Feels like a Flat Tyre but not??

[Camboa]

My 99, VT Wagon was starting to feel like it had a flat tyre but tyres were fine.
Kept driving for a while until it got worse.(About a month)
Like something was gonna fall out of the rear end with all the jolting so I stopped.
Went on a holiday and now I'm back.
It started OK but when I shift to Neutral and Reverse and Drive it Jolts and shakes sort of drops in the back end like a big flat??
Tyres are fine, it looks fine but I feel like I don't want to drive as unsafe.
What to do?
It is Duel Fuel.​

 

[uniacidz]

Take to a respected mechanic

 

[devilly]

sounds to me, like it's the uni joints in the tailshaft, have a look at the joints your looking to see that all 4 sit at the same height.

and then grab tailshaft and give Chinese burn to it to see if you can feel any movement/play in it,or hear and noises from it.

when s the last time diff oil was changed ? is it at the correct level of fluid ?

 

[Drewie]

Are the wheel nuts tight?

 

[AdventraAddict]

Check tyres for a bulge on the tread

 

[Turtl3]

Are the wheel nuts tight?

i was also going to suggest that, its a quick and easy check to jack the car up and go over them...but if uve been driving around for a while and they ARE loose, chances are that the studs, and possibly the rims are now stuffed.

when u say it started to feel like it had a flat, do u mean it was just making a rumbling sound? or was the car shaking and pulling to one side?

would hurt to check the rubber center bearing on the tailshaft...and this next one is highly unlikely, but the whole diff itself could actually be loose on the sub frame.

chock the front wheels, leave the handbrake ON, stick ur head under the car and have a look around while someone else changes back and forth between reverse -neutral -drive. have them keep their foot on the brake as another precaution.

 

[Camboa]

Turns out it was a full tearing bulge on the tyre, about 6-8 inches long. I just rotated the wheel and Bingo! There it was staring at me.
Lucky I stopped driving.
Now I have put on the spare but it is a different size I think. 205/65 15 as opposed to other three being 215/60 16
Would this be a problem driving to servo to pump up spare then to tyre guy to balance a replacement onto old rim.
Thanks for the insights guys.
Cheers

 

[Turtl3]

Glad it was something simple and relatively cheap. Those tyres r virtually identical. 2.7% difference in rolling diameter. That wont cause any dramas to drive on

 

[vc commodore]

i was also going to suggest that, its a quick and easy check to jack the car up and go over them....

not really the ideal way to check the wheel nuts....the ideal way is to have the wheel on the ground, so you're not fighting against the turn of a wheel, whilst tightening

 

[Jxfwsf]

Even though the spare is a different size, the diameter/circumference will be pretty close to the same so won't be an issue for a short time.

A whopping 1.7cm difference in diameter.... probably less if the spare has more tread and the other 16" on the car is worn with less tread on the same axle.
General rule is if you go up 10mm in width (205/215) you go down 5% in the profile/aspect ratio (65/60) to maintain the same diameter.
The aspect ratio/profile is the percentage of the tread width (not 60-65mm)

205/65r15 Sidewall height = 133.25mm(x2), 15" rim = 381mm, 64.75cm diameter
215/60r16 Sidewall height = 129mm(x2), 16" rim = 406.4mm, 66.44cm diameter.