S4 Transmission Shunt! what is it?

AndyC

AndyC

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Hey guys

the S4 drives well.... BUT!

its got a slap (dulled knock!) when you back off the throttle.

there are so many bushes..... I was hoping it was a common problem that one of you guys had come across....



here is hoping...

Andy
 
imo first point of call would be your snub mount
2 options:
a. buy a new snub mount+bush from somewhere like 034motorsport.
b. get some Tigerseal and stuff the current mount full of it, and leave for 24-48hrs to fully solidify

your engine mounts and gearbox mounts are prob abit soggy aswell, and wont be helping matters, you could go for OEM RS4 mounts, or again, get some aftermarket ones from 034, stern get good write-ups on audizine.

a DTS would also help to reduce this, but your best addressing the above items first.
 
as craig says. Our 1.8T was really bad, huge thud when backing off the thottle.

We replaced the snub with an poly mount from Awesome GTI, helped but still did it, replaced the engine and tranny mounts then it vanished.
 
I had this problem too....I took off the main diff mount (nearest the front), bought some polyurethane in a tube(sikaflex 252 is good) and packed it solid with the stuff. Really pack it in there untill its flush with the metal surrounds that hold the stock rubber mount. As prementioned, leave to harden. When I put it back on the car ALL knocking from both changing up hard through the gears and lifting off was gone. There is a side-affect though....Now, because the mount is solid I can hear the noises the diff is making when I press the throttle. It can best be descibed as the hum thats heard when blowing into an empty bottle. At first I thought it was damage inside the diff (When I changed took the mount off I changed the diff fluid too, the old stuff was slightly low and absolutely minging!) but a couple of thousand miles later and the polyurethane is a little more supple (after being worked very hard) and the noise isnt as prominent....
 
The diff is a bit different to the engine mountings i think.

The diff mounts when worn make more of a bang/clunk on hard throttle. The engine mounts dont really make any noise, the best way i can describe it is as though there is a heavy weight in the boot, when you lift off you can imagine it sliding and thumping into the back of the seats or something similar. There also seems to be very slight delay between the thump and actually lifting off.

Since mark refitted my snub mount when we did the engine, i've noticed a vibration transmitted thru the car, mostly at idle. When i originally fitted it, i went with the instructions that say centre the bush in the hole to minimise vibration, but because there isnt any "preload" on the bush theres still a bit of movement under hard throttle, as the engine can "lift" up before the bush starts to work. Mark pulled the mounting frame down as much as he could when he fitted it to maximise the preload, and as a result theres a bit more vibration, but less movement.
 
Yeah as with everything performance related there is some kind of price to pay usually in the form of sacrificing some comfort or the odd thing becoming slightly noisy!
 
I get bad shunt when lifting off and applying the throttle. In the last 3 years i've had new engine mounts, new gearbox mounts, checked the snub mount (it's fine) and i've fitted a DTS. I think in my case it's the centre diff inside the gearbox which has gone. Has gradually got worse over the last year too.
 
I found that pretty much every bush on my 100k miler was sloppy if not split.
whilst watching my car on an engine dyno I could not believe how much the engine moved, blooody thing nearly jumped out of the engine bay!
That is a combination of the snub mount being crap from the factory and the engine mounts being soft over time.

I have a new snub and new engine/gearbox mounts to go on

I also had a clunk from the rear which was a combination of the rear diff front mount and the diff mount plate that bolts to the rear subframe.
I replaced the former and tigersealed the latter.

IMAG0092.jpg

IMAG0091.jpg


IMAGE_039.jpg

IMAGE_040.jpg
 
I personally think the rear diff mount is more significant than the bigger front one when it comes to noise (its the one I tigersealed above).
very small ond soft OEM bushes
 
as an experiment I forced two fuel hose sections under the larger of the two mounts........ and hey presto the lift off shunt has gone........... so its 100% the problem area.

I am going to get the smaller ones in poly bushes and probably make or buy the 034 bogbone type mount
 
Having stopped the slap........

I have ordered some goodies from the US!

http://www.034motorsport.com/product_info.php?cPath=25_66_74&products_id=1214

to lock down my driveline as they put it!

Density line diff bushes
Main alloy bush with poly
snub mount

will have a gander at the tranny mounts as well as engine while i am at it... (but may opt for filling them with rubber compound etc)


andy
 
Well fitted these today....

the old bushes were not split but very soft, you could twist with your fingers easily.

034DiffMount.jpg


difference is no movement at all....

I also fitted the snub mount, but the cage for it (std one is simply too large) and now I have engine movement. So going to make a smaller one to suit.

Overall well worth it...

I did have a small problem, pressing the old smaller rear bushes out of the alloy carrier, it cracked.... so had to do a little TIG repair in the process
 
@JCB - How long did it take the tigerseal to dry enought for refitment? Think my rear diff mount is the cause of my rear-end clunking.

I'm guessing the photos you took of yours were with the bushes removed... or had they just disintegrated??
 
ok............. diff is locked down with new mounts

I am getting a clunk when unloading the power... sounds from back

sub frame looks ok,
small amount of rotational slack in prop
rear arm bushes are intact but showing age


ANY IDEAS
 
dont "think" so...... i had it up on our MOT ramp today and the tranny ones looks ok.... they didnt move much when i jacked up the tranny
 
the subframe mounts themselves could be shot?

Still, check the mounts by watching the stick.

If the snub mount and enine mounts are knackered, the motor will rock back and forwards on the mounts when you apply/release power.
 
if you have done everything else it can only be the subframe.
PITA to do, possible in situ but for all the ballache you may as well pull it right off and get a good look at it.
if it is flexing enough to create its own slap then it could have cracks etc (not uncommon in S4/RS4's)
 
snub mounts done
diff mounts done
i think i will change the engine and tranny anyway as they are 100k old....

will update with some pics....

cheers lads.

A.
 
Blue_Thunder said:
@JCB - How long did it take the tigerseal to dry enought for refitment? Think my rear diff mount is the cause of my rear-end clunking.

I'm guessing the photos you took of yours were with the bushes removed... or had they just disintegrated??
Click to expand...

sorry didnt see this.
I didnt take the old mounts out of the rear diff hanger, just force the tigerseal in around teh old one and built it up so it comes up flush with teh subframe when fitted.
not sure how long it takes to set but at least 24 hours to be sure that it is not going to be compressed
 
aragorn said:
the subframe mounts themselves could be shot?

Still, check the mounts by watching the stick.

If the snub mount and enine mounts are knackered, the motor will rock back and forwards on the mounts when you apply/release power.
Click to expand...

Umm, have this problem with her TQS ( 11 years old but only 77k miles) , a sort of 'thud' whenever you get on/off the power - and the gear lever does rock. I was concerned it may be the dual mass flywheel.........
However having just done the tranny mounts in my old 80 Sport and the subframe bushes ( well I actually paid somebody else whilst they were under the car !! ) it is amazing how much better that drives --- 25 years and 111k miles had seen some wear !
 
Last edited:
Most rubber components will be dead after 10years.

Time kills rubber just as much as mileage does, if not moreso.

I'm slowly collecting bits to rebuild the whole rear end, with new bushes etc all round, then once thats done i'll move to the front and do the same.
 
Yep, tell me about it.

Its cost me more because i've baught a spare set of wishbones, uprights, a spare subframe, and another diff, so i can sort them all without taking the car off the road.
 
ah but you can punt the old one off to someone else when you are done with it :)
 
ye, tbh though i'm a spares hoarder.

I'll happily lend them out if folk want to do the same, so long as i get their old one back.
 
Yes but if you look at the cost of a new / newer car the it is still much cheaper !
In our case she loves driving the car, as do I when i get behind the wheel !
 
audi upgrades
I'll post up some prices once i've actaully got them!

So far i'm out 80quid for the Alloy rear subframe mounts. Still waiting on everything else.
 
U buy them we borrow them and get some made up lol, hopefully work out cheaper
 
Doubt you'd get them much cheaper tbh.

They came streight from the engineering shop that made em, and are hard anodised in black.

user "Bambridge" on SRS if you want some.
 
make sure you bond them in and put a good smear of sikaflex/toger seal between bush and frame and bush and washer.
They apparently squeak like a bitch if you dont!

full set of poly bushes for the B5 is about £330 IIRC
You can "repair" most of the rear diff bushes with Tigerseal or similar, couple of tubes will do you £20.
£80-100 for solid rearsubframe bushes or you can get uprated rubber ones from 034 or similar but they will cost you more.

I have the powerflex suspension kit, Apikol "front" rear subframe hanger, tigersealed "rear" rear diff hanger, solid rear subframe, 034 front subframe, 034 gearbox, snub and engine mounts.
Whole lot probably works out about £6-700 but I have done it over the years. two part poly bushes are the key, they dont need pressing in like some. if you bought yourself a Machine mart hydraulic press you could probably do them all over a long weekend.

transforms the car.
 
do like how easy the polys are to fit as i did my old track corsa and like you say just push in.
could save myself loads if i wasnt so anal about having everything refreshed and like new,
 
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