Need some help here. Truck making odd noises.

Any mechanics haging around? I have a '93 Nissan 4 cyl standard transmission truck with around 220K miles on it that is sounding bad in the transmission/drivetrain area. And of course this always happens on a dang Friday evening, when all the shops are closed... Any ideas would be appreciated.

Here is the deal. I have noticed over the last month or so, a slight noise when it is time to shift gears. Not redlining, just the normal shift speed. It is kinda like valve/timing clatter, but it is different. Not sure how to describe it. Now on the way back from work, this noise is very noticable. A cross between a roar and a clatter? Now, if I shift into a higher gear than I should be, the noise goes away. If I press in the clutch while moving, the noise is gone, even if I rev up the engine.

It is parked for the weekend. But I need help figuring out what I am looking at getting fixed. I got a new timing chain on it last year, a new clutch within a year, and a new water pump. I can do some work on motors, but when it comes to transmissions, I am lost. They work on Freaking Magic!

Any help would be greatly appreciated. :confused

 

when you replaced the clutch did you replace the throw out bearing do you think the noise could be coming from the bell housing

 

I had the clutch replaced. I am not sure about the bearing. If I am remembering correctly, a bearing was replaced. Not sure though. I will find out Monday.

'Bell housing...' Ok, you got me there. I have no clue what you are talking about! :confused

Thank you very much for your help!

 

Ok Fred basics first, with the motor cold check the oil level in the transmission there is a plug on the side of the trans you normally have to get under the auto to do it but not on ramps or you will get a false reading.

unscrew the plug and push your finger in the hole,you should be able to feel the oil level, if not top up with trans fluid until the fluid runs back out of the plug.

 

the bell housing is at the front of the gearbox it attaches the box to the back of the motor its the housing for the clutch assembly or in the case of a automatic the torque converter but in your case a manual has the clutch the throw out bearing sits on the front gear shaft and slides back and forward when you press the clutch peddle in and out it sounds as though the bearing case may be loose this would make a loud noise when there is no load on it like when you are in gear and traveling a long but when you place a load on the bearing changing gears the noise disappears not saying this is your problem but not much can go wrong with a manual gearbox

 

oops sorry thought you were taking about a manual gearbox silly me and manually changing the gears my mistake

 

You are right in what you said,if it has a clutch it must be a manual gearbox.

@Fred is it noisier in any one gear more than the others?

 

yeah bill i saw that after i posted your comment on a transmission threw me out over here when talking about an auto we say transmission and gearbox for a manual

 

to check the throw out bearing, from under the auto there is a large dish shaped coupling between the motor and gear box at the bottom is a plate normally with 4 bolts,take it off, this is the inspection plate,it should be dry or just moist but no oil should run out,if the hole is big enough (they vary) put your hand in and you will see/feel a piece of cast steel shaped like a fork and between the two forks is the throw out bearing check to see if there is any movement in the bearing(there should be none) if all these are OK then we need to search farther.

 

Yep in OZ you are the same as us in Europe a transmission is automatic but in the US all gearboxes are transmission.

we are separated by a common language.

 

yeah the old language barrier a bit like when the yanks say gas their talking about petrol but we are talking about LPG i have live a sheltered life way down here in the south pacific until the internet came along

 

Thanks for the ideas folks! I was able to borrow a car for the weekend, so the truck is parked untill I figure this out.

Will check the trans fluid when I get off work. Why don't they put a freaking dipstick on it..? :-D

And the noise is more noticable in 3rd, 4th and 5th gears. But those are gears I drive in, 1st and 2nd I usually just shift through while I accelerate.

Thanks for the help!

 

They don't use a dipstick because of the pressure inside the box.

wont bore you with the details but inside the box are normally 4 shafts input/output and 2 idler shafts.
1st and 2nd gear are normally on the lower idle shaft and 3rd 4th and 5th on the upper with 2 bearings to each shaft,if one bearing is worn it can give the noise you describe.

don't get panicky Fred it's not as serious as it sounds but with the mileage you have on the motor it's a possibility.

 

"wont bore you with the details but inside the box are normally 4 shafts input/output and 2 idler shafts.
1st and 2nd gear are normally on the lower idle shaft and 3rd 4th and 5th on the upper with 2 bearings to each shaft,if one bearing is worn it can give the noise you describe."

Now I know you are not telling the truth. I know for a fact transmissions work using F.M. (mmm Freaking Magic is the G version). Inside the 'box' are bits of metal, transmision fluid, and lots of concentrated Magic Smoke. How many transmissions with smoke pouring out of them have you seen that still work well... Like computers, let the magic smoke out, it no workey any more.:-D

And now that I think about it, it does make the noise in 2nd gear as well.

Appreciate the help!

 

Sorry Fred i forgot to mention the magic smoke.

If you get really desperate this might help

 

It truely amazes me how Karma works. I buy a laptop, my mechanic gets a Linksys router he needs flashed to the Tomato firmware...

http://www.youtube.com/watch?v=qzz1VEN1SEk

He needs the flash ASAP, which means I most likely get my truck fixed for close to free! :cool

And there is a song for my fellow Geeks as well...

 

Just an update. The shifter bushings need to be replaced. Ironicly, I have see simular bushing in some older Mercedes when I worked at the shop. And I need new fan and A/C belts. The shifter bushing, I will have done for me.:confused I can handle the belts.

My little network setup job at his shop went great, so I will most likely only have to pay for the parts, and maybe buy the mechanic lunch! I love the Tomato router firmware!

Thanks for the help on the magic gear box.

 

Need your advice if you don't mind. My truck has been making progressively louder noises that seem to come from under the truck. I was thinking my transmission was about shot. But every time I went to the shop, it would not make the noise!

I mean at times, it sounded like someone had tossed some nuts and bolts off into the engine or the transmission! But it drives just fine. It finally made the noises when I drove the guy around. He said it was the Catalytic converter. Sound right to you mechanically inclined folks? I had the oil changed, and the transmission fluid changed. But the sound is awfull, but it drives great?:confused

Thanks.

 

Does the catalytic converter have aluminum heat shields or are there heat shields on the other parts of the exhaust system?
When the bolts holding them together rust, the shields can start vibrating and rattling at specific engine RPMs. Can make a crap load of noise.

 

Will crawl under and check Sunday. Have no idea. I talked to a friend and he said a failing CAT can damage the engine? If the CAT is failing, can it cause damage? I thought that was just enviro stuff.

Someone else said don't worry, it will just break up and blow out. Don't know who to believe.

 

Yes and no. Depends on how it fails.

http://autorepair.about.com/cs/generalinfo/a/aa080401a_2.htm

 

Thanks for the link ibmest. But it does not really answer my question. The engine has around 220K miles on it. Drives great, great acceleration. Just makse horrible noises.

Can a bad CAT damage an engine? I need this truck to run for about another year.:confused

 

HI Fred
I personally have never heard of a damaged CAT causing any mechanical problems with the engine.
Where the trouble lies is if the CAT is blocked it will reduce engine performance but you say it starts and runs well so we can assume it is not blocked,inside a CAT are a number of baffle plates and over a long period these can come loose or break off and this will give you a lot of noise transmitted through the body of the truck,normally you would hear this if you hit a bump in the road.
If the Platinum/Palladium coated mesh breaks up it will as your friend said it will blow out of the system but beware ,if it all comes loose and just blows to the back of the box it will cause loss of performance.
When you crawl under the truck just give the CAT (it is the firs box nearest the engine) a thump with your fist and if you hear a rattle you know it's that.
Let me know how you get on.

http://img296.imageshack.us/img296/2659/000201d21632292ht2.gif


Bill

 

Thanks Bill and lbmest! That was an excellent idea Bill. I only saw one 'box' on the exhaust (about midway from the exhaust manifold to the tailpipe), so I hit it a few times and it rattled. After that, I had to go to the store, and no noise!

This looks like the object of discussion http://www.car-stuff.com/carparts/nissand2119901994easterneast40075361526.html

Couple more questions. On O'reilly's website, they list several 'converters' which look just like the one in the above link. But they also list one catalytic converter, but it has no picture. Are they the same thing? (Cat and converter) Part #15038 http://www.oreillyauto.com/EW3/Disp...chFor=15038&bid=1225048557007&cycleCount=1411

And how difficult are they to replace? Looks like just a few bolts. (horribly rusted into place) But does not look too hard. Thanks!

 

It is the COST that is an issue. They steal cats and sell them in some areas they command over $1000 at the recyclers!

 

BOOM, that is why I love my 'hooptie'! They have them from about $80 to $180 for mine! I know for some of the Mercedes, they are a grand or two!:cool

 

they are not difficult to replace Fred.
the normal way is to just cut the two clamps on each end of the box and then try to break the rust that has built up in the point where the box connects to the system.

when you have it loose force the box to slide (backwards or forwards) until one end is free then move the exhaust system to the side as far as you can and if you have enough space pull the box clear,( you may have to make the front or the back half of the exhaust loose to gain enough movement to free the old cat.

replacement of the new part is just a reverse of the procedure.

A suggestion get enough replacement U clamps to replace any that you have removed, even if you are able to loosen any of the clamp on the system the will not normally tighten to the same degree that they were. usually they break when you put them under tension.

http://img520.imageshack.us/img520/2820/0002028a7695501id8.gif

 

gotta read the posts all the way thru!