TH350 rebuild tech
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| − | ==Overview== | + | ==T-350 Overview== |
The GM Turbo Hydra-Matic 350 transmission (aka "T-350", "Turbo 350", THM350, etc.) was used between 1968-'86 in RWD and 4WD GM domestic vehicles. The TH350 was still produced many years beyond 1986 for export sales. It is a relatively rugged, compact transmission that lends itself to a wide variety of applications and modifications. | The GM Turbo Hydra-Matic 350 transmission (aka "T-350", "Turbo 350", THM350, etc.) was used between 1968-'86 in RWD and 4WD GM domestic vehicles. The TH350 was still produced many years beyond 1986 for export sales. It is a relatively rugged, compact transmission that lends itself to a wide variety of applications and modifications. | ||
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{{Note1}}If you have a light duty core with low count low pack, unless it is a transbrake application or will be manually shifted into low for engine braking often, fewer clutches is OK. In some cases where you are after every last bit of ET, using fewer clutches can cause less frictional loss in 2nd and high gear. "Turbulator" steel plates from a 4L60E will also help and are a direct drop-in. | {{Note1}}If you have a light duty core with low count low pack, unless it is a transbrake application or will be manually shifted into low for engine braking often, fewer clutches is OK. In some cases where you are after every last bit of ET, using fewer clutches can cause less frictional loss in 2nd and high gear. "Turbulator" steel plates from a 4L60E will also help and are a direct drop-in. | ||
| − | There are Alto red frictions in this unit, however a stock tan clutch ( like Borg Warner brand) is more than adequate for even very high HP cars. A Hi-Energy Borg from a 4L60E is also a good choice. | + | There are Alto red frictions in this unit, however a stock tan clutch ( like Borg Warner brand) is more than adequate for even very high HP cars. A Hi-Energy Borg Warner friction from a 4L60E is also a good choice. |
Once the low clutches are installed, you can install the anti-clunk spring (or case-saver). Hold in place with assembly gel or vaseline and then install the low-reverse support. | Once the low clutches are installed, you can install the anti-clunk spring (or case-saver). Hold in place with assembly gel or vaseline and then install the low-reverse support. | ||
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[[File:T-350_ring_gear_with_washer.jpg|thumb|300px|left|Front ring gear with 3-tang thrust washer in place installed into case on front planet]] <br style="clear:both"/> | [[File:T-350_ring_gear_with_washer.jpg|thumb|300px|left|Front ring gear with 3-tang thrust washer in place installed into case on front planet]] <br style="clear:both"/> | ||
| − | ==Direct drum assembly== | + | ==T-350 Direct drum assembly== |
For racing and heavy towing use, you will want to machine the direct clutch piston down approximately 0.160" 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. | For racing and heavy towing use, you will want to machine the direct clutch piston down approximately 0.160" 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. | ||
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If the piston is too low, the bottom flat steel plate can drop below the grooves in the drum and bind up the piston. You can leave out center cushion seal if dual feed is used. | If the piston is too low, the bottom flat steel plate can drop below the grooves in the drum and bind up the piston. You can leave out center cushion seal if dual feed is used. | ||
| − | [[File:T-350_direct_piston.jpg|thumb|300px|left| | + | [[File:T-350_direct_piston.jpg|thumb|300px|left|T-350 direct clutch drum pistons, piston on left cut for 5 friction use]] <br style="clear:both"/> |
| − | Heavy duty applications should also get a heat treated intermediate sprag race. The heat treatment makes the race less brittle. A heat treated intermediate sprag race is darker colored than a stock part. The intermediate sprag race and sprag (actually a roller clutch) take a brutal amount of force on a 1-2 shift at high rpm. Even more so with harsher shift calibrations. It is the single weakest part of a TH350. This is not to say a TH350 is not tough; they can reliably handle power in the 600 HP or lb/ft range if properly assembled using the right parts. | + | Heavy duty applications should also get a heat treated intermediate sprag race. The heat treatment makes the race less brittle. A heat treated intermediate sprag race is darker colored than a stock part. The T-350 intermediate sprag race and sprag (actually a roller clutch) take a brutal amount of force on a 1-2 shift at high rpm. Even more so with harsher shift calibrations. It is the single weakest part of a TH350. This is not to say a TH350 is not tough; they can reliably handle power in the 600 HP or lb/ft range if properly assembled using the right parts. |
[[file:TH350intspragraces.jpg]] | [[file:TH350intspragraces.jpg]] | ||
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Several companies offer an even heavier duty direct drum/sprag assembly. It uses a 36 element sprag (similar to what is used in the TH400) and a machined drum; it will withstand more torque than a stock unit or one with just a hardened race. These units can cost $300.00 or more. | Several companies offer an even heavier duty direct drum/sprag assembly. It uses a 36 element sprag (similar to what is used in the TH400) and a machined drum; it will withstand more torque than a stock unit or one with just a hardened race. These units can cost $300.00 or more. | ||
| − | [[File:T-350_HD_drum_sprag.jpg|thumb|300px|left| | + | [[File:T-350_HD_drum_sprag.jpg|thumb|300px|left|T-350 direct clutch drum with 36 element sprag]] <br style="clear:both"/> |
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The parts go on the direct drum. | The parts go on the direct drum. | ||
| − | [[File:T-350 drum sprag race.jpg|thumb|300px|left| | + | [[File:T-350 drum sprag race.jpg|thumb|300px|left|T-350 direct clutch drum with sprag, race, retainer]] <br style="clear:both"/> |
Assembled direct drum sprag and race with retainer. | Assembled direct drum sprag and race with retainer. | ||
| − | [[File:T-350_drum_sprag_assembled.jpg|thumb|300px|left| | + | [[File:T-350_drum_sprag_assembled.jpg|thumb|300px|left|T-350 direct clutch drum with assembled sprag, race, retainer]] <br style="clear:both"/> |
| − | 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 T-350 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|300px|left|The direct drum should use a wider bushing even on stock rebuilds]] <br style="clear:both"/> | + | [[File:TH350directbushings1.jpg|thumb|300px|left|The T-350 direct drum should use a wider bushing even on stock rebuilds]] <br style="clear:both"/> |
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 acceptable. | 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 acceptable. | ||
| − | [[File:T-350_direct_drum_bushing.jpg|thumb|300px|left|Direct drum with wide bushing, piston, springs and retainer installed]] <br style="clear:both"/> | + | [[File:T-350_direct_drum_bushing.jpg|thumb|300px|left|T-350 Direct drum with wide bushing, piston, springs and retainer installed]] <br style="clear:both"/> |
Next you will install the direct piston lip seals, and install the piston in the drum. Take note of the orientation of the seals, the lip will face towards the "oil" side of the piston, not the clutch side. | Next you will install the direct piston lip seals, and install the piston in the drum. Take note of the orientation of the seals, the lip will face towards the "oil" side of the piston, not the clutch side. | ||
| − | Below is a high performance | + | Below is a high performance T-350 piston for a drum without a center seal that would separate the two halves of the direct piston. |
| − | [[File:TH350directpistonseals1.jpg|thumb|300px|left|Direct piston with lip seals installed]] <br style="clear:both"/> | + | [[File:TH350directpistonseals1.jpg|thumb|300px|left|T-350 Direct piston with lip seals installed]] <br style="clear:both"/> |
==Dual feeding== | ==Dual feeding== | ||
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[[File:T-350_fwd_drum.jpg|thumb|300px|left|Check forward drum for wear.]]<br style="clear:both"/> | [[File:T-350_fwd_drum.jpg|thumb|300px|left|Check forward drum for wear.]]<br style="clear:both"/> | ||
| − | ===Pump assembly=== | + | ===T-350 Pump assembly=== |
| − | '''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 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 low reverse friction in the intermediate piston cavity]]<br style="clear:both"/> | + | [[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. | Intermediate piston installed. | ||
| − | [[File:T-350_pump_n_piston.jpg|thumb|300px|left| | + | [[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 pump stator. Remove the second ring from the bottom if dual feeding. | + | 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"/> | [[File:T-350_stator_rings.jpg|thumb|300px|left|Sealing rings on pump]] <br style="clear:both"/> | ||
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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. Incorrect installation will result in pump failure and converter damage. | 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 inner pump gear tangs, they must be '''up''' as seen here]] <br style="clear:both"/> | + | [[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. | 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 pump halves shown]] <br style="clear:both"/> | + | [[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 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. | + | 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. | 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 clutch drums in the pump shown. Refer to build manual for locations]] <br style="clear:both"/> | + | [[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"/> |
| − | 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. | + | 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 clutch drums installed with braking band shown]] <br style="clear:both"/> | + | [[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=== | ===Braking band=== | ||
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[[File:T-350_HD__braking_band.jpg|thumb|300px|left|Heavy duty brake band should have weld reinforced struts]]<br style="clear:both"/> | [[File:T-350_HD__braking_band.jpg|thumb|300px|left|Heavy duty brake band should have weld reinforced struts]]<br style="clear:both"/> | ||
| − | =Intermediate clutch= | + | =T-350 Intermediate clutch= |
6 cylinder applications use an intermediate piston measuring 1.175"-1.185" thick. The 6 cylinder uses two frictions. | 6 cylinder applications use an intermediate piston measuring 1.175"-1.185" thick. The 6 cylinder uses two frictions. | ||
| − | The V8 intermediate uses three frictions. The piston is about 0.990" thick. | + | The V8 T-350 intermediate uses three frictions. The T-350 piston is about 0.990" thick. |
The wavy cushion plate should be used. | The wavy cushion plate should be used. | ||
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There are two types of intermediate return spring/retainers. With the early type you had to manually place the loose springs onto the piston's spring locator bosses,then the retainer went over that. The later retainer has the springs attached to their respective retainers (the bosses are not used). So if the intermediate piston is smooth, use the retainer with the springs attached to it. The late retainers will work in a transmission that originally used the early type retainer, but not vice versa. | There are two types of intermediate return spring/retainers. With the early type you had to manually place the loose springs onto the piston's spring locator bosses,then the retainer went over that. The later retainer has the springs attached to their respective retainers (the bosses are not used). So if the intermediate piston is smooth, use the retainer with the springs attached to it. The late retainers will work in a transmission that originally used the early type retainer, but not vice versa. | ||
| − | ==Intermediate clutch clearance== | + | ==T-350 Intermediate clutch clearance== |
| − | After the pump is set into place to test end play clearance, you can also check the clutch clearance on the intermediate clutch pack. Clearance of 0.050" to 0.070" will work well. There are thicker intermediate steel plates available if need to tighten up the clutch pack clearance. Intermediate steels | + | After the pump is set into place to test end play clearance, you can also check the clutch clearance on the intermediate clutch pack. Clearance of 0.050" to 0.070" will work well. There are thicker intermediate steel plates available if need to tighten up the clutch pack clearance. T-350 Intermediate steels are available in 0.068", 0.078" and 0.089" thicknesses, some manufacturers may use slightly different thicknesses than these. |
| − | Also, a scraped low-reverse friction can be used under the intermediate piston if need be. A scraped friction will measure about 0.032". | + | Also, a T-350 scraped low-reverse friction can be used under the intermediate piston if need be. A scraped T-350 friction will measure about 0.032". |
| − | [[File:T-350_intermed_clearance_ck.jpg|thumb|300px|left| | + | [[File:T-350_intermed_clearance_ck.jpg|thumb|300px|left|T-350 intermediate clutch pack clearance can be checked through this hole]] <br style="clear:both"/> |
=Valve body= | =Valve body= | ||
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=Filter= | =Filter= | ||
| − | Brass screened filter allows for more flow. Avoid the cloth looking material filters for the | + | Brass screened filter allows for more flow. Avoid the cloth looking material filters for the T-350 |
[[file:T-350HPfilter.jpg]] | [[file:T-350HPfilter.jpg]] | ||
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=Gear ratios= | =Gear ratios= | ||
| − | Ratios of the | + | Ratios of the T-350 were consistent throughout its production: |
*First gear- 2.52:1 | *First gear- 2.52:1 | ||
*Second gear- 1.52:1 | *Second gear- 1.52:1 | ||
*Third gear- 1.00:1 | *Third gear- 1.00:1 | ||
| − | *Reverse- 1.93:1 | + | *Reverse- 1.93:1 |
=Aftermarket parts= | =Aftermarket parts= | ||
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=Reference material= | =Reference material= | ||
| − | [[File:Sessions- ATSG-Haynes manuals.jpg|thumb|600px|left|Left to right: [http://www.amazon.com/Turbo-Hydra-Matic-350-Handbook-Sessions/dp/0895860511 Turbo Hydra-Matic 350 Handbook] by Ron Sessions; [http://www.northernautoparts.com/ProductModelDetail.cfm?ProductModelId=786 ATSG manual] p/n 44400; Haynes [http://www.amazon.com/gp/product/1563924234/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=0895860511&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=0J4A1QHT1Y8B032P3Z6P GM Automatic Transmission Overhaul] manual, p/n 10360.]] <br | + | [[File:Sessions- ATSG-Haynes manuals.jpg|thumb|600px|left|Left to right: [http://www.amazon.com/Turbo-Hydra-Matic-350-Handbook-Sessions/dp/0895860511 Turbo Hydra-Matic 350 Handbook] by Ron Sessions; [http://www.northernautoparts.com/ProductModelDetail.cfm?ProductModelId=786 ATSG manual] p/n 44400; Haynes [http://www.amazon.com/gp/product/1563924234/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=0895860511&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=0J4A1QHT1Y8B032P3Z6P GM Automatic Transmission Overhaul] manual, p/n 10360.]] <br> |
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[[Category:GM]] | [[Category:GM]] | ||
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