Interesting drivetrain noise - 89 C4
08-30-2011, 10:00 AM
#1
Three Wheelin'
Thread Starter
Interesting drivetrain noise - 89 C4
This is one of those daft, "I've got a noise that I can't quite describe, that's coming from I don't know quite where" type threads but please bear with me.
Noise seems to be coming from the front end of the car. But that can be deceptive...
It's not a whine, not a rumble, not knocking. It's like a distant coffee grinder, minus the electric motor noise. Or maybe like a http://www.bigstockphoto.com/image-6...arpening-stone being used at low speed, with the axe you're sharpening jumping about a little. There is a high speed rattle quality to it.
Noise is loudest in 3rd and 5th but detectable in 4th, at 40-60mph, only with throttle applied. Noise disappears with throttle off, and reappears even with light throttle.
Noise is just detectable at lower speeds, but only because I've got bat like hearing. Obviously nice flat quiet road surface makes it easier to hear. No noise when stationary. No noise when on the move in neutral.
At a given road speed, the noise is the same pitch/frequency in 3rd as 5th.
No change in left or right turns.
The noise has been there since I've owned the car ~6000miles. But more noticable now and is much more pronounced since changing rear engine mounts a couple of weeks back.
I've taken a bonefide expert for a ride and he says its probably nothing to worry about, almost certainly not transmission, or any of the three differentials. He suggests
a)loosening off a little the rear, centre, and front mounts for engine, tranny and front diff, and driving around to get everything aligned nicely and re-tightening. Which sounds sensible to me. I can image the new higher resting point of the new rear mounts maybe loading up the centre tranny mount.
b)looking at the gear linkage for loose items. again a decent suggesting given the sounds reduces if you grip the gear level firmly and brace it against your knee. Although to perform this maneuver you also are effectively blocking the sounds from the gear stick opening with your knee.
Any thoughts folks?
Noise seems to be coming from the front end of the car. But that can be deceptive...
It's not a whine, not a rumble, not knocking. It's like a distant coffee grinder, minus the electric motor noise. Or maybe like a http://www.bigstockphoto.com/image-6...arpening-stone being used at low speed, with the axe you're sharpening jumping about a little. There is a high speed rattle quality to it.
Noise is loudest in 3rd and 5th but detectable in 4th, at 40-60mph, only with throttle applied. Noise disappears with throttle off, and reappears even with light throttle.
Noise is just detectable at lower speeds, but only because I've got bat like hearing. Obviously nice flat quiet road surface makes it easier to hear. No noise when stationary. No noise when on the move in neutral.
At a given road speed, the noise is the same pitch/frequency in 3rd as 5th.
No change in left or right turns.
The noise has been there since I've owned the car ~6000miles. But more noticable now and is much more pronounced since changing rear engine mounts a couple of weeks back.
I've taken a bonefide expert for a ride and he says its probably nothing to worry about, almost certainly not transmission, or any of the three differentials. He suggests
a)loosening off a little the rear, centre, and front mounts for engine, tranny and front diff, and driving around to get everything aligned nicely and re-tightening. Which sounds sensible to me. I can image the new higher resting point of the new rear mounts maybe loading up the centre tranny mount.
b)looking at the gear linkage for loose items. again a decent suggesting given the sounds reduces if you grip the gear level firmly and brace it against your knee. Although to perform this maneuver you also are effectively blocking the sounds from the gear stick opening with your knee.
Any thoughts folks?
08-30-2011, 10:15 AM
#2
IHI KING!
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A few thoughts. Did you check the fluid levels in the front diff and the tranny? I'm wondering if your mechanic checked that. Also check the tightness of the CV joint bolts.
08-30-2011, 10:37 AM
#3
Three Wheelin'
Thread Starter
good questions.
I changed and checked the tranny oil and front diff oil about 18mnths ago. About a year back I changed the input oil seal on the front diff, as there was fair old leak. The level was checked and OK at the time of purchase ~28mnths ago as part of PPI. Front CV joints are correctly torqued, I've not checked the rears but they haven't been disturbed during my ownership.
I'm pretty wary of jumping to my own conclusions, I don't have a great record on diagnosis for noises, having once changed an entire gearbox for what turned out to be a wheel bearing, a double whammy as the replacement gearbox wasn't as good as the original! Still that was a VW so a used tranny was £150, so I only cried for a week or so.
I changed and checked the tranny oil and front diff oil about 18mnths ago. About a year back I changed the input oil seal on the front diff, as there was fair old leak. The level was checked and OK at the time of purchase ~28mnths ago as part of PPI. Front CV joints are correctly torqued, I've not checked the rears but they haven't been disturbed during my ownership.
I'm pretty wary of jumping to my own conclusions, I don't have a great record on diagnosis for noises, having once changed an entire gearbox for what turned out to be a wheel bearing, a double whammy as the replacement gearbox wasn't as good as the original! Still that was a VW so a used tranny was £150, so I only cried for a week or so.
08-30-2011, 05:11 PM
#4
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Coffee Grinder Noise
Ah yes, the dreaded coffee grinder noise.
I think what you are hearing is some sort of vibration inside the transmission I've heard it described as "gear chatter". As I understand it, this is a normal condition that is caused by transmission of engine vibration into the transmission through the input shaft. It is more prominent in the the '89 C4 since it uses a single-mass flywheel. My '89 C4 does the same. 964s from '90 up are equipped with a dual mass flywheel to dampen this vibration in an attempt to alleviate this issue.
My '89 with 55,000 miles does the same thing and has since I purchased it at 47000 miles.
Tim
'89 C4
I think what you are hearing is some sort of vibration inside the transmission I've heard it described as "gear chatter". As I understand it, this is a normal condition that is caused by transmission of engine vibration into the transmission through the input shaft. It is more prominent in the the '89 C4 since it uses a single-mass flywheel. My '89 C4 does the same. 964s from '90 up are equipped with a dual mass flywheel to dampen this vibration in an attempt to alleviate this issue.
My '89 with 55,000 miles does the same thing and has since I purchased it at 47000 miles.
Tim
'89 C4
08-30-2011, 05:20 PM
#5
Three Wheelin'
Thread Starter
That sounds hopefully, don't spose your in the south east uk? Maybe we could compare noises.
Its one of those things where people look at you like you are a bit mad:
There! Now do you hear it?
Hear what?
The kschsksch noise!
The what noise?
Oh, we're going over some noisy tarmac you cant hear it now.
Yeah right, now let me out of the car you are clearly mad as a badger!
Its one of those things where people look at you like you are a bit mad:
There! Now do you hear it?
Hear what?
The kschsksch noise!
The what noise?
Oh, we're going over some noisy tarmac you cant hear it now.
Yeah right, now let me out of the car you are clearly mad as a badger!
09-03-2011, 03:46 PM
#6
Three Wheelin'
Thread Starter
Cheaky bump, I like Tim's explaination, but hanker after some corroboration, there are a few 89 c4 owners one here, any others of you out there with the coffee grinder noise?
