A4LD issue - heavy vibration, highway speeds

[Eddie94]

heavy vibration on deceleration, highway speeds

Spent a couple of hours searching around on the forums but haven't found anything to shed some light on my newest issue. I notice it most at highway speeds-- when I take my foot off the gas to coast after accelerating or maintaining speed there is a large vibration from the transmission area which ceases if I step back on the gas.

I understand 90% of the theory and principles behind the vehicle's systems, but I'm fuzzy on the nitty gritty details of automatic transmissions and torque converters. What happens when you accelerate up to 70, then take your foot off the gas to coast down to 60-65? Whatever engages or functions at that time is probably the problem, I'd think.

Thanks for taking the time to help!

 

[acschilling]

Is all your suspension tight? Tires balances? That's about the speed out of balance tires will start scaring the **** out you..

 

[Eddie94]

Tires are less than a year old and freshly balanced and alligned.

There's a sound too, almost a rattling. This noise & vibration happens only when I let off the gas and coast at higher speeds. Accelerating while driving at the same higher speeds produces no noise/vibration, maintaining speed with foot on the gas a little produces no noise/vibration, it only happens when my foot comes off the gas pedal and the vehicle is coasting, it is very noticable-- starts as soon as I take foot off the gas pedal and stops as soon as I lay on a little gas again

 

[FR-425]

This can be caused by the slip yoke on the rear drive shaft binding, as well as u-joints going bad.

Time to pull the drive line for service.

You can just cut the bands off the dust boot over the slip yoke, pull the yoke out clean and re-grease. Replace the bands with zip ties.

This does not sound like a transmission issue.

 

[jackrussell]

I agree with FR-425. Also if you feel the vibration in the steering wheel it's probably the front drive axle u-joints. You would feel slip-yoke or main drive shaft u-joints vibration in your (truck's) seat.

 

[Eddie94]

Ok thanks! I'll start there

 

[iamdurkee]

Did you find a resolution?

 

[Eddie94]

No, not yet, it only really does it at 50mph or higher, and I live 1/2 mile from work so I've just been keeping off the highway. I plan to give fixing it a go in the next week or two, but first the garden must be planted

 

[vq5speed]

One of your wheels could of thrown off the balance weight making that wheel out of balance. You could try moving your front wheels to the back and your back wheels to the front see it that stops the vibrations.
Bad shocks could cause vibrations.

 

[Eddie94]

Fixed! It was the driveshaft's rear u-joint, problem completely fixed now ^^