Boost Lab, Inc. rebuilds the Garrett AiResearch turbochargers that made the 1978 to 1987 turbo Buicks legends: the TB0348 (466748 family) on the intercooled 1986 to 1987 cars, the TB0330 (466112) hot air unit, the carbureted-era TB0304, TB0309, TB0317 and TB0332, and the GNX ceramic-impeller Garrett under GM 12336213. We restore original units to factory spec so your numbers-matching car keeps its original hardware, and we service the TA-49 and other period upgrade turbos too. Ship it in from anywhere in the country.
Every turbocharged 3.8L Buick V6 from the early carbureted cars through the 547-unit GNX run. Boost Lab, Inc. rebuilds all of them.
The first turbo Buicks ran carbureted 3.8s with Garrett AiResearch TB03-family hardware that changed by year and model: TB0304 (465404) on the 1979 Riviera S-Type, TB0317 (465736) on 1981 Regal and Riviera, TB0309 (465562) on the 1982 Riviera, and TB0332 (466218) on the 1984 Riviera T-Type. Simple journal-bearing turbos, but 40-plus years of heat cycles means most cores need a full rebuild. Originality matters, so we rebuild your unit rather than substituting.
Sequential fuel injection arrived in 1984 but without an intercooler, hence the "hot air" nickname. These cars run the Garrett TB0330, part number 466112-0001, GM 25515636, with CHRA 409174-0040. Hotter charge temps than the later intercooled cars accelerate seal and bearing wear, and a properly rebuilt hot air turbo with fresh seals stops the classic oil-smoke-at-idle these cars are known for.
The definitive combination: Garrett TB0348, catalog numbers 466748-0004, -0005 and -0006, GM part numbers 25526630, 25527600 and 25536314, with the factory intercooler. 245 hp and 355 lb-ft in 1987 trim. This is the turbo we see most. Common core condition after decades: worn journal bearings, shaft play, hardened seals, and light compressor wheel rub. Almost all are rebuildable.
The 547-unit GNX ran a revised Garrett T3 with a ceramic impeller for faster spool, serviced under GM part number 12336213 and tagged with a .60 A/R compressor. GNX turbos deserve extra care: documentation photos at every stage, original hardware preserved, and factory-spec balancing. With concours GNX values where they are, do not let a general machine shop learn on yours.
Pontiac's 20th Anniversary Turbo Trans Am ran a GNX-related Buick 3.8 with reworked heads and its own turbo calibration on the TB0348 / 466748 architecture; it even shares the turbo inlet bell gasket with the 1986 to 1987 Regals. All 1,555 cars rebuild on the same bench with the same process as the GN units.
Thousands of turbo Buicks run period aftermarket upgrades on Garrett T3/T4 hybrid architecture. The TA-49 in particular is getting hard to replace new, which makes rebuilding the one you have the smart move. We rebuild T3/T4 hybrids with 360-degree thrust upgrades where the housing allows.
Original turbo assemblies for these cars now trade for thousands of dollars when they surface at all, and GM discontinued most GN-specific components decades ago. Rebuilding your original Garrett preserves the casting numbers and date-coded hardware that matter at judging and at sale time. Tell us the car is a numbers-matching or concours build when you send the unit and we will document the rebuild with photos and preserve every original external component.
Verified Garrett catalog numbers, model designations, and GM OE numbers for every factory turbo Buick application. Search by any number, model, or year.
| Garrett PN | Model | GM OE PN | Application | Notes |
|---|---|---|---|---|
| 465404-0001 / -0002 / -0003 | TB0304 | 1264729 | 1979 Riviera S-Type 3.8 turbo | First-generation carbureted Riviera unit; -0004 also seen in service |
| 465736-0001 / -0003 / -0004 | TB0317 | 25506628 | 1981 Regal Sport Coupe, Riviera T-Type | Carbureted era |
| 465562-0003 | TB0309 | 25512270 | 1982 Riviera 3.8 turbo | Riviera-specific calibration |
| 465562-0004 | TB0309 | 25516170 | 1982 Riviera 3.8 turbo | Later revision of the 1982 unit |
| 466218-0001 | TB0332 | 25516838 | 1984 Riviera T-Type | Last carbureted-family Riviera unit |
| 466112-0001 | TB0330 | 25515636 | 1984-1985 Grand National, Regal T-Type (hot air) | Alt 466112-1; reman 466112-5001S under GM 25519874 |
| 409174-0040 / -0046 | TB0330 CHRA | 25519876 | 1984-1985 hot air center section | Cartridge for the 466112 turbo; reman 409174-5040S |
| 466748-0004 | TB0348 | 25526630 | 1986-1987 Grand National, T-Type, Turbo T | Intercooled SFI; the definitive GN turbo |
| 466748-0005 | TB0348 | 25527600 | 1986-1987 Grand National, T-Type, Turbo T | Running revision of the -0004 |
| 466748-0006 | TB0348 | 25536314 | 1986-1987 Grand National, T-Type, Turbo T | Late revision; also tied to 1989 TTA service |
| 466748-5004S / -5006S | TB0348 reman | 2200348 | 1986-1987 factory reman program | GM service number also written 22-00348 |
| 466748-9004 / -9006 | TB0348 reman | 8299739792 | 1986-1987 exchange units | Additional reman-channel identifiers |
| GNX Garrett T3, ceramic impeller | TB0348-based | 12336213 | 1987 GNX, 547 units | Tagged .60 A/R compressor; concours documentation rebuild |
| 466748 family, TTA calibration | TB0348 | See RPO | 1989 Pontiac Turbo Trans Am, 1,555 units | Shares inlet bell gasket with 1986-1987 Regals |
| TA-49 | T3/T4 hybrid | n/a (aftermarket) | Period street upgrade for 1986-1987 cars | New production ended; rebuild your core |
| TE-44 / TE-45a | T3/T4 hybrid | n/a (aftermarket) | Period street/strip upgrades | 3-bolt turbine inlet matches the TR manifold |
| 1997157 | Wastegate solenoid | 1997157 | 1984-1987 SFI cars, 1989 TTA | Frequent failure point misdiagnosed as turbo trouble |
| 25523720 | Fuel pressure regulator | 25523720 | Turbo TA and Somerset | Common companion part on rebuild jobs |
What we actually find when 35-to-45-year-old GN turbos come across the bench.
The number one condition on original units. Decades of heat cycles and period oil-change habits wear the journal bearings until the shaft can walk. You feel it as in-and-out or side-to-side play at the compressor nut. Caught early it is a routine rebuild; run too long, the wheels contact the housings and machining costs go up.
Original seals harden with age even on low-mileage cars. Oil migrates into the compressor housing and intercooler, or drips into the exhaust housing and burns off as blue smoke at idle and on decel. New seals plus a properly set up bearing system stops it for good.
The 1984 to 1985 non-intercooled cars run brutal charge temperatures. We see coked oil passages in the center section and heat-checked turbine housings on these more than any other Buick variant. A rebuild includes cleaning the CHRA passages back to bare metal.
These cars predate water-cooled center sections. Shutting down hot after a pull bakes the oil sitting in the bearing housing into carbon, which then grinds the bearings. If the car sat for years after being driven hard, expect coking. Fully serviceable during rebuild.
Original internal wastegate actuators lose diaphragm integrity, causing boost creep or low boost that owners often blame on the turbo cartridge itself. We test actuators on every rebuild and advise honestly on whether yours holds spec.
A large share of the GN turbos we open have been apart before, and not always kindly: mismatched bearings, missing thrust parts, silicone where gaskets belong, and unbalanced wheel assemblies that vibrate at speed. We put them right and balance every rotating assembly before it leaves.
Yes. Rebuilding the original Garrett is exactly what we recommend for collector cars. Original turbo assemblies command premium prices when they can be found at all, so preserving yours protects the car's value. We photograph and document collector rebuilds on request. Start at repair.theboostlab.com and note the car in your submission.
The intercooled 1986 to 1987 cars used the Garrett TB0348, catalog numbers 466748-0004, -0005 and -0006, under GM part numbers 25526630, 25527600 and 25536314. It is a journal-bearing turbo with an internal wastegate, and it is fully rebuildable.
Yes. The 1987 GNX used a revised Garrett T3 with a ceramic impeller for quicker spool, serviced under GM part number 12336213. Only 547 GNX cars were built, so these turbos get our full documentation treatment and factory-spec balancing.
Yes. The TA-49, TE-44, TE-45a and similar period upgrades are built on Garrett T3/T4 hybrid architecture and are rebuildable. With new TA-49 production ended, rebuilding your existing unit is usually the most sensible path.
Usually it is seals, not a dead turbo. Hardened seals let oil into the exhaust housing where it burns as blue smoke. A rebuild with new seals and bearings normally cures it. Ship the unit in and we will confirm the core condition before any work begins.
Start at repair.theboostlab.com, fill out the form, and ship the unit to Boost Lab, Inc., 37833 Pineapple Ave, Unit A, Dade City, FL 33523. We serve turbo Buick owners nationwide.