General Motors
Source-verified model
General Motors TH125C
The 3-speed automatic transmission GM 3T40 named as Turbo-Hydramatic 125C was installed on FWD cars with engine capacity from 2 up to 3.1 liters. The first modifications of this transmission did not have the torque converter, later versions (1995) had an electronic control and letter E was added to a new name GM 3T40E. The most significant modification was introduced in 1984. Since then sets of gaskets and seals have not been changed.
Speeds
3
Type
AT
Drive
FWD
Max torque
250
ATF capacity (L)
8,5
ATF change (L)
3,8
ATF type
Dexron III
Other and alternative codes of this transmission
3T40
TH-125C
TH 125C
MD9
TH125C
TH125
M34
TH 125
TH-125
125C
verified naming
OEM designation
source name
Common problems & symptoms
Problems and symptoms reported for this transmission, compiled from repair sources. Not a complete list.
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About this transmission
Transmission general data
The 3-speed automatic transmission GM 3T40 named as Turbo-Hydramatic 125C was installed on FWD cars with engine capacity from 2 up to 3.1 liters. The first modifications of this transmission did not have the torque converter, later versions (1995) had an electronic control and letter E was added to a new name GM 3T40E. The most significant modification was introduced in 1984. Since then sets of gaskets and seals have not been changed.
Technical issues and repair guidelines
The GM 3T40 is a reliable, simple transmission that operates over 300 thousand kilometers. It served as a prototype for the 4-speed family 4T40E -4T60E.This transmission rarely gets in repair services. The main spare parts ordered for repair of this transmission are the repair kit of gaskets and seals (Overhaul kit) or a complete Masterkit (with clutches and seals).
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