Is that possible? 4.0 and 4.2 engines are relatively the same as I am concerned. Anybody tried it? I really feal that there should be 6th gear

 

I’d be thinking long and hard about getting rid of the Mercedes 722.6 transmission that the 4.0 XKRs have. It’s much tougher (durable) than the ZF 6 speed.

The rpm drop at full throttle up shifting with the Mercedes 722.6 transmission puts you right at the maximum torque point in the next higher gear.

How can having another gear beat that ?


Z

 

Well, I've got kenne bell supercharger, and straight pipe exhaust, so torque is not really a problem. It is just that I cruise the car on 140-150 km/h on the highway, and I get 14.5l/100km on 3000 rpm.
I just thought that it would be nice to have one more gear.
I know that 5 speed is better in terms of reliability considering it has been installed on SL65 with 1000NM of torque though

 

Oh, I get it now.


my usual highway speed is 85 to 90 mph (when traffic allows), about the same as yours. That’s, and even up in the reasonable 3 digit range too, is really a sweet spot for the 4.0 L cars.

I don’t pay much attention to the gas mileage, if that was a meaningful concern I’d be driving something else. but even so, I don’t think I’d like the car to have less rpm in too gear than it already does.

most automatic transmissions shift into high gear way too soon as it is anyway.

Z

 

Electronically, it would be a problem. The TCM for the six speed would not be recognized by the 4000 ECU and the old TCM would not work with the ZF. Better to sell the 4.0 car and buy a 4.2, then modify the engine.

 

I have both the 5 spd and the 6spd. The early 6spd's are problematic in the speed sensors. I would stay away from them if possible- repair cost is in the $1200 range.

 

What 6 speed are you referring to? I haven't seen any threads about speed sensor problems with the ZF 6HP26.

 

My mistake. I have both Jaguar and Mercedes, and was referring to the Mercedes trans. Get my forums mixed up sometimes--guess that happens with age

 

Vadim..im,

The real question here is: WHY?
Why would anyone ever want to make this change? You've got a great "Gear Changer" as it is....Why would you want to spend the Money and the Time switching out Tranny's? There's just no benefit in doing this.....

Question for you??? Do they sell XKR's in Russia? I don't think I have ever seen a Post on the Forum from someone in Russia.....I am amazed.....!

Billy Clyde @ Cinco Ranch...