Editing TH350 rebuild tech (section)
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==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. 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. ===Dual Feed direct drum=== 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. Internally dual feeding is preferred because it leaves out the additional gasket and eliminates that one extra possibility for a pressure loss resulting in burnt 3rd gear clutches. All transbrake applications will require dual feed of the direct clutch, possibly as well as manual valve bodies. Shown below is the passage that must be blocked. One method is to tap this hole with a 3/8" tap, and cut off the end of a 3/8" bolt. The head of the bolt can be slotted so a screwdrive can be used. Don't thread the passage completely to bottom; it's best to have the "plug" seat against 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:T-350_dual_feed02.jpg|thumb|300px|left|Plug the hole indicated for dual feed on TH350]] <br style="clear:both"/> {{Note1}}Don't assume you need to plug this hole. Only plug this hole if you plan on doing the dual feed modification yourself. You can omit the center seal, plug this passage, enlarge the 2nd and 3rd feed holes in the stock separator plate and you will have greatly increased the torque capacity of a stock TH350 as well as gained a firmer shift. Almost all aftermarket kits use a feed plate between the support plate in front of the valve body and the separator plate. This feed plate 'dual feeds' the directs, so plugging this hole is unnecessary. Also most manual valve bodies, trans-brakes, etc. will call for omitting the direct drum center seal and the sealing ring on the stator, but plugging this hole is also unnecessary due to the design of the separator plate. Even firmer shifts can be accomplished with check ball removal and modifications to the accumulators. It is recommend to NOT modify 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 "shade tree" method. You can also block the feed in the valve body to the 2-3 accumulator. Installing the direct piston will require some patience, a lip seal installed or 0.010" feeler gauge, and a trick to 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 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. 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, and a be sure to verify using an air check. Once you have the piston seated in the drum you can install the return springs and retainer. You can buy or make a tool similar to the one pictured below, or use several 5" or larger C-clamps. [[File:T-350_direct_sprng_compress.jpg|thumb|300px|left|One method to compress springs to install the snap ring]] <br style="clear:both"/> ===Forward drum inspection=== 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. Pay attention to this polished stub of the input shaft, it goes into the bushing that is in the end of the output 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 passage, no pressure, no lateral loading. [[File:T-350_fwd_drum.jpg|thumb|300px|left|Check forward drum for wear.]]<br style="clear:both"/> ===T-350 Pump assembly=== '''Notice''' the scraped and split T-350 low reverse friction in the intermediate piston cavity. This slightly tightens the intermediate clutch clearance to achieve cleaner 1-2 shift. [[File:T-350_intmed_piston_spacer.jpg|thumb|300px|left|Scraped and split T-350 low reverse friction in the intermediate piston cavity]]<br style="clear:both"/> Intermediate piston installed. [[File:T-350_pump_n_piston.jpg|thumb|300px|left|T-350 pump with intermediate piston installed]]<br style="clear:both"/> Sealing rings on the T-350 pump stator. Remove the second ring from the bottom if dual feeding. [[File:T-350_stator_rings.jpg|thumb|300px|left|Sealing rings on pump]] <br style="clear:both"/> Pump gear install. Note the orientation of the tangs on the inner gear. They are offset. They should face away from the seal. Incorrect installation will result in pump failure and converter damage. [[File:T-350_pump_half.jpg|thumb|300px|left|Notice the T-350 inner pump gear tangs, they must be '''up''' as seen here]] <br style="clear:both"/> Notice the dowel pins threaded into the case, you use these and the case to align the pump halves. [[File:T-350_pump_alignment.jpg|thumb|300px|left|One method to align the T-350 pump halves shown]] <br style="clear:both"/> This is an example of to air check the T-350 forward and direct drum. After everything is assembled, I place the T-350 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 usually be some minor leakage at the sealing rings. Iron rings air check better than teflon on the bench. [[File:T-350_air_check_pump.jpg|thumb|300px|left|One method to air check T-350 clutch drums in the pump shown. Refer to build manual for locations]] <br style="clear:both"/> T-350 Drums installed in the transmission case. 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 sun shell. If you do not get complete engagement, the input shaft will not turn when you install the pump and begin to tighten it. You can also see the braking band installed. [[File:T-350_coast_band01.jpg|thumb|300px|left|Both T-350 clutch drums installed with braking band shown]] <br style="clear:both"/> ===Braking band=== Install coasting band aka braking band. This band provides engine braking in manual 2nd gear.This slides in the case around the direct drum. Check band for wear at the struts. The servo pin can wear a hole through the strut. [[File:T-350_coasting_band.jpg|thumb|300px|left|Check band for wear in the area the servo pin rides]]<br style="clear:both"/> There are HD versions of this braking band. These HD bands should have welded reinforced band struts as show in photo. [[File:T-350_HD__braking_band.jpg|thumb|300px|left|Heavy duty brake band should have weld reinforced struts]]<br style="clear:both"/>
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