Strange vibration under full throttle acceleration. Any ideas?

[Prawn]

Strange problem this one, and I can't seem to figure out what it might be, so I thought I'd ask.

the car is an A3 1.8T, about 230bhp / 260lbft, and has a quaife ATB. The gearbox was rebuilt last week, and the problem existed both before and after the rebuild, so I don't think it's box related.

Under full throttle acceleration in 2nd and 3rd mainly, I get a strange vibration front the front wheels, felt through the steering and the seat slightly..

I thought it was the wheels/balance at first, but on a new set of wheels it's still there, and they're been balanced twice, and it's made no difference.

it doesnt do it at a constant speed, and doesn't do it when braking either, or accelerating slowly.

it ONLY happens under full throttle, so I'm thinking possibly a CV joint breaking up under heavy load?

It seemed to start after my last ring trip in the car.

Would anyone suggest anything other than CVs? or should I start there and see what happens?

 

[lnewland]

i have no clue but what abpout a bearing?

 

[BENJAMIN]

I had the exact same thing in my mk2 vr6, it was the n/s inner c.v made worse by the fact it was v low so the shaft was at a stupid angle.

 

[s3dave]

Ive had this on a mk4 golf and one of the driveshafts was out of balance,,,

 

[S3 Paul]

I had this recently with my s3...
Turned out the mount on the gear box wasnt tight ( due to a ******** thread) i helicoiled all the mounting holes on the braket. Realigned the mount so it was sat bang in the middle of the bolt holes... Its fine now.
Worth a quick check

 

[Rosso TT]

Nackered engine mounts?

 

[Westy]

I had this recently with my s3...
Turned out the mount on the gear box wasnt tight ( due to a ******** thread) i helicoiled all the mounting holes on the braket. Realigned the mount so it was sat bang in the middle of the bolt holes... Its fine now.
Worth a quick check

Funny you should say that because Nick helicoiled his dogbone mount earlier in the week.

 

[Prawn]

I had this recently with my s3...
Turned out the mount on the gear box wasnt tight ( due to a ******** thread) i helicoiled all the mounting holes on the braket. Realigned the mount so it was sat bang in the middle of the bolt holes... Its fine now.
Worth a quick check

Cheers Paul, I'll check out the alignment of the mount tomorrow. It's definitely all tight, as it only went on last week, and the vibration hasnt changed since the gearbox swap.

Nackered engine mounts?

New INA track density uprated engine mounts all round matey, so almost certainly not that!

Funny you should say that because Nick helicoiled his dogbone mount earlier in the week.

Yup, just helicoilled the dog bone thread on Wednesday night. Vibration was there before and after though, so not that

I'm currently thinking Dave might be right, and its an unbalanced driveshaft/inner CV causing the issues

 

[s3dave]

Did you not have issues with the drive shafts undoing them selves...that would lean strongly to a vibrating drive shaft

 

[Prawn]

yea, CONSTANT issues with shafts comming undone, and CV joints breaking

This is all starting to add up

 

[Westy]

yea, CONSTANT issues with shafts comming undone, and CV joints breaking

This is all starting to add up

Bingo.

Every time you fix one issue on this car another one rears it's ugly head. 5 Weeks today till the Ring trip, lets hope no more issues appear!

 

[sam4191]

This sounds just like the missus' mini. Has done it ever since we lowered it. The cv joints apparently suffer this when lowered. So may be worth checking them out?

 

[s3dave]

yea, CONSTANT issues with shafts comming undone, and CV joints breaking

This is all starting to add up

hmmm You dont think this could have caused the loose nuts in the gearbox too?

 

[Prawn]

gearbox blew up recently and was JUST rebuilt last week. haha.

Time for new shafts I think