TH350 rebuild tech
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| + | ==Overview== | ||
| + | The GM Turbo Hydra-Matic 350 transmission (aka "T350", "TH350", "T-350", "Turbo 350", etc.) was used between 1968-'86 in RWD and 4WD GM vehicles. It is a relatively rugged, compact transmission that lends itself to a wide variety of applications and modifications. | ||
==Rebuilding the T-350== | ==Rebuilding the T-350== | ||
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==Basic rebuild information== | ==Basic rebuild information== | ||
| + | [http://www.nastyz28.com/forum/showthread.php?t=53671 Rebuild article by Jakeshoe] | ||
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'''NOTE:''' | '''NOTE:''' | ||
*This WIKI is not intended to be a replacement for an ATSG or factory tech manual. First time builders will likely need a tech manual. Recommended is Ron Sessions' book "TH350 Handbook" in the HP book series. It has good pictures, a lot of good info, but has some outdated info. Outstanding value for the money. | *This WIKI is not intended to be a replacement for an ATSG or factory tech manual. First time builders will likely need a tech manual. Recommended is Ron Sessions' book "TH350 Handbook" in the HP book series. It has good pictures, a lot of good info, but has some outdated info. Outstanding value for the money. | ||
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==Tailshaft (extension housing) lengths== | ==Tailshaft (extension housing) lengths== | ||
| − | You will find the TH350 with 6 | + | You will find the TH350 with 6", 9" and 12" tail housings. Overall lengths are 27-11/16”, 30-11/16”, and 33-27/32”, respectively. There is also a 4WD output (seen below). |
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| + | [[File:3504WD output.jpg]] | ||
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==Gear ratios== | ==Gear ratios== | ||
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===Valve body modifications=== | ===Valve body modifications=== | ||
| + | Removing check balls and opening up orifices in the separator plate is also a common modification to firm up shifts. Just remember the one check ball that needs to stay is the one just below the modulator. | ||
====Shift kits==== | ====Shift kits==== | ||
| + | Often shift improver kits are installed at the time of the tranny rebuild. Various manufacturers make shift improver kits, Trans Go has a good reputation. | ||
==Shift point changes== | ==Shift point changes== | ||
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===Detent cable adjustment=== | ===Detent cable adjustment=== | ||
<Blockquote> Unclip the cable locking mechanism and then press the accelerator pedal to the floor. Be sure there's nothing under the pedal and the linkage is allowing full throttle at the carb. Floorboard the gas pedal and the detent cable should just pull tight as the throttle reaches wide open. THAT'S IT! If it doesn't pull tight, readjust, bend bracket, or whatever is necessary to achieve this. If it doesn't pull tight you will not have full detent at wide open throttle. If it pulls tight BEFORE full throttle, you'll break the cable end.</Blockquote> | <Blockquote> Unclip the cable locking mechanism and then press the accelerator pedal to the floor. Be sure there's nothing under the pedal and the linkage is allowing full throttle at the carb. Floorboard the gas pedal and the detent cable should just pull tight as the throttle reaches wide open. THAT'S IT! If it doesn't pull tight, readjust, bend bracket, or whatever is necessary to achieve this. If it doesn't pull tight you will not have full detent at wide open throttle. If it pulls tight BEFORE full throttle, you'll break the cable end.</Blockquote> | ||
| − | + | {| | |
| + | |[[File:Kickdown1.jpg|thumb|180px|center|Unlock detent clip by prying up on it.]] | ||
| + | |[[File:Kickdown2.jpg|thumb|180px|center|Clip in unlocked position.]] | ||
| + | |[[File:Kickdown3.jpg|thumb|180px|center|Open throttle (should be done from inside the car to assure proper travel).]] | ||
| + | |[[File:Kickdown4.jpg|thumb|180px|center|Push clip down to lock.]] | ||
| + | |} | ||
<Blockquote> Now that the detent and modulator are set correctly, we are ready to think about shift scheduling. ROAD TEST THE CAR. You will need to know minimum and maximum throttle shift speeds for the 1-2 and 2-3 shifts, the RPM for the max throttle shifts, and the highest speed you can get a 3-1 and a 3-2 kick down. Also, what is the [http://www.crankshaftcoalition.com/wiki/Gear_ratio_check axle ratio].</Blockquote> | <Blockquote> Now that the detent and modulator are set correctly, we are ready to think about shift scheduling. ROAD TEST THE CAR. You will need to know minimum and maximum throttle shift speeds for the 1-2 and 2-3 shifts, the RPM for the max throttle shifts, and the highest speed you can get a 3-1 and a 3-2 kick down. Also, what is the [http://www.crankshaftcoalition.com/wiki/Gear_ratio_check axle ratio].</Blockquote> | ||
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Be sure you have the output ring gear to case bearing in the case. | Be sure you have the output ring gear to case bearing in the case. | ||
| − | Also be sure on dis-assembly you inspected and replaced as necessary the input shaft to output bushing shown here ( | + | Also be sure on dis-assembly you inspected and replaced as necessary the input shaft to output bushing shown here (red arrow). |
| − | [[ | + | [[File:Input shaft to output bushing.jpg|frame|none|Check this bushing for wear, replace with new metal bushing or slip-in plastic insert.]] |
==Rear planetary unit install== | ==Rear planetary unit install== | ||
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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. | ||
| − | [[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"/> |
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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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. Most bushing kits include the wide one. There is a lot of load on this bushing, and it should ALWAYS be replaced on overhaul. | 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. Most bushing kits include the wide one. There is a lot of load on this bushing, and it should ALWAYS be replaced on overhaul. | ||
| + | |||
| + | [[File:TH350directbushings1.jpg|thumb|400px|left|The direct drum should use a wider bushing even on stock rebuilds.]] <br style="clear:both"/> | ||
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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. | 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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| + | [[File:TH350directdrumbushing1.jpg|thumb|400px|left|]] <br style="clear:both"/> | ||
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Next you will install the direct piston lip seals, and install the piston in the drum. | Next you will install the direct piston lip seals, and install the piston in the drum. | ||
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| + | [[File:TH350directpistonseals1.jpg|thumb|400px|left]] <br style="clear:both"/> | ||
Take note of the orientation of the seals, the lip will face towards the "oil" side of the piston, not the clutch side. | Take note of the orientation of the seals, the lip will face towards the "oil" side of the piston, not the clutch side. | ||
| − | This is a | + | This is a high performance T-350 and I did NOT install a lip seal in the drum that would separate the two halves of the direct piston. |
==Dual feeding== | ==Dual feeding== | ||
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[[file:TH350directspringtool.jpg]] | [[file:TH350directspringtool.jpg]] | ||
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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). | 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). | ||
| + | ===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 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 | + | 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. | 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:TH350forwardwear.jpg]] | [[file:TH350forwardwear.jpg]] | ||
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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. | 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. | ||
| + | [[File:Scraped and split low reverse friction in the intermediate piston cavity..jpg|thumb|600px|left|Scraped and split low reverse friction in the intermediate piston cavity.]]<br style="clear:both"/> | ||
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Intermediate piston installed. | Intermediate piston installed. | ||
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==Fastener size and torque values== | ==Fastener size and torque values== | ||
*Pump Cover to Pump Body- (5/16-18) 15 ft/lb | *Pump Cover to Pump Body- (5/16-18) 15 ft/lb | ||
| − | *Pump assembly to case- (5/16-18) 20 ft/ | + | *Pump assembly to case- (5/16-18) 20 ft/lb |
| − | *Valve body and support plate- (5/16-18) 13 ft/ | + | *Valve body and support plate- (5/16-18) 13 ft/lb |
| − | *Oil channel support plate to case- (5/16-18) 13 ft/ | + | *Oil channel support plate to case- (5/16-18) 13 ft/lb |
| − | *Parking lock bracket- (5/16-18) 29 ft/ | + | *Parking lock bracket- (5/16-18) 29 ft/lb |
| − | *Oil suction screen- 40 in/ | + | *Oil suction screen- 40 in/lb |
| − | *Oil pan to case- (5/16-18) 13 ft/ | + | *Oil pan to case- (5/16-18) 13 ft/lb |
| − | *Extension housing to case- (3/8-16) 35 ft/ | + | *Extension housing to case- (3/8-16) 35 ft/lb |
| − | *Modulator retainer to case- (5/16-18) 12 ft/ | + | *Modulator retainer to case- (5/16-18) 12 ft/lb |
| − | *Inner Selector Lever to Shaft- (M10-1.5) 27 Nm (20 ft/ | + | *Inner Selector Lever to Shaft- (M10-1.5) 27 Nm (20 ft/lb) |
*External test plugs to case- (1/8-27) 8 ft/lb | *External test plugs to case- (1/8-27) 8 ft/lb | ||
*Transmission mount to transmission (M10-1.5) 48 Nm (35 ft/lb) | *Transmission mount to transmission (M10-1.5) 48 Nm (35 ft/lb) | ||
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*Detent cable to case- (M6.3-1.0) 8.5 Nm (75 in/lb) | *Detent cable to case- (M6.3-1.0) 8.5 Nm (75 in/lb) | ||
*Nut on outer end of shift selector shaft- (M10-1.5) 27 Nm (20 ft/lb) | *Nut on outer end of shift selector shaft- (M10-1.5) 27 Nm (20 ft/lb) | ||
| − | *Converter to Flexplate Bolts- 35 ft/ | + | *Converter to Flexplate Bolts- 35 ft/lb |
| − | *Torque converter dust cover pan to transmission case- 110 in/ | + | *Torque converter dust cover pan to transmission case- 110 in/lb |
| − | *Transmission Case to Engine- 35 ft/ | + | *Transmission Case to Engine- 35 ft/lb |
====Oil cooler line connectors to transmission case==== | ====Oil cooler line connectors to transmission case==== | ||
*Straight Pipe Fitting-25 ft/lb | *Straight Pipe Fitting-25 ft/lb | ||
| − | *Tapered Pipe Fitting- 15 ft/ | + | *Tapered Pipe Fitting- 15 ft/lb |
| − | *Oil Cooler Pipe to Connectors- 10 ft/ | + | *Oil Cooler Pipe to Connectors- 10 ft/lb |
====Other torque values==== | ====Other torque values==== | ||
| − | *Gearshift bracket to frame- 15 ft/ | + | *Gearshift bracket to frame- 15 ft/lb |
| − | *Gearshift Shaft to Swivel- 20 ft/ | + | *Gearshift Shaft to Swivel- 20 ft/lb |
| − | *Manual Shaft to Bracket- 20 ft/ | + | *Manual Shaft to Bracket- 20 ft/lb |
| − | *Detent Cable to Transmission- 75 in/ | + | *Detent Cable to Transmission- 75 in/lb |
| − | *Intermediate Band Adjust Nut- 15 ft/ | + | *Intermediate Band Adjust Nut- 15 ft/lb |
[[Category:Transmission]] | [[Category:Transmission]] | ||
[[Category:Good articles]] | [[Category:Good articles]] | ||
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