| Manufacturer | General Motors |
|---|---|
| Production | 1964– |
| Predecessor | Dynaflow Hydra-Matic Powerglide Jetaway Super Turbine 300 |
| Successor | 4L60-E/4L65-E 4L80-E/4L85-E |
| Class | 3-speed longitudinal automatic transmission |
| Related | Turbo-Hydramatic 125 Turbo-Hydramatic 180 Turbo-Hydramatic 425 |
Turbo-Hydramatic is the registered tradename of a family of automatic transmissions developed and produced by General Motors. These transmissions mate a three-element torque converter to a Simpson planetary geartrain, providing three forward speeds plus reverse.
The Turbo-Hydramatic (THM) series was developed to replace both the original Hydra-Matic models and the Buick Dynaflow. In its original incarnation as the Turbo-Hydramatic 400, it was first used in the 1964 model year in Cadillacs. The Buick version, which followed shortly thereafter, was known as the Super-Turbine 400. By 1973, THM units had replaced all of GM's other automatic transmissions including Chevrolet's Powerglide, Buick's Super Turbine 300, and Oldsmobile's Jetaway. Starting in the early 1980s, the Turbo-Hydramatic was gradually supplanted by four-speed automatics, some of which continue to use the "Hydramatic" trade name.
Although the Turbo-Hydramatic name alludes to the Hydramatic developed by General Motors' Cadillac division in the late 1930s, the two transmissions were not mechanically related.
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The THM400 can be visually identified by an oil pan shaped similarly to the state of Texas. It was first introduced for the 1964 model year under the name "Turbo Hydra-Matic" in Cadillacs[1]. and "Super Turbine" in Buicks[2] . The following year, application expanded to Oldsmobile and Pontiac and to some full-sized Chevrolets. Many of the Buick, Cadillac, and Oldsmobile THM400s produced between 1964-67 were equipped with a Switch-Pitch torque converter variable-pitch stator, which is sought after by collectors and drag racers. These can be identified outside the vehicle (with the torque converter removed) by a narrow front pump spline. Externally the switch pitch version has two electrical connections, where the non-switch pitch THM400 has only one. GM used a Switch Pitch torque converter in the Buick twin turbine Dynaflow transmission between 1955-1963 and the Super_Turbine_300 two speed transmissions used by Oldsmobile, and Buick divisions between 1964-1967.
A variant of the THM400 known as a THM375 is a THM400 with a long output shaft that mates to the smaller THM350 drive shaft yoke. It can be identified by "375-THM" cast into the tailhousing. Internally the clutch packs originally had fewer friction plates. Some "Heavy Duty" THM350s were also designated THM375-B. Another variant is the 3L80HD, often referred to as a Turbo 475. The 3L80HD has a straight-cut planetary gear set. There is no externally visible way to determine whether the transmission contains the straight-cut planetary gear set. The THM425 front wheel drive transmission shares almost all its internal parts with the THM400.
By 1980, the relatively heavy THM400 was being phased out of usage in passenger cars in response to demand for improved fuel economy. The Presidential Limousine used during the Reagan Administration, a modified 1984 Cadillac Fleetwood Brougham, was the last known GM passenger vehicle to use the THM400, alongside the C- and K-series (full size) Chevrolet/GMC pickups and G-series (full size) vans ending in 1986 thereafter it was renamed to the 3L80. Today, the United States Army HMMWV is the only vehicle using the THM400. The civilian Hummer H1 originally had the 3L80s, but the current model has had a 4L80E since the mid-1990s.
Through the end of the '70s substantially more CBOP (Cadillac/Buick/Oldsmobile/Pontiac) bellhousing THM400s were produced than any other THM400. Chevrolet bellhousing THM400s, while not rare, can be hard to find and are, as a result, usually more expensive to buy. Other bellhousing patterns are, accordingly, rarer. The THM400 was never produced with a multicase bell housing.
Other auto manufacturers have used the THM400 and its 4L80E successor, including Ferrari (in the 400/412); Jaguar/Daimler (in pre-1994 XJ12 and XJ-S coupes) and their Daimler stable mates; Rolls-Royce (in 1965–1980 Silver Shadow and 1980-1992 Silver Spirit series cars, along with their Bentley stable mates); the Nissan Prince Royal; AM General; and Jeep (usually found in the FSJ pickups and SUVs. Early Jeep THM400s used an adapter between the engine and transmission bell housing while later models had an AMC specific housing. Though identical except for the bell housing pattern used through the '60s and ending in 1979 the THM400 was mated to the Dana model 18,20 and was the only transmission used with the Borg-Warner 1305/1339 all-wheel-drive transfer case used only in Jeeps, It has been known to adapt a THM400 to other engines using adapters.
THM400 transmissions are very popular in automotive competition due to their great strength. Much of this strength comes from the use of a cast iron center support to suspend the transmission's concentric shafts that join the clutch assemblies to the gear train. The center support, which is splined to the interior of the transmission's case, also provides a robust reaction point for first gear (the gear train's reaction carrier is restrained from counter-rotating the engine in first gear by a roller clutch whose inner race is part of the center support). Since the first gear reactive force is evenly distributed around the periphery of the case, the types of mechanical (and some times violent) failures that have plagued other competition transmissions are rare.
The THM400 was the first three-speed, Simpson-geared automatic to use overrunning clutches for both first and second gear reaction, a feature that eliminated the need to coordinate the simultaneous release of a band and application of a clutch to make the 2-3 gear change. Owing to this feature, as well as the use of a large, multi-plate clutch to provide second gear reaction, the THM400 is able to withstand very high input torque and an enormous number of shifting cycles, as would be encountered in frequent stop-and-go driving. As a result, it has met with considerable success in commercial vehicle applications.
For 1987, GM changed the nomenclature of their Turbo Hydramatic transmissions — the THM400 was renamed to the '3L80' (three forward speeds, longitudinal positioning, and an arbitrary 'strength' of 80, the second highest such rating assigned). The 3L80HD was introduced in 1987 as the HD unit used in passenger trucks. In 1991, a four-speed overdrive version, the 4L80-E, replaced the THM400 in Chevrolet/GMC pickups, vans, SUVs, and commercial vehicles. The 4L80E (and its successor 4L85E) was the first Hydramatic to incorporate electronic controls — almost all of the THM400/3L80/3L80HD's components are interchangeable.
Transmission fluid cooler line connections are found on the right hand side of the THM400. The lower connection is the cooler feed, and the upper connection is the return[3]. The case is tapped for either self-sealing 1/4"NPT fittings, or 1/2"UNF fittings with a washer seal. 5/16" or 3/8" rigid coolant lines are generally connected via appropriate double-flared adapters.
Gear Ratios are:
The Turbo Hydra-matic 350 was first used in 1969 model cars. It was developed jointly by Buick and Chevrolet to replace the two-speed Super Turbine 300 and aluminium-case Powerglide transmissions. So, although it carries the Turbo Hydra-matic name, the Hydra-matic Division of General Motors had little, if anything, to do with its design. The 350 and its 250, 250c, 350c and 375b derivatives have been manufactured by Buick in its Flint, Michigan, plant and by Chevrolet in Toledo and Parma, Ohio, and Windsor, Ontario.
Some would suggest that the THM350 (or Turbo 350 as called by drag racers and car enthusiasts) was based on the earlier Buick Super Turbine 300 — some components interchange between the two. Both Chevrolet and Buick divisions produced the THM350.
The THM350 was also regarded as a 'three speed Powerglide' and during its development, was generally called this. Although it uses the same torque converter as the THM400 (sans variable pitch stator) it has a familial resemblance to the 1962-'73 Aluminum Powerglide from Chevrolet and was largely derived from the Chevrolet design. One important difference in the THM350 compared to the THM400 is there is no fixed center support midway through the geartrain, this important difference in layout permitted THM350 to be adapted to the Corvair where the drive and driven ends are the same. This feature was not exploited but Corvair may have eventually used the THM350 had it remained in production, and Chevrolet was experimenting with mid-engine Corvette designs that might also have used this advantage had they ultimately reached production. Air cooled versions (with a baffle on the torque converter and air intakes cast into the bellhousing) of the THM350 appeared mid 1972 in Chevrolet Vega and Nova 6.
There is a rumor that the reason for the THM350's release after the THM400, is that although the THM350 had been in development longer (disputable), it often failed under heavy torque loads. One THM350 weak point was excessive end-play between the pump and center support and resulting wobble of the direct clutch drum due to both the end play and use of a relatively narrow bushing in the drum. This weak point can be addressed by using an extra thrust washer between the planetary gear and direct clutch to remove the end play and using a wider aftermarket bushing in the direct clutch drum. Another weak point is the relatively thin center support and the lightweight matching splines in the case. This weakness can be addressed by using an inexpensive aftermarket case saver kit. It is claimed that fixing these two issues will result in a THM350 that is as durable and reliable as a THM400.
Around 1980, a lock-up torque converter was introduced; this transmission was phased out in 1984 in GM passenger cars for the 700R4. Chevrolet/GMC trucks and vans used the THM350-C until 1986. The lock-up torque converter was deemed unpopular with transmission builders — B&M Racing once marketed a conversion kit for THM350-Cs during the early 1980s until the advent of high-stall lock-up torque converters when its overdrive counterpart (THM700R4/4L60) were modified. The standard TH350 is still very popular in drag racing.
The THM250 is a derivative of the THM350 and was introduced in 1974 in Chevrolets as a Powerglide replacement. Internally, the THM250 is a THM350 without the intermediate clutch pack with a band adjuster similar to the Powerglide. It was later reintroduced in 1979 as the THM250-C in the wake of the failure-prone THM200/200C. Gear Ratios: THM350,250,250-C
Right after the 1973 OPEC oil embargo, GM developed a lighter-duty version of the THM350 with lightened materials — primarily alloys in place of ferrous materials (e.g. clutch drums and oil pump). The Turbo-Hydramatic 200 was born; however, this transmission was notorious for its failure rate when used behind a V8 engine — especially the Oldsmobile V8 350 Diesel.
1976 GM vehicles first saw use of the THM200 — from the GM T platform to GM X-Bodies (Chevrolet Nova et al.).
Transmission shops nationwide, along with GM repair facilities, have swapped in THM350s since the 200s were failure prone. Starting with the 1979 model year, vehicles which had the THM200/200C as standard equipment were optioned with the THM250-C, actually a THM350 without the intermediate clutch pack along with an adjustable band similar to the Chevrolet Powerglide.
Around 1979, it received a lockup torque converter, and some internal components (primarily the low/reverse clutch drum and planetary gears) were later shared with the Turbo-Hydramatic 200-4R.
THM200/200Cs were produced until 1987.
The gearing for the 200C is:
In 1980, for the 1981 model year, the 200-4R (sometimes called 200R4) was introduced for use in GM vehicles. Internally, the components which were prone to failure in the THM200 were improved, and this transmission was used with high-power applications — primarily the Buick Grand National and the 1982 Chevy Corvette. GMs powered with the Oldsmobile 5.7 L Diesel powerplant were coupled with the 200-4R in place of the 200. The 200-4R was configured with several different torque converters and gear ratios depending on the vehicle application.
Unlike the 700R4, the 200-4R has a multicase bellhousing for use with Chevrolet, Buick/Olds/Pontiac (BOP), and Cadillac powerplants. Since the external dimensions are similar to the THM-350, 200-4Rs are often swapped in place of THM-350s in older vehicles to provide an overdrive gear. (However, in situations where case clearance and the need for drive shaft modification isn't an issue, the TH400 is more of a close mounting match to the 200-4R. Placement of the mount is identical. The yoke needs to be changed in most circumstances, and the drive shaft length will be different as well.)
Early models had PRND321 on the cluster, while later models had PRN(D)D21, with the left D identified as the overdrive gear by a square or oval ring.
The THM200-4R was phased out after 1990 — its final usage was in the GM B-body lineup (Chevrolet Caprice, Oldsmobile Custom Cruiser station wagon, Cadillac Brougham) coupled to either a Chevrolet 305 or an Oldsmobile 307 engine. It is believed that an HD version of the 200-4R was used in the late 80s Caprice 9C1 police package using the internals from the Buick Grand National.
The Hydramatic 700R4 was introduced in 1982 for use in Chevrolet/GMC vehicles.
In 1990, the 700R4 was renamed the 4L60. Under the new designation, the "4" stands for the number of forward gears, the "L" for longitudinal applications (rear-wheel-drive), and the "60" relates to the relative torque capacity.
1992 was the last year of widespread usage of the 700R4 (4L60).
1993 Camaro, Corvette and Typhoon were equipped with the last production 700R4's. The last design change of the 700R4 was an added checkball to the valve body.
In 1992 electronic controls were added, and it became the 4L60-E. The 4L60E went into service in trucks, vans, and SUVs in 1993 (for the record, some HD trucks had the 4L60) and in all RWD passenger cars (Corvette, F and B/D bodies) in 1994.
In 2001, an updated version — the 4L65-E, was introduced. Five-pinion planetaries, along with a strength-improved output shaft, were improved to withstand the 300+ ft·lb (400+ N·m) of torque of the 6.0 Vortec engine.
The 700R4 can be identified by the oilpan having a rectangular shape being longer front-to-rear than side-to-side and held to the transmission by 16 bolts: three bolts front and rear; five bolts left and right sides.
The tailshaft housing is held onto the main case by four bolts (the bolt spacing is similar to the THM350), and uses a square-cut o-ring seal, and not a gasket. The typical width of this transmission where it bolts to the engine is 20 in (51 cm) overall. From the engine/trans mating surface to the crossmember mount bolt is 22.5 in (57 cm), and engine/trans surface to output shaft housing mating surface is 23.375 in (59.37 cm) overall, with the tailshaft housing typically measuring 7.625 in (193.7 mm).
Transmission fluid cooler lines on the 700R4 the bottom fitting on the right side of the transmission is the "out" line to the cooler and the top fitting is for the return line from the cooler. These fittings are .25 in (6.4 mm) pipe thread, and CAN include an adapter from the factory for threaded steel lines in a SAE size. 4L60Es manufactured after 1995 use the modern-day snap-in connections as opposed to threaded SAE fittings.
The original version of the transmission had a 27-spline input shaft which was a common failure point. In 1984, 700R4's designed for use behind Chevrolet small block V8's received a 30-spline input shaft similar to those found on classic TH400 transmissions and which also used a different torque converter than its 2.8 V6 and 2.2 L4 powerplants. Between 1984-1987, internal components, from the ring gear to the oil pump housing, were updated, ending with the auxiliary valve body (for 700s manufactured after October 1986).
In 1995, the 4L60E received a PWM-controlled lockup converter. 1994 fullsize chevy trucks have been seen with PWM; Late year 1994s are equipped with PWM (referred to as model year 1995). Only for sure way to know is pull the transmission out and PWM will be stamped into the front of the transmission below the input shaft.
In 1996, GM introduced a redsigned 4L60E tranmission case that incorporated a bolt-on bellhousing and an 6 bolt tailhousing. The 1996 and up model 4l60Es are referred to Late-model 4L60Es, and the 1993-1995 are referred to as the Early-model 4L60E. Both transmissions are essentially the same internally with only minor modifications. The Early-model and Late-model 4L60Es are not interchangeable.
For the model year 1996 GM trucks, there was 2 versions of the 4L60E transmissions. One had a bolt on bellhousing the other did not. Both designs have been interchangeable. PWM (Pulse Width Modulated) is a term referred to on how the Torque Converter locks up. The early designs simple lock or unlock while the later design can varibly lock as to not feel the lock up occur.
The gearing for the 700 is:
(commonly rounded off to 3.06, 1.63, 1.00, 0.70, and 2.29).