When Are Bearing Noises Loud Enough To Cause Damage?

[rorz]

Hey guys, my R33 Rb25DE manual has a really loud input shaft? becuase when i lift my foot off the clutch i can hear a rattling scraping noise. I have owned other RB's and the sound is usually a slight whirring which is fine..

The sound is also audible while in gear driving the same rattly scraping rotating sound, which DOESN'T sound normal to me...

My question is, how do i know when it's time to pull the gearbox out and get the bearings done? i have searched and most people talk about getting the bearings replaced but not what happens if you chose to ignore it?

Thank you

[turboedsloth]

if you choose to ignore it the bearing in question could collapse and cause quite extensive damage. I'd say now would be the perfect time to get your unit overhauled.

[rorz]

Is it worth throwing in some nulon 70 additive in there before i fork out $1000 for a refurbish? Just trying to get a grasp on the necessity of this procedure..

*on a side note, if i did get some oil additive can i just throw it in the top where the gear stick comes out? It's a RWD not 4WD

[turboedsloth]

you'd be wasting your money. Alot of people stick redline in to stop a worn synchro from crunching. IMO that is also a waste of money, the synchro is f**ked get it fixed.

If you want to stick the additive in then yes you can put it in through the gearstick hole

[rorz]

ok cheers for the help mate but the main question i guess here (that can help everyone and not just me) is:

at what point do you decide that the noise level is loud or rough enough to justify taking out the gearbox etc? I mean does it have to be popping out of gear to justify this or just be really noisy? My gearbox in particular has no crunches and shifts really well it just has noisy bearings, hence my problem with determining the health of the gearbox.

[jrm]

Ask a specialist - I'm sure any gearbox specialist familiar with the box should be able to give you sound advice on the bearings ..

[Trozzle]

Nissan gearboxes have that horrid bearing. Mine does it, but not audible while driving.

The VL we had spat the whole bearing cage out with the oil when we changed it....lol trust me, you don't want what came out floating around inside the gearbox. Could do serious damage....unless it's a VL, then who gives a f**k. lol

[bubba]

It's also just a shitty 25DE box.. put a real box in there

One of my old RB20 boxes developed an input shaft bearing noise after too many 2nd gear clutch drops.. I ignored it until it got so loud it sounded like the gearset was trying to exit the housing, then put a 25DET box in there.

[rorz]

Well i just went to a specialist and he said that if i leave it the input shaft bearing will break up and run through the gearbox and i could destroy something else in my gearbox (the teeth i think he said) and that he can fix it up for me for $2000 NZD. I said no thank you.

Does anyone here have experience with loud input shaft bearings and how long theirs lasted (or didn't last) before something happened? I am too poor to afford a new box let alone a rehaul.

Edited July 29, 2010 by rorz

[bubba]

Does yours go BANG BANG BANG BANG BANG BANG BANG when loaded up? that's what mine was doing before I decided I couldn't handle it any more, it was quite loud and offensive.

[rorz]

Nope it just has a rotating sound as if there is like a marble in the gearbox somewhere with a sort of scraping background noise although it's not hugely loud. It's unfortunate becuase my exhaust is extremely loud so quite hard to diagnose the severity of the problem. Im draining the oil out tomorrow so till be interesting to see what comes out!

[turboedsloth]

i'd probly go to someone who will give you a realistic price. or buy another box from off here or the local trader mag

[Spurdo]

the box in my car was doing this when i bought the car back in 2007. i rebuilt it around christmas 2009 by which time the gearbox had done about 15,000kms with that noise going on, and hadnt seen much abusive driving because i knew the gearbox wasnt well (some synchros were worn as well). one thing is that the noisy bearing will start generating a LOT of extra heat. mine was getting steadily worse and towards the end of it, it was getting so hot that the leather boot around the gearstick was hot to the touch and if i removed it then the air coming in through the hole was as if there was a hot stove element there. fark it got warm. when i got the box apart there were a couple of bits and pieces that had turned blue from such extreme heat.

now with all new fresh bearings and fresh smurf blood the thing runs like a dream, ridiculously smooth and cool as a whistle.

so if your hearing the noise, the box's days are definately numbered. i consider myself lucky it didnt get to the point where it caused further damage.

[rorz]

Ok thanks for that mate i'm going to assume based on what you have said and what i have read elsewhere on the forum that i can leave it be for some time while i save up for a replacement of some description. Cheers

[Birds]

at what point do you decide that the noise level is loud or rough enough to justify taking out the gearbox etc? I mean does it have to be popping out of gear to justify this or just be really noisy? My gearbox in particular has no crunches and shifts really well it just has noisy bearings, hence my problem with determining the health of the gearbox.

The bearing will decide when the noise level is loud enough. Once it starts making noise it can collapse at any moment because it all comes down to the job of the bearings and the kind of pressure exerted on it. People have driven for thousands of KM on noisy bearings, they have driven for 50km on noisy bearings. Popping out of gear is a synchro hub issue and not a symptom of shot bearings. My advice is to either drive it into the ground and replace with a second hand gearbox or recondition it as soon as possible because when a bearing does collapse it tends to result in shaft damage which will cost more to fix than just reconditioning.

Nissan gearboxes have that horrid bearing. Mine does it, but not audible while driving.

The VL we had spat the whole bearing cage out with the oil when we changed it....lol trust me, you don't want what came out floating around inside the gearbox. Could do serious damage....unless it's a VL, then who gives a f**k. lol

More than often this is the thrust bearing rather than gearbox bearing as the sound will go away with slight pressure on the clutch pedal (not engaging, just touching). But genuine gearbox sounds should go away when the clutch is completely engaged.

[jiffo]

Probably wasting my breath, but have you downloaded the workshop manual so at least you know what's going on inside the box?

Worn bearings aren't just noisy, they don't do their job properly, in this case locating the input shaft.

Once the input shaft starts to walk in/out, you'll either jump out of 4th or the drive gear will chew into the layshaft driven gear/sub gear.

If the input shaft gear is worn, so is the layshaft front bearing.

From then on even with a set of new bearings, you'll always have a noisy box as the drive gears will have a wear pattern.

[Deano 1]

just buy a second hand box mate, off ebay or the wreckers, screw rebuilding it, way to much money. you could buy 2-3gearbox for the price of rebuilding the one, unless its a race car dont bother

[Trozzle]

More than often this is the thrust bearing rather than gearbox bearing as the sound will go away with slight pressure on the clutch pedal (not engaging, just touching). But genuine gearbox sounds should go away when the clutch is completely engaged.

Nah man definitely input bearing, only shuts up when clutch is completely depressed (gearbox not spinning)

my current 33 has very minor input bearing noise, but the thrust bearing also chirps when idling in neutral. Staring at the clutch pedal hard causes this to shut up.

[wlspn]

The common Nissan gearbox bearing noise isn't actually the input-shaft bearing, it is normally the cluster-shaft bearing, located in the sandwich plate. Have had this with my RB20 & RB25 gearboxes. As mentioned is there in neutral until pedal is fully depressed so does seem like input-shaft...

After 2+ years my RB20 got to the point where like the guy above, I drained the oil & a whole squashed bearing cage fell out

Replaced the bearing, thrashed the hell out of the box & had noise again 6 months later.

Then drove it like that for another 2 or more years & all was fine.

Only fitted RB25 box because I fitted RB25 engine & had it laying around...

[Kinks]

My R33 made some noise in neutral with the clutch out when I bought it, it was noted in the pre-inspection report. At the time the car had 33,xxxkm on it. It now has 115,xxxkm on it and the noise is no louder.

So my answer is unless the noise is actually getting louder over time, don't worry about it. When the noise level exceeds your budget for stereo equipment it's time to fix it

Of course, keep up regular gearbox oil changes and if you find misc bits of metal that shouldn't be there in the old oil then you know you've got a problem.