bchadwick03

Hey I've got a really bad vibration coming from the rear end in my 01 mustang by auto trans. I did the cheap fix I changed the gear oil and its still there. Its only really noticeable at low sleep while slowing down if I throw the cat in neutral it almost goes away. Its def not the brakes either I checked them over. Any insight would be great thank you

TfcCDR

When's the last time you lubed the U-joints in your drive shaft? Or changed the trans fluid (or oil if it's a manual)?

PNYXPRESS

If the vibration goes away when in neutral then its the trans or engine not the rear end or driveshaft

And it doesn't matter is its manual or auto they all use ATF now.

TfcCDR

Worn U-joints can torque out of line under power, then re-align when power is reduced. Keeping a good lube schedule gives a chance to see if things are getting loose.

bchadwick03

its not the driveshaft or ujoints could it be the torque converter?

TfcCDR

Possibly, but not too likely. TQ problems don't come and go, they come and come worse.

You've already checked rear-end lubrication and U-joints. How about the suspension? If you have loose suspension that lets the axle role forward a little under acceleration, that could feel like "vibration."

Could also be pinion bearings in the rear end.

BabyGT

Why are we jumping to the expensive or labor intensive issues, go get your rear tires balanced, you might have lost a wheel weight. Start simple, it saves money and time.

And are you POSITIVE its the rear? I thought I had a problem with the rear of my car recently. First I swapped a known good set of wheels on to make sure that wasn't the issue, then double check over all bushings and suspension points, when I found the rear tight and straight I decided to peak at the front, all suspension, ball joints, tie rods were good up front. Turns out my steering rack bushings are almost non existent.

PNYXPRESS

I agree babyt, however when OP said the vibration is prevelant while in gear at slow speeds but almost disappears when shifting to neutral, that screams engine/trans issue most of the time. Tire, suspension, driveshaft, and rear gear vibrations are normally present at all times and go away as you slow down.


edit: you may want to check your motor mounts.

BabyGT

Well see that's why I pointed out steering rack bushings, I thought it was my rear, and when letting off throttle or coasting it got better. I guess decel pushed down on the front and held rack tight enough to keep everything straight.