Shudder Symptoms: Not
Always the Converter!
by Matt Dixon,
SIUC Automotive Technology
W
hich came first, the chick-
en or the egg? A troubled
2008 Dodge Avenger with
a 41TES recently made me ponder
this age-old question. My version was
which came first: engine misfire or con-
verter clutch slip? I found the answer to
my dilemma while performing simple,
routine checks.
I’ll never forget a seasoned tech
in the shop telling me many years
ago: KISS (keep it simple, stupid).
The customer complaint was a bucking
or shudder-like sensation during light
cruising speed. The condition was eas-
ily duplicated.
A check of service bulletins
revealed a match of the complaint in
Figure 1: After removing the air box, access to the pressure taps are easy on the Dodge
Chrysler bulletin 21-003-08. The vehi-
41TES.
cle, being under warranty, was taken to to the issue at hand. I dropped
the local dealership and a new torque the car off at the dealership
converter installed for purposes of what again for what was supposed
the bulletin described as “revised fric- to be a quick flash. I became
tional composition.” concerned when I didn’t hear
That’s where I expected the story anything for a while… a long
to have a happy ending. But this story while.
wasn’t at all happy, especially since this Turns out that even after
was my Avenger and within two days the PCM update, the vehicle
the shudder was just as bad as before. was still shuddering during light
Thoughts raced through my mind: cruise. I didn’t know the guys
• Did they get the fluid right? at the dealer nor them me, but
• Did they get the wrong part num- I was pretty much convinced at
Figure 2: As the torque converter entered lockup,
ber? the time that the converter was
the converter-off pressure dropped to zero PSI,
• Did they initiate the quick learn at fault.
exactly as it should.
procedure with the scan tool? I kept emphasizing that the prob- installed it on the converter-off pressure
It felt weird not working on my lem only occurred during lockup. The tap (figure 1). This is where I learned a
own vehicle, but it was good for me to guys at the shop rightly disagreed with few things. For one, the torque convert-
see things from the customer’s point of me and insisted the issue was driveabil- er entered lockup at speeds lower than I
view. This vehicle actually has a fluid ity-related. But they wrongly started to was used to; as low as 24 MPH.
dipstick, so it was easy to check the replace parts… lots of parts. After they I also drove with and without the
fluid level. became frustrated they returned the variable line pressure connecter con-
Ironically, that same week, another car, hoping that corporate tech support nected to eliminate that as a variable. It
bulletin, 21-003-09, had been issued to would soon come up with a fix. They was interesting that no DTCs set with
flash the PCM for numerous transmis- said they’d call me. the variable line pressure connector
sion improvements that seemed close I dusted off my pressure gauge and unplugged. In any case, pressures were
32 GEARS March 2010
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