3.3L downshifting by self after replacing Engine

Any advice for my wife's '96 T&C Chrysler Minivan that is doing
strange things after replacing blown 3.3L engine with lower millage
engine:

Background:

1) My mechanic is competent and have used him for years;

2) 3.3L engine blew at 135,000 miles and asked my mechinic to
find/replace the 3.3L engine;

3) After much time, found 65,000 mile engine and I said to go with it
since it took so long to find this one;

4) Engine seems to work very well, even better than original;

5) First strange thing that showed up in first 200 miles was that the
front windshield wipers would cycle one time only by itself. I can add
that the T&C did do this when new and it took dealer three tries to
fix which they said it was a bad series of 6-way switch on column;

6) Second strange thing was that the transaxle downshifts by it self.
This is much more serious and also showed up in first 100-300 miles
after reinstallation of low mileage engine;

7) Tried adding "Lucas Transmission Fix" product since the minivan was
laid up for about three months and both my mechanic and I thought it
might be the inactivity causing problems with fairly high mileage
transaxle. However, Lucas didn't help and still have downshifting
problem;

8) My big concern is that I have had one downshift on highway doing
about 60 MPH and RPMs jumped from normal 2300 to 5000. I pulled over
quickly, turned engine off and on again, and was off again with no
more incidents on that specific trip;

9) Check engine light has not come on yet, but mechanic wants to see
if any codes show up, which I'm trying to get done today; and

10) Another observation: problems occur 50-70% of time when hitting
bump which is causing my mechanic and I to think it might be
intermittent electrical connection in one of the engine connectors.

Any advice (keep it clean and constructive, please) would be
appreaciated.


Bob

 

1) Phantom wipers and trans behavior sound like marginal, disconnected,
severed or missing grounds. Trans shifts to 2nd and stays there if it gets
no signal from controller, so if controller loses ground, trans is going
to hit 2nd "right now".

2) You need a trans flush, fluid and filter change now that you have
contaminated your *critically formulated* trans fluid with that Lucas
gunk.

 

Also casts doubt on the competence of your mechanic. I had a shop I
trusted for over ten years when they suddenly, inexplicably to me,
began doing many obviously dumb things: claiming on-off-on-off-on
didn't work to give codes on a '95 Neon, after I had the codes it had
given me; claiming a Toyota truck clutch wasn't adjustable when the
procedure was on Page 2 of the service manual; claiming R-134 AC
compressors use the same shaft seals as R-12 (three! you're
outtathere!). Manager had not changed in the meantime, so I don't
know what happened. And I'm not likely to find out, since I haven't
been back.

 

Dan

Thanks for your input, especially on the ground theory. I'm out of
state for couple of days and already (prior to your suggestion) have
mechanic checking connectors when I get back.
Will advise after that. Also, no tbl codes in computer last night as I
sat in van watching machanic running computer tests using Snap-On
DBII(?) tester.

Joe,

Thanks for your input, but still trust my machanic, not that he can't
make mistakes.


Bob

 

Sounds like a loose connection to either the input speed sensor or
output speed sensor on the transmission. Could also be a loose main
connector at the tranny control module. The phantom wipers are usually
either the multi-function switch or a bad ground connection to the Body
Control Module.