2008 Super V8 with an interesting problem.

I recently pulled the SC to fix the stupid leaking hose that Jag puts under the SC, and at the same time, rebuilt my SC and ported the entire intake system with new smaller pulley. Big gain in HP....

As a result, I am experiencing a big increase in power and while trying to enjoy that HP increase, I find that the J gate only allows a manual shift hold in 2 gear by the selector.

SO as I pull off the line and get wheel spin (and smoke), it shifts and I lose the benefit of 1st gear.

When I put on traction control, I get similar results.

IS there a mod that will allow the transmission to hold first so they when I get wheel spin, it will allow me to manually feather to regain traction and continue in first gear?

It was a lot of fun hearing my wife say, something strange happened when I pulled away from the light.....it sounded funny.

 

Doesn't putting it in Sport make it launch with 1st gear?

 

It launches is first, but as soon as I get wheel spin (which happens pretty fast), it shifts and I lose first and stuck in second for the rest of the RPM range until I go back to a slower speed.

If I use Traction Control, it helps, but does not stop second gear from engaging. Wheel spin is good for better speed but you have to know how to feather your way through it in the same gear.

 

Sounds like you need stickier tyres; why not just put some 285 section high performance summer tyres on the back? That should be more than enough to put the power from a pulley to the ground with minimal spin. Then install a quaife LSD or try fitting a 8.8" diff from a 4.0 S- type with a LSD which is the cheaper option.

 

Findre,

I few years back I modified a XJ40 J gate shifter to work with a GM L460E transmission in a Series III sedan. The XJ40 only had enough movement to allow me to drop the transmission into second gear only. I removed some of the plastic material on the shifter bezel to allow the J gate shifter to have additional stroke beyond the second gear stop and it allowed me to hold 1st gear on the GM transmission.

Fast forward to current times with my 2005 XJR.

Some forum members have had an issue with the shift cable nut coming loose where the cable connects to the transmission.

I decided to check mine while on the lift one day. I removed to cable bolt and played with the shifter linkage and could have sworn it had an additional detent beyond 2nd gear meaning 1st gear. After all they did use this transmission in Ford products like the Mustang GT. Surely Ford allow them to hold 1st gear.

My thinking is why not modifiy the J-gate in my 05 XJR like I did with the XJ40 shifter and allow the additional stroke of the shifter to get to the 1st gear detent.

I would of course go back under the car a recheck what I thought I discovered when I was checking the shifter cable nut and look below the shiter bezel and shifter movement before I made this modication.

What I dont know is what this may trigger as far as transmission fault codes.

You should have access to a IDS/SSD program to clear any issues this may create, but if it works, now you can hold 1st gear.

Some forum members may have other experiences or reasons whay this may not work.
I have not tried this modification on my car as of yet myself but was going to try it when time allowed.

Woodford Jag

 

Hello,

I used to drive BMW E39 540 with the same gearbox and it had + and - options for shifting manually. I am sure that can be somehow installed on Jaguars too, although such modification might be harder than I suppose it can be.

 

You guys got me in the right direction.

Great suggestions. It made me think more about where the solution may come from, so I was able to find the proper ZF6HP26 transmission guide and it addresses the problem with how to.

Jaguar has 1st Generation 6hp26. Newer ones has Gen 2.

It looks like larger tires will mess up the "curve recognition" that Jag built into the TCM. It will also mess up the shift points. Super V8/XJR has LSD, 2 wheel spin in wet and on drift (yes) I've drifted a saloon. Tires sounds great but may effect drivability. I still think it will not hold 1st long enough.

The J Gate has specific sensor that tell the transmission electronically which gear to select and "Mechanical Mechatronics" It likely cannot be modified like the GM because the shifts are controlled electronically from the J-Gate. At the point the J gate is modified it will throw a code to tell computer that the gear selected from J Gate is "Implausible J Gate Position (Jaguar)". It's a CAN bus problem in programming.

So here is what I learned. The BMW has a "E-Shift" unlike the Jaguar "M-Shift" gearbox. E is for electric shifting. That does not mean that the Jaguar cannot be controlled electronically, actually the shifts are controlled electronically, but the mechanism is not electronic like the BMW with their funny console shift wand. Also there BMW has display for gear selected, unlike Jaguar (outside of sport mode with factory paddles).

I will up load the guide because it has a lot of good info to diagnose this transmission. It appears that I may be able to tap into the harness and use the + and - shift selector for a rocker or paddle. Not sure how that will go, so I will make a stop by the Jag dealer service dept and see if they have a sense of humor.

I'll post when I figure it out.


M-Shift harness pin for ZF6HP26 transmission with M-Shift

 

I am not that good in understanding all that, but does that mean paddleshifters (or at least usual buttons on the wheel) are possible to be installed?

That would be amazing and useful (moreover with my 3.0 engine )

 

As far as I know no XJR/STR/XKR with the 4.2 S/C engine had a LSD stock. Cambo helpfully summarises here:

https://www.jaguarforums.com/forum/j...ntials-134733/

It was not until the 5.0 S/C "R" cars did Jaguar fit their e-diffs, so people have gone to much expense fitting quaifes and supposedly 8.8" LSDs on our models. I know because I plan to do the 8.8" diff swap myself.

With good sticky tyres you will have no problems red lining first gear even without a LSD. I previously had almost 500hp in my STR (which takes a lot more than SC porting and a pulley) and in dry conditions I could launch relatively hard and hit 5500rpm before it would change into second. Unfortunately my STR and others shortshifts 1st and 2nd. I'm guessing you have the 255s on the back? Many members with modified X350/X358 XJRs have gone to 285s with good effect.

Would be nice if true manual control of the gears could be achieved, it will always be a shame to me that these cars weren't offered wth a manual. My friend has a 4.3 AM Vantage with a 6 speed manual (essentially a bored Jag 4.2 engine) and I wish Jaguar had offered the same on the V8s.

 

Hmm, never considered no LSD because I usually get spin on 2 wheels, but maybe DSC is kicking in and throwing power to drivers side. I get a full 5500+ if there is no spin, so LSD maybe the answer. There are also upgraded solenoids for the ZF tranny.

My SC is probably at around 430 ish HP and power curve is really decent. I also did a PCV oil catch can which cleans the air going into the Throttle body and doesn't rob HP like before. Also the TB is squeeky clean now.

The differential on the right, from the forum link you sent, looks like it has clutch packs for LSD to me. If it is a 8.8 Ford, then LSD are easy to find. The fastest easiest way to resolve this would be a lunchbox locker, if it doesn't make too much clicky click on tight turns. The Quaife LSD looks like an Eaton True Trac (Torsen). I just installed one on my Sterling 10.50 and it was pretty straight forward with proper measuring tools. I'll have to open JAG up (to change the oil as my Wife would ask why am I opening it up) and take measurements during "routine maintenance".

285's changes the rotations per mile by quite a bit. 746 vs 724. not sure how the puter will like that. It's my Wife's driver, so I have to tread lightly on the MIL lights.

I think it is possible to rig paddles but it will take further research as will the LSD possibilities. I saw the LSD post and there are really knowledgeable guys like AVOS, etc on there so I am not going to try to out think the guys that have been doing this for years with success.

Basically, I told wife when its time for her new car, I may keep the SC and put Sparco's in it, then it's clear to mess with. At least Sparco's wont kill my lower backside like the factory torture seats.

 

findre,
You have to put a 285/30 R20 or 295/30 R20 to replace the 255/35 R20.
Look here:
https://www.jaguarforums.com/forum/x...ack-xjr-77305/

 

Ouch 295/30's are not cheap, 50% used they are almost $250 each. Look like it may be a better choice to get a pair of 20x10.5 rims and throw a pair of used on for play day. I'll be into the setup for about the same as LSD. Bet the wide boys look good though.

 

The J-Gate should have had a "1" position for first gear, and automatically switched to sport mode when moved into the manual gear request position. The message center should have shown the current gear when in manual gear request position. Just one of the many design flaws in these otherwise outstanding vehicles.

A manual transmission with that high winding Jag engine would be a joy to drive, if I have the time I might so modify mine.

 

I have made a few modifications to my 2005 XJR and probably have around 430 hp plus.
Also cleaned out the cool chargers and throttle body which prompted me to install an oil catch can!
The best mod tho by far was installing the Quaife. My gear changes at wot are at the red line. However I have not gone above 100 mph with wot and I get there rather quickly on "local" roads.

I wasted a LOT of time looking at trying to mod a 4.0 Jag diff to take a ford 8.8 LSD due to some bad info in this forum. Rarely is there any bad info in this forum however I sure found it with regards to that particular suggestion.

I detailed my experience in the differentials thread.

The only other mod left to do would be the Cambo ECU remap. Of course there is the twin screw mod but that is way over my budget.

 

What about borrowing the J gate from the XK? Some of them are 4.2 V8

 

That would have been really cool, although there is still some delay in shifts using the j gate. I drove an f type r on track last weekend and the 8 speed zf in it is awesome, very fast and gave you gears when requested (whilst displaying which gear you're in).

After that I drove a 911 gt3 with a manual and shifting at 9k on that was unbelievable, it cemented my belief you can't beat a proper manual for pure driving enjoyment.

 

With the quaife is it the case that you only know it's there when driving very hard? As well as pulling out of junctions from a stop? I'm gutted the 8.8LSD didn't work for you, I was hoping to copy you if it did.

Cambos ECU tune would bring together your mods nicely, but TS gives a different level of power. I would love to go in a 2.1 or 2.6 KB car to see how fast it feels compared to my old 1.7 and experience driving an XFR.

 

JagSTR2004 I do only notice the Quaife when driving hard. Without it the car would give me a "zigzag" feeling in the butt taking off under hard acceleration with traction control active and would be dangerous trying that coming out of a T junction. Now no problems at all and a lot more fun.

My truck has an LSD , Dodge Dakota, and it "judders" in the rear when reversing and turning at low speed because one wheel turns in exact unison with the other around a sharp corner.

That does not happen with the Quaife.