Torque converter problems?

[Shannen Durphey]

This isn't necessarily a sign of a failing tcc.  There's a definite possibility
that the problem is caused by the engine running poorly.  When the tcc is unlocked,
the converter "absorbs" engine vibrations.  Once it locks up, the engine and
drivetrain are locked together.  

My experiences with 700R4's, fullsize pickups, and disconnected tcc's is that any
extended driving without the tcc connected ends with a visit to the trans
rebuilder.  It's just not a good idea to do this for a long period.   You can press
down lightly on the brake pedal to force the tcc off during a road test.

Misfires like to show up around 30-40 mph, under medium acceleration, when the tcc
first engages.  I've also felt misfires in trucks around 70-75 on the highway which
were reported as trans issues.  Changing from OD to D while driving will change the
load/rpm of the engine and will often seem to
"cure" a misfire related vibration.

Migh want to check the condition of the tune up.

Shannen


Gabe wrote:
> 
> Got a father-in-law with '92 4x2 Chev full size pickup with either a 4L60 or
> 700R4 tranny & a 350...
> 
> Recently it has developed a pretty nasty vibration/shudder it seems when the
> torque converter locks up under light throttle & at low RPMs...  As a side note,
> my work van (92 Astro) does the same thing & has for the last couple years (I
> only put about 4-5K miles on it a year).
> 
> Is this a sign that the torque converter is preparing to expire and send
> shrapnel thru the tranny or just that the ECM is getting a bad signal from
> somewhere or is in need of reprogramming for better lock up points?  Don't
> really have much experience with lock up converters & OD tranny's - have always
> had TH400s or TH350s.
> 
> We were contemplating disconnecting the wires for the lock up converter for the
> time being to see if that would cure the problem for now.
> 
> TIA for any input.  BTW, the truck has not had any programming work done to it.
> 
> Gabe
>
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