alternatives to th auto trans - Pennock's Fiero Forum
If it is the transmission mount I need to know, stick or auto and if it is an auto I need to know if it is the 3T40 or the 4T40E transmission. You can rent the engine . Beretta, , THC/3T Beretta, , L4 L, 3 Spd FWD, C( 3T40) C(3T40). Cavalier, , L4 L L L, 4 Spd FWD, 4T40E. Transmission Model Number 3T40 Applications, Specifications, Dimensions, Ratios.
Design The Hydramatic used a two-element fluid coupling not a torque converterwhich has at least three elements, the pump, turbine and stator although Roto HydraMatic has a fluid coupling and a fixed stator and three planetary gearsetsproviding four forward speeds plus reverse. Standard ratios for the original Hydra-Matic were 3. The Controlled Coupling HydraMatic used 3. And Roto Hydramatic a three speed, four range automatic has a 3.
The front pump was a variable displacement vane unit driven from the fluid coupling housing, which meant oil pressure would be available immediately upon starting the engine.
A relatively constant pressure was maintained by moving a slide inside the pump, which had the effect of changing the pump's displacement and therefore the volume of oil being delivered. The rear pump was an unregulated gear pump driven from the transmission output shaft, which meant it was capable of pressurizing the transmission if the vehicle was in motion.
At higher speeds, the rear pump provided all the oil volume that was needed to operate the transmission and the front pump's slide was nearly centered, causing that pump to produce little output.
In first gear, power flow was through the forward planetary gear assembly either 1. That is, the input torus of the fluid coupling ran at a lower speed than the engine, due to the reduction of the forward gear assembly. This produced an exceptionally smooth startup because of the relatively large amount of slippage initially produced in the fluid coupling.
This slippage quickly diminished as engine RPM increased. When the transmission upshifted to second gear, the forward gear assembly locked and the input torus now ran at engine speed. This had the desirable effect of "tightening" the coupling and reducing slippage, but unfortunately also produced a somewhat abrupt shift.
It wasn't at all uncommon for the vehicle to lurch forward during the shift, especially when the throttle was wide open. Upon shifting to third, the forward gear assembly went back into reduction and the rear gear assembly locked. Due to the manner in which the rear gear assembly was arranged, the coupling went from handling percent of the engine torque to about 40 percent, with the balance being handled solely by the gear train. This greatly reduced slippage, which fact was audible by the substantial reduction that occurred in engine RPM when the shift occurred.
The shift from third to fourth gear locked the forward gear assembly, producing 1. The result was a remarkably efficient level of power transfer at highway speeds, something that torque converter equipped automatics could not achieve without the benefit of a converter clutch. Many Hydramatics did not execute the shift very well, as the shift involved the simultaneous operation of two bands and two clutches.
Transmission Applications | GM Automatic Transmission Applications
Accurate coordination of these components was difficult to achieve, even in new transmissions. As the transmission's seals and other elastomers aged, the hydraulic control characteristics changed and the shift would either cause a momentary flare sudden increase in engine speed or tie-up a short period where the transmission is in two gears simultaneouslythe latter often contributing to failure of the front band. Much of the difficulty in staging a "clean" or shift in any cast iron Hydramatic was the changing elasticity of the governing springs in the valve bodies.
Even ambient temperature would affect this variable, so that a Hydramatic that would shift perfectly on a summers day would usually exhibit "flare" when cold.
Another long-standing driver complaint would be "flare" when trying to get a "" downshift when going around a corner, which usually resulted in a neck snapping jolt upon band application. Fromthe reverse anchor was used to lock the reverse unit ring gear from turning by engaging external teeth machined into that ring gear.
From on, a cone clutch did the same thing when oil pressure was up, and a spring-loaded parking pawl was allowed to lock the same ring gear in the absence of oil pressure. This worked better as the anchor would not grind on the external teeth if that ring gear were turning that is, unless the engine stalled as reverse was engaged.
Reverse was obtained by applying torque from the front unit band on, in reduction through the fluid coupling to the rear unit sun gear. The planet carrier of this gearset was splined to the planet carrier of the reverse unit. The rear unit ring gear hub had a small gear machined on its end which served as the reverse unit sun gear. Because the rear unit band was not applied for reverse, the rear unit and reverse unit compounded causing the combined planet carriers to rotate opposite to the input torque and at a further reduced speed.
The output shaft was machined onto the rear unit and reverse unit planet carriers.4T40E/4T45E Transmission - Parts BrakeDown/
Shutting off the engine caused the transmission oil pressure to rapidly dissipate. If the selector lever was in reverse or moved to reverse after the engine stopped, two mechanical parts combined to provide a parking brake. 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 THM has only one. GM used a Switch Pitch torque converter in the Buick twin turbine Dynaflow transmission between — and the Super Turbine two speed transmissions used by OldsmobilePontiac, and Buick divisions between The switch pitch is not the only THM that utilizes an external 2 prong connector.
Other units to include the 2 prong connectors had an internal pressure switch that was used to control spark timing retard. It can be identified by "THM" cast into the tailhousing. Internally the clutch packs originally had fewer friction plates. It is a THM Chevrolet bolt pattern case that has a longer 27 spline output shaft and matching extension housing with "TH" cast into the housing.
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Another variant is the 3L80HD, often referred to as a Turbo 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.
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Bythe relatively heavy THM was being phased out of usage in passenger cars in response to demand for improved fuel economy. The civilian Hummer H1 originally had the 3L80s, but the current model has had a 4L80E since the mids.
The THM was never produced with a multicase bell housing. Early Jeep THMs used an adapter between the engine and transmission bell housing while later models had an AMC specific housing - which bolted to its inline six and V8.
THM 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.