Mid-Road-Trip Vibration (DONE)

[reckless413]

Hi mudders, having some trouble today…

My 2000 LX470 is struggling with a driveline vibration, and I’m hoping for some help diagnosing it. I’ve searched for posts and read as much as I could, but I can’t find a conclusive answer.

The vibration is first noticeable at about 35-40mph, and increases in severity as I speed up. I’m trying to do 70mph on the highway, but it’s tough, 65mph is about as fast as I can go without making myself nauseous. The vibration is absolutely unbearable 80-90mph, like it shakes the whole dashboard and all of the seat backs.

301,000 miles on my LX. Tire pressures at 32psi front, 35psi rear. Stock wheels and stock AHC suspension. Currently running Michelin Defender LTXs in the stock size that are about 7 years old, but good tread. No dry rot. All lug nuts are torqued to spec (I checked before I left). No obvious visual defects with the tires. I’ve had them rotated and rebalanced twice in the last 10,000mi with no change in the vibration (they were NOT road force balanced).

I pulled over at a rest stop and touched all four brake calipers and rotors, they are all the same temp and not abnormally hot (no sticking brakes). Parking brake is adjusted and not dragging.

I am currently towing a U-haul rental auto transport flatbed trailer. About 2500lbs on a factory tow hitch. The vibration got worse when I attached the trailer. It has always been there subtly at highway speeds, but now with the trailer it’s much more prominent. The trailer has 4 new tires that are inflated to spec…which is about as good as it gets with U-haul.

Currently on my way to go pick up a Volvo wagon on the trailer. Loaded weight will be almost 6000lbs once the car is on. Stock AHC is in proper working order, holding the weight of the trailer in N height with no issues. I’ve towed with this setup before, most recently about a month ago, and I didn’t notice vibrations of this severity last time.

Vibrations do not change with throttle application (stepping on the gas/applying torque on the driveline and/or letting off the gas to coast makes NO DIFFERENCE). Vibration also does not change in any AHC stiffness setting (Comfort vs Sport).

Alignment is good, the vehicle tracks straight (with and without the trailer) and there is no shake or shimmy in the steering wheel.

The vibration is definitely in my seat and behind me (rear axle?) and as far as I can tell, the u-joints on the rear driveshaft are good. I grabbed and twisted and I don’t feel any slop or play, no obvious visual signs of wear.

I’m just hoping it doesn’t get worse when I put more weight on the trailer. Gotta make it about 300 more miles home. Any advice is seriously appreciated, sorry for the long post!

 

[GerLC100]

Remove front dust caps and check CVs seated properly.
Panhard bar (would perhaps explain why additional load makes it worse) or trailing arms on the rear bad?
Engine not shaking too much when stepping on gas (open hood and check when starting/ reving engine)

 

[reckless413]

Remove front dust caps and check CVs seated properly.
Panhard bar (would perhaps explain why additional load makes it worse) or trailing arms on the rear bad?
Engine not shaking too much when stepping on gas (open hood and check when starting/ reving engine)

Thanks for the input, here’s what I found…


Front CVs appear to be fully seated, and I crawled under to look for torn boots or grease that slung everywhere. Looks clean.

Rear suspension bushings seem to be tight, I’ve got some tools with me so I got in there with a pry bar and wiggled around. The upper AHC strut mounts in the rear look like they’re done for, totally collapsed and dry/cracked.

Motor mounts seem tight, normal amounts of movement under load. Trans mount also seems tight, maybe slightly collapsed.


My gut is telling me that it’s a rear tire out of round? It feels more wheel-related than power-delivery-related. I might stop somewhere and have them do a quick rotation/rebalance and see if they notice anything when they spin the wheels on the balancer.

 

[Mike NXP]

When did the issue start? Sorry if I missed it.

Your symptoms sound similar to an out of balance tire, check wheel weights.

Also, I just nearly lost a tire from the exact same symptoms recently, *** Start simple and check your lug nuts **** I lost two lug nuts recently because I convinced myself my tire was just out of balance after a few days of off-roading. Ignored it until the wheel almost came off

Otherwise, it's a guessing game without being able to get the rig on a lift and shake some stuff down. Not a bad idea to stop at a tire shop if you have the time / budget

 

[Trapper50cal]

When did the issue start? Sorry if I missed it.

Your symptoms sound similar to an out of balance tire, check wheel weights.

Also, I just nearly lost a tire from the exact same symptoms recently, *** Start simple and check your lug nuts **** I lost two lug nuts recently because I convinced myself my tire was just out of balance after a few days of off-roading. Ignored it until the wheel almost came off

Otherwise, it's a guessing game without being able to get the rig on a lift and shake some stuff down. Not a bad idea to stop at a tire shop if you have the time / budget

Beat me to it, was thinking the same thing...suddenly unbalanced tire due to loss of wheel weights.
But checking the lug nuts is also a great thing to eliminate as well.

 

[MongooseGA]

Check inside your wheels- do you see sign of a thrown weight? What happens in a turn when the truck leans from one side to the other?

The Michelins should be pretty round, especially after 7 years, but very possible a weight let go. Swapping tires around to different corners can help isolate which wheel is bad, if any. I'd also be inspecting the inner sidewalls for bulges.

You likely won't feel a bad u-joint in the hand without removing the drive shafts from the truck. If they're very very loose or very very tight, they're bad. You should get just a small amount of resistance in a good joint- if you go to position it in a direction, it should largely stay in that position. If it flops around freely or doesn't want to move, it's done. Since your issue isn't throttle dependent, I'm doing to suggest the problem is not a u-joint. You'd feel a difference between throttle and coasting.

Additionally, and I know this sucks while you're on the road with a trailer, but you can pull the drive shafts out one at a time, lock the center diff, and drive in either fwd/rwd. They're 4x 14mm on each end of each shaft.

 

[GerLC100]

Easy check: take a look at the wheels and check for lost weights.
I‘d be surprised though as it‘s starting at very low speed. But you never know

 

[aging fleet]

Maybe try disconnecting the trailer to see if the issue persists? And definitely check the lugs to be sure your not about to lose a wheel.

 

[reckless413]

Hi all, everything is fine!! Time for an update/conclusion:

It seems like a bad trailer tire was the culprit. I unhooked the trailer and the vibration stopped. Everything was tight and in proper working order on my LX, but at some point near the start of the trip we believe a belt slipped on one of the trailer tires, or maybe it lost wheel weights? Who knows. That’s U-haul’s problem.

I ended up stopping at a Belle Tire to meet up with one of the technicians there, we got connected through a Michigan off-roading Facebook group. He gave my vehicle a thorough inspection and test drive, then told me his diagnosis (thank you Spencer!!!) Seriously, I can’t thank this guy enough.

I may have been a bit of an automotive hypochondriac today, but aren’t we all? Better to be safe and cautious than sorry and upside down in a ditch somewhere. Anyways, might as well add some pics of the Volvo project I picked up (the whole reason for this trip) and my first drive across the Mackinaw Bridge! Bonus 944s in the background (those are my girlfriend’s projects)

Lastly, thank you ALL for your comments and input. I’m so happy to be home, with the car unloaded and that stupid U-haul trailer off my hitch. Spencer was a godsend today and definitely earned his good karma. Safe travels and happy mudding!

 

[Trapper50cal]

Glad to hear of a positive outcome and no harm to the Cruiser! I think we all have hyper sensitized minds
when it comes to squeaks and clunks and rattles. It comes with the habit.

I secretly want to LS a 944, is that bad? (or a 928 for that matter)