youre forgetting the trans is adaptive, it learns....I have a customer with a xkr and he is either at idle, or the pedal is on the floor. the traction does not intervene at all and the tires spin super easy. I got on it part throttle and spun the tires across the parking lot with no intervention. His car is extremely responsive to drive, alot more than any other XKR ive driven.
Oh and I do have a early model diff with 3.54 trac lock new from Jag sitting in the garage I might sell

 

Hey Brutal..

Just another Idea. We can't CUSTOM program the TCM. But there seems to be different programs out there for it.

Since it seems that all of the later RWD cars, S-types, XJ/r's and Xk/r's All seem to be using the ZF 6hp26 trans, what are the chances you (or a friendly jag tech) could flash the trans with a file from a different car, say.. oh a 3.0 S-type that has a 3.31 final drive.

If we could find a rear that would bolt into the XKR, as well as a matching trans flash that is calibrated to that rear we'd have a winner no?

George

 

The 2010 XKR has a 3.30 rear.
Doesn't it use the same transmission? Could the relevant computer be flashed with 2010 software?
If so, then a 3.30ish gear ratio could be used. Is the '10 differential different? Can't that gear range also be obtained in that approximate ratio?

Would it be harmless try? Meaning attempting to use 2010 TCM or (?) software to convince the 05 to accept 3.30ish gears? If it failed, would it then just be reflashing it with 05 software restoring the 05 if the attempt at -10 flash/software failed?

 

i wouldnt want to chance that, there are to many things unknown that can cause issues.
The diff is differant for part of 09 and up. Would require new prop shaft and axle shafts. But it is a bolt in

 

This isn't going to come easy, is it? (LOL)

 

The 3.0 S-Types use a 3.31 rear with the ZF6hp26.

Maybe that might make a more affordable combo with the same net result?

 

Sorry for the delay in posting,
I added a K&N in 2000, changed it every year, and car runs great, I add the stock setup when I need to smog in CA and can really feel the difference driving there and back.
Then changing air box setup back to K&N for 2 years.
with over 150,000miles in 10 years I would say it's not detrimental to the overall reliability.
Because I have ready access to a dyno, I assure you we were shocked at the initial result, and over time we have retested it when its hot and when its cold, and it a solid power gain.
As this is now my wife's daily driver I leave it alone, but I really am interested in the gearing problems we are discussing as it would really wake up the off the line jump of these 4000+lb cars.
Regarding brakes, IMHO if you want to throw a large car like an XK or XJ around, get the brembo setup Jaguar put on the newer XKR's.

 

Brembos are on older 1's 2, but remember its an option and not on all. Also EBC reds are a great upgrade for brake performance using standard brake sizing

 

I have the Brembo's (reds) and the handling upgrade on my 2005 XKR coupe and I am running on Yokahama Advan S4's. I am also using Hawk street performance pads. The car is absolutely rock solid at high speed in the turns and in repeated/challenging start/stop runs. I am not troubled by the Porsches, Mercs or Vetts and have lots of fun with the occasional P. Cayman S that wants to paly tag.

For those having the need for greater speed, there is an interesting write up in the Jaguar XK8 & XKR Performance Portfolio Book, ISBN 185520-7575. It chronicles the specs and driving experince associated with the 2001 XKR-R which utilized the 3996cc power plant.

Regards and enjoy the road ahead.

Tim V.

 

Same Brembo reds on my 05 coupe. 20 inch 235-30-20 Falkans.
It took a couple days to get used to the brake pedal as it felt "spongy" like one reviewer wrote.I haven't pushed it enough to give an opinion on brakes or tires.

So far no luck on altering the rear gear ratio from anyone. Frustrating for sure. I would think the XK8 guys would particularly be interested in lowering the ratio even more than us XKR guys as they would even more feel the difference in acceleration ability.

 

WE don't have a problem with it. My trans doesn't hvae the same issues yours does I can swap the rear end and be done with it.

 

Well ain't you the lucky one.

 

Don't be jealous of my 5spd N/A shaguar!

 

You're really rubbing it in, aren't you

 

There's no better time to kick a man than when he's down. They're just that much closer to your foot.

 

I agree the best time to kick someone is when they're down...

Hey, we had a great discussion going on about how to get around the computer preventing lowering the rear gear ratio. That is a topic very dear to my heart. It seemed to really be getting somewhere tangible and then just stopped.

Any more thoughts on the topic?

I noticed that my speedo at 60 is showing about 2 miles per hour slower than what I've put into the cruise control. I think (not sure) I have slightly smaller diameter tires on it. Of course one or the other could just be off. If not, it suggests that the speedo and cruise control are working off of different sensors?

That may have some relevance to attempting to use a generic speedometer correction box for cars that change wheel/tire combos or ratios??

 

From an engineering standpoint, considering the control module and output shaft sensor are both internal to the transmission, I believe your only hope is as I said earlier, finding a different rear end from a Jag that used the same trans, and getting someone to flash the TCM so the car thinks it has those gears in it.

Even if the speedo and cruise control are working off different sensors, (wheel speed v/s calculated via gear ratio) by the time you get the signal it's already outside of the transmission. Hence the dilemma you are experiencing.

Let me look at the wiring diagrams and see what I can come up with.

George

 

As I suspected...

Everything is internal to the transmission and there is NO external wiring harness.

All the info coming out of the trans is over serial data on the CAN-BUS.

Take a look for yourself, see the file attachment.

 

Now depending on what the TCM uses the output shafts information for, there may be another solution. it is mechanical not electrical. Think about this, speed sesors use 2 basic parts to measure speed. a reluctor (cogged gear, or a plate with holes in it) and some form of sensor which measures the cogs or holes. What I propose is changing the number of cogs or holes to reflect the same difference the change in gears would represent. The side effect of this is if the TCM is using the output shaft speed in relationship to the revolution sensor or CAS sensor count, it will throw a trouble code because it thinks the trans is slipping. If the TCM problem is caused by this, then the modification has to be done between the wheel senors output(down stream from any other computer) and before the TCM. Even though the TCM is in the transmission, it would have to get the signal from outside the transmission. So modifying the input signal to the transmission from the wheels may do it in that case. Now if the vehicle operates on a CAN system it would be more difficult. Can anyone shed light on this??

 

Wouldn't work, as the TCM is also using the OSS (Output Shaft Speed) to check internal workings with the ISS. It is indeed using the information placed on the CAN bus for reading the individual wheel speeds.

But there might lie the key to the solution actually. You may be able to put a device in-between the CAN and TCM, to alter the wheel speed signals for the TCM. The beauty here is that the rest of the computers on the car will still get the correct signals, but the TCM gets the altered values.