Hi...5 Speed noises issue

plantguy

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Joined
Oct 23, 2022
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4
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Make
Volkswagen
Model
Caddy 2lt SDi
Year
2006
Miles
180000
Engine
2lt SDI (BST)
Hi everyone.

I'm Martyn....I'm a Plant machinery guy and have an issue with my Volkswagen Caddy.

I bought it around 18months ago and Immediately needed to change the gearbox (AUM) as 1st gear synch had gone....I got a replacement from a gearbox refurbishment company for £600.
Being reasonable with spanners...I replaced the box myself....filling the box with the correct 75-90 for dry fill.

Although the engine is clattery as it comes for a NA 2lt Diesel.... For some time I noticed a chatter from the side of the replacement box which has now turned into a light drone./hum.....the drone/hum happens in gear and also at idle and is more pronounced when dipping throttle....also the issue occurs when warmed up and un-noticed when cold.

I inspected everything to be fine when I swapped the boxes...and have checked the fluid today (approximately 16months old oil that has no burning smell)....the oil is clear and has a slight standard gear oil smell.

I don't appear to have signs of flywheel wear...(unless I've missed a symptom).. although the starter sometimes slurs, tho I'm going to blame crap windings /starter age as all starter electrical tests come back ok.
The van has a single mass flywheel

id be very grateful for any questions or queries or advice..I'd love to learn something about what the drone/hum noise may be..

many thanks

Martyn
 
Last edited:

plantguy

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Thanks BP

I was thinking (worrying) that whilst. I bought a reconditioned box, the company may have only replaced a few components and not all of it.....

The gears work great, there's no crunching or anything

I hope it's nothing

Thanks again
 

billr

wrench
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I assume this is a FWD transaxle. There are many things that could cause a noise from that area, and noises are notorious for being hard to determine the precise location. Besides the gear-box itself, you might also be hearing a noise from a wheel bearing, or axle CV joint, or clutch, or even brakes.

Does the noise frequency seem to follow the vehicle speed, or engine rpm? Is the noise different when accelerating hard as opposed the closed-throttle deceleration? Does the noise change if you disengage the clutch or apply the brakes? How about coasting in neutral?
 

plantguy

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I assume this is a FWD transaxle. There are many things that could cause a noise from that area, and noises are notorious for being hard to determine the precise location. Besides the gear-box itself, you might also be hearing a noise from a wheel bearing, or axle CV joint, or clutch, or even brakes.

Does the noise frequency seem to follow the vehicle speed, or engine rpm? Is the noise different when accelerating hard as opposed the closed-throttle deceleration? Does the noise change if you disengage the clutch or apply the brakes? How about coasting in neutral?

Hi Bill, thanks so much for your reply...yest standard transverse 5 speed on a 2lt natural derv engine.

Il summarize..

1- noise is only heard after around 5 miles....
2- noise seems to get louder , peaking when engine upto temp.
3- Noise is a harmonic noise/hum....that can be heard at idle on the outside of engine (near wheel)
4 - noise can be heard inside only when throttling..
5-noise can be heard when throttling, irrespective of gear used....
6- noise does not change in pitch or tone with different gear selection.
7- noise disappears when the power range peaks(top of a gear) and re-appears when gear is low in its power.
8- dipping the clutch to coast...the noise is there, irrespective of speed...
9- noise only appears when throttle is applied...coast and no throttle is quiet (not wheel bearing)

I was wondering about input shaft bearings...I don't recal this box having a pilot bearing either.

Many huge thanks for taking the time and reading

Martyn
 

billr

wrench
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#3 above, are you saying the noise is there when the vehicle is not moving?

If so, then we head in a completely different direction! The noise would most likely be from the engine or an engine-driven accessory (alternator, water pump, etc). There are very few scenarios for the trans, axles, brakes, etc. making a noise when not moving. If you have the vehicle stopped, engine idling, in gear, and clutch disengaged is the noise still present? Having it in gear with clutch disengaged would prevent any motion of trans gears, totally eliminating the trans. But not the clutch, that still has to be considered in the "engine" category.

Once the engine is warm enough to make the noise, remove the drive belt(s) to all accessories and see if that makes a difference. Don't run it for more than about 30 seconds that way, as the water pump may not be in operation.
 

plantguy

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#3 above, are you saying the noise is there when the vehicle is not moving?

If so, then we head in a completely different direction! The noise would most likely be from the engine or an engine-driven accessory (alternator, water pump, etc). There are very few scenarios for the trans, axles, brakes, etc. making a noise when not moving. If you have the vehicle stopped, engine idling, in gear, and clutch disengaged is the noise still present? Having it in gear with clutch disengaged would prevent any motion of trans gears, totally eliminating the trans. But not the clutch, that still has to be considered in the "engine" category.

Once the engine is warm enough to make the noise, remove the drive belt(s) to all accessories and see if that makes a difference. Don't run it for more than about 30 seconds that way, as the water pump may not be in operation.

Thanks Bill.

The noise can be heard when idle and stationary from the end casing of the gearbox...no gears or clutch engaged....
The drive belt.elements alternater etc are at the opposite end /side of the engine and I don't suspect anything from that area

If I put my head into the wheel arch I can hear the noise at idle.....( But not inside the cab)....the noise is only heard inside the cab when throttling....

Noise is irrespective of clutch and gear activity....and only from throttling..

Remember I drive a right hand drive, so the noise I hear near my glove box when throttling is definitely the gearbox end...

Thanks again Bill.

Martyn
 

billr

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OK, a few more questions to help me clarify things in my mind:

The trans and glove-box are on the left side of vehicle, correct?

Have you listened for the noise with the vehicle stopped, trans in gear, and clutch disengaged? I want to make sure the noise is still there when the trans input shaft is not rotating (as it would in neutral, probably regardless of clutch state).

I would not be so quick to dismiss the accessories, noises are notorious for seeming to come from the wrong place.

Have you checked for simple banging of something in the exhaust system too close to a shield or frame?

When you say "throttling", you mean applying heavy load to the engine by opening the throttle (accel pedal down), correct?

Have you checked end-play on the crank? It is easy to do, and may give us some clues.

Which brings me to my best, and ugly, guess. Crank main bearings or something loose or cracked in the clutch/flywheel area.
 
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