grinding noise from gearbox?

[chaserbuddy]

Hey all, I'm currently running a r154 box which was bought from a place up in Adelaide not
too long ago. I bought a new exedy hyper single clutch and installed them. Ive been having
a weird grinding noise when cruising along around 50kph in 4th. It only does it when applying power, when i take my foot off the accelerator the noise disappears. The noise slowly
disappears when u accelerate to a faster speed such as 80kph in 4th the is no noise at all.
not as bad in 3rd, hardly noticeable, but Im guessing it only does it when theres an excessing
load on the gearbox/drive train. Also should note that theres a custom tailshaft. could this noise be tailshaft or gearbox related??

[RA35GT]

It could be either gearbox or tailshaft related dood. (A busted uni joint can give all sorts of funky noises and is the easiest to check).

[chaserbuddy]

cheers mate ill check the uni's tomorrow

[Snich]

I've never heard a uni's make a grinding noise, if the uni's were rooted, u would get more of a vib, and it would increase as ure speed increases... I would bet my money on something in the gearbox..
ya box was 2nd hand yeah??? I'm thinking maybe more so synchro bearings, thats why u get it a bit in 3rd gear aswell, i think that the roller bearing has worn uneven..
do u know what the box came out off??

[allencr]

Instead of 'grinding noise', could it be better described as a whine or whirr or humming noise?

[chaserbuddy]

nah checked uni's look fine lol, anyway it definitely is an abnormal grinding noise, whines aswell but that seems to be normal as r154's are noisy boxes. sounds like the grinding noise is coming near the back of the shifter.

[RA35GT]

I've heard unis make clicking noises, scratching noises, grinding noises and the usual clunks etc.

Even if the uni looks fine, you need to grab both sides and see if it has any play within it.

If it isn't the uni joints, then its likely bearings in the gearbox which need doing.

Rudi

[chaserbuddy]

ill take out the tail shaft and see how they are anyway if its not them ill probably take the gearbox to a specalist

[Kedderz]

had the same noise in 5th, put redline uber expensive oil number 999 in syncro shock proof stuff and its gone. The oil that was in my GB was burnt however, it STANK like the worst shit.

food for thought.

[chaserbuddy]

i think u might have had bad lubrication, anyway ive just recently replaced the oil put some penrite fully synthetic stuff 3.5l ish. also might like to note that redline shock proof oil glazes syncro's. Redline MTL is best for r154's

[big_zop]

The noise slowly disappears when u accelerate to a faster speed such as 80kph in 4th the is no noise at all.

Are you sure it isnt just the road noise overpowering the gearbox noise at higher speeds. I have a similar issue in my car where i hear a weird noise but any sort of load or speed seems to produce way more noise than it?

And from re-reading over your initial post - you noted that it only made a moise while under load. Which could mean the bearings or thrust washer are worn excessively. Do you know what condition it was in before and if it had been rebuild (ie. to replace broken thrust washer)?

[Kedderz]

i think u might have had bad lubrication, anyway ive just recently replaced the oil put some penrite fully synthetic stuff 3.5l ish. also might like to note that redline shock proof oil glazes syncro's. Redline MTL is best for r154's

Indeed I used mt90 and syncro additive.

[chaserbuddy]

Apparently it was tested and in good condition, not sure if it has been rebuilt or not
anyway if helps the owner before me bought this gearbox and an orc clutch(in good cond). And managed to destroy the clutch within a week of having it on the road.

[big_zop]

And managed to destroy the clutch within a week of having it on the road.

Show how much sypathy he had for his car!

[chaserbuddy]

oh well, it was a fairly stock 1j, aswell 400 hp rated clutch= must been doing something nasty(riding clutch)