Strange sound from gearbox

Adam Vinnicombe · Apr 22, 2021

Hi all need some advice and some help with an issue with the new edge.
First of the new edge is a manual. There is a metal on metal grinding sound coming for my gear box in all gears between 1000 to 2000 rpm when holding a steady speed. As soon as you go over 2000rpm the noise stops.
It’s definitely not the engine making the noise nor is it the pilot or release bearing. When parked and in neutral there is no strange gridding sounds at any rpm with the clutch pedal up or down it’s only when driving between 1000 to 2000rpm. It sounds just like a rotating metal disc grinding on a metal plate when a a steady rpm. If I accelerate through this band rpm range there is no grinding sound it’s only when at a light steady throttle.
Any ideas?
Cheers

PS the gear box is a tremec 3650

lwarrior1016 · Apr 22, 2021

Have you checked the oil level or changed the oil in the trans recently? It could be as simple as that, or as much as a bearing going out or gear chatter. Does it do it in every gear at that rpm?

Adam Vinnicombe · Apr 22, 2021

The oil was changed around a year ago.
It’s had two new throw out bearings and pilot bearings fitted in the last year along with a new clutch,pressure plate and flywheel trying to solve this issue. I don’t have any issues at all changing gears and I have to be honest I’ve not actually check the gear oil level.
yes it makes the same noise in all gears when trying to hold a steady road speed with the engine rpm between 1,000 and 2,000 rpm. As soon as I go above 2,000 rpm the sound just stops

lwarrior1016 · Apr 22, 2021

I would check the oil level first, but it sounds like it might be the transmission input bearing.

Adam Vinnicombe · Apr 22, 2021

Is that easy to change mate or will it need to go to a machine shop?

lwarrior1016 · Apr 22, 2021

Adam Vinnicombe said:
Is that easy to change mate or will it need to go to a machine shop?

If it is that, it would have to go to a transmission shop unless you can pull the trans and you have access to a press, then it’s not terribly difficult.

Frank.JD.Perez · Apr 22, 2021

maybe thats the issue i have with mine

ttocs · Apr 22, 2021

Just out of curiosity have you stuck your head under the hood/car to take a look. I had a room mate that when we were out drinking(away from the car or too drunk to care) would tell me about this rattle he had on his car at exactly 1800 rpms. I heard this for a good 3 months "Not at 1750, not 1850, 1800 and it doesn't matter what gear." Finally one day we were at the house and thought about it so I had him pop the hood and I didn't even go to put the hood up completely before I diagnosed it. He didn't latch the hood prop rod under the factory latch so it was just hanging out across the motor tapping on the top of it.

skidoo · Apr 23, 2021

Have you tried it in gear with the clutch pedal pushed in, but car not moving? That would eliminate the input bearing.

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lwarrior1016 · Apr 23, 2021

skidoo said:
Have you tried it in gear with the clutch pedal pushed in, but car not moving? That would eliminate the input bearing.

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How would that eliminate the transmission input bearing?

skidoo · Apr 23, 2021

lwarrior1016 said:
How would that eliminate the transmission input bearing?

Because the input shaft can't rotate if it's in gear, not moving, with the clutch pushed in.

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lwarrior1016 · Apr 23, 2021

Roger that, I’m following your thought there. He says the noise is only while driving between 1-2k rpm.

skidoo · Apr 23, 2021

lwarrior1016 said:
Roger that, I’m following your thought there. He says the noise is only while driving between 1-2k rpm.

Yeah it really would be difficult to diag through Tapatalk.. really the car needs to be on a hoist with someone is in the driver's seat engine running going through gears and someone else below it with a stethoscope. Hard to imagine any bearing in the transmission getting quieter as the engine or vehicle speed increases. Maybe it's low speed pre-ignition or an exhaust shield rattle.. ?

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lwarrior1016 · Apr 23, 2021

My t45 makes terrible noise at low load/rpm but as soon a rpm comes up, it’s quiet. Mine is definitely bearings.

His might possibly be exhaust rattle, the engine had a certain resonation at those rpms. I wouldn’t think it would be detonation though as different gears at that same rpm would be different load points in the timing map.

Adam Vinnicombe · Apr 24, 2021

Hi sorry for the late reply I’m on a short weekend holiday.
It’s definitely not a rattle it is a rotating metal disc rubbing on metal sound.
The sound is only when travelling at a constant speed or a very very light acceleration from 1000 to 2000rpm. A good moderate to hard acceleration there is no grinding noise.
There is no noise at all if I select any gear and rise the rpm with the clutch depressed.
I’ve check exhaust heat shields and system and found this. One of the rear silencers had most definitely been hitting the prop shaft at some time but saying that there was still a gap between them when I jacked the car up and had a look.

ttocs · Apr 24, 2021

is the exhaust not held in place well and shifting to hit it, or is the rear end not held in place well and its shifting to make contact? Something is moving too much.

Connie · Apr 24, 2021

Just curious if MAYBE one, or both Axle Bearings are going out. Bob.

lwarrior1016 · Apr 24, 2021

Maybe the exhaust isn’t what’s moving, have you checked or replaced the upper and lower rear control arms? Maybe there are some bad bushings and the rear end is shifting too far.