element sprag and a machined drum, it will withstand more torque than a stock unit or one w/just a hardened race. These units can cost upwards of $300.00.
  
[[File:ATI direct drum and sprag.jpg|thumb|300px|left|ATI TH350 direct clutch drum with HD 36 element sprag]] <br style="clear:both"/>
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[[File:ATI direct drum and sprag.jpg|thumb|300px|left|ATI T-350 direct clutch drum with HD 36 element sprag]] <br style="clear:both"/>
 
   
 
   
  
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===Forward drum inspection===
 
===Forward drum inspection===
Forward drum procedures are almost identical. No center seal to worry about on a TH350, it typically already has a 5 clutch pack, except light duty applications. Same 0.700" thickness piston for 5 frictions and steels. Removing the wave plate will cause harsh forward engagement. Reduce clearance of the stack to 0.040".
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Forward drum procedures are almost identical. No center seal to worry about on a T-350, it typically already has a 5 clutch pack, except light duty applications. Same 0.700" thickness piston for 5 frictions and steels. Removing the wave plate will cause harsh forward engagement. Reduce clearance of the stack to 0.040".
  
 
Forward clutch pack clearances can be tighter than usual; however it must have some clearance. If too tight it can creep in neutral.
 
Forward clutch pack clearances can be tighter than usual; however it must have some clearance. If too tight it can creep in neutral.

Revision as of 03:44, 27 March 2012

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