2003 XKR shifts too soon between 1st & 2nd gear

[JagHead]

Although my question involves a Jag I think some of you late model Mercedes guys have the same transmission as my XKR and maybe you could help me a bit.

I recently purchased a 2003 XKR. It has the ZF6HP26 6-speed automatic transmission. I love everything about the car except for one thing. When I take off from a stop the transmission will immediately shift to 2nd gear unless I really get into the gas pedal. This is aggravating because there is virtually no way to take off normally and then kick the throttle for that rush that you know the car can provide in 1st gear. Even if I floorboard it from a dead stop it shifts into 2nd at about 4500 rpm. If I take off from a stop to make a turn the transmission will always be in 2nd just when I want to punch it. The dealer tells me there is no throttle/transmission interface cable to adjust and that these functions are all controlled electronically. How can I remedy this situation? I cannot believe they all shift this way.

[speedy_thrills]

JagHead said:

I recently purchased a 2003 XKR. It has the ZF6HP26 6-speed automatic transmission. I love everything about the car except for one thing. When I take off from a stop the transmission will immediately shift to 2nd gear unless I really get into the gas pedal.

Yes, I believe its all electronically controlled now. Isn’t this basically the same car as Aston Martin produce and sell much more expensively? If the transmissions are the same you could just try and swap your transmissions control unit for one from an Aston or Mercedes, I guess they must be individually tweaked to suit the cars purpose by manufacturers. The alternative is to see if a tuner can come up with a piggy back unit or a compatible control unit that will allow you to program shift changes.

Edit: Oops I misread what you said about 2003 rather than 2005 XKR earlier. Is it wise to be perusing this path of over stressing your existing gearbox? Maybe a new transmission is in order given the comments bellow (Especially if you plan further engine modification in the future).

>> Edited by speedy_thrills on Thursday 29th September 16:26

[laurieb]

(Copied from my post on the Jaguar topic)
**
I am afraid it is a feature of that particular ZF box. The electronics are programmed to dump 1st gear asap after launch in order to prolong gearbox life. I dont think there is much you can do about it. Personally on my own modified S-type R I dont find it that much of a hindrance as on a "full bananas" launch (track days of course) I am struggling for traction in 1st on any surface so for me a short shift to 2nd is no bad thing.
**

I should also say that that box has a number of other electonic tricks up it's sleeve. As you say it will start by default in 2nd unless you give it plenty and well as it's dumping 1st trick. Also if it thinks the torque going through the box is too high it will inhibit an upshift. This can be a real pain as you then bump into the rev limiter. I think this one is more pronounced on the modified cars - where presumably the torque is higher. On mine if it does this you practically have to fully lift off before it will shift.

Bedford : Yep good thought but RG tell me there's nothing they can do to over-ride this behaviour.

Cheers,

L

[Marquis_Rex]

[quote=Bedford RascalPerhaps with a Jag a call to Racing Green or someone else who peps them up might be a good starting point?[/quote]


I wouldn't trust them as far as I could throw em!


>> Edited by Marquis_Rex on Thursday 29th September 18:00

[JagHead]

Thanks for the tip. I just did a search and a lot of hits come up for Racing Green. Do you have a url or phone number for them?

[JagHead]

Sorry if you took offense. I thought that sharing knowledge was the whole spirit of these forums. I just thought you might have the info handy in your database. Sorry again for asking.

[JagHead]

I will try that. Thanks.