TH350 rebuild tech
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For racing and heavy towing use, you will want to machine the direct clutch piston down approximately .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. I try to keep a few machined on hand, and machine several at a time when I do so. If you need one email me and if you can supply a core, I MAY be able to sell you a piston. | For racing and heavy towing use, you will want to machine the direct clutch piston down approximately .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. I try to keep a few machined on hand, and machine several at a time when I do so. If you need one email me and if you can supply a core, I MAY be able to sell you a piston. | ||
| − | Stock measurement is ~.835, I cut them to . | + | Stock measurement is ~.835, I cut them to .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 ~.010" clearance per friction. So a 5 friction direct setup would work great with .050" clearance. It will work with less, I wouldn't go less than .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 4 piston direct piston vs. machined for 5. Check the thickness of the piston, it should be NO less than .700 thick at the widest point. If the piston is too low, the bottom flat steel plate can drop below the grooves in the drum and bind up the piston. May leave out center cushion seal if dual feed is used. Set maximum clearance at 0.050. | Stock 4 piston direct piston vs. machined for 5. Check the thickness of the piston, it should be NO less than .700 thick at the widest point. If the piston is too low, the bottom flat steel plate can drop below the grooves in the drum and bind up the piston. May leave out center cushion seal if dual feed is used. Set maximum clearance at 0.050. | ||
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[[file:TH350directpistons.jpg]] | [[file:TH350directpistons.jpg]] | ||
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