Advice needed from a proper mechanic

[the repair man]

Hi all, I have been having a problem with my car for a few months now. Thought I had tried everything. I clearly haven't tried one thing, the one that will fix it.
I was hoping there might be someone on here that knows the component theory, rather than just the mechanics.
My car has a bad knock/vibration under acceleration above about 50mph, It used to be 40mph, but since some recent work, it is now above 60mph.
When I say bad, with the windows half way down, they slap the car violently.
It does it in a straight line, steering makes NO difference. Have rotated and balanced all the wheels. No apparent engine mount failures. 4 months ago I changed the o/side driveshaft. Recently the nearside ( not new unit but guaranteed )
The vibration manifests itself in the n/s/f wheel I think. Its a toyota corolla T sport. Today I jacked the car up on the A frames, so as to load the suspension like normal running. I ran the car, starting in sixth gear to put a torque load on it, and up to about 150 mph. The knock was apparent in the car but not from outside. What I did notice and don't know if its relevant, it was only ever the n/s wheel driving, unless I put considerable load on it, then the o/side would kick in. Does this suggest that the car is trying to drive mostly on the n/side? That would no doubt cause trouble, but I don't understand differentials well enough to know. ( the o/side wheel is free to turn by hand with no drag.
2 other notes. With my father in the passenger seat, the vibration is reduced considerably ( he is about 16 stone )
If at any speed when its vibrating, I reduce to a neutral throttle, it disappears, but a slight incline or torque load and its trying to start an earthquake.
Please help, I have had the guts out of this car and still no luck!

Sorry for the long post, but thought I would be thorough!

 

[pedrobedro]

Have you checked if the driveshaft is straight and is the CV joint fitted properly ? Also is it fully entered into the differential ?

 

[Wozzaaah]

Also is it fully entered into the differential ?

^This!
Even slightly displaced it will try and shake itself to pieces.

 

[the repair man]

Well I had both driveshafts replaced, I assume they were fitted properly and neither made any difference so the assumption is, driveshafts ok

 

[bs2236]

I had a similar issue a few years ago that turned out to be either the wheel bearing or the outer cv joint, they were both stripped and inspected and looked ok but i just changed them both and the car was fine.

hope you get sorted.

 

[rocketron]

A cv joint seems suspect to me?

 

[the repair man]

Had both complete drive shafts replaced though! Also, there is a rubber sleeve half way along the drive shaft, what is it? It doesn't seem to house or hold anything, could this be for balancing?

 

[pedrobedro]

Driveshafts are not usually balanced as they are short and have CV joints which allow both ends to move in out and up down independent of the centre not like prop shafts which have UJ and are fixed at at least one end. The rubber sleeve is probably part of a CV boot which has been left in place. If you are assuming your driveshafts are OK check the tyres for lumps.

 

[DrNik]

your right about the rubber sleeve, MR2 have these when you have unequal driveshafts, they are used as a harmonic balancer/damper, when they make driveshafts they are not normally balanced (ive welded some together and they were not very straight and worked fine), also with the twisting load they do flex, the rubber is supposed to help this, do you get a ticking noise when you drive in a tight circle??? i think the outer cv joint is failing

 

[the repair man]

No I haven't had any ticking noise. There is a tiny amount of play ( maybe 1mm ) where the n/s shaft enters the gearbox. It's not in the bearings, it's where the cup/shaft actually go in. I don't know if this would cause it, I'm hoping not as that will mean a gearbox rebuild grrr

 

[p0689109]

The n/s" not new but guaranteed" driveshaft would be my starting point.

 

[the repair man]

Yep, I can't help thinking the same, but they aren't cheap and would hate to buy another to no avail. The rubber part isn't part of a C.V boot, it is certainly some sort of harmonic balancer.
Is there any way the gearbox/differential could be causing it on one side? A cheap fix might be to hide 150kg's of steel in there somewhere lol

 

[captain-destructo]

2" of concrete in the foot well NO!!!!

i would start with the recon part contact the supplier and tell them you think its failed and see if they will send out a replacement

have you checked all the bushes tie rods subframe mounts etc etc

 

[the repair man]

Yes it's been in 2 separate garages so I got fed up and skint and decided to do it myself.
Its starting to cost more than the cars worth, but i've put so much in, I refuse to give up...yet!

 

[AndyStobbs]

Did a gearbox on a yaris not so long ago, the diff mount bearings inside the box had worn out and diff had considerable play - would expect that would be evident when replacing shafts though. Brake discs are a large rotating mass, have you looked into them?
Does the problem seem independant of gear selected? ie. its road speed that dictates the issue not engine speed or certain gears?

Wouldn't think driveshafts a likely problem. They take alot to bend and you wouldnt be likely to have 4 all bent. Ditto on cv's.

 

[AndyStobbs]

Why not jack one side up only and make it solid. Try to isolate which side is at fault. Leave one wheel on the ground and the other will spin on its own. You could rule out rear wheels and potentially one or the other front (as you already suspect nsf) with this method.
Put car in gear and spin it upto speed.

 

[the repair man]

Hi Andy, It's had new disks and pads, the problem is kinda gear dependant rather than road speed. It only happens above 40-50mph, but as far as I can remember it tends to only happen under a torque load ie if I was hammering it in second, it wouldn't do it as much. But simply going from 40-48 in 4th 5th or top quite gently it will start. It does stop again above 85 ish, but for cruising speeds, 45-70 it is undriveable . Say at 55mph on neutral throttle it is pretty smooth, a slight incline or headwind, any need for any throttle it is ferocious, but come off the throttle, all is tranqil!
With the car on stands today, there was no visible vibration or movement, but when I got in the car, put it in 6th, then throttle hard on from any speed, there was an initial thump sound. Sorry, it's very difficult to articulate what you see and hear sometimes!

 

[AndyStobbs]

Does it have a dual mass flywheel?

 

[the repair man]

Nope, it is road speed dependent to"!

 

[the repair man]

Sorry, the Nope was to my own last comment!
Dual mass flywheel, I dont know.
It's the T-sport, vvtil 190bhp, don't know if that helps