wow, great explanation. thanks for the in-depth response Paul. sorry for the
delay in getting back on this, but for anyone still interested i have an
update. it's kinda long, so consider yourself warned :)
took the truck in to the dealer today and explained the problem with the
"thunk" in the back end. also wanted them to look at the front end cuz i
started noticing a squeak from up there. and while they were at it, i wanted
them to check out a 3rd problem. best way i can describe it is like the tire
is folding when i pull out of a parking space (wheels turned quite a bit,
but not fully). it doesnt always happen, but since it was gonna be in there
anyway i figgered they should check it out.
they call me back later in the day and tell me it's fixed so i ask what was
wrong and what did they do to fix it. the service writer said the thunk was
caused by the gas tank hitting a cross-member on the frame and that they put
some insulation in there. ummm...okay. then she said they couldnt reproduce
the squeak in the front end. ummm...okay. then to top it all off, the
mechanic only noted that i had replaced the stock wheels and tires and didnt
denote any other troubleshooting for the "wheel-folding" in the front end.
keep in mind i have the tires/wheels that come with the tire and handling
group (GY 255/65/16 on 16x8's).
it nearly took an act of congress and a hunt for a 2001 brochure to get them
to admit that the tires and wheels were in fact factory trim. and after much
persuasion, the service manager finally admitted that there was prolly not a
whole lotta troubleshooting done past that.
so i decide to pick up the truck and be happy that the mysterious thunk is
gone from the rear-end. i figgered i would wait for a while and then take it
to another dealership. i pick it up and as soon as i get home and hear the
same exact noise going over a speed-bump.
i drive back to the dealer. i had the mechanic who worked on it ride with
me to hear that what he said he fixed wasnt even the problem. i was able to
reproduce the sound easily and he immediately blamed the vibration dampener.
according to the mechanic, thats how it should sound going over a meduim
sized speed-bump at 8 mph. ummm..okay. after much haggling back at the
dealership i convince them that there is no way a rubber-filled metal tube
could make a sound like that hitting the rubber housing it sits in. and if
it did, they'd have dakotas lined up into the street wondering WTF that
sound was. so they pull a new one off the lot and we drive it. no sound at
all. went over the same bumps soft as a baby's bottom.
so i ask the service manager what else could it possibly be. they just
replaced the rear shocks, shackles, and leaf springs a couple weeks ago, how
could they be bad already? "rear shocks?" he says, "i dont think they
replaced the shocks, just the shackles and springs". WTF?!?! then why did
you tell me before that they had replaced them???? and why couldnt at least
a half-way competent mechanic fix that instead of some kooky story about the
gas tank?? better yet, why even blame the dampener if you said the thunk was
fixed? and couldnt he have noted that there would still be a sound but that
it was normal, even if it was a bald-faced lie? or better yet, why even look
at the truck at all and just say i was imagining things.
so now we are waiting for some "hi-performance" mopar shocks from the
warehouse. at that time they said they'll replace the front sway-bar
bushings that were squeaking. that was the problem the mechanic said he
couldnt duplicate but easily heard driving around with me. sheesh...
all in all, i've had a great day. maybe a meteor will fall from the sky and
crush the truck tonight, that would make this the most perfectest of all
since the history of ever. sigh...
-adam
----- Original Message -----
From: <Tubamirbls@aol.com>
To: <dakota-truck@dakota-truck.net>
Sent: Wednesday, August 21, 2002 1:04 PM
Subject: Re: DML: Rear suspension problems
>
> Hi Adam
> Truck rear suspension is basically very simple. In concept it is a
> carryover into motor vehicles from horse-drawn wagons, buggies and stage
> coaches with not a lot of refinements in 100+yrs.
> Your rear axle assembly is supported by a multiple leaf spring
parallel
> to the driveshaft at each rear wheel. The springs are mouted to the truck
> frame by a shackle at each end, a single forward and a double aft. A pair
of
> shock absorbers are mounted vertically next to each spring to dampen
rebound
> from upward movement of the axle as you drive over irregular pavement
> surfaces. On many Dakota models after 1997, a stabilizer bar is attached
to
> the axle housing and suspended from the truck frame to work as a torsion
bar
> to resist body lean when cornering. Since movement is necessary for each
of
> these components, they are all mounted on some kind of rubber bushing to
> allow for that. That's it.
> When you drive onto a speed bump, both springs contract, both shocks
> contract and the stabilizer bar simply moves in free travel upward. If
any
> of these components have worn and/or defective parts they may be
transmitting
> to the chassis the "sound" you're hearing. The extreme aft end of your
> exhaust system is routed over the rear axle housing. If that tailpipe
> assembly is incorrectly positioned it can contact the axle when
substantial
> upward movement is caused by a tall speed bump and you would hear such
> contact.
> So where does one look for the annoying sound you're hearing (again
> assuming it's not coming from cargo in the bed, a loose tailgate or toneau
> cover, loose rear bumper or trailer hitch, loose fastenings of the cargo
bed
> to the truck frame, loose spare tire, an incorrectly hung tailpipe or some
> part of your fuel tank and its plumbing). If your truck is still under
the
> 36k warranty it is not likely any of these are the cause however there is
a
> possible exception to anything these days.
> I'd concentrate on the rear suspension components. If everything
> appears normal for them, you can disconnect the shocks, one at a time,
drive
> over the test bump and see if you noise disappears from either of them,
same
> for the left & right connections for your rear stabilizer bar, if so
> equipped. If neither has any impact, then look for a defective shackle
> bushing, loose fasteners on the shackles and carefully inspect both
springs
> and each leaf in same for a crack.
> If none of these lead to the cause, then stay out of parking lots
with
> speed bumps.
>
> Paul Sahlin
>
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