While driving around yesterday, I noticed that there is a knocking sound coming from the engine when the car is in "D" and the brake pedal is pressed down (stop lights, stop signs, etc). However, the knocking goes away as soon as I put it in "P", or while it's actually driving.

Any ideas? It's a 2000 4Runner LTD with 64k miles.

 

Have you changed your transmission fluid? I believe there is also a filter in there. It sounds like it could be torque converter related because the torque converter slips when stopped and in gear. In either park or neutral, it does not slip because the transmission itself is in neutral. It should not slip much when driving. If you hold the brake and rev the engine while the transmission is in drive does the noise get louder?

 

Can you tell where about the sound is comming from>?
Is there any relation to the knock and RPMs?

 

When it's in "P" with the brake on does it make the same noise?

 

sorry to hack his post but I am having the same issue..dynamo seems has not been around for a while to answer your questions so would it be fine if I ask something here??

 

Sorry guys, for some reason i didn't get any notifications of replies in this post.

I think I may have over-stated the problem. The sound is not loud (albeit audible enough for me to hear it). The sound only happens when I am in D and pressing on the brake. It goes away when it's in neutral and park.

However, I noticed another possible identifier - the sound is audible only when I am in AWD/Hi4 modes.

And yes, I have recently changed all fluids (complete tranny flush, xfer case and the diffs with Amsoil).

And again, to clarify - the sound is not a loud banging, but it's a distinct knocking noise coming from the engine/tranny area when pressing the brakes in D and while in AWD/4WD. The sound is not there when I am in 2WD mode.

 

it is not loud?? mine either....does it sound like if you would hold a plastic ruler and pickup the other end and letting it slap against a desk?? that what it sound to me it is when it is on gear but the car is stopped .

 

Yep, that is about what it sounds like. It's not a loud sound, but I can definitely hear it every time I am stopped.

 

Dynamo this is worrying the crap out of me, some stupid mechanic said...well it sounds like lower end noise...could be a rod bearing but that is what everyone says I mean..the car runs fine on neutral but I am sure it is not transmission related because my transmission is perfect condition. Anyway the truck has not lost power I guess if it is something not worth to fix I will run it until it fails and then put a new engine on it as I plan to keep this truck forever, not a money issue I just like the truck.

But if anyone has any ideas please help us.

 

Get a mechanic's stethoscope:

http://www.harborfreight.com/cpi/cta...emnumber=41966

Use it to listen to the transmission, the engine, and the area where they connect. If the sound is where they connect then it is probably the torque converter or something with the transmission or fluid.

 

I already did get a stethoscope and the sound is most noticeable on the the ac pulley cover??

any ideas??

 

I took my rig into the stealership for a knock this past summer...When I would put my truck in Drive and lets say I was pulling out on a hill, if I didn’t give it enough gas to really lock up and pull out I get a knock from either the engine or the front of the trans. The stealership called me and told me it is my #1 piston wrist pin slapping and that I would be lucky to get another 5,000 miles out if it if I baby it and that for $4500 they would put a new engine in it, I laughed and told them, that I would rather flip it over on a very steep trail and total it than give them almost 5 grand for an engine, especially when I can get an entire donor Supra for under 3k!!! I thought to myself, it has made this same sound since the truck had 30,000 miles on it when I bought it! Now at 152,000 12,000 miles after I took it to them it is still running strong and hasn’t left me anywhere! I’ve towed with it, got it stuck and WAY over revved it and held my 3.0 in the 5,000 range in a violent rage! , pulled LONG loaded hills with it on the highway and NOTHING, not a louder noise or worse. I was told that the injectors on my 3.0 are noisy and that they will make a knocking noise, I was also told that it could be the Trans locking up at low RPMs. I say unless it is really a terrible noise at any and all RPMs or in any gear keep your oil changed with a high quality filter like a Mobile 1 or at the least a Purolator Pure ONE and full synthetic oil and you shouldn’t have a problem. ONCE again just Matts .02!!!

 

I had a similar knocking sound happen on my truck. I found that the lower mounting bolt on the alternator was loose and that is what was causing it. Maybe one of your ac compressor mounting bolts is loose.