TH350 rebuild tech
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[[file:TH350intspragassemb.jpg]] | [[file:TH350intspragassemb.jpg]] | ||
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| + | The direct drum should use a wider bushing even on stock rebuilds. Most bushing kits include the wide one. | ||
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| + | There is alot of load on this bushing, and it should ALWAYS be replaced on overhaul. | ||
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| + | Also check the inside bore of the drum for wear from the sealing rings. A small amount of wear can be honed out. Visual shiny spots with no detectable wear are OK. | ||
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| + | Next you will install the direct piston lip seals, and install the piston in the drum. | ||
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| + | Take note of the orientation of the seals, the lip will face towards the "oil" side of the piston, not the clutch side. | ||
| + | Also take note, | ||
| + | this is a hi-performace TH350 and I did NOT install a lip seal in the drum that would seperate the two halves of the direct piston. | ||
| + | This is part of the process of "dual-feeding" the direct clutches. On a stock rebuild you would normall install this lip seal. | ||
| + | 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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| + | Dual feeding doubles the area of the piston that has pressurized fluid on it in 3rd gear, more than doubling the capacity of the clutch. It is accomplished by most valve body kits without doing so internally but requires a "transfer" plate and gasket to be added under the support plate in front of the valve body. | ||
| + | I prefer internally dual feeding because it leave out the additional gasket and eliminates that one extra possibility for a pressure loss resulting in burnt 3rd gear clutches (Yes it has happened to me). | ||
| + | All transbrakes will require dual feed of the direct clutch, as well as many manual valve bodies. | ||
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| + | Here 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. | ||
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| + | Also of note, | ||
| + | if you are using almost any aftermarket kit, these kits use a feed plate between the support plate in front of the valve body and the seperator plate. This feed plate dual feeds the directs and plugging this hole is unnecessary. Also most manual valve bodies, trans-brakes, etc will have you omit the direct drum center seal and the sealing ring on the stator but plugging of this hole is also unnecessary due to the design of the seperator plate. | ||
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| + | Don't assume you need to plug this hole. Only plug this hole if you plan on building a unit yourself. | ||
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| + | You can omit the center seal, plug this passage, enlarge the 2nd and 3rd feed holes in the stock seperator plate and you will have greatly increased the torque capacity of a stock TH350 as well as gained a firmer shift. | ||
| + | Even firmer shifts can be accomplished with checkball removal and modifications to the accumulators. I recommend NOT modifying the 1-2 accumulator. Retain the cushion spring and do not block the circuit. The 2-3 accumulator can be blocked by several methods. | ||
| + | Removing the 2-3 accumulator spring and using a spacer (nut, washers, cut down section of tubing) between the piston and the e-clip is the "shadetree' method. You can also block the feed in the valve body to the 2-3 accumulator. | ||
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| + | Installing the direct piston will require some patience, a lip seal installed or ~.010" feeler gauge, and a trick I use is a section of plastic cut from a 3 liter soda bottle to use as an outside installer tool. Set it in the drum, and it will force the lip seal into the drum without using a tool around the entire circumference. You may however need to work the exposed part of the seal into the drum with the feeler gauge or seal tool. | ||
| + | Use care using the lip seal tool, I use a push-in technique more than a work around the drum technique. If you slide around the drum, and it catches the seal it will cut it and then you must get a new lip seal and start again. Good lighting, patience, and technique are key here, oh, and a good air check | ||
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| + | Once you have the piston seated in the drum you can install the return springs and retainer. | ||
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| + | You can buy or make a tool similar to the one pictured or use 2-3 5" or larger c-clamps (much more of a PITA). | ||
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| + | photos needed above.......... | ||
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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 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: | ||
| + | Pay attention to this portion of the input shaft, it goes into the outout shaft bushing. It is a high wear area. Be sure it is smooth. Minor scoring can be smoothed down. | ||
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| + | Notice the scraped and split low reverse friction in the intermediate piston cavity. This slightly tightens the intermediate clutch clearance to achieve cleaner 1-2 shift. | ||
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| + | Intermediate piston installed | ||
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| + | Sealing rings on the pump stator. Notice the missing selaing ring 2nd from bottom. You can remove this ring if dual feeding. | ||
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| + | Pump gear install. Note the orientation of the tangs on the inner gear. They are offset. They should face away from the seal. Mis-installation will result in pump failure and converter damage. | ||
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| + | Notice the dowel pins threaded into the case, you use these and the case to align the pump halves. | ||
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| + | This is an example of how I air check the forward and direct drum. After everything is assembled, I place the drums on the pump (above a hole in the bench) with all sealing rings in place, thrust washers or bearings. | ||
| + | Use a rubber tipped air nozzle to apply air to the passages around the pump circumference. As you apply air to the correct passages, you will see and hear the drums apply the clutches. Be sure there are no leaks from the lip seals. There will be some minor leakage at the sealing rings usually. Iron rings air check better than teflon on the bench. | ||
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| + | Drums installed in the transmission. Ready for intermediate pressure plate install. Ensure the lugs of the direct drum are engaged with the sun shell. They should be slightly below the top edge of the suin shell. If you do not get complete engagement, the input shaft will not turn when you install the pump and begin to tighten it. | ||
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| + | Coan reverse manual valve body. Notice the machining of passages. | ||
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| + | Photos needed ABOVE..... | ||
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