Hey guys, I'm just wondering how to check a differential mount. I misplaced my haynes book and I think that might be my problem.

 

i would really like to know too, because i keep hearing a clunk when i shift

 

have some one power brake the car (forward and reverse) and watch the mounts. there are three mounts. one on the pinion and the two on the sides. my front mount by the pinion was sheared at the metal piece bolted to the diff. also the side mounts are probably worn or weak and broken.

 

does that mean apply power while hte ebrake is on?

 

Much like what was said above, you could jack the rearend up. Then put someone in the drivers seat while you observe safely from the side of the car, if the mount is broken or not.

Have the driver start the engine and put it in gear. Then have him accelerate and then tap the brake several times. If broken you should see/hear the thump as the front of the differential moves up/donw as he applies the brakes.

 

or you could be safe and take a crow bar and wedge it between the subframe and rear end and pry. if it moves than its broken.(the rear end, diff. )

 

So let's say my eyes are bad, and I hear a thump when I'm doing this test, is there a distinction between the kind of thump a bad differential mount will make compared to the thump a bad u-joint would make, because I know my problem is one or the other?

 

The thump is caused by a piece of rubber on the mount hitting the chassis. PUt some grease on that item/piece of rubber, and go for a ride. Then look and see if you have grease on the chassis.

Go to mazdatrix.com to see what the mount looks like. http://www.mazdatrix.com/g8.htm

EDIT: I'm double thinking this. If it's broken I'm thinking that the above might not apply. Go do what I suggested in the other post. If the driver is in first gear the car, if it fell, would go fwd, not reverse. I see no saftey issue if you use common sense. Heck, I've done it by my self using a long pole to stab the brakes while watching the differential.

Or if you uneasy about that, go to a lube shop and have them put it on a lift and run the engine and stab the brakes while watching from below.

Or just use the pry bar.

 

if it the u joints and its thumping hard when you take off then you would see it visably because they would be snapped like my old drive shaft. it was hanging on by a thread. if its the rear end it will feel like something kicking the bottom of the car, if its the rear end mount it would be a loud clunk that may chatter.

 

it would be a loud clunk with possible chatter if its the u joints.*** sorry i messed up

 

Well kinda similar to what Fc3sna said, but adding on.........................

Well it isn't necessarily just the differential mount, it also could be the u-joints in the driveshaft, because my car does the same thing also. As my friend was looking under my car, when i was going at low speeds, 2 or 3 mph, I stuck the clutch in and accelerated and reversed, so on and so on, and he didn't see nothing moving, so I'm now looking into buying a new driveshaft, buy the after market ones, not only because it is cheaper but you are able to switch the u-joints out.

 

OK so another quick question. I've tested my u-joint probably 50 times since this problem has surfaced. When I put the car in first gear and have the car off and go under the car and twist the driveshaft, it moves very slightly, Im mean like a few cm, it moves the same whether I twist it to the right or the left. Does this mean my u-joints are bad? It does not move when I push the driveshaft up and down and left and right. There is also the same distance of movement when I push up on the halfshafts.