[scoss]

I’ve noticed that when I brake hard and come to a stop. When pulling away I have a very slight jolt before the car moves off. Once off there is no other issue. If I lightly brake, and say crawl to a set of lights and stop, I have no jolt.

So, my question is, why does this occur when braking hard only?

Thanks

[Busted]

Could just be the brakes binding slightly because they are hot

[Eddamoo]

Does it come from the gearbox? I occasionally get lag from the gearbox when braking firmly and quickly jumping back on the accelerator. Like the gear isnt engaged and suddenly clicks in.

[Watsey]

Sounds like your brakes are sticking but there are several potential causes.

Hot pads can stick to the discs, the abutment surfaces between the pads and discs may need lubricating, or there could be a sticking piston in one or more of the callipers. .

[HighlandPete]

Can you sense if it is brakes or the gearbox? There's a different feel to brakes freeing off, to something like a gear change before moving off.

[scoss]

Originally Posted by HighlandPete

Can you sense if it is brakes or the gearbox? There's a different feel to brakes freeing off, to something like a gear change before moving off.

It’s feels my gearbox related. I’ve had a ZF and TC oil change back in October.
It’s not transfer case related is it?

[scoss]

Originally Posted by Eddamoo

Does it come from the gearbox? I occasionally get lag from the gearbox when braking firmly and quickly jumping back on the accelerator. Like the gear isnt engaged and suddenly clicks in.

Could possibly be this I suppose.

[HighlandPete]

Originally Posted by scoss

It’s feels my gearbox related. I’ve had a ZF and TC oil change back in October.
It’s not transfer case related is it?

Brake evaluation could be involved. Depending on deceleration rate and braking time can select a different shift map.

Do you sense it may be changing down to 1st, rather than a possible pull away in 2nd after light braking?

I wonder if it is different if you were to shift manually to 1st gear, before pulling away, after heavy braking. May give a further clue to which part of the drivetrain is directly involved, if there are differences.

I would of thought the transfer box would give you a jolt at other times, but rule nothing out.

[scoss]

Originally Posted by HighlandPete

Brake evaluation could be involved. Depending on deceleration rate and braking time can select a different shift map.

Do you sense it may be changing down to 1st, rather than a possible pull away in 2nd after light braking?

I wonder if it is different if you were to shift manually to 1st gear, before pulling away, after heavy braking. May give a further clue to which part of the drivetrain is directly involved, if there are differences.

I would of thought the transfer box would give you a jolt at other times, but rule nothing out.

The car is def in 1st when this happens. It’s not every time.
Sort of reminiscent of the slip you get when you first drive the car in the morning. You sense the slip, and then it kicks in, which leads to the jolt.

Will def try the manual suggestion. To clarify, would you keep in auto, then when stationary move to manual?

Regarding the TC and other jolts. Not sure if it’s related but sometimes in stop start traffic, when coasting between 3rd and 2nd and lightly pressing the accelerator I have a jolt.

[HighlandPete]

Originally Posted by scoss

The car is def in 1st when this happens. It’s not every time.
Sort of reminiscent of the slip you get when you first drive the car in the morning. You sense the slip, and then it kicks in, which leads to the jolt.

Will def try the manual suggestion. To clarify, would you keep in auto, then when stationary move to manual?

Regarding the TC and other jolts. Not sure if it’s related but sometimes in stop start traffic, when coasting between 3rd and 2nd and lightly pressing the accelerator I have a jolt.

I'd try with the shifter in D and try M/S position, both as an auto and manual start, see if there are differences.

I'm wondering if it is the TC lockup clutch reacting in a different way to heavy braking. Could also be involved in the 3rd/2nd jolt.

BTW, what mileage are you at? Condition of tyres?

[scoss]

Originally Posted by HighlandPete

I'd try with the shifter in D and try M/S position, both as an auto and manual start, see if there are differences.

I'm wondering if it is the TC lockup clutch reacting in a different way to heavy braking. Could also be involved in the 3rd/2nd jolt.

BTW, what mileage are you at? Condition of tyres?

I’m around 75K and all four tires are only 5 months old.

Is there anything that can be done with TC lockup?

[HighlandPete]

Originally Posted by scoss

I’m around 75K and all four tires are only 5 months old.

Is there anything that can be done with TC lockup?

It's trying to identify what is going on. Do you get the feeling the TC lockup may be slipping? Revs flare at times?

I do wonder if the oil level is correct after the change. May be worth checking.

[scoss]

Originally Posted by HighlandPete

It's trying to identify what is going on. Do you get the feeling the TC lockup may be slipping? Revs flare at times?

I do wonder if the oil level is correct after the change. May be worth checking.

I def think it’s linked to some sort of slipping. I’ve noticed that the slip goes if I’m stationary for 2-3 secs. Car is composed and in 1st, due to XHP. Issue will come about when coming to a junction/roundabout where I’m not totally stationary for 2/3 secs. It’s like car is searching for the gear and slips for a sec.

Interestingly I’ve had a service the other day and the tech said I’ve got a fault code linked to my gearbox.

Now I don’t quite understand how I’ve got this code how my gearbox is working.

Any ideas?

The tech has recommend that I get XHP removed and then get GB re-encoded to sort fault code, prior to XHP going back on.


Info given on Ista.


EGS 421326 SysFunktion: Control unit newly programmed and not yet coded OR control unit is working with default net coding data.

A fault occurs if the control unit was newly programmed and is not yet coded OR the
control unit is working with the default net coding data.

For fault elimination, it is imperative that you perform the guided troubleshooting
procedure.



Carry out the followng measure:
Re-encode control unit

[Eddamoo]

XHP doesn't overwrite the EcoPro gearbox map so try using that to see if exhibits the same behaviour. You don't need to reflash to try a stock map.

[bishbosh]

I think that's the best course of action, to flash back to stock removing xhp from the equation. Then fdl code the egs module. Then see how the gearbox behaves.

If you have Esys you could do this yourself.

[scoss]

Originally Posted by bishbosh

I think that's the best course of action, to flash back to stock removing xhp from the equation. Then fdl code the egs module. Then see how the gearbox behaves.

If you have Esys you could do this yourself.

Is the EGS module the gearbox unit? What does FDL mean?

Just seems odd how this code stats the actual gearbox needs to re-encoded.