Rumble from Rear of Mach

[Rare Pony]

My 2004 Mach 1 has developed a noise from the rear of the car. It only happens occasionally, but kind of sounds like running over rumble strips (at first I thought it was a rough spot in the road, but does it on smooth pavement). I've only heard/felt it about 4 times, but I wife also noticed it when she drove it. Seems to do it under slight acceleration. I have not looked under the rear yet. It has an auto transmission.

Any ideas?

[turtle5353]

I have heard of an auto tranny developing a shudder that comes and goes with acceleration. How many miles on the tranny? May be due for a flush and new filter. But if you do make sure you have it flushed on a machine to get the old fluid out of the converter because if i remeber correctly thats usually where the shudder originates. Hope this helps let me know if im on the right track guys.
Good luck Kevin

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Also could be something as simple as worn u joint in driveshaft. But they are usually consistent. They dont come and go much. U joints alot easier and cheaper to check or replace.

[1969jimmach]

Agreed I have a friend who has a lincoln and it does the same thing a shutter and after he has it flushed it goes away.Make sure they use ford fluid or equivalent.

[Steven Harris]

I would also suggest checking the u-joints. I know you know this but for others who come along - a visual may say they are okay but also check for tell-tale rust seeping around the u-joint as a tell-tale sign of a bad u-joint.

[Rare Pony]

Thanks for all the tips!

Another suggestion I received on another site is to change the rear end gear oil and use Royal Purple. Looks like I'll be crawling around under the car soon!

The Mach is approaching 100K miles anyway and time to change the rear end and trans fluid.

[Steven Harris]

Let us know how it all turns out.