Whining sound when accellerating

D

DJSimca

Well-Known Member
Messages
333
Reaction score
0
Location
Denmark
I recently swapped the standard 4-speed gearbox with a Getrag dogleg gearbox. As part of this swap I only 'touched' the exhaust system and the prop shaft - as well as the new gearbox of course :D

Ever since assembling everything the car has developed a very annoying 'whining sound' which kicks in somewhere between 3500 and 4000 rpm :? The sound is only present above approx. 3500 rpm and when the engine is under load. It sounds as if the sound comes from the engine compartment.

I tried to disconnect both the alternator and the power steering pump ... unfortunately the 'whining' remains :(

Any ideas/suggestions are much appreciated

br
Torben
 
Troben,
Assuming that you only changed the gearbox and really did not do any other work then here are some ideas for you to think about....

1... Any part of the gearbox/engine touching the body?
2... Gearbox rebuilt? if no it could be the bearings - lots of miles / kilometres?
3... Gilbo (rubber donut) connection to prop shaft ok?
4... Pre load on prop shaft centre bearing ok?
5... prop shaft alignment ok?
6... Clutch ok?


The dogleg boxes are quite noisy, even when new
It maybe just a case of resonance with the different ratios of the dogleg gearbox inter acting with the engine compared to the old 4 speed box
Malc
 
Malc said:
1... Any part of the gearbox/engine touching the body?
2... Gearbox rebuilt? if no it could be the bearings - lots of miles / kilometres?
3... Gilbo (rubber donut) connection to prop shaft ok?
4... Pre load on prop shaft centre bearing ok?
5... prop shaft alignment ok?
6... Clutch ok?
Click to expand...

Hi Malc,
Thanks for the quick response and your suggestions.

1. I am certain that no part of the gearbox touches the body
2. The gearbox is rebuilt and new ... I certainly hope that this is not where the sound is coming from :(
3. I will be replacing the guibo tomorrow .. don't believe that this could be causing the sound though
4. Pre-load on centre bearing... please elaborate what you mean by that.
5. Alignment is OK
6. I put in a new clutch as part of the operation ... would it be possible for the clutch to be 'whining'??

Do you have any suggestions as to how I can isolate and thereby test the various components you suggest??

Thanks
Torben
 
Is the whinning dependant on engine speed as opposed to the ground speed?

Everything after the tranny output bearing is groundspeed related so the guibo, centre shaft bearing and diff change with the speedo and everything the other way (tranny, clutch, flywheel and engine) change with the tach.

If the whinning changes each time you shift at 3500 - 4000 then I think the problem is not the drivetrain. Somewhere upstream of the output bearing is more likely.

Of course, I have been wrong before.
 
Have you checked to see if any of your kids are in the back seat? That's been the source of a chronic whine which appears no matter what I'm driving.-Paul
 
4. Pre-load on centre bearing... please elaborate what you mean by that.
5. Alignment is OK
6. I put in a new clutch as part of the operation ... would it be possible for the clutch to be 'whining'??

Do you have any suggestions as to how I can isolate and thereby test the various components you suggest??

Thanks
Torben
Click to expand...

Pre load on centre bearing is that it has to be move forwards about 10mm from its rest place. IE slacken off the bolts, push forwards and hold, tighten bolts.

THe clutch thrust bearing could be contacting the clutch when released, Does the whining disappear when holding rpm but push the clutch in?
car on the move. If the noise disappears we have to think about
1... Revs only have an effect when the drive is under load.
2... Somewhere from the clutch/flywheel back through the system is it happening (Maybe)
If it's still there then other things to think about....
Could be fan,
PS pump and altenator belts.
Flywheel centre bearing (one that takes the shaft from the gearbox)
Make sure there are no tie-wraps (cable ties) etc loose near moving parts
Where abouts are you?
I expect to be in Frieseland (Spelling) Northern Holland in a week or so so could always have a "day trip" :wink:
Malc
 
Have you checked to see if any of your kids are in the back seat? That's been the source of a chronic whine which appears no matter what I'm driving.-Paul
Click to expand...

Given that it happens while accelerating, I thought maybe my wife was with him... :shock: She hates to go fast. And yes, she's aware that she married the wrong guy, and has been trying to figure out how to correct that mistake for 20 years... :lol:

Regards preloading the center bearing -- you should slide the mount tabs forward about 2mm from their resting position before tightening.
 
Another thought -- you could be hearing the engine fan making contact with something -- as the revs increase, it naturally flexes forward, and you may have slightly disturbed the position of the engine, just enough to cause a minor contact. Check the fan and surroundings for signs of contact.
 
Thanks a lot for the suggestion so far... unfortunately I am still puzzled about this thing.

After reading Malc's original msg I got very worried that the 'new' and completely rebuilt gearbox was faulty :( so I lifted up the rear wheels and 'drove the car' with the rear wheels spinning... not a whine or any such sound .. only my wonderfully free revving straight six. :) i.e. the sound is only there when the engine is under load.

The sound does disappear when the clutch is engaged. If the clutch thrust bearing is causing this how do I then fix it .. as far as I can see there is nothing I can adjust with regard to the clutch!! Besides why would the sound only kick in at around 3500 rpm?

Earlier on I did try to disconnect the PS pump and the alternator (boy does the engine heat up quickly when the water pump is not working :shock: ) but they were also not to blame.

With regard to the flywheel centre bearing .. could I possibly have damaged this when assembling everything .. and again, how do I test?

Apart from the clutch (and the gearbox, which I pray is not to blame) could it be something stupid as incorrectly mounted gaskets between the manifold and the front exhaust pipes?

Regards,
Torben
 
Torben,
From you last post you have two areas to think about

1....Only makes the noise under load
2.... stops when you push the clutch in (no load again)

May I suggest you very, very carefully check that the engine cannot move, ie rock from side to side. Remember it tries to rotate when putting power out.
look for any contact marks between say the front pulley and the anti roll bar

PS pump and or altenator hitting something- underside of the battery tray, fuel filter sounds daft but it has happened!

30csl has had problems with his engine moving about, but under braking. I suspect this could be happening with your car. If it is a whine then this suggest it's something rotating that is touching.

As to you other point, clutch bearing or center bearing in flywheel thats and engine/gearbox out job I'm afraid

One other thought is to "stab" the throttle ie push to teh floor and let off very quickly, you might here something"thud" if the engine is moving.
Malc
 
Thanks to all for excellent advice ...
I was finally able to find the culprit of the whine... the prop shaft centre bearing...
Now nothing detracts from the wonderful sound of the straight six as I accellerate through the gears :D :D

Thanks again
Torben
 
Cool 8)
Now that your car flies watch out for speed cameras :roll:
Maybe you don't have too many in Denmark?
Looks like I will be in NE Holland in a week or so, are you nearby could possibly meet up?
Malc
 
You must log in or register to reply here.
Back
Top