[gts-tom]

I've had this problem for a while now and I'm hoping one/some of you can help. The 4WD system appears to work fine, ie on launch it engages also showing on the torque split gauge. Now if I'm cruising along at about 60-70 mph and go over a fairly harsh bump then the car will vibrate like you're running over rumble strips. The torque gauge will also hover around 10-20 until I come off of the throttle, then the vibration will stop and the gauge will return to 0. Any ideas.
Thanks, Tom.

 

[gts-tom]

Still no joy, I've swapped the 4wd ecu in the boot but still the same results. Any ideas anyone.

 

[R32 Combat]

How hard is your suspension?

 

[gts-tom]

Fairly stiff but it's not caused any issues in the past.

 

[R32 Combat]

Can you soften it?

 

[gts-tom]

Maybe a little as they do have some adjustment on them. What's your thinking.

 

[R32 Combat]

Over a set speed, the 4WD engages slightly in improve stability. I wonder if shocking the G-Sensor is somehow making the ATTESA think its doing something its not, like accelerating hard of something. That will increase the front torque and cause vibration.
Just a though. I am just guessing. Can you swap the g-sensor over or something?

 

[gts-tom]

That's better than anything I've come up with. I'll try changing the sensor as I'm not sure the suspension will adjust enough to make a difference. Also it does only happen at certain speeds.

 

[R32 Combat]

Is it over a certain speed or at a certain speed?

 

[gts-tom]

Seems to be over a certain speed.

 

[R32 Combat]

That figures.

 

[FRRACER]

Those old G sensors are probably at the end of their life now after some 20 years they are a mechanical device. Best to swap to a new digital one, mr combat will sell you one

 

[MobileLPG]

That's interesting! Why would the increase in front torque cause vibration?
The reason I ask is that I have a grid dancer I fitted into my 33, doing some timed laps around Curborough and thought I would compare the times between full rear wheel drive and 50/50 split.
I set the controller to 50/50 and every time I tried to accelerate out of a corner the whole car was shaking like crazy so I had to turn the controller off.... Instantly the vibration stopped.

It was something I was going to look into before my next track day and assumed I had a worn front CV/diff/shaft etc.

Thanks,
Edward.

Over a set speed, the 4WD engages slightly in improve stability. I wonder if shocking the G-Sensor is somehow making the ATTESA think its doing something its not, like accelerating hard of something. That will increase the front torque and cause vibration.
Just a though. I am just guessing. Can you swap the g-sensor over or something?

 

[R32 Combat]

That's interesting! Why would the increase in front torque cause vibration?
The reason I ask is that I have a grid dancer I fitted into my 33, doing some timed laps around Curborough and thought I would compare the times between full rear wheel drive and 50/50 split.
I set the controller to 50/50 and every time I tried to accelerate out of a corner the whole car was shaking like crazy so I had to turn the controller off.... Instantly the vibration stopped.

It was something I was going to look into before my next track day and assumed I had a worn front CV/diff/shaft etc.

Thanks,
Edward.

I don't think anything is particularly at fault. You need a smoothly operating transfer clutch pack to take high pressure slip without juddering. I suspect thats what is felt when cornering or indeed whenever there is torsional stress between the front and rear axles. Its no different to clutch judder when pulling away in a manual car with a poorly operating clutch.
The ATTESA in standard form spends a lot of time with very low or no pressure massively reducing or even eliminating the chance of judder.

 

[gts-tom]

Ron has been kind enough to lend me a new sensor so I'll stick it in tomorrow and let you know how I got on.
Also combat how does your digital setup work. Is it a plug and play item that replaces the old sensor.

 

[MobileLPG]

Thank you for that information, very useful.
It did cross my mind whether it was the clutch pack in the transfer unit as it shakes under hard acceleration.
When I first bought the car I had to diagnose an issue where it was constantly stuck in four wheel drive and I have always wondered if any damage had been done to the clutch pack as the car used to give a large heavy jolt when reversing round a corner (clutch pack slipping) and I suspect it had been abused throughout the 'stuck in four wheel drive' period.

Edward.

 

[R32 Combat]

Also combat how does your digital setup work. Is it a plug and play item that replaces the old sensor.

Yes. Well, the R33 one plugs in, on the R32 you would need to solder your old plugs into the Skylab Fusion. Its all very straight forward. Hopefully a different g sensor will sort you out. Post up your findings.

 

[gts-tom]

So I swapped the sensors over today. The first thing that I noticed is upon removal of the centre arm rest is that only the passenger side bolt that holds the sensor in was done up, with the other completely missing and the sensor bracket sat at an angle on top of the stud. I changed the sensor for the new one and went for a drive. I couldn't get it to judder as normal so pulled over and changed it for the original sensor. I pulled away, hard acceleration, and it juddered as like before but then at a constant speeds I couldn't get it to judder. I swapped the sensor again for the new one and the same outcome, only juddering when accelerating hard but not at constant speed and not when accelerating slowly. It will now do it nearly every time I accelerate hard in 1st, 2nd, 3rd, and sometimes 4th.
Any ideas.

 

[gts-tom]

Been for another drive. Just to make sure I pulled the plug on the g sensor and although there's plenty of wheel spin it doesn't judder so is definitely a 4wd problem. Any ideas why the sensor would have been put on, on the p#ss.

 

[DazGTR]

This may sound stupid but have you checked the fluid levels