TH350 rebuild tech
m (spelling tidy up) |
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Stock measurement is ~.835, I cut them to .675". 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 measurement is ~.835, I cut them to .675". 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. | + | 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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| + | Drill cooling holes from 0.0250 to 0.310 may add some to cool clutches. | ||
[[file:TH350directpistons.jpg]] | [[file:TH350directpistons.jpg]] | ||
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| − | The direct drum should use a wider bushing even on stock rebuilds. Most bushing kits include the wide one. | + | The direct drum should use a wider bushing even on stock rebuilds. Stock is 0.500 a wider 0.750 is available in some bushing kits. The wide bushing that will work is Lempco #6015. Most bushing kits include the wide one. |
There is a lot of load on this bushing, and it should ALWAYS be replaced on overhaul. | There is a lot of load on this bushing, and it should ALWAYS be replaced on overhaul. | ||
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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. | ||
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| + | May also use roller from a direct drum or sprag to drive into the passage, will not be able to remove! | ||
[[file:Dualfeed.jpg]] | [[file:Dualfeed.jpg]] | ||
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| − | 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. | + | 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. |
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. | ||
Forward drum inspection: | Forward drum inspection: | ||
| − | Pay attention to this polished stub of the input shaft, it goes into the bushing that is in the end of the out put shaft. It is a high wear area. Be sure it is smooth. Minor scoring can be smoothed down. | + | Pay attention to this polished stub of the input shaft, it goes into the bushing that is in the end of the out put shaft. It is a high wear area. Be sure it is smooth. Minor scoring can be smoothed down. May consider use of teflon bushing, only a lubrication passaage, no pressure, no lateral loading. |
[[file:TH350forwardwear.jpg]] | [[file:TH350forwardwear.jpg]] | ||
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