We have begun to experience an unsettling shaking when accelerating above 60 mph. Here are some details:
The shaking feels mostly from the front end, passengers in the rear can barely feel it if at all. The driver and front passenger can feel it easy. My interpretation of the shake appears to come from the front right, but I can’t be certain.
The shaking occurs when using the accelerator pedal, above 60mph. Meaning, the pedal needs to be pressed roughly 10% down in order for the shaking to start, anything less and there is no shaking. For instance, just cruising with my foot lightly on the pedal and maintaining the same speed results in no shaking. Likewise, slowing down using the brakes produces no shaking.
The shaking is not felt as much in the steering wheel as compared to the floor and seats where it is quite prominent.
When we first started experiencing the shaking, it was always typically on road trips at higher elevations. Road trips at lower elevations and we never experienced it. Until recently, it began to show itself at all elevations.
We can get the shaking to occur at speeds below 60mph, say 40mph but only if going uphill or if having been driving for an extended period of time. Cold start 40mph up hill results in no shaking. But highway driving 60mph + will for sure result in shaking, again only while accelerating not coasting or braking.
I have hooked up the BMW reader as well as a run of the mill OBD2 and found no codes.
Here are the repairs we have had conducted so far, since the onset of the shaking:
All wheels balanced and checked at tire shop
Front Flex Disc
Rear Flex Disc
Transmission (transfer case) Mount
Replace Front Differential Fluid
Replace Transmission Fluid
Other items that have been completed since the onset of shaking, but not due to the shaking (in case this helps narrow things down):
Oil and oil filter change
MAF sensor cleaned
Intake air filter changed
AC tensioner and belt, accessory tensioner and belt, idler pulley
Power steering fluid drain and refill
DISA cleaned and upgraded
Casual inspection of the front end shows nothing obvious. CV boots are intact with no rips or traces of grease leaking.
The last works completed on the car before the shaking begun were about a year prior to the onset of the shaking, we did fuel filter and spark plugs. But then we drove the car around 10 months with no issues until the shaking began.
In typical car talk fashion, I want to further confound things by throwing out there that we also have a very noticeable vibration at idle, in gear. Park and neutral have no vibration, but drive and reverse produce a pretty jaw rattling vibration at idle. When put into gear, the RPMs drop from around 700 to around 650 if that helps. AC seems not to affect it, but turning on high beams does (while low beams are already on, turning on the high beams while in gear makes the vibration increase). Although annoying, I can forgive this for an 20 year old car.
It’s the shaking at highway speeds that has me worried it will leave us stranded in the desert or in the snowy mountains somewhere.