Driveshaft Vibrations – The NVH App


Hello, my name is John Kelly and this is
the WeberAuto YouTube channel. Today I am going to demonstrate how to use the new
NVH app to diagnose a driveshaft speed related vibration. I have a vehicle set
up with a vibration installed on it, and we are ready to go
drive, do a road test, so let us set the app up for the vehicle that we are
going to use here, so if we start the app, agree, the vehicle that I’m driving is an
older vehicle that is not in our database of vehicles, but you can
actually use this app on any vehicle as long as you enter the vehicle
information that’s required, so in this case we will go with “Unlisted Vehicle” in
the upper right hand corner, this is a four-wheel drive truck, so I will
click on four-wheel drive, we have to enter the number of cylinders in the
engine, this is a six-cylinder engine, we have to enter the rear axle gear ratio,
to find the rear axle gear ratio and we have a link, that reads “Find my Axle
Gear Ratio” right there on the screen, scroll down, this is a GMC, so we will select GMC. General Motors vehicles have a code label somewhere in usually the glove
box or the trunk area, and you will find a code that begins with the letter F or
the letter G, four trucks it is the letter G, and this truck has a GU6
axle code, so scroll down to where you find GU6 and look in the next column, it gives us
the axle gear ratio of 3.42, so we will hit done, we will come to the axle gear
ratio box and punch in 3.42 it asks us for the transfer
case gear ratio on this four-wheel-drive truck, if you’re driving
around in two wheel drive, or four-wheel drive high, what you normally wouldn’t do
on dry roads, the transfer case gear ratio is just simply 1.0, alright so the
next thing that we need is the transmission gear ratios, so we will click on
transmission gear ratios, this is a four-speed transmission, but notice we
can hit the plus or minus buttons to select the number of speeds in the
transmission, and that this is a four speeds, so I selected 4, we can just go
with default gear ratios if you don’t know your gear ratios are. but I do know
what transmission this this has. and the way I find that out is to look at “Find my Transmission Gear Ratios”, the
link right there on the screen, and scroll down to GMC, and on the code label
that I have on this truck, I have a M30 and so M30 here is a 4L60-E transmission,
and if I scroll over there is the gear ratios; 3.059, 1.625, 1.0, 0.696, so I will come back here and punch in 3.059, 1.625, 1.0, and 0.696. the app needs to know the transmission
gear ratios to calculate the rotational speeds of some of the parts on your
truck, so the last thing you have to enter for whatever vehicle you want to
test is the tire size, this truck has 235 75, 15, tires on it, so now we hit start, it
brings us to the “Vehicle View” where we have a powertrain view of a
four-wheel-drive vehicle, and now we are going to hit “Start Recording” and go
drive it and see if we can pick up this vibration, so let us go ahead and and see
if we can find. I am going to sit the iPhone on the dash, cover it up with the
piece of paper, so the Sun does not overheat it, let us go see what we can find. there it is showning up driveshaft first order it looks liee we have got a third-order tire along
with it so here we are at 73, 74, miles an hour
we have got glowing driveshaft, glowing tires, it looks like we have multiple
vibrations on this vehicle looks like it is worse at the higher
vehicle speeds driveshaft speed is around 50, 50 revolutions per second I am going tell the app to stop recording,
we can get off and go back I will give it a name 2001 GMC, Sonoma, with a D1 driveshaft vibration and hit save, the app will analyze
the data it has recorded and tell us thinks it has found as the source of the
vibration. Remember the app will give us the highest average amplitude frequency
over the time that we drove, so it is telling us to have a third-order tire
speed related vibration as the primary cause of the shaking as we drive, and of
course you can click on “How do we fix this vibration” brings up a help file
that tells you how to repair that, but lets go back and look at the totals, notice we
have third order tire was detected 225 times during our
road test, and a first-order drive shaft was detected 156
times, and let’s see what speeds they were worse at. On the third-order tire, it
looks like 70-74 miles an hour it was detected 158
times all the other vehicle speeds were pretty minor, let us look at the
first-order driveshaft, it was detected 109 times between 70 and 74 miles an
hour, and the rest of the time looks like 50 to 54 miles an hour it was
detected 14 times, so a lower speed at lower speeds it came in and again at
higher speeds. Engine vibrations, there were few they
were picked up, second order engine was the most, second order engine vibration
on a V-6 engine is is one of those normal vibrations that we should not be
feeling in the passenger compartment, so this old ruck actually has three
different vibrations, but the one with the highest average amplitude of 0.148
was the third order tire, followed by first-order drive shaft at 0.169 now that is a higher amplitude, but it was only detected
156 times versus the 225 times for
the third-order tire, so it’s not just amplitude, it’s a weighted amplitude
level based on how many times it was detected. let us look at our graph there is a lot of blue there, that blue is
the drive shaft speed related vibration this graph shows amplitude versus time
and the color represents the frequency of the part on that on the vehicle Okay, well, that is how to manually enter
into vehicle’s information, once again this app will work on any vehicle as long
as you can come up with the gear ratios and tire size, and number of in
engine cylinders, and so on it will work. Alright now the app
gave us help for the third-order tire speed vibration, but if we go all the way
back to the first menu here, and look under the diagnostic help icon, and then
diagnostic procedures, it has a separate menu item, as you can see here, for tire
speed related vibrations, and it breaks it down by the orders, drive shaft speed
related vibrations and the their particular orders, engine speed
vibrations and their orders, and each type of vibration has its own specific
diagnostic procedures that all of those procedures are in these help file links.
while we are driving here, if we click on if you go back to the main menu and
click on Tools, there is several tools here are available and we’ll take a look
at these in in different videos, but one of them is just simply a vehicle speed
signal that would be based off of the GPS speed signal as we drive, so it says
we are doing 33 miles an hour, and that matches our speedometer The GPS vehicle speed is actually more
accurate than your speedometer because your speedometer is based on the tire size
that you have on your vehicle, and as your tires wear out your speedometer
becomes less and less accurate, we have a Live Data tool wherer we can just look at
the frequencies and the amplitudes that are being measured as we drive down the
road, so it will show you the top five frequencies as far as amplitude levels
with a tool, we have a strobe light tool that will actually flash your camera’s
flash a certain number of times per second and will use that tool in another
video for engine, for abnormal engine vibrations, and then we have another tool
for measuring driveshaft u-joint working angles, and help for correcting those.
This has been a demonstration of using the NVH app to detect driveline or drive
shaft speed related vibrations, It turns out we picked up a few other unexpected
vibrations on this old truck at the same time, thanks for watching.