Hello everyone,
I've been searching the forum for awhile and I'm trying to grasp the differences between the 2012 and 2013 XFR. Besides the change from 6 speed to the 8 speed, are there any other changes? Is the 8 speed that much better of a tranny? I currently drive an 07 Mercedes E63, great 6.2l motor but terrible transmission. The Merc 7G trans takes a lot of the enjoyment out of driving the car hard.
Any feedback would be appreciated!

 

I purchased my '12 XFR (w/ 28K mi.) about 4 months ago now, and the 6 spd auto has performed flawlessly. In a marketplace full of 8, 9, and now 10 spd automatics it seemed inadequate at the time, however, the ZF transmission is highly regarded as one of the best out there. The shifts appear quick and crisp, at least in my experience...especially compared to my previous vehicles (GM vehicles).
I would imagine the '13 XFR's 8 spd would improve MPG's. Aesthetically I believe they're the identical, but I'll leave that to the seasoned forum members to confirm.

 

Thank you for your insight. Might you know how much less torque the 6 speed can withstand versus the 8 speed? Thinking about future modifications. Also, is there a difference in active dampening system for 2013 vs 2012?

 

As with most cars, every newer year, comes improvements over the last...If the wallet allows, I'd always go with the newer..considering also warranty life, etc....That said, Providing the basics of Engine size (V8) is the same.

 

I have the 6 speed in my XF and the 8 speed in my LR4. I'm actually happier with the 6 speed. That, the facelift and the lack of start stop bullcrap is the reason I looked exclusively for a 2012

 

Amen to that

 

I have run the 6-spd XKR vs the 8-spd XFR on the track back-to-back. The 6 spd is a dog coming out of corners as compared to the 8-spd.

Would I have noticed without a track run? Probably not.
I have an 8-spd 2013 XFR-S and really enjoy it. Not sure that I notice 7/8 very much in the car but I do notice the 1-2 gears

 

Good feedback thank you. Curious if anyone knows the limits of torque on 6sp vs 8sp? Might modify in the future.

 

I believe the 8 speed is rated at 515 lbf-ft and the 6 speed is around 440. Don't quote me for sure but I seem to recall that. If you are doing the normal mods to it, I wouldn't worry about either transmissions ability to survive. There are diesel guys putting more torque through these than we could ever dream to make and doing just fine up to around the 8-900 lbf-ft mark stock.

 

Best I can tell the ZF 6HP26 is rated to 600 Nm, I see this figure bandied about quite a lot.
Thing is, the XFR AJ133 SC motor puts out 625 Nm, and the early XFRs (such as mine) supposedly came with the 6HP26 trans, and my Topix build sheet says 6HP26. Why would JLR fit a trans that isn't rated to cope with the max engine torque, doesn't make sense. Then there is the ZF 6HP28, which is an upgrade of the 6HP26, and I understand it was fitted to later XFRs before they got the 8 speed ZF box. The 6HP28 is rated to 700 Nm, see this doc for a brief explanation of the difference between it and the 6HP26: http://www.ukrtrans.biz/files/2010/0...ansmission.pdf
I have a sneaking suspicion that even the early XFRs got the upgraded 6HP28 despite what the Topix build sheet says.
According to this page the 8 speed box is rated to 750 Nm: The New Generation of the 8-Speed Automatic Transmission from ZF - ZF Friedrichshafen AG

Edit - I vaguely remember reading somewhere that the Transmission Control Unit (TCU) works together with the Power Control Module (PCM) to limit available torque to the max rating of the trans. I think Cambo might be able to shed some light on this.

 

Yep, before I got the XFR I had an XFS, a 3.0 litre V6 diesel intercooled twin turbo rated at 600 Nm, with the 6HP26 box. I chipped it so that it was putting out at least 700 Nm and there was never a problem with the box. I believe the ZF figure of 600 Nm max for the 6HP26 box is quite conservative.

 

 

The TCU is definitely a big factor on these cars. From what I understand, they've cracked the engine code but not the transmission code. So even though we can extract more power, we still aren't able to put it all to the ground. I believe a forum member saw this first hand when he put drag radials on his and it actually went considerably slower because it was pulling so much power due to the added traction. The TCU just wouldn't allow it.

 

Thank you all for the great information! The reason I ask the question is that someday (fingers crossed) someone will be able to crack the files on generating the power that this 5.0 supercharged engine can really produce. Then at the same time put it to the rear wheels without the TCU interupting. Just look at the Merc E55 ... tons of power and torque out of the 5.5L supercharged engine.

On a different note, is the active suspension on the 2012 the same as the 2013? I thought I read somewhere that they were different?

 

My 2010 XFR makes about 20% more HP and torque over stock. At the strip, my half-shaft was sheared in the middle. Not a fun day to say the least (had to be towed off the track AND flatbedded the 200 miles home) but the tranny had no issues putting down enough power to literally break the half shaft like a pencil. It also has no issue putting down enough power that traction, even on a really well prepared track, was difficult to find.

So I hear about TCU limits, but I don't know they are actually there. I don't feel them, and trust me, I'd know if I didn't gain anything down low from stock.

 

That really sucks to break at the track especially so far away. At least you can still honestly say it could have been worse! Thankfully it was just the half shaft that decided to let go.

I haven't felt the TCU limit either but I don't think I would off the line because there is more than enough torque to smoke the tires which wouldn't require any limiting to take place because the transmission isn't under severe load when the tires are just spinning. Spinning the tires wouldn't trigger a TCU safety, lots of traction combined with aggressive throttle input would though. I'm thinking rolling starts and/or sticky tire launches.

What makes me think there is some interference going on is the member who put the sticky drag tire on and both his 60ft and 1/4 time increased noticeably. I believe he reported that the car just refused to leave the line hard with the presence of so much traction.

That tells me something is being triggered, and the car is backing off. I don't know as I wasn't there but thats just how it looks to me.

Also, what do you think of your Pole positions? They are on my short list for summer tires right now. Would you buy them again?

 

Again, I don't think you can shear a half shaft if it's limiting torque. If someone can give me a better idea of why that can happen with the limiter in place, I'd love to hear it.

If you want a great performing tire for a reasonable price, then by all means get the S-04's. I've heard the Michelins are slightly better, but significantly more expensive. If you want it to be a great highway cruiser, the Hankooks are good for that, but it won't handle anywhere near as good.

 

What exactly did you do to your XFR to get 20% more torque?

 

Tune and pulley. Search for my Jailbreak Tuning thread and you can see the increases on the dyno charts and power listings.

 

Wasn't that just the best day? Everyone at the strip definitely joked about Jaguar reliability under their breath. Hell, the announcer even made a poke at the topic!