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Unusual 4wd Problem

deadly32gtr

By deadly32gtr,
in General Maintenance

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deadly32gtr Apprentice

deadly32gtr

Posted
Posted

Hey all,

Need alot of help here. When the car is running in 4WD, at the begining when I start up the car (engine is cold), the 4WD works fine.

As the car heats up, in matter of 10 mins or so... the car is jolting during acceleration.

Ive changed the 4WD pump. and also changed 4WD computer. And still the same. WHAT IS GOING ON?

And this is defenetly the 4WD, cos I took the 4WD fuse out and ran it on RWD and it drives like a dream.

But i want it in 4WD to be the same. Has anyone come accross this? Will appreciate any advise.

Cheers Zac

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vinnie32GTS4 Mentor

vinnie32GTS4

Posted
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have you checked the attesa pump and fluid in your boot...i have a R32 GTS4 which is pretty much the samt awd system and when u start hitting boost the awd guage starts to go up. Therefor ur attesa pump is rooted or u may have low/no attesa fluid left.

hope this helps

vinnie

deadly32gtr Apprentice

deadly32gtr

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Posted
have you checked the attesa pump and fluid in your boot...i have a R32 GTS4 which is pretty much the samt awd system and when u start hitting boost the awd guage starts to go up. Therefor ur attesa pump is rooted or u may have low/no attesa fluid left.

hope this helps

vinnie

Yea I actually replace the Attesa pump and bleed it and all that. The fluid in my boot is in level. I will double check.

deadly32gtr Apprentice

deadly32gtr

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Too right! I have lost count of how many times this point has been made - AWD NISSANS MUST HAVE THE SAME ROLLING DIAMETER ON ALL 4 CORNERS.

I never thought about that. So are you saying that this could be the reason for my car jolting when accellerating???

Could it having anything to do with the oil in my gear box or transfer case? I have red line oil in there. Could the grade of the oil make a difference?

djr81 Grand Master

djr81

Posted
Posted
I never thought about that. So are you saying that this could be the reason for my car jolting when accellerating???

No he is saying that it IS the reason.

Could it having anything to do with the oil in my gear box or transfer case? I have red line oil in there. Could the grade of the oil make a difference?

No.

deadly32gtr Apprentice

deadly32gtr

Posted
  • Author
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Thanks alot for all your help guys. Im gona get the tyres changed immediately.. And will let you know the outcome. Cheers Zac.

Hi Guys,

Just went to the car and double checked the tyre size for fronts and back..

Fronts - 245/40/18

Rears - 265/35/18

Can you guys just confirm again that it is defenetly the tyres that causing this stupid jolting problem for me. And can you explain to me why and how this is happening.

Appreciate your help guys .Cheers

djr81 Grand Master

djr81

Posted
Posted

Pull the fuse on the 4WD system & go for a drive. If the problem has gone then it is your tyres.

Much of the input for the system is differential wheel speed front to rear. If the system detects it it thinks wheelspin & pushes torque forward. This is almost certainly the cause of the jolting as the locked up system & differential wheel speeds need to somehow get back to normal - hence the car jolts.

What is your front torque gauge reading when you drive around normally?

deadly32gtr Apprentice

deadly32gtr

Posted
  • Author
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Pull the fuse on the 4WD system & go for a drive. If the problem has gone then it is your tyres.

Much of the input for the system is differential wheel speed front to rear. If the system detects it it thinks wheelspin & pushes torque forward. This is almost certainly the cause of the jolting as the locked up system & differential wheel speeds need to somehow get back to normal - hence the car jolts.

What is your front torque gauge reading when you drive around normally?

Thanks Guys.

blind_elk Grand Master

blind_elk

Posted
Posted

It's definitely the tyres

Fronts - 245/40/18
sidewall = 98mm
Rears - 265/35/18
sidewall = 92.75mm

So, rear tyre has a smaller rolling diameter. This means that the rears turn faster than the fronts. ATTESSA sees this as "wheel spin", and sends some drive to the fronts.

deadly32gtr Apprentice

deadly32gtr

Posted
  • Author
Posted
It's definitely the tyres

sidewall = 98mm

sidewall = 92.75mm

So, rear tyre has a smaller rolling diameter. This means that the rears turn faster than the fronts. ATTESSA sees this as "wheel spin", and sends some drive to the fronts.

I replaced the tyres at the back...to be the same as the front tyres. And wahlahhh... the jolting had ended. BUT when I was boosting it up ....there was still quite a slighhhht jolt...i guess im noticing it cos I know it. But it was still there. I want it to be smoooth ass...What needs to be done???

im gettin brand new tyres put all around.... 265/35/18 front and back this week.

Appreciate the help.

blind_elk Grand Master

blind_elk

Posted
Posted

The diameters are obviously the same. The offset is probably not so important (at least in a straight line).

The tyre fitter should be able to measure the widths (although that info is usually cast on the inside of the rim). I'm only guessing here, but if you are already running different width tyres front and rear, then it is likely the rims are different widths front and rear.

The rims really need to be the same all round, otherwise you can spend hours working out what combination of tyres (makes / models / sizes) will give the desired equal rolling diameters.

This is what happens when you go for "the look" without regard to the technology underlying the performance.

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