Dale Schultz wrote:
>
> 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 mountain 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.
>
Just adding an update.
Tonight I took on the task of re-indexing the propeller shaft at the
transfer case yoke. Removing the bearing caps was pretty easy since I
just replaced both U-joints. Note to self: remove the grease fitting
first otherwise it will snap off flush with the cross when the cap is
pressed out on the fitting side (thank the guy who invented screw
extractors).
Just to confirm if there would be any change I removed the wheels and
brake drums and ran the engine up until the vibration was noticeable:
about 70kph without the load of the wheels etc. The vibration changes
intensity between 70 and 110+ at a couple of points. If I put my hand
on the leaf spring I can feel the up/down vibration being induced into
the suspension (and ultimately into the passengers seats). I also
re-measured the run-out to see if there is a change.
After re-indexing I re-measured the run-out, 0.045 at the front and
0.040 at the back just as before. Running the engine revealed the same
vibration as before.
I think the next step is, see if the propeller shaft can be rebalanced,
if not then I guess I’ll be looking for a new one.
Dale
This archive was generated by hypermail 2b29 : Fri Feb 06 2004 - 11:47:04 EST