Engine/Transmission (1998.5 - 2002) Assistance needed with Auto Trans and mileage issue

[Sticks]

A coworker of mine with a 99 2500, had his transmission replaced about 2 years ago (@ 400k miles) with a rebuilt trans - not dealer - and a supposedly upgraded torque converter.



A few weeks ago (140k miles) the torque converter started leaking and he took it back to the same shop to have it replaced. Immediately he noticed his highway speed engine RPMs were 300 higher, and his mileage dropped like a rock.



I am not familiar with autos, but this one seems a little odd. He is still working with the shop to have the issue resolved, but they are insisting that it is the exact same torque converter installed as the replacement.



This truck is otherwise stock. The only modifications are 80hp injectors done at 300k miles.

 

[HBarlow]

If your friend is correct about his engine rpm increase at a given road speed and a corresponding fuel mileage decrease either he has lost overdrive, torque converter lockup, or it is a malfunctioning slipping torque converter.

 

[cerberusiam]

Sounds like the TC is not engaging the lockup clutch correctly. In lockup mode there should be no difference in rpm to speed on any converter. The differences would be in the fluid coupling before the TC locks. A tight converter with better efficiency at speed will take less throttle to get the truck moving and use less throttle to maintain speed sans lockup.

The 300 rpm is about what a normal converter losses between lockup and fluid coupling at speed with no load. Could be a bad TC, a bad solenoid, a bad connection in the wiring harness. On good aftermarket built trans lockup should be very noticeable and obvious when missing.

 

[Sticks]

Thanks guys, I will pass along this info.