RS Motorsport :: Classic Speed Restored

Can anyone suggest why a loud roaring occurs when changing into 5th above 5000 rpm?
At lower revs the noise isn't noticeable.
I don't think it can be a bearing because the roaring doesn't occur at higher revs & speed in 4th.
No problems changing gears.
I've taken off the top cover & the extension housing, & everything looks & feels fine!

Thanks, Gregg

Loose rear nut on cluster or bearings

Thanks Danny,

Nut on end of countershaft cluster has not come loose as it is peened into slot - but I will check if torqued up because this noise has been there since I bought g/box from Eurospeed.
Don't know if significant, but whole cluster (which includes 5th driving gear) can move 0.4mm in fore/aft direction.

Gregg

shim it

Thanks Steve

I don't understand why loose nut or axial movement would cause noise in 5th only. Obviously all gears are on same cluster shaft & run on same bearings.
You would think a noise in one gear would be a gear tooth problem, but that looks fine!

Cheers

Countershaft nut was torqued up & axial movement is inbuilt in bearing.
5 speed uses roller brg. to take thrust. Inner ring is located between shoulder on shaft & washer held by 5th gear & nut. Outer ring is held between g/box case & circlip in intermediate housing

No wiser on noise, so seeing its not doing damage I'll ignore!

When the cluster nut loosens and or the bearing is worn the noise in 5th is loudest because it's not in the cast iron housing but in an alloy extension. Prettty straight forward stuff

have you tried different oil ??

gregg
I run redline shockproof light and have never had a problem
ring paul wagner at beresfield auto parts
49665544
mal

mal & gregg , a lightweigt type oil should make a bit more noise than a hvy weight oil
a light weight oil should make easier cold gear changes than a heavy oil
if its a road car put some thick GOOP in it & slightly over fill it
if its a race car wear a helmet

gregg it is that straight forward
What oil are you using

Danny,

Redline MTL - it's full synthetic GL4 70W80 for manual synchro transmissions.
G/box shifts well & gears look good.
You've convinced me it's a noisy brg (also everything else checks out fine). I just couldn't understand why it was just in 5th

Steve,
"if its a race car wear a helmet" - I like that one

Mal,

I had that lovely coloured redline shockproof in my nissan, but took it out because it's a GL5 oil which are for diffs etc & apparently eat synchros (according to Redline usa- but they don't specifically say shockproof)
This will probably set off much discussion as heaps of people use it successfully
See 1st paragragh 2nd page on MTL pdf

Cheers Gregg

"I had that lovely coloured redline shockproof in my nissan, but took it out because it's a GL5 oil which are for diffs etc & apparently eat synchros (according to Redline usa- but they don't specifically say shockproof)."

Have come across this issue a few times now concerning the different grades of heavy weight oils. It seems that if the gearbox has any brass or bronze bearings/bushes internally then you need to be careful what oils are used as "it will dissolve the brass". A lot of industrial reduction gearbox's that i see now have big red stickers telling you this and also voiding the warranty.

Mik

I have used Liteweight shock proof for many years and a lot of those with T9's wit hthe standard brass synchro's and have never had a drama with deterioratings or even slipping for that fact and it has done it's job better than any other oil bar NONE! as it was Mark King that put me onto it as it was the only oil he could keep his Mitsubishi Evo boxes together with!
Gregg as a side when I used MTL and another of their gearbox oils in my Quife Heavy Duty T9's it burnt the oil sending it black and I had to send oil samples back to Redline for testing and apparenty I took the oil past 190c! and then they even recommended Liteweight Shockproof!!


Danny

I forgot to post the outcome on g/box noise in 5th, so will now..

Running short of time at the start of this year, I put ext housing back on without removing or renewing bearings. Suprisingly noise was gone!
I remember thinking when pulling off extension housing that bolts undid easily, but didn't think anymore of it. When I reassembled I torqued them to specs of course. The 5th gear & brg housing is sandwiched by these bolts.
Next time I buy a g/box I'll check all bolts are torqued before installing!

Gregg