Automatic 6-speed shifts too soon between 1st & 2nd gear
Discussion
Although my question involves a Jag I think some of you late model Mercedes guys have the same transmission as my 2003 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 already 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.
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 already 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.
It might be worth checking that your car is not subject to this recall, or has had the work done:
www.theaa.com/allaboutcars/recalls/recalls.jsp?modelID=B2&modelName=XKR&makeName=Jaguar&makeId=B8
Was this gearbox also used by Mercedes? The last generation of Merc boxes were five speed, and the latest are seven speed. I don't recall any Mercedes road cars with a six speed auto, but I could be wrong.
www.theaa.com/allaboutcars/recalls/recalls.jsp?modelID=B2&modelName=XKR&makeName=Jaguar&makeId=B8
Was this gearbox also used by Mercedes? The last generation of Merc boxes were five speed, and the latest are seven speed. I don't recall any Mercedes road cars with a six speed auto, but I could be wrong.
I don't recall a 6 speed Merc either. Merc's generally have a button (w/s or c/s) which forces the car to start in 2nd anyway. Merc recommend driving in Comfort mode all the time but I don't use it as it still drops to 1st with a jolt if you do boot the throttle.
Some guesses:
Perhaps it's a sort of limiting thing on your car - how much power could it put down in first anyway, without the traction control cutting in? Perhaps the car's various computers just recognise that there's no point in allowing the car to remain in 1st? Can you turn off the traction control, and does the same thing happen?
Have you tried one of the Jag specific forums - http://forums1.roadfly.com/jaguar/forums/xk8 (and XKR) looks quite active?
>> Edited by deva link on Thursday 29th September 14:12
Some guesses:
Perhaps it's a sort of limiting thing on your car - how much power could it put down in first anyway, without the traction control cutting in? Perhaps the car's various computers just recognise that there's no point in allowing the car to remain in 1st? Can you turn off the traction control, and does the same thing happen?
Have you tried one of the Jag specific forums - http://forums1.roadfly.com/jaguar/forums/xk8 (and XKR) looks quite active?
>> Edited by deva link on Thursday 29th September 14:12
You sound like a lunatic, but I like your style. 
I can only assume that the car's trying to stop you from wrecking the drivetrain by having max torque suddenly (and aggressively) put into it (at the drop from 2nd to 1st as you boot it). Even some diesels here are limited in output in lower gears due to their torque outputs.
Although that doesn't really explain why it will work OK if you boot it hard from rest? Maybe the car just thinks it's un-neccessary to drive like that, and a downshift to 1st would be pointless - after all, you'd surely reach max speed (or max wheelspin) in 1st pretty quickly!
I can only assume that the car's trying to stop you from wrecking the drivetrain by having max torque suddenly (and aggressively) put into it (at the drop from 2nd to 1st as you boot it). Even some diesels here are limited in output in lower gears due to their torque outputs.
Although that doesn't really explain why it will work OK if you boot it hard from rest? Maybe the car just thinks it's un-neccessary to drive like that, and a downshift to 1st would be pointless - after all, you'd surely reach max speed (or max wheelspin) in 1st pretty quickly!
My point exactly. This car has the 100k 6 year Jag warranty so I am not too concerned about drivetrain damage. I am trying to replace my 85 Corvette with this car. The Corvette has a 406 with all the necessary interals to produce something close to 500 hp. You can imagine my disappointment when I call on the 390+ hp and it dogs into 2nd gear.
It's sounding more and more like I should keep the Corvette for when I want to have some serious fun and use the Jag when I need a gallon of milk. The Jag is still under the bumper-to-bumper until Sept. 2007. It also has the Jaguar Select warranty up until Sept. 2009. I cannot make any mod that would jeapordize that. These warrantys add an incredible value when you go to sell your car. The guy I bought it from made a good point. He said "nobody can afford to have the local Jaguar dealer fix one of these when it breaks". I don't want to find out.
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