Reading through the trial and tribulations, you've proven that the issue is
not at the wheels, tires or outbound.
Driveshaft:
The CCs are known for a driveshaft vibration. You said you tried a 180*
index. But there is a few more ways to play with this. Do the 180* at the
rear by unstrapping the driveshaft from the yoke. Also, disconnect the
front yoke and rotate that 180*, and then again flip the rear to the two
available possibilities.
Axles:
Possibly a bent axle?
Rims:
The possibility of this was removed by testing with the wheels off.
Good luck
TonyC
-----Original Message-----
From: Dale Schultz <d.schultz@sympatico_NOSPAM_.ca>
To: dakota-truck-moderator@bent.twistedbits.net
<dakota-truck-moderator@bent.twistedbits.net>
Date: Thursday, October 23, 2003 8:55 PM
Subject: DML: Vibration in Chassis (very very long post)
Hello:
I've recently acquired a Dakota truck, 1998 Sport CC 5.2L 4x4. I really
enjoy the truck and wish I had got one sooner. It's primary use is to
cart around a couple of trail bike (motorcycles) and mountian bikes.
I apologize up front for the length of this post but I wanted to include
all the info I have and steps I've taken in and attempt to solve this
vibration problem that's plaguing me. I'm looking for relevant
practical info that I can do at home. My last resort is the dealer.
Thanks for your assistance in advance.
Dale
Here goes...
Vibration investigation
The initial test drive of truck before purchase did not reveal any
feeling of vibration. The speed driven at was up to 90kph. At the time
there was significant bounce in the front end which resulted in a loose
feeling. After the test drive pressing down on the front right bumper
revealed the shock was bad. The front left did not bounce as much.
After the purchase of the truck only another short test drive was
completed, again I do not recall any significant vibration in the truck.
The day after acquiring the truck all four shocks were replaced. At the
same time I found the emergency brake could not be adjusted to hold the
truck on a slight incline. The drums were measured and out of spec.
New drums (Best Price Auto) and shoes were installed as well as one
automatic adjuster cable. The emergency brake will now lock the rear
wheels while the truck is rolling at 50kph.
The next day a trip was made at 100kph+ and a slight vibration was
noticeable. The truck has 32x11.5x15 tires on it. Two tires were worn
in the centre as if they had been over inflated for quite a while. The
two tires were on different corners of the truck indicating that they
had been rotated as some previous point. The tires were suspected of
causing the vibration which didn't seem severe but more of a nuisance as
if one of two wheels weren't balanced.
The truck was taken for a safety check and required new inner and outer
tie rod ends on the front right. The tires were balanced and an
alignment done. The tires passed the safety but the mechanic commented
that they were really too big for the truck and the ride would be
greatly improved with smaller tires. After the balance and alignment
there was not change to the vibration.
New tires were installed in an attempt to rid the vibration from the
truck. The tires installed are 225/70x15. The vibration was noticeably
increased. I suspect the higher rotational speed of drive shaft, axles,
wheels etc. brought the vibration done to about 85kph from just over
100kph. The vibration is noticed in the seat. The steering wheel is
smooth and steady. Putting your hand on the 4-wheel drive shift lever
does not indicate any vibration as if the mount was damaged.
The tires were re-balanced as I suspected a lost wheel weight. No
change to the vibration was noticed. I made an 1100km trip with the
truck at speeds mostly above 110kph and the vibration was present pretty
much the whole time. A few times during the trip I noticed after some
stops (gas, food etc.) that the vibration was less noticeable but after
about 15 minutes of driving it would return to its original level.
Is it possible that the vibration change was caused by the two rear
wheels being phased differently from each other do to sharp turns into
and out of parking spots?
In an attempt to detect the vibration the drive shaft was re-indexed at
the pinion yoke 180 degrees. No change.
The U-joints do not appear to be faulty but I replaced them anyway with
Spicer grease-able type. No change, but I got to buy a new tool ;-)
The truck was put on jacks with the wheels on and the vibration starts
at about 85kph and continues past 110kph. The wheels and drums were
removed and the vibration was only noticeable at about 110kph.
The drive shaft run-out measured 6 inches in from the welds revealed
about 0.040 at the pinion and about 0.045 at the transfer case. The
service manual indicates 0.020 is the limit. The propeller shaft does
not show any sign of dent or damage. The plane of the high and low spot
on the shaft is the same at each end which suggests that the propeller
shaft was welded with this run-out. The weights, one at each end are
also in the same plane and mounted at the high spot on the shaft. Is
this acceptable?
The run-out of the pinion yoke was measured as a Y-axis movement and
found to be 0.010. Is that okay?
The propeller shaft balance check procedure in the service manual was
completed (with wheels on) and there was no noticeable change in the
vibration between 80 to 110kph. Other than the out-of-spec run-out on
the propeller shaft, it appears to be balanced???
In the mirrors at night the objects vibrate in the Y-axis, not X or
circular. The vibration feels like a bouncing movement.
The transmission mount was inspected and the rubber is attached. Could
the rubber be weak and therefore not absorb the vibration, the truck has
265000km on it?
The axles where checked to see if there is excessive play in the wheel
bearings. A dial gauge against the hub indicates only 0.010 of play in
the y-axis when the axle shaft is lifted and lowered. This applies to
both sides. Is this okay?
The tires where rotated (front to rear etc) and no change was noticed in
the vibration.
While the truck was on jacks checking the propeller shaft balance, it
was noticed that the brake drums (replaced the day after obtaining the
truck) are not perfectly round as viewed from the outside. They appear
to be round on the inside as there is no pulsation in the brakes at any
speed or application pressure. The drums do have weights installed.
What I still need to do:
- I know a guy at work that may let me take some measurements on his
truck to see if I’m close on the tolerances.
- Check the engine mounts.
- Replace the rear drums again…with Mopar?
- Re-index the propeller shaft at the transfer case yoke to see what
happens.
- Change the wheel bearings (and seals). There is no sign of fluid leak
in the drums.
- Replace or rebalance the propeller shaft. It turns at about 3000RPM
at 110kph with the transmission in third gear (ratio 1:1)
- Take it to the dealer and pay them big bucks to diagnose the problem.
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