Thud sound coming from the rear of the cougar

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Thud sound coming from the rear of the cougar

February 15, 2011, 01:22:02 PM

I can get the sound when I'm driving and take my foot off the gas and then put it back on the gas. It is a thud that sound, that sounds like it is coming from the axle. Any advise would be great! I would like to fix it on my own but not sure where to start.

Thud sound coming from the rear of the cougar

Reply #1 – February 15, 2011, 01:56:29 PM

Rear u-joint is the most likely possibility. You'll need to get under the car and put your hands on the driveshaft and twist it around by hand and check things out. You should check it out before you have a failure.

Another possibility, if the u-joints are good, is the ring and pinion in the rear end is wearing out.

Thud sound coming from the rear of the cougar

Reply #2 – February 15, 2011, 02:48:49 PM

If it's not the U joint check the bushings in the rear control arms.

Thud sound coming from the rear of the cougar

Reply #3 – February 15, 2011, 03:40:37 PM

I just went out and had a look at the u joints and they seem tight. I looked at the bushings on the control arms and there is no movement from left to right but Im not sure how to check them. but it feels like there is play in the rear end in the differential, how do I make certain that that is where it is coming from, or is that the only place it could be coming from?

Thud sound coming from the rear of the cougar

Reply #4 – February 15, 2011, 09:32:00 PM

jack up rear pass wheel
put car in "N"
place safety block in front / rear of the driver rear tire
place safety block in front of one of the front wheels.
***basically make sure it cant roll forward or back
get under car
grasp drive shaft
rotate drive shaft cw and CCW and observe the motion of the rear pass wheel.
feel the slop?

If so,, then your going to find the spider gear and thrust or crush shims worn out in the rear differential.

In short,,, welcome to the world of fords.

Now if you have a CFI engine ( two fuel injectors) then continue reading.

go to the idle control motor on the front driver side of the CFI.
-remove air cleaner and temp plug off vac line.
-start engine
-move throttle linkage and observe the plunger on the idle control motor.
-if it does not extend out, theres a problem.
-release throttle linkage and observe the plunger.
-the plunger is suppose to extend out while under acceleration and when you let off the gas, the idle control motor will sort of "catch" the throttle linkage and slowly bring it down to the closed position.

This is one of the cs of the idle control motor is to soften or buffer the very thing you feel now.
For the longest time mine wasnt really adusted correctly so I messed with it unil I had it adjusted forward enough to see it was working right plus the idle rpm was correct.

OR........
as stated earlier, the rear end is just sloppy and you either add thicker rear gear fluid or get it fixed.
The spider gears or spider gear pin is worn out.

Thud sound coming from the rear of the cougar

Reply #5 – February 15, 2011, 10:27:49 PM

I have never pulled apart a rear end myself; that's the next big project I'll sometime tackle myself to say I can. I know I can do it, just have to well, DO it. Are there shims on the spiders as well? My silver cougar has way too much endplay in both shafts really, and sometimes cornering hard, or just doing what you said makes a bang noise back there because the axles are getting rammed back and forth. I read somewhere that worn trac-lok clutches can do this. The car leaves a nice deep set of marks like it ought to, soooo I dunno. But be sure to check that too. You shouldn't be able to pull/push on the wheel in/out any more than a hair. Certainly shouldn't hear "clunk clunk" as you pull/push on it.