I've been looking at XKR, XKR-s for the past few days. Today, I limited my searches to 2013 models, thinking that they'd have the 8sp transmissions, something I'd much prefer over the 6sp.

To my surprise, I am realizing that none of the XK(R)s are equipped with the 8sp. All '13 or '14 V8 XJs, F-types as well as V6s carry the extra 2 gears.

Did Jaguar forget about the XK(R) models when it came to the upgrades?

Albert

 

Not that i can speak for the "R" series, but I have always felt the 6spd to be an amazing configuration and beautyfully suited to its role..... Besides introducing "hunting for gears", why would 2 more be needed?


V

 

I think of at least 3 reasons for preferring the 8speed:

1) Closer ratios help acceleration. I just assume closer ratios for the 8sp. as I have not seen the ratios listed side-by-side.

2) The cruising RPMs at 70MPH drop from about 1950 to 1500. That will give the car a good 2 - 3 MPG more in freeway driving. 10 percent improvement is significant.

3) Many V8 engines (Ford, Chevy, Jaguar) tend to develop a drone near 1900 - 2000 RPM. It is much more apparent when trying to use a free flowing muffler in place of the stock one. With the cruise RPMs dropp to the 1500 range the drone is eliminated allowing the use of free flowing mufflers with their increased performances.

Albert

 

I wonder if it's because the X150 is near the end of the product cycle and so they rather not spend the money to include a 8 speed. Hopefully the new XK will have some sort of beefed up version of the ZF HP9(speed) in the 2014 Range Rover.

 

I was thinking along the same lines. In that case, it is not right to leave out the XK line's last two years of production ('13 and presumably '14).

Albert

 

7 & 8 speed transmissions are just a marketing gimmick. Its just manufacturer bragging rights. More complexity, higher repair costs. I would think these trans weigh more with more gears in them? These cars & many other have tons of torque and dont even need anything more than a 5-spd auto. Where does this end? 12 & 13 speed trans & the car is shifting every 3/4 of a second? Its just getting silly....

 

Does anyone know if the XF and XJ mileage and acceleration times improved with an 8 speed? I can see more gears compensating for modest power, but the XKR has so much torque that I think an 8 speed would benefit Jaguar's marketing efforts a lot more than actual owners. Btw, what is the ideal number...8? 9? 11?

 

maybe they are better but if it is more money to fix, like you guys said it be on the next xk, but it be expensive...our xkr will live well, there won't be so many i am glad indeed. its good to keep them low mileage but then with those folks changing the odometer,...I guess it is then paying to go to the main jag dealer so you can prove all the maintenance and true mileage.

 

I think the chief motivation for the 8sp has been the increased highway driving MPGs. There are no doubts about the MPG improvements at freeway speeds; you are turning 450 RPMs less. Just think back how much the highway MPG numbers improved with the similar changes from 4sp to much more over-driven 6sp. However, closer ratios have never hurt any car's acceleration. That is why even the V8 powered GT-1 race cars that weight only 2400 lbs with their tons of torque use close-ratio trannies.

When I drove the 8sp XJL I could tell the difference at freeway cruising. While the '11 or '12 cars had been muffled sufficiently, I can still hear the very slight echo of that 2000 RPM drone under light accelerations, slight uphill or any time you open the throttle slightly. The 8sp felt more relaxed in comparison, just about soundless under the same scenarios.

So, what is the "ultimate" number of gears? As fuel efficiency guidelines are tightened, manufacturers will be forced to squeeze all available MPGs out of their models. So, if high torque V8 or SC engines with torque converter multiplications can support cruising at near idle RPMs than we may see 10 or 12 speed trannies in the future. As of now, it is simply amazing that you can get an easy 30MPG (freeway cruise) out of a huge sedan, like the 8sp XJL.

Albert

 

Can't remember where, but saw an article somewhere recently where the word 'overdrive' was mentioned in connection with future Jag gearboxes.

That would effectively double the range of ratios available, giving a proper 'economy' mode for highway cruising, rather than the simple difference in change points and rev levels that the Drive/Sport options give now.

 

This. It really is an aging platform. Personally, I think 6 gears is plenty.

 

Heres something I found pertaining to gear ratio/lowering the RPM's to increase MPG:

Going to a gear ratio (in the transmission or rear axle) that is too low puts too much load on the engine and results in worse fuel economy. Alot of people think that just because an engine is revving high, it automatically has to be using more fuel. Thats not to say the revs are not important: engines are designed to operate in their own power band where the right conditions are created for optimal power and fuel economy. It's all about the load the engine is handling that determines fuel economy. If your tranny is in neutral and you are revving your engine at 6000 RPM, it will probably still use less fuel than that same engine pulling a fully loaded trailer, yet only spinning at 2000 rpm.

 

sometimes during downshift or re acceleration, 6 gear seems a bit long, and 8 speeds will helps. I am in for sure.

 

warranty.

several years ago, when Mercedes introduced the 6 speed, certain high powered models retained the 722.6 5 speed that is also used in the X308 SC and earlier XKR. the reason was that the newer 6 speed could not handle the torque output without breaking. broken transmissions on new cars under warranty are an expensive mistake for the manufacturer to make.

the 8 speed transmission might have much smaller parts because it has more parts. those parts would be weaker even given the same materials.

the 8 speed could be built just as strong ... only the unit would have to be a lot bigger ... but that impinges on the passenger compartment packaging.

 

That is probably not the issue since the 8-speed is used in all other V8 SC applications within Jaguar including in the 550HP XF-RS.

As to the issue of having too many gears; if you drive the car hard on the track or road, you would likely only use gears 2-5 since the rest is way over-driven. You could likely achieve top speeds in 5th. 6,7,8 are MPG and cruising gears and you should not even notice their extra numbers under normal driving. Like in the F-type or in the XF under normal driving parameters I could not tell if it was 6 or 8 speed, since you hardly feel the shifts. The transmission is good enough to take care of selecting the right gear for the conditions.

I think that if you had an 8sp and you were only using 6 of that, you'd feel something not right. Just like if you suddenly only had 4 out of your present 6 speeds available.

Albert

 

How about why does the F-Type not have a DCT?

 

Haha. Well then that might explain why you wouldn't want an 8-speed transmission in a sports car. 3 gears that are just there for highway cruising? Dead weight!