TH350 rebuild tech
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[[file:TH350caselowtool.jpg|frame|none|Spring compression tool installed into case.]] | [[file:TH350caselowtool.jpg|frame|none|Spring compression tool installed into case.]] | ||
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==Output shaft install== | ==Output shaft install== | ||
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[[file:3_tang_whr_t-350.jpg|frame|none|Front ring gear with 3 tang thrust washer in place.]] | [[file:3_tang_whr_t-350.jpg|frame|none|Front ring gear with 3 tang thrust washer in place.]] | ||
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==Direct drum assembly== | ==Direct drum assembly== | ||
For racing and heavy towing use, you will want to machine the direct clutch piston down approximately 0.160" to allow for one extra friction and steel plate for a total of 5 frictions, and 5 steels in the directs. This can be accomplished on a brake lathe. | For racing and heavy towing use, you will want to machine the direct clutch piston down approximately 0.160" to allow for one extra friction and steel plate for a total of 5 frictions, and 5 steels in the directs. This can be accomplished on a brake lathe. | ||
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Stock measurement is 0.835", I cut them to 0.700". Ideally you would pre-assemble, and check clearance using a 4 clutch pack. Measure the additional thickness of the extra friction and steel, then cut the exact amount needed to leave you the exact clearance you desire. Rule of thumb on most auto trans friction clearances is ~0.010" clearance per friction. So a 5 friction direct setup would work great with 0.050" to 0.070" clearance. It will work with less, I wouldn't go less than 0.040", and will work with quite a bit more, but excessive clearance can result in delayed engagement, busted lip seals, and unsatisfactory shift quality. | Stock measurement is 0.835", I cut them to 0.700". Ideally you would pre-assemble, and check clearance using a 4 clutch pack. Measure the additional thickness of the extra friction and steel, then cut the exact amount needed to leave you the exact clearance you desire. Rule of thumb on most auto trans friction clearances is ~0.010" clearance per friction. So a 5 friction direct setup would work great with 0.050" to 0.070" clearance. It will work with less, I wouldn't go less than 0.040", and will work with quite a bit more, but excessive clearance can result in delayed engagement, busted lip seals, and unsatisfactory shift quality. | ||
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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. | ||
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[[File:ATI direct drum and sprag.jpg|thumb|300px|left|ATI TH350 direct clutch drum with HD 36 element sprag]] <br style="clear:both"/> | [[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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I also like to always use a NEW intermediate roller clutch for HD builds. My theory on a long lived setup is that the springs that force the rollers against the race must be in good condition to help the rollers grab quicker and more evenly on apply. | I also like to always use a NEW intermediate roller clutch for HD builds. My theory on a long lived setup is that the springs that force the rollers against the race must be in good condition to help the rollers grab quicker and more evenly on apply. | ||
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==Dual feeding== | ==Dual feeding== | ||
This is part of the process of "dual-feeding" the direct clutches. On a stock rebuild you would normally install this lip seal. | This is part of the process of "dual-feeding" the direct clutches. On a stock rebuild you would normally install this lip seal. | ||
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You can do this on any rebuild but you must also block a passage in the case near the pump to prevent loss of pressure to the reverse circuit. | You can do this on any rebuild but you must also block a passage in the case near the pump to prevent loss of pressure to the reverse circuit. | ||
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All transbrakes will require dual feed of the direct clutch, as well as many manual valve bodies. | All transbrakes will require dual feed of the direct clutch, as well as many manual valve bodies. | ||
| − | + | Shown below is the passage that must be blocked. I usually tap this hole with a 3/8" tap, and cut off the end of a 3/8" bolt. I then slot the head of the bolt so I can use a flat-tip screwdriver. | |
I don't thread the passage completely to bottom. I want the "plug" to seat on the unthreaded portion. | I don't thread the passage completely to bottom. I want the "plug" to seat on the unthreaded portion. | ||
| − | + | This passage may also be plugged by using a roller from a direct drum or sprag to drive into the passage, but this will be a more or less permanent modification due to the difficulty in removing the roller. | |
[[file:Dualfeed.jpg]] | [[file:Dualfeed.jpg]] | ||
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