Ok, I really don't but I am a gearhead. Looking to install a Mina pulley on the XJR for a few more ponies. I'm trying to figure out why a metal pulley is $320, but anyway.....


Anyone here done this? Is it worth it? Labor intensive?


Just trying to get a little more out of her....


Thanks!

 

Change the diff gears that will make it get up and go
I'll let you know how my XJ8 goes in the next couple weeks just bought a diff with 3.06 gears in it am going to install a magnetic drain plug while its out make oil changes easier also going to fit a phantom grip as well

 

Look up stage 1 intake tube on here and go buy one. That in combinatiin with a modified MINA gallery air intake kit will not only make your car sound better but will be a nice performance improvement as well. Any restriction you remove before the supercharger will increase boost and performance. You can also change pulley, exhaust, bore out the TB....

 

Are you sure you can change the rear end ratio without some programming?

On the S Type if you change the rear gear ratio the car will be thrown into limp home mode as soon as it rolls a tire.
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Im not so sure about the gears. Perhaps you could get away with one of those devices that modify the signal to correct speedo readings. In that case the car wouldnt know it had gears. Id imagine traction control and torque management may have a hissy fit however.

Im going to start documenting my mods as soon as I get to a dyno for a baseline. Just keep an eye out for it

 

I had read something like that on the S type forum

Correct me if I am wrong I read it was going from 2.87to1 to 3.36 to 1

I am going from 2.87 to 3.06

I did 3.24 to 3.54 on my XJR6
Best power adder I did on my XJR6

I started with cold air induction then larger intercooler pump s/c port block of plate plus every sensor,coil and air flow meter new oh and a full custom exhaust then remapped ECU last mod was diff gears

What I found the car was winding out instead of just going there by only going up the one set of ratios basically going to the N/A car diff ratio it lifted my 100 kmh cruise to the bottom of the torque curve

Hey presto finally a fast car with the XJR6 nothing changed car still changed gears at the same speed as the speedometer is driven by the back wheel abs sensor which also sends signal to the gearbox the XJ8 is the same
Going up a higher ratio might be a problem with the XJ8X350 so going to reset the gearbox computer from scratch so it learns a again

I know with the XJR6 I just left the battery disconnected for a couple days
the diff gear change was also the best value for money when I look at all the other mods no point having 180 mph top speeds when you cant get there unless you are on an autobahn in Germany

I have designed a new dump pipe and new high flow cats new 02 sensors plugs map sensor and a few other sensors as well and not just the diff gears got to get the engine running as sweet as possible first

A lot of people buy an older cars and think it needs to be hotted up when all it needs it being tuned and sorted first

 

X300 XJR6 uses a GM 4l60e tranny;X308 XJR uses MB 7226 and X350 XJR uses a ZF 6hp26.

If you change a gear ratio on a X308 or a X350 XJR you'll get a transmission failure message and tranny will fall into limp home mode.

TCM sees a differense between a output shaft sensor and a vehicle speed, provided by ABS module via CAN bus. If there's a difference, the TCM thinks that it is a transmission failure and here you go
So, it is not possible to swap a gear ratio w/o reprogramming a TCM (there's no known way to do that) or w/o totally disabling an ABS module.
On a X350 XJR you may try to upload a TCM s/w from a N/A engined car, which have a different gear ratio, but it won't work on a SC vehicle.
On a XJR6 and X308 XJ8 (ZF 5hp24) the gear swap is easy job, since the TCM of these gearboxes doesn't compare a output shaft speed vs vehicle speed. They are totally different animals.

 

MoscowLeaper is correct

The speed output from the wheel sensors will be way off as compared to the output of the transmission

The TCM will see this is a massive fault in the trans. IE rotation of the trans is not procucing the correct rotation at the wheels

Your first obvious way is to correct the signal from all 4 wheels sensors.
You cant do just the back as you will upset the ABS
Correcting all 4 wheel sensors will work but will also throw out the speedo massively

As the transmission uses controlled slip you cant modify the trans output speed sensor as its used by the TCM to detect the slip.

So without the ability to modify the TCM you can go with correcting the wheel speed sensors but you will have a speedo way out of wack

Many have searched and none to my knowledge have found anyone with the ability to reprogram the TCM. Anyone that can send them my way

Cheers
34by151

 

Thanks for the info guys (Damn this modern Rubbish) as my car is non S/C its just an 4.2 XJ8 but driving it around I have noticed when you get on it it seems to be wasting time winding out that's why I wanted to change the gears like I did on my XJR6

I had a specialist tuner mate of mine out here last month putting a tune in my diesel van

He was talking about reprogramming gearbox torque limiters
Apparently that's the next big gain in performance flash tuning gearbox torque limiters

He is a diesel specialist but does do petrol as well I will get hold of him in the next couple weeks and see how far he is along with the gearbox side of things as they must be using the ZF gearboxes in a few different cars by now
I will keep you all informed on what I find out

 

The big issue is that jaguar as well as others have thier own controllers. So if there isnt something out thier to tune the jaguar specific transmssion it cant be done

 

Hi Moscow leaper,
thank you for your invaluable competent inputs. I am just about to rebuild the final drive of my 98' XJ 4.0 n/a and could get a secondhand 3.27 (from a 3.2). I followed some of the threads concerning diff-ratio-change, which seems to be an issue with the s/c cars, but as per your quote no problem with the n/a (ZF 5HP24). Do you have personal experience? I want to avoid buying, rebuilding and installing the 3,27 just to find out in the end that it does not work.
Thank you
Mark