'93 Intrepid - shudder at 35~40mph

Hello,

Whenever I reach between 35 and 40mph, I hear a shuddering sound
toward the front of the car. It only does this during accelerating up
to/through this speed range. It does not happen when decelerating by
coasting/braking. It also does not happen if the shifter is not in
the Drive position. ("3" for example.) During the shudder, I can see
the speedometer slowly moving up and down over about a 2~4mph range.
Once the shuddering stops, the speedometer is rock solid again.
I don't feel the shudder in the steering wheel when it happens.
This seems odd to me, but then again, this is my first front wheel
drive car, and maybe front end problems aren't as easily communicated
to the steering wheel as they are with rear wheel drive?


I had the tranny rebuilt back in 9-03. It was starting to make very
loud thunks when downshifting, finally reaching a point that a strong
thunk when coming to a stop would leave the tranny in limp mode. (I
would have to turn the car off/on again at the light to continue on
normally.) Ever since then it will occasionally make a thunking sound
that can be felt/heard when slowing down to stop. It varies in
severity from barely noticeable to quite loud, but nowhere near as bad
as before the rebuild.. The people at the transmission shop insist
that "all Chryslers do this when downshifting". I've owned the car
since it had 14K miles on it to the present ~70K, and in the seven
years before the problem that led to the rebuild it never acted this
way.
I'm on the last month of the warranty, so any information and/or
links that supports my side of the situation would be greatly
appreciated!


Thanks for any help,
DSF

 

Some things to check: CVJ's (outer axle joints) and DOJ's (inner axle
joints), also steering parts, especially loose inner tie rod bushings
(where the tie rods attach to the steering gear). Almost a dead
giveaway on the axle joints would be a split boot, but good boots don't
necessarilly mean good joints. Most likely if tires were the problem
(out of round, out of balance, broken belt), it wouldn't be that much
dependent on acceleration vs. coasting, but don't ignore the
possibility. Also brakes: rotors, loose calipers (slides).

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

That could very well be that the torque converter clutch (TCC) is chattering
because lockup is coming at a too slow a speed. I had never experienced
this problem until just recently when I had the tranny rebuilt on my '94
LHS. Instead of occurring at 40+ MPH, the converter would lockup at ~35
MPH, which was causing the shuddering that your describing. A new
Transmission Control Module (TCM), with the latest firmware, fixed the
problem. I'm guessing that the rebuild resulted in different pressures in
the tranny which didn't work well with the original (day 1) firmware in the
TCM.

I would have the shop that rebuilt your tranny drive the car with a scan
tool connected to the data port. They'll be able to verify that the TCC is
(or isn't) the problem.

 

{My stuff snipped}

I forgot to mention in my previous post that I had both front axles
(CV joints and all) replaced a few months ago. I will have the rest
checked out.

BTW, I also neglected to mention that the problem doesn't occur when
the car is cold. I had to drive it several miles today before I could
get it to shudder. (I live in Florida, so 'cold' means avg temp of
about 80F today.)


DSF

 

Sure sounds like torque-convertor lockup clutch shudder to me. TC lockup
is altered when you select "3" so you don't get the shudder. TC lockup
is inhibited until the engine reaches a certain temperature, so you
don't get it when "cold."

I bet whoever rebuilt it didn't put ATF+3 in it- typical of a shop that
would say "all Chryslers do that." They probably put in Dexron and a
tube of some magic monkey whizz that they claim "makes it work like
ATF+3." Drain the fluid, change the filter, and fill it up with +3 and
see if that fixes it. Also, if you haven't had the transmission
controller flash memory upgraded to the latest software, get that done
at the dealer as well.