M3 J0N

My car is a 100k+ mile avant and Im having some drivetrain issues/noises/clunks/etc. I figured this would be a great opportunity to start a thread for reference for those people that would like to diagnose/isolate specific issues to specific mount failures. For those who have experienced issues with mount failures (diff mounts, tranny mounts, or engine mounts), your input would be really helpful.

I figured it could go something like this:

Engine mount
Failure Symptom:
Replaced with XX brand:
Purchased from:
Price:
Happy with new part:

Tranny mount
Failure Symptom:
Replaced with XX brand:
Purchased from:
Price:
Happy with new part:

Diff mount
Failure Symptom:
Replaced with XX brand:
Purchased from:
Price:
Happy with new part:

donromani

You left out the snub mount. Replace with APR 40 bucks or so.

Engine and tranny mount failure = more noise and vibration. A few people have said it causes other engine components to wear out faster but I don't buy it.

034 is pretty popular - they offer both street and track density versions. Some do RS4 mounts.

Haven't had the diff mount fail - do you mean the drive shaft support? I hear this one is the most serious - lots of noise and vibration, problems with driveability. A b1tch to replace and costly.

bcr84urq

Good timing - my car recently developed a slight knocking (not motor knock) when I start it and get the car going from a stop. Wondering if it is a control arm, motor mount or tranny mount. Leaning heavily towards motor or tranny mount as it knocks when car not even moving at start up. The bummer is all my mounts are less then 3 yrs old - most prolly less than 2 yrs!

I have yet to get under the car - can you usually see torn rubber? or does fluid leak out? Any visible signs? Any insight on figuring out what is wrong appreciated - TIA.

Brandon
'84 ur-quattro 20Vt
'01.5 S4

M3 J0N

oooh, tell me more about this snub mount and drivetrain support! I am having some driveability issues....

Same here. I have a knocking in the drivetrain. More noticeable from a stop/low speed, but definitely there when shifting through all gears. Very noticeable knock when slamming on the brakes as well. Also, if I am cruising at a constant speed, there is something in the drivetrain that creates a rhythmic thumping from the rear. We lifted the car the other day to install my JHM SSK, AWE DTS, and Milltek exhaust and didnt see anything apparently damaged, however, the awe DTS was a bitch to get aligned properly, so Im assuming there was some extra play in a motor mount or tranny mount.

I really would like to figure this out, because the car really isnt fun to drive. The 2000 s4 sedan that I have with the same mileage feels solid as a rock compared to this one.

donromani

Hard to see anything unfortunately. The mounts do occassionally show signs of fluid leaking out when they fail.

I doubt the knocking is a problem with the mounts. Even a bad mount won't let the engine or drivetrain move around enough to cause knocking. Most likely you have something else that is loose.

bcr84urq

Hmm I don't know don. My understanding is the motor moves around quite a bit with stock rubber mounts. Ever watched a dyno day? Plus me thinks that is why so many guys like the harder mounts and DTS from the tuner shops. My money is on a motor or tranny mount - but we'll see...

Brandon
'84 ur-quattro 20Vt
'01.5 S4

donromani

But isn't the problem with a failing stock mount that it ceases to let the motor move around as much? That's pretty much what the shop told me when the mounts on the Passat started leaking.

So a bad mount would actually cause the engine to move around less, kind of like upgrading to a more solid mount.

billdapart

Absolutely false. When a motor mount (side mounts on our engines) fails, it leaks silicone fluid. This silicone fluid acts as a damper for the two rubber pieces of the engine mount. When all the silicone has leaked out the two rubber pieces can move more and even make contact with each other and have nothing to slow them as they move apart. If not caught at this point, this can lead to seperation. This is a literal seperation of the top and bottom halves of the motor mount. This means that when the motor is put under stress (i.e. torque in a clockwise fashion) the motor will tilt in a counter-clockwise fashion and have nothing to stop it from tilting. This can create clunk noises as well as break plastic and rubber hoses and create contact between other components like the fan and fan shroud/etc. In this case I would suspect tranny mount. A bad tranny mount in our cars can cause some veru strange effects, but really it makes sense. If it clunks or rattles when the gears change or when you brake hard (i.e. when the weight of the car is put towards the front and the lock up of the wheels puts the full effort of the engine forward against the brakes, the tranny tilts upwards with the side mounts acting as fulcrum and the stub mount and the tranny mount acting as stops) and you hear a big clunk or multiple small clunks.. it's because the trans mount has seperated. Of course the problem with this is that noises and feedback from the pedals and steering wheel is totally subjective and you could have a loose bolt in the heatshield that causes a slight rattle and most people wouldn't notice but you are a total freak and it's gonna drive you nuts making it's little bop which is completely out of time with the arythmic style of your europa experimental electronic music and as I said most people would never notice but you will and you'll do your damndest to find fault where there is none instead of lifting the car and LOOKING at the damn thing and seeing what is not right or not... wait a second.. sorry.

yeah. lift the car and look at your mounts. If the side mounts are leaking silicone replace them. If the rubber part of the tranny mount is not in ONE piece, replace it. If the snub mount looks yellow.. replace it. Eat 2 cookies, drink a couple shots of jager, call me in the morning.

billdapart

sorry, I just realized that your were trying to start a thread about aftermarket replacement for mounts and had a format. I apologize. I will now try and stick to your format.

Engine mount
Failure Symptom: Clunking on acceleration and braking, underpan covered in purple, torque steer like a mother.
Replaced with XX brand:stock, solid mount
Purchased from: dealership, custom made
Price:75.00, 200.00
Happy with new part: yes and no

(stock works well and lasts an average amount if you're not popping the clutch at every stoplight. A solid mount sends more vibrations through to the driver and overall decreases the overall appeal of the vehicle. Then is doesn't last as long at normal paces and lasts for **** at a autocross or race pace.. Of course if you are racing this car, you have the money and resources to replace them every time you take out the car.)

Tranny mount
Failure Symptom: Loud clunk or machine gun clunking/hard shifting while shifting gears or decelerating.
Replaced with XX brand: stock, solid mount, 034
Purchased from: dealership, custom made, 034
Price:75.00, 200.00, 45.00
Happy with new part: yes, no, definitely
(again, stock works as it should.. custom made solid mounts are very harsh.. work very well at transmitting power and vibration.. 'feel' and last about as long as a race does.. the 034 is a good middle man. More performance, heavy duty.. lasts as long as it should.)

Diff mount
Failure Symptom:Oversteer, esp light on heavy braking, rear end clunk on heavy acceleration.
Replaced with XX brand: stock
Purchased from: dealership
Price:75.00
Happy with new part: sure
(no sure what to say here.. our diff mounts are good. if you want a solid mount I hope you have rebuilt that diff and have a diff cooler hooked up. If you are looking for an aftermarket solution that will last longer or perform better.. you're crazy)

M3 J0N

thank you very much for the input. can you tell me a bit more about the snub mount? is this the same as the main diff mount that these companies sell?