Hope one of the techs can help me, is it possible to change the diff ratio using IDS/SDD?
I remember seeing a video of the old IDS (before SDD) being used on a Ford & they had the option of choosing the diff ratio.

Been through the SDD, & can't seem to find anything....

Background to the question;

I want to change the diff in my X350 XJR from the factory 2.87:1, to the gearing from the 3.0L V6 which is 3.31:1, some more info here https://www.jaguarforums.com/forum/j...76/#post540512

I've heard that if you swap the diff ratio, the ECU/TCM absolutely must be programmed to that ratio, otherwise the very different "speeds" of the front & rear wheels messes up the ABS, DSC, and any other 3-letter acronym you can think of.

But if it can't be re-programmed with the IDS/SDD then i'm stuffed...

Hope it's not one of those locked away features in the Engineering Mode that we talked about before...

Anyone know if this can be done? And how?

 

The XKR is using the same 3.31, so you could try to load the transmission code from that one to yours. To do this you need to rename the XKR transmission files to the one that is used for your car, and then just update the TCM with the IDS. Would first try this before swapping diffs of course to be sure your TCM is accepting the code, but I guess chances are high.

 

I found the post where the chap mentioned the problem after swapping ratios "MIL light was on constantly" Differential Ratios but that was in a 2001 S-Type...

I'm not so sure if changing the TCM program alone will do the trick. For example when you change the wheel size in the SDD it mentions about programming multiple modules with this information, I didn't take screen shot but there were at least three or four different modules that need the informaton of the wheel/tyre size, I guess it would be the same for the diff ratio? Both are related to wheel speed measurements...

If just re-naming the XKR file did work, how would I know without actually having the new diff in the car? The speedo would mis-read, and i'd get multiple errors?

Can't find that video with the diff ratio selection now, maybe i was imagining things...but there must be a way...

 

Cambo, with my understanding of how modern day cars are sensing speed and whatnot, changing the gear ratio is not going to affect the speed indication of the car. The speedo is sensed through the ABS wheel speed sensors. So, as long as you are not changing the size of tires, you are golden there. Where the problem comes is the computer is programmed that under a certain load, at a certain speed, with the engine at a certain RPM to shift. The problem comes, all of this 3 dimensional graphing assumes a certain gear ratio in the car. When you change the gear ratio, the computer can not adequately use this graph to figure out where to shift the tranny (only 2 of the 3 factors will ever line up), hence the MIL code. You would need to get a custom programmed computer to account for the new gear ratio. Any speed shop should be able to do this for you. It isn't all that difficult to do.

 

I am quite interested in knowing how to change gear ratios as well. Please list some of the speed shops who can do this for us. I have be unable to find anyone in the US.

 

Hmmm...yeah good point Thermo, come to think of it the guy with the S-Type never mentioned anything about the speedo misreading, so perhaps it's really just a problem with thee TCM program?

Just re-read that other post, he said "BTW, Jaguar was not prepared to hand out the master password to re-program the new diff ratio into the electronics, as obviously there is no way to predict what else happens." so it must be possible, just not for us...

And found another thread where this very same idea was already discussed https://www.jaguarforums.com/forum/j...50/#post178249

Seems we are back to the TCM needing reprogramming, I'm thinking that maybe I'd need to contact ZF (they're actually not too far from me) or maybe a BMW tuner who has cracked the 6HP26 & able to re-write the map...?

Or maybe just get lucky by re-naming the XKR file like Avos suggests, could it really be that easy?

 

For the fords it's easy, besides changing rear end ratios you can even use the sct tuning tool to tune the gearbox (so alter shift strategies etc). No such thing yet for our cars, at least I haven't seen it yet.

The gear ratio is in the software for the TCM, I have no doubts about that, so your best bet is as suggested. I have used the same trick to change the ECU tune from a US XKR to flash it with EU maps.

 

Would you happen to have the name of the file for the XKR?

The TCM file for the X350 4.2 SC is z65y5656x350row.phx (from when I re-flashed mine), i also found another file z65y5656x350row_data64k.dhx, both are in C:\Program Files\JLR\IDS\Flash

I found z65y5656x103row.phx and z65y5656x103row_data64k.phx, that would be them?

 

I didn't find anyone in the US, but it seems that the ZF has been cracked down under Australian Ford Forums

The 6HP26 is used in the current generation Ford Falcon in Oz, and there is a big scene down there, I guess the problem in the states is that the biggest user of the 6HP26 is the BMW crowd, which isn't as into Tim Taylor "More Power" like the Ford Heads...

 

Remember the blue top solenoids?

Maybe it is time to revisit the mother of all hard core W5A580/NAG-1 tuning information sources: the Chrysler hi-po sites

Drag racers are never satisfied with the ratios that the factory ships.

NAG1 tranny + 3.73 rear gear = what RPM? - Dodge Challenger Forum: Challenger & SRT8 Forums

One sig includes:
++

 

Was actually thinking of the x150, not the x103. Have had a look just now, and I can't find similar files for your car model, so am afraid it is not possible as suggested. Iirc the x150 got the 2nd gen 6HP26, which may have different programming, but key is the IDS will use the legacy tool for your car and as said there are no x150 files for that one. Sorry.

 

That's a bummer...yes I didn't realise the X100 only got the W5A580...

I think the problem using an X150 map will be that they all had sequential shifters & that JaguarDrive gear selector, completely different to the X350.

The ZF in the Australian Fords is done with the SCT tool, it really doesn't work for us?

Looks like i'll be placing a call to Friedrichshafen then...

 

The x103 has the 1st gen 6hp26, and the older x100 had the W5A580.

According to the Australians, the SCT tool will not work on other cars, so only chance would be to try to SCT Performance - More Power! Less Fuel! to extend the vehicle range.

 

And from what I can find the X103 had a 3.06:1 in it...so another dead-end...

 

No good news from ZF either....just got a reply from the Technical Projects department;

That's my translation from German anyhow, reading between the lines, it seems to me that it can be done, but they "can't" for whatever reason.

For all you German speakers here is the original;

 

Dammit i'm not giving up on this!

What are the odds of the TCM file from the 3.0L V6 working? I mean it uses the 6HP26, it's the car that the 3.31:1 diff comes from, I wonder....?

Only problem I can see is that the V6 has a 6800rpm redline, whereas the 4.2 is 6100.

So if the shift point is defined in the TCM, then the engine will hit the rev limiter, but the tranny won't shift up?

Anyone know the TCM file name for the 3.0L V6 X350?

 

I dont see your concern cambo,
first the tcm looks at road speed, rpm, throttle angle and engine load value to determine shift points and line pressure.
2 and thermo said the abs module determine the road speed from the whl spd sensors. The only thing that will upset this is tire diameter change, this can be somewhat corrected by reflashing the instument pack and knowing the differant(factory) diameters for 18,19,20's then telling the ipack what size wheel is on the car. Not really what on the car but the one thats closest based on factory vs changed size.
Now while not a jaguar. When i change my 05 nissan frontier front and rear diff gears from 3.36 to 4.56 nothing changed for speedo accuracy, shifting and my mileage actually went up alittle(your results may vary )
and of course the smile on my face when accelerating was much bigger

 

Thanks Brutal!

My only concern is after dropping $2000 on a new diff with an LSD in the UK, shipping it over here, & then another $???? in labour to fit it, that the car chucks a fit & won't run....

Been reading up on the TCM in a workshop manual I found, unfortunately I can't print out the whole section as a pdf (damn thing is locked) but here is the bit about the inputs for the calculations;

So what happens when the road speed doesn't match up to the rpm & selected gear? I know these ZF boxes are adaptive but...?

I'm glad it worked on your truck, but i'm still not confident enough to go ahead & try it though...

But I do wonder, there seems to be only the one file with that name for the X350, one for the X103 and one for the X202. They all run the same 6HP26 and at least with the XJ & S-Type you had a variety of ratios.

If I can find someone in the UK or even around here with a 3.0L X350, hook up the SDD, look at the file name used during a tranny re-flash, and it's the same file, then i'd be pretty convinced that it'll work...

I've got access to a 2.7D X350, that runs a 3.07:1, if the file is the same there that might be enough evidence to move forward...

 

The V6 program is also based on the rpm/power output, so it will be some pioneering here, as the shifting program might not work as nice as the power delivery is very different. But the main problem will be that the engine ECU has a rev limiter, so at 6300 (iirc for your car), it will kick in before the TCM will issue a shift.

Now it would be worth a try to adjust your ECU so the rev limiter will be just as high as for the V6, but then it will still be a little gamble if the shift strategy will work out nicely.

 

Cambo look down between your legs, yes you have ***** also. But yours cost more and are British Racing Green. I have a 05 V6 4.0 Frontier with a Titan truck front differential and suspension. a super charged 400hp(265 STOCK) offroad daily driven truck. Soon the to be 500hp with a used Kenne Bell twin screw kit from a Vette similar to the ones Avos uses. Nothing is left much like Nissan intended it. The new twin screw will take some work and engineering to fit but very doable as Ive been looking hard at it for the last 3 yrs.
My trip to Moab Utah was expensive and what prompted this continued list of mods, spun rod bearing. damaged non repairable crank, damaged piston and cylinder wall.
Over bore, deck, align hone. new crank, new pistons, bearing, rings, gasket set and machine work. $3000, used twin screw kit $2900. cost to build new drive system????
retune motor for 15psi $500
little odds and ends needed to finish you never think of. $500.
so there $7k plus and that doesnt even touch the work and parts previously done that dont need to be replaced like cams, valves, port work, and rods. Or suspension, armor etc....
My point is this, you can do as much studying as you want and its wise too. But in the end sometimes you have to JUST DO IT and work from there. There are always people that are there to tell you it cant be done. But I can tell you from lots of experiance at doing many things people say wont work and then they do. Or it may not work exactly as you intended, but you just adapt, change and work till it does...
You just need to go for it, be the innovator.
Now what little I know of mapping and programming and you might want to talk to Xj engineer on here since he worked for Jaguar in the 90's and is into mapping ecu's even today is this. you have tables in a ecu that the ecu referances based on inputs. in both 2 and 3 dimentional xy , and xyz. if you have a road speed of X and a rpm of Y it referances this results. it doesnt say that it cannot happen. it sees and adjust accordingly with what is programmed by the software engineers to do at that point on the graph. This is why I didnt have an issue with mine, and why Avos runs his car and has NOT tuned for it. The engine looks at parameters, and inputs and gives the corresponding results and same with the trans. all you engineers on here dont flame me this is a simplistic look. But all the info is there in programmed tables to referance and its not cut in stone so that if something happens outside the norm it wont function, it keeps right on going. This is why you can unplug differant sensors on a car and the car still runs fine because it either referances a preceeding table or referances another signal and subs that and calculates with this info of the need.