Mechanics

MODELS RANDOM KNOCKING SOUND AND JUMPI

1998 Oldsmobile Other

Noises problem
1998 Other Oldsmobile Models V8 Automatic 83000 miles

1998 Olds LSS is making a knocking sound at times and is also jumping when it is switching gears. Both happen at random times
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Kristabroshears
October 6, 2010.



Is the noise under acceleration or when taking off from a stop?
When you say the car jumps, do you mean it surges forward as if you pressed the gas?
Does it feel like the car is actually jumping around?
Do the 2 things ever happen at the same time?

Try this forst and if it is not the problem, get back to me with some ore details and I wil try to help.

Open the hod of the car and get in with the car running. Place the car in drive and put one foot on the brake and while you are watching the motor itself, press the gas while still holding the brake with your other foot. You don't need to do this long, just a quick blip of the throttle.
If the motor moves excessively or makes the noises and types of jumping that you have been experiencing, then the motor mounts are in need of replacement.
Be sure to replace all of them at the same time.
This is because when one mount fails, the others take the load of the faild mount and quickly fail too.
If you replace the on mount and the others are near failure, then they will fail and cause the replaced motor mount to fail.

Let me know how it goes.

Thank you SO MUCH for your reply. To answer your questions. The knocking happens at random times (The first time I noticed it was yesterday when I was backin up out of my driveway. Just a loud knock (I thought I hit something). I heard it again this morning several times. I would say it is under slow accleration (forward or backward) but not every time and it has not happend while I've been on the hiway.

The " jumping" is from one gear to the next. It is an automatic transmission that randomly seems to " jump" into the next gear vs. Shifting smoothly. It does not do it every time it switches gears though.

The two mentioned problems do not happen at the same time, however, they did both seem to start around the same time.

Thank you so much for your help.

Tiny
Kristabroshears
Oct 6, 2010.
The transmission shift problem is probably the pressure control solenoid. It sounds like it has failed. This may be the source of both issues. It can cause very hard shift into and between gears which will slam gears violently and also cause them to slip in between shifts.

You should take yur car to a certified tranny specialist.
There are links on this site that will guide you to repair shops in your area that are certified and have a good reputation.

Youshould mention all the symptoms as I would not rule out the motor mounts, but I think it is all due to the transmission solenoid.

I hope it turns out well for you.