Knocking in gear

Hi guys I just bought a 2002 4Runner and I noticed when the truck in cold and in gear, there is no sound. But after letting the truck warm up for a few minutes I put it in any gear and I hear a knock kinda near the back end of the engine. I crawl under and I can really feel a knocking near the bottom part of the engine close to the transmission. Any thoughts on that thanks guys

 

Might be a u-joint. Welcome to the forum.

 

Welcome.

Manual or automatic trans?

Does knock occur when the wheels are turning or sitting still?

Does the knock change when engine RPM changes?

Does the knock change depending on which gear it’s in?

Was it in gear when when you were underneath feeling the knock? (VERY DANGEROUS)

 

Slvrslug thanks for the input and the warm welcome

 

hey 4x old guy? So here are my answers to your question btw thanks for the reply


automatic

it occurs when I’m at a stop

The knock changes with the rpm

it doesn’t matter what gear it’s in it still does it

I had someone with the brake on while I was diagnosing the unit.

 

Hmmm.

“Any gear” for an automatic that’s going nowhere means 1st gear in reality. When trans is put in gear, that puts a load on the engine (as evidenced by a slight drop in RPM) and the trans torque converter. Due to the torque, the engine and trans will roll a bit putting a little stress on the engine and trans mounts.

“Doesn’t do it when it’s cold but does do it after it warms up” suggests oil viscosity or oil pressure might be a contributing factor. Colder, thicker oil will fill gaps in worn bearings better than warm oil. Crankshaft journals slide against the smooth bearing surface relying on pressurized oil to keep them apart. If the oil pressure is not high enough, the crank journal will knock about on the inside of the bearing (especially the piston rod bearings). Oil pressure will also drop slightly when the oil warms up.

Check oil pressure.

Possible causes for low oil pressure:
Low oil level.
Too low of oil viscosity.
Oil filter cartridge not installed properly.
Oil pressure relief valve stuck open.
Oil pump worn out.
Engine bearings worn out (more than just the one that is making the noise).

Band-Aid temporary “fix” (and also a diagnostic test), run a notch higher viscosity oil (the second number).

 

Also, there are oils available for older cars that will help compensate for worn bearings or oil pump. Not a permanent fix, but will postpone the inevitable engine rebuild.

 

Thanks for the info I appreciate it. Actually it’s a rebuild engine from jasper and it only has 22k put on it since it was replaced

 

Welcome!

Most likely it's the VSV in that gen 4Runner. Totally normal. That VSV has caused more threads to be started than any subject in thread history.

 

What is a “VSV”?

 

Id also make sure the torque converter/ flex plate bolts are all snugged up.

 

I remember in the older days when you are in your car and are going DOWN hill and let off the gas if there is a knock it could very well be slap in the piston...if your going UP hill and pushing on the gas and there is a knock in the engine it could very well be a wrist pin...so multiple questions...you said it was rebuilt? Is it a big knock like a hammer hitting an anvil or a small knock like a screw driver shaft hitting a metal valve cover like a lifter or a valve guide, have you ever seen the oil look gray? are your lifters adjustable, hydraulic or solid? I know in my 85 4 Runner when I use different oil beside Red Line now...I do get a knock, while ever so slight in the morning in freezing weather until it warms up and everything expands. You know something that could help us all is use your phone to record the noise...many of us could get a clearer understanding on what you are hearing and could help more...lastly...if it was rebuilt main bearing that are loose or not plastic gauged correctly can cause and early morning knock...and can at times show up in a loss of oil pressure...I hope this helps.

 

Hello Daveoheight, I am a new member here and saw your post. I am having the exact same issue you had. Were you able to get your issue resolved??

I too have a Jasper engine with about 70K miles. Unfortunately the engine had issues from the start. Debating if I will keep my truck! Any help would be appreciated!

 

I know this is crazy...but check and tighten the starter bolts...there are only two of course...if your a gear head you know what a wrist pin sounds like, solid lifter out of adjustment sounds like, U joint sounds like driving, axle bearing sounds like on a turn in particular...it's funny how different sounds resonate...take a video and put it on this forum...there are some sharp guys and girls on it...let them hear what you are hearing...

 

NightOwl,

Thank you. I'll take a look at that!

Actually, my truck knocks at low RPM's when accelerating. It idles just fine and when at speed it seems fine! Long story short but I recently took my truck to the dealer for a cylinder 2 misfire and it turned out to be the spark plug wires. While there I did the coolant, belts, and oil change. Unfortunately when I took it home it started to knock!!!! I took it back to the dealer and they did absolutely nothing!!! I later changed the oil to 10W30 and had the dealer readjust the belts. The belt readjustment seemed to lessen the noise but it was still loud and worrisome. The different weight oil did nothing. My thought is maybe it could be the spark plugs and may change those out but the dealer had told me they looked ok.

Very frustrating considering it was NOT knocking when I took it in. Well, hope I am able to fix it and it's nothing major. I have already changed the engine once because it had a cracked cylinder if I remember correctly. This is a Jasper engine that has given me problems from day one. It was repaired under warranty SEVERAL times but now the warranty has expired! I would hate to sell it and hoping the knocking is nothing major. I am the original owner and the truck is in excellent condition expect for the engine issues of course. If I can't fix it, considering another engine so doing some research for that.

Any help would be appreciated!

 

I will record the knocking soon.

 

I hate to hear you have a knock in the engine...what oil did they use?...I had tried about five different oils in my 22 Re until I landed on Red Line...all, even Mobil 1, that I love, that I have used since the 80's knocked like crazy...once I switched to Red line 10w 30w it never knocked again...winter or summer. i then switch all of my fluids to Red Line...very expensive...but my differential on turns never made a noise, transmission shifted like glass, transfer case shifted in and out of 2H, 4H to 4L flawlessly...so I went all in...may be worth a try...

 

Just out of curiosity...is the knock continuous? Does it knock going up hills, down hills...wrist pin knocks and piston slap sound entirely different and occur differently. Wrist pin knocks are really hard under load...piston slap are more noticeable on coasting down hill with no load...Yep...try recording while driving up hill under load, downs hill off the gas that will tell a bunch!

 

Thank you for the reply NightOwl. The dealer used synthetic 5W30 mobil oil. I had actually used that same oil on my original engine for many years and maybe that's why it failed? I don't know but many have said the oil is too thin. I immediately changed it when the dealer told me they used mobil oil. Felt like a waste of $$ but needed to give it a try. I used 10W30 conventional oil and it did not make a difference. Maybe I'll wait till I get to 2K before changing it since I already changed it from the expensive oil change!! I normally do my own oil changes but figured to do it while at the dealer but maybe I shouldn't have done that.

When it idles it's completely quiet with no knocking. I am not a mechanic but there is no piston slap or knocking when coasting or on the freeway so the knocking is not continuous. I know what the engine sounds like and will notice any changes considering I've had this truck for 23 years. When driving on the freeway, it sounds normal with no knocking. Seems it only knocks when getting up to speed. Just drove to San Diego and it drove just fine on the freeway. Went uphill just fine with no knocking sounds. It only started knocking when I got to LA and got stuck in stop and go traffic! The mpg seems normal as well and probably did notice a slight loss of power.

I haven't driven my truck just yet but will record the noise soon when I head back to Nevada. The knocking is definitely loud and sounds like a diesel! Sometimes I think everyone car hear it and sounds like it's falling apart.