Recently bought a 69 coupe and when backing up, making a loud noise and really have to give it gas to make it move and when it does also makes a clunking noise, I have the car on jacks with rear tires off and with the transmission in neutral, it is very hard to rotate the rear wheels, should they turn more easily or am I looking at trailing arms or possibly a new differntial rebuild, car has been sitting in a garage for about 5 years

 

Does it make the clunking noise when moving forward? It could be something easier to fix than a rear differential, trailing arm rebuild. It sat for a while so things may have frozen up. I’d try to adjust the parking brake and see if that helps. I had a clunking noise in the rear of my 77 and it turned out to be the outboard u joint on the passenger half shaft. Good luck.

 

My WAG: e-brake shoes are sticking.

 

Thanks for your input, yes it only clunks in reverse

 

Dont ever put your car on jack stands and put it in gear the half shafts will bind and you will have bigger problems

 

So the parts that could cause issues are the:

• rear wheel bearings
• drive shaft u-joints
• half-shaft (axle) u-joints
• differential wear/misadjustment
• worn out improper gear oil

With the wheels off the ground, I would start by feeling how much top in/bottom out movement there is for each rear tire; grasp the tire at the top and bottom and try to wiggle it top to bottom. This will give an idea for bearing wear in the trailing arms. You shouldn't feel much movement if any. While you're there, check the shocks and strut rod mounting points too.

Then with the wheels removed, try to pull/push on the trailing arms inward/outward from the differential. This will be an indicator of u-joints and excessive end-play inside the differential. Again, there should be minimal to none. (If you notice movement in the forward attachment of the arm, that could indicate worn out bushings.)

Grasp the each half-shaft and rotate back and forth to also feel for bad u-joints. There shouldn't be any feeling of movement that does not also rotate the wheel hub. Do the same for the driveshaft.

That pretty much examines all of the components that cause the car to move except for what's inside the diff. If nothing else has shown itself, before tearing apart the differential, I'd change the oil and put in real AC Delco rear diff oil and 2 containers of AC Delco Positraction additive. You can get this online but I prefer my local Chevy dealer. The clutches may be slipping and in need of refreshed lube.

 

Thanks for everyones help

 

Congrats on new car..pics would be cool..
my ebrake as mentioned fell apart and did very weird stuff..
pull half shafts, measure bearing and feel..and check u joints would be my start

 

Don't forget to check both the upper and lower snubbers on the differential mount. Good luck with the new acquisition. Jerry

 

 

YYYYYYY ........... 1/2 shaft universals bottom out / break and the drive shaft beats the hell out of you battery box or your passenger side shaft takes out your pass seat