Knocking under acceleration 172 Cup

[ex-Chinese Dave]

I sometimes get a knocking noise which feels like it’s coming from the right front of the car when accelerating fairly quickly out of a left-hand turn. It’s the same kind of sound and feeling as you get if you lose traction upfront, and the engine revs high i’ve had a similar noise when I was accelerating in second gear on the straight, and the wheels spun up a little.. I’ve had almost all of the suspension components renewed recently, so I am wondering if it could be solved by replacing engine mounts or the gearbox dog bone. The car is on 130k. I’m obviously no expert on this, but just wondered what you guys think.

 

[JamesBryan]

First culprit would be the dogbone.

 

[adamlstr]

Vibra-technics engine mounts and new / poly dog bone, will make a WORLD of difference. No more knocking, barely any wheel hop, and much more positive In everything.

 

[ex-Chinese Dave]

What’s the difference between poly-bushed and OE spec for daily driving a Cup? I’ve read many times that poly-bushed cars are a hard ride although I would only be changing engine mounts/dogbone?

Also, are these jobs a driveway DIY job? (I’ve a few tools and axle stands)

 

[Matt Cup]

You will get more nvh with a polybushed bone mount. I’m pretty sure mines got one one along with the engine mount insert.

 

[JamesBryan]

You will get more nvh with a polybushed bone mount. I’m pretty sure mines got one one along with the engine mount insert.

Engine mount insert is terrible on them.

Polybushed Dogbone isn't too bad.

 

[Matt Cup]

Engine mount insert is terrible on them.

Polybushed Dogbone isn't too bad.

I don’t find it too bad 🤷🏻‍♂️. But then I only drive it once or twice a month.

 

[JamesBryan]

I don’t find it too bad 🤷🏻‍♂️. But then I only drive it once or twice a month.

Caused massive dash vibration on mine.

Had to take it off and fit Vibratechnic mounts instead.

 

[Matt Cup]

Caused massive dash vibration on mine.

Had to take it off and fit Vibratechnic mounts instead.

Yeah true it is a noticeable difference in the cabin. I take it you don’t get that at all with the vibratechnic mounts yet they are more firm than regular engine/gbox mounts?

 

[Brigsy]

Yeah true it is a noticeable difference in the cabin. I take it you don’t get that at all with the vibratechnic mounts yet they are more firm than regular engine/gbox mounts?

Vibratechnic upper engine mount, gearbox mount and poly dogbone are decent for road use. Run them on my trophy no dash rattles etc.

 

[NorthloopCup]

If you press the original dogbone bush out, rotate it 90 degrees and refit it into the dog bone, you get 90% of the benefits of a poly bush with 0% of the NVH.

 

[Matt Cup]

Good to know. Will be on the hunt for some vibratechnic goodies.

 

[Brigsy]

If you press the original dogbone bush out, rotate it 90 degrees and refit it into the dog bone, you get 90% of the benefits of a poly bush with 0% of the NVH.

Tempted to try that on my dci, engine moves all over on stock dogbone. Tried pu filled dogbone and the nvh on idle was insane.

 

[NorthloopCup]

Tempted to try that on my dci, engine moves all over on stock dogbone. Tried pu filled dogbone and the nvh on idle was insane.

Trust me mate, it’s probably the best free modification you can get/make on them.