Description
About This Transmission
The GM Turbo Hydra-Matic 350- universally known as the TH350 or Turbo 350- is the most widely used automatic transmission in General Motors history. Introduced in 1969 as a 3-speed replacement for the two-speed Powerglide, it was used in virtually every rear-wheel-drive GM passenger car and light truck from 1969 through 1986. Chevrolet, Pontiac, Oldsmobile, Buick, GMC, and Cadillac all used the TH350 in one form or another across seventeen production years. During that time it appeared in Camaros, Novas, Chevelles, Malibus, Monte Carlos, Corvettes, Firebirds, Grand Prixs, Cutlass Supremes, and virtually every GM rear-drive truck and van of the era.
The TH350 was developed jointly by Chevrolet and Buick- giving it the CBC350 designation (Chevrolet-Buick Combined)- and was manufactured at multiple GM facilities in Flint, Michigan, Toledo, Ohio, and Windsor, Ontario. Its one-piece aluminum alloy case measuring just 21.75 inches (shorter than the TH400 by a significant margin) and weighing only 120 lbs made it the transmission of choice for GM's small-block V8 applications where weight and size mattered. The TH400 was reserved for big-block applications where the extra torque capacity justified its larger size and weight.
The TH350 remains one of the most popular transmissions for classic car restoration, restomod builds, and engine swap projects decades after production ended. Its fully hydraulic control system (no electronics to fail), straightforward valve body design, and enormous aftermarket support make it the transmission of choice for anyone building a classic GM vehicle on a budget. Novak Conversions- specialists in Jeep drivetrain conversions- specifically call out the TH350 as the shortest and one of the strongest automatics adaptable into a Jeep.
Signs You Need a Replacement Transmission
- Slipping between gears- clutch pack wear or low line pressure from valve body or pump wear
- No 2nd gear or no 3rd gear- band or clutch pack failure inside the transmission
- Transmission will not engage from park- linkage adjustment issue or manual valve in valve body
- Fluid leak at pan gasket or tailshaft seal- common on aged TH350s with original rubber seals
- Hard or delayed shift from 1st to 2nd- vacuum modulator failure (the modulator is the primary shift-timing control on the TH350)
- Lockup converter failing to engage or disengage (TH350-C)- lockup solenoid or electrical feed issue
Known Problems With This Transmission
- Chevy vs BOP bellhousing incompatibility- the most common TH350 sourcing error: The TH350 came with Chevrolet bellhousing pattern (for SBC, BBC, and GM inline engines) OR BOP bellhousing pattern (for Buick, Oldsmobile, and Pontiac engines). A Chevy-pattern TH350 will not bolt to a Pontiac, Olds, or Buick engine without swapping the bellhousing. We confirm bellhousing pattern before every order.
- TH350 vs TH350-C compatibility: The standard TH350 and the TH350-C use different pumps, input shafts, and torque converters that are NOT interchangeable. The TH350-C can be identified by an electrical connector on the driver's side of the case. We document lockup vs non-lockup before every order.
- End play issue- the TH350's known weak point: There is excessive end play between the fluid pump and center support, allowing the direct clutch drum to wobble slightly. This causes accelerated wear on the drum bushing and pump. The fix is simple during rebuild: install a thrust washer between the forward clutch drum and primary planetary gear, and replace the drum bushing with a thicker unit. We note any obvious drum wobble or pump noise before shipping.
- Vacuum modulator wear: The vacuum modulator controls shift timing. A ruptured modulator (which allows transmission fluid into the intake manifold) causes harsh or erratic shifts. We inspect for modulator integrity and leakage before shipping.
- Tailshaft length must match application: The 6-inch tailshaft is for most passenger cars. The 9-inch is standard for square-body trucks and Suburbans. Using the wrong tailshaft length puts the driveshaft yoke in the wrong position. We confirm tailshaft length before every order.
TH350 Key Variants and Bellhousing Patterns
Critical buyer information for ordering the correct TH350:
| Variant | Identification | Notes |
|---|---|---|
| Standard TH350 (1969 to 1979) | No electrical connector on case. Single vacuum modulator port. | Fully hydraulic. No lockup converter. Simplest to rebuild and modify. Most popular for performance builds. |
| TH350-C (1979 to 1986) | Electrical connector on driver's side of case. | Lockup torque converter for fuel economy. Pump, input shaft, and converter NOT interchangeable with standard TH350. |
| Chevrolet Bellhousing Pattern | Block flange has a peak at the top center. | Fits SBC, BBC, Iron Duke I4, GM inline-6 (60 degree block engines need different pattern). |
| BOP Bellhousing Pattern | Block flange has a valley at the top center. | Fits Buick, Oldsmobile, and Pontiac V8 engines. Also most Cadillac applications. |
| Universal Unicase | Has both Chevy and BOP bolt patterns. | Fits virtually all pre-LS GM engines. Useful but not as common as single-pattern units. |
What Is Included- What Is Not Included
| INCLUDED | Complete TH350 transmission assembly with all internal clutch packs, bands, valve body, governor, vacuum modulator, and output yoke. |
|---|---|
| NOT INCLUDED | Torque converter (confirm- may or may not be present on the unit. The TH350 and TH400 share the same torque converter), transmission fluid (fill with Dexron II or III, or Type F with a shift kit), kickdown detent cable, flexplate. |
| FLUID | Fill with Dexron II or Dexron III. Some shift kit manufacturers recommend Type F for firmer shifts- acceptable with a shift kit installed. |
| Core Note | No core charge. |
Vehicle Compatibility
The TH350 was used in virtually every GM rear-wheel-drive vehicle from 1969 to 1986. Key applications:
| Chevrolet Camaro | 1969 to 1981- with Chevy-pattern bellhousing |
|---|---|
| Chevrolet Nova | 1969 to 1979 |
| Chevrolet Chevelle and Malibu | 1969 to 1977 |
| Pontiac Firebird and Trans Am | 1969 to 1981- with BOP-pattern bellhousing |
| GMC and Chevrolet Trucks (C/K series) | 1969 to 1986- standard 9-inch tailshaft |
| Chevrolet Monte Carlo and El Camino | 1970 to 1977 |
| Oldsmobile Cutlass, Toronado (select), and others | BOP pattern |
| Virtually all GM rear-drive cars and trucks | 1969 to 1984- confirm Chevy vs BOP bellhousing for your specific application |
The TH350 is the single most popular swap automatic transmission in the classic car community. Its short 21.75-inch length, 120-lb weight, and compatibility with virtually any pre-LS GM engine (with the correct bellhousing pattern) make it the default choice for restomod and engine swap builds. The same output shaft yoke as the 700R4, Powerglide, and Muncie 4-speed simplifies driveshaft selection. For applications where overdrive is desired, the 700R4 (4L60) can be swapped in place of the TH350 in most truck applications with only a 5/8-inch driveshaft shortening.
Engine or transmission: Pairs with any Chevy SBC or BBC (Chevy bellhousing pattern) or any Buick, Olds, or Pontiac V8 (BOP pattern). Torque converter interchanges with TH400.
Not sure if this fits? Call (240) 301-0095. We verify fitment before every order ships.
Common Names and Search Terms
| TH350 | Most common buyer search code |
|---|---|
| Turbo 350 | Classic community designation |
| TH350 transmission | Full designation |
| Turbo Hydramatic 350 | OEM name buyer |
| GM 350 automatic | Brand and type designation |
| Chevy 3-speed automatic | Configuration buyer |
| TH350C | Lockup version buyer |
| 350 turbo automatic | General search variation |
| GM automatic transmission | Broad buyer |
| Chevy truck TH350 | Application-specific buyer |
Used OEM vs Rebuilt- Which Is Right for You?
Used OEM is the right choice for a classic car or truck restoration where a gear-tested unit with bellhousing pattern, tailshaft length, and lockup status confirmed is the starting point. The TH350's proven durability means a well-maintained used unit provides reliable service life.
A rebuilt TH350 from a performance shop makes sense for a build requiring a shift kit, upgraded clutch packs, and a performance torque converter installed and calibrated to your engine combination. Performance TH350 builds from $600 to $1,400 or more. Call us and we can discuss what your build requires.
Condition and Inspection Process
- All 3 forward gears and reverse tested- shift quality and gear engagement assessed
- Chevy vs BOP bellhousing pattern confirmed before every order
- Tailshaft length confirmed- 6, 9, or 12 inch documented
- TH350 vs TH350-C lockup status documented- electrical connector presence confirmed or absent
- Vacuum modulator integrity inspected- rupture indicator check
- Pan inspection for clutch material or metal debris in fluid- mechanical failure indicator
- Direct clutch drum end play assessed- the TH350's known weak point
Mileage and operating hours vary by unit. Where available from the donor vehicle or equipment, we provide this information. Where it cannot be confirmed, we disclose this before your order is placed.
Buyer Tips- What to Know Before You Order
- Confirm Chevy vs BOP bellhousing before ordering: This is the most important question. Look at the engine you are pairing this with- Chevy SBC or BBC = Chevy pattern. Pontiac, Buick, or Oldsmobile V8 = BOP pattern. A BOP-pattern TH350 will not bolt to a Chevy engine without a bellhousing swap.
- Tailshaft length must match your driveshaft: Passenger cars typically use the 6-inch tailshaft. Square-body trucks (1973 to 1987) and Suburbans typically use the 9-inch tailshaft. Measure your current driveshaft-to-transmission distance to confirm which length you need.
- TH350 vs TH350-C- lockup distinction: If you want the simpler non-lockup version for a performance build, you need the standard TH350 (pre-1979, or non-C marked unit). The TH350-C with lockup is fine for stock applications and fuel economy but requires working with the lockup electrical system.
- The detent cable is not a TV cable: The TH350's kickdown detent cable is nothing like the 700R4's TV cable in terms of criticality. If the detent cable is missing on a TH350, it will still work- it simply will not have kickdown passing-gear function. Leaving the 700R4 TV cable disconnected destroys that transmission. Know the difference.
- Shift kit strongly recommended: For any performance application, install a B&M or TransGo shift improver kit at installation. Cost is $40 to $80 and it provides significantly firmer, faster shifts that reduce slippage and heat.
Why Buy From Vaz Auto Solutions
- Chevy vs BOP bellhousing confirmed before you pay- most critical TH350 compatibility distinction
- Tailshaft length confirmed- 6, 9, or 12 inch documented
- TH350 vs TH350-C lockup status documented- simplifies build planning
- All 3 gears and reverse tested- shift quality assessed
- Vacuum modulator integrity checked- most common shift quality concern
- No core charge- keep your old transmission
- Free freight pallet delivery to all 50 states
- 15 day replacement warranty on internal defects
- Call (240) 301-0095- speak with someone who understands TH350 bellhousing patterns, tailshaft lengths, and the TH350 vs TH350-C distinction
Tom Wilson (verified owner) –
Grabbed a 350 Turbo from Vaz Auto Solutions for my Chevy rebuild. Smooth shifter, handles power well. Needed a rebuild kit, but that’s expected with used transmissions. Solid choice for a street or strip setup.
Rick Anderson (verified owner) –
Found a decent 350 Turbo on Vaz Auto Solutions. This transmission’s a workhorse – tough and reliable. Shifts are crisp after a good service. Great match for my small block, doesn’t break the bank either.
Jim K., Dallas TX –
Replaced the TH350 in my Nova. Vaz confirmed Chevy bellhousing pattern and 6-inch tailshaft before I bought — the two details that determine whether the thing actually bolts in. All 3 gears tested clean. Good shift feel right out of the box. Added a TransGo shift kit at installation for firmer shifts. Runs great.
Bob T., Phoenix AZ –
Needed a 9-inch tailshaft TH350 for my square-body truck. Vaz confirmed the 9-inch tailshaft and Chevy bellhousing pattern before shipping. TH350-C lockup vs non-lockup documented — got a standard non-C unit as requested. All 3 gears worked fine. Vacuum modulator had a minor seep — disclosed before I bought and replaced at installation. Good honest transaction.