TH350 rebuild tech

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===Bushings and thrust washers===
 
===Bushings and thrust washers===
A TH350 is known to be rough on bushings. Bushings are critical in that they allow the rotating parts to ride true on center, and for the lube to make it to the rear of the trans.
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A T-350 is known to be rough on bushings. Bushings are critical in that they allow the rotating parts to ride true on center, and for the lube to make it to the rear of the trans.
  
Be prepared to replace almost ALL the bushings in a TH350. Might as well order a bushing kit, as well as a thrust washer kit. It is also recommended to get two additional sun gear bushings individually.
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Be prepared to replace almost ALL the bushings in a T-350. Might as well order a bushing kit, as well as a thrust washer kit. It is also recommended to get two additional sun gear bushings individually.
  
 
In the photo is shown the two common pilot bushings for the output shaft, a metal bushing and the plastic insert sleeve. The plastic sleeve design is very durable, you will find professional builders have their own preference.
 
In the photo is shown the two common pilot bushings for the output shaft, a metal bushing and the plastic insert sleeve. The plastic sleeve design is very durable, you will find professional builders have their own preference.
  
 
{|
 
{|
|[[File:T-350_bushings.jpg|thumb|300px|left|TH350 bushings]]  
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|[[File:T-350_bushings.jpg|thumb|300px|left|T-350 bushings]]  
|[[File:T-350_thrust_washers.jpg|thumb|300px|left|TH350 thrust washer kit]]
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|[[File:T-350_thrust_washers.jpg|thumb|300px|left|T-350 thrust washer kit]]
 
|}
 
|}
  
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While it may be true that removing the accumulator spring from the 1-2 servo will firm up the 1-2 shift, leaving the 1-2 accumulator spring out is not recommended. One reason is the accumulator protects the failure-prone intermediate sprag and another is the spring keeps the cover loaded against the snap ring. Photo shows accumulator cover, spring and piston (snap ring not shown). This is located on right side of transmission case. Check the bore in the case for scratches or other damage if the spring was found broken.
 
While it may be true that removing the accumulator spring from the 1-2 servo will firm up the 1-2 shift, leaving the 1-2 accumulator spring out is not recommended. One reason is the accumulator protects the failure-prone intermediate sprag and another is the spring keeps the cover loaded against the snap ring. Photo shows accumulator cover, spring and piston (snap ring not shown). This is located on right side of transmission case. Check the bore in the case for scratches or other damage if the spring was found broken.
  
[[File:T-350_acumilator01.jpg|thumb|300px|left|TH350 Accumulator cover, spring and piston with sealing rings]] <br style="clear:both"/>
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[[File:T-350_acumilator01.jpg|thumb|300px|left|T-350 Accumulator cover, spring and piston with sealing rings]] <br style="clear:both"/>
  
  
Right side of TH350 case. Pressure ports are circled.  
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Right side of T-350 case. Pressure ports are circled.  
 
*Rear port (yellow) is main line pressure. You will see pressure here in all gears for most valve body configurations. Some race-only valve bodies may not have pressure at this port or the others
 
*Rear port (yellow) is main line pressure. You will see pressure here in all gears for most valve body configurations. Some race-only valve bodies may not have pressure at this port or the others
 
*Middle port (red) is 2nd gear pressure
 
*Middle port (red) is 2nd gear pressure
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Then push it into the rear of the case evenly by hand, aligning it properly so it will seat (there is a "tang"). Look at the park pawl notch to help index it.
 
Then push it into the rear of the case evenly by hand, aligning it properly so it will seat (there is a "tang"). Look at the park pawl notch to help index it.
  
[[File:T-350caselowpiston.jpg|thumb|300px|left|TH350 low-reverse piston installed into case]] <br style="clear:both"/>
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[[File:T-350caselowpiston.jpg|thumb|300px|left|T-350 low-reverse piston installed into case]] <br style="clear:both"/>
  
  
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Next you install the output shaft.
 
Next you install the output shaft.
  
[[File:T-350_output_bearing.jpg|thumb|300px|left|TH350 output shaft with bearing that fits between case and ring gear]] <br style="clear:both"/>
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[[File:T-350_output_bearing.jpg|thumb|300px|left|T-350 output shaft with bearing that fits between case and ring gear]] <br style="clear:both"/>
  
  
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Now you can install the low/reverse clutches, beginning with a steel, then a friction, alternating, ending with a friction.
 
Now you can install the low/reverse clutches, beginning with a steel, then a friction, alternating, ending with a friction.
  
[[File:T-350_low_clutch_install.jpg|thumb|300px|left|TH350 low-reverse frictions and steels installed with planetary and output shaft]] <br style="clear:both"/>
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[[File:T-350_low_clutch_install.jpg|thumb|300px|left|T-350 low-reverse frictions and steels installed with planetary and output shaft]] <br style="clear:both"/>
  
 
{{Note1}}If you have a light duty core with low count low pack, unless it is a transbrake application or will be manually shifted into low for engine braking often, fewer clutches is OK. In some cases where you are after every last bit of ET, using fewer clutches can cause less frictional loss in 2nd and high gear. "Turbulator" steel plates from a 4L60E will also help and are a direct drop-in.
 
{{Note1}}If you have a light duty core with low count low pack, unless it is a transbrake application or will be manually shifted into low for engine braking often, fewer clutches is OK. In some cases where you are after every last bit of ET, using fewer clutches can cause less frictional loss in 2nd and high gear. "Turbulator" steel plates from a 4L60E will also help and are a direct drop-in.

Revision as of 08:23, 4 July 2023

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