HELP! '92 Corolla

[Bertdogg]

Hello,
I have an automatic. Whenever I shift from P to REV or D to REV, I get a strange "knock" coming from underneath the passenger side floorboard. It only happens when I shift into REV. The odd time it won't make the noise but most of the time it does. This just recently started happening. Othewise the engine runs great with no slipping and smooth gear changing.No noise problems through hard acceleration or regular highway/city driving.Only when backing out/in of parking stalls basically. Any ideas as to what it could be?
Thank you

[blb]

Bad motor mount.

[Bertdogg]

Really? Roughly how much does it cost to replace this?

[blb]

It's just a possibility and would be good to have it checked, at least as a starting point. Can't tell you about cost, because I personally never replaced one.

Another thing to check is make sure there is least a fingers width between all exhaust system components and other components. I'm thinking when you are putting it into reverse, the engine is rocking slightly causing something to touch, making the sound you are hearing. If the motor mount is bad, the amount of rocking may be excessive.

[Bertdogg]

One more question. Is this something I can do at home by jacking up the vehicle or does it need to be serviced at a garage.

Thanks for all your replies. You've been a great help!

[tashirosgt]

Of the 4 engine mounts and one transmission mount, you can replace the side mounts without jacking the car up or having it on jackstands. Whenever you replace a mount you have to put a jack under the engine and jack the engine itself up a few inches. So it won't be as simple as
unbolting and bolting something. You can replace front mount if you are willing to put the car on jackstands and crawl under it to work. Replacing he rear mount and the transmission mount would probably require hoisting the engine up out of the engine compartment.

On a '92, it is likely that some of the mounts are bad, but this may not be the cause of your noise. It could be something like a sticking ball joint that pops loose. You should look at the whole suspension.

Since mounts are the first topic to come up, check them by finding pictures of good mounts ( ebay sellers often sell engine mounts that fit the '90-'93 Corolla). The mount has a cylinder in its center suspended inside an outer metal ring by some thick rubber members. When a mount goes bad the rubber members crack and center cylinder doesn't stay in the center. Also look in the engine compartment while someone revs the engine and see if the engine twists noticeably. That would be a sign of bad engine mounts.