TH350 rebuild tech
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The T-250C has a band adjuster stud and locknut on the passenger side of the case near the cooler lines. It looks much like a T350 other than the adjuster (same physical size, same pan shape), so don't be fooled by it. | The T-250C has a band adjuster stud and locknut on the passenger side of the case near the cooler lines. It looks much like a T350 other than the adjuster (same physical size, same pan shape), so don't be fooled by it. | ||
| − | + | =Rebuilding the T-350= | |
===Bushings and thrust washers=== | ===Bushings and thrust washers=== | ||
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| − | Right side of T-350 case. Pressure ports circled. | + | 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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=Transmission reassembly= | =Transmission reassembly= | ||
==Low-reverse piston install== | ==Low-reverse piston install== | ||
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The first item to go in the case will be the low/reverse apply piston. | The first item to go in the case will be the low/reverse apply piston. | ||
Its function is for oil to force it towards the front or bell housing side of the trans, applying the low/reverse clutches. This allows reverse when applied simultaneously with the direct (high gear) clutches, and allows manual low gear when applied with the forward clutches. Manual low gear creates engine braking on deceleration. The low/reverse clutches do not apply in automatic range 1st gear. The low sprag (low roller clutch actually) causes first gear when only the forward clutches are applied. | Its function is for oil to force it towards the front or bell housing side of the trans, applying the low/reverse clutches. This allows reverse when applied simultaneously with the direct (high gear) clutches, and allows manual low gear when applied with the forward clutches. Manual low gear creates engine braking on deceleration. The low/reverse clutches do not apply in automatic range 1st gear. The low sprag (low roller clutch actually) causes first gear when only the forward clutches are applied. | ||
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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. | 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. | ||
I am using Alto red frictions in this unit, however a stock tan clutch (I prefer Borg Warner) is more than adequate for even very high HP cars. A Hi-Energy Borg from a 4L60E is also a good choice. | I am using Alto red frictions in this unit, however a stock tan clutch (I prefer Borg Warner) is more than adequate for even very high HP cars. A Hi-Energy Borg from a 4L60E is also a good choice. | ||
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Once the low clutches are installed, you can install the anti-clunk spring (or case-saver). Both are pictured, the case-saver is solid and spreads the load over a larger area. Hold in place with assembly gel or vaseline and then install the low support. | Once the low clutches are installed, you can install the anti-clunk spring (or case-saver). Both are pictured, the case-saver is solid and spreads the load over a larger area. Hold in place with assembly gel or vaseline and then install the low support. | ||
Be sure the low sprag inner race is not brinelled or has any unusual wear. | Be sure the low sprag inner race is not brinelled or has any unusual wear. | ||
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[[file:TH350lowsupportcasesaver.jpg|frame|none|Photo shows OEM anti-rattle spring and a replacement piece known as a case saver used in cases with heavy wear in case lugs.]] | [[file:TH350lowsupportcasesaver.jpg|frame|none|Photo shows OEM anti-rattle spring and a replacement piece known as a case saver used in cases with heavy wear in case lugs.]] | ||
Once it is pushed into place, install the snap ring, with the ends on each side of the spring or case-saver. | Once it is pushed into place, install the snap ring, with the ends on each side of the spring or case-saver. | ||
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Now is the time to air check the low clutches. You do so by applying pressurized air to the passage at the rear pan area of the worm casting in the case. | Now is the time to air check the low clutches. You do so by applying pressurized air to the passage at the rear pan area of the worm casting in the case. | ||
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[[file:T-350_center_support.jpg|frame|none|Center support, inner race, thrust washer shown.]] | [[file:T-350_center_support.jpg|frame|none|Center support, inner race, thrust washer shown.]] | ||
| − | Next you install the 4-tang thrust washer into the large splines of the low sprag inner race (picture above), and then the sun shell and gear assembly. Before this step, for HD use, you would have wanted to install additional sun gear bushings, 2 on each end, and re-drilled the lube holes. | + | Next you install the 4-tang thrust washer into the large splines of the low sprag inner race (picture above), and then the sun shell and gear assembly. Before this step, for HD use, you would have wanted to install additional sun gear bushings, 2 on each end, and re-drilled the lube holes as shown below. |
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[[file:TH350sungearbushings.jpg|frame|none|Double bushings installed. You MUST drill oil holes in bushings.]] | [[file:TH350sungearbushings.jpg|frame|none|Double bushings installed. You MUST drill oil holes in bushings.]] | ||
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