Just be aware that someone had a 6 cylinder rear end installed in a V-8 car by accident at the Jaguar dealer. It will throw the car into limp home mode and until we have some kind of programming there is no way around this. So we can't change the rear end ratio with out problems right now.

The Lincoln LS does not have this problem. So you can put any rear end ratio in a LS. Since the speedo comes from the wheel sensors changing the rear gear does not even mess with the indicated speed! Several LS guys have installed 4:10 gears.
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I figured it would wreak havoc on the trans pcm, BUT If you use a v6 rear in a V8 / STR AND flash the trans with V6 software (which is readily available for the v6 rear end gear ratio) maybe we'd have a winner? I wonder if someone with access to IDS could confirm if the engine and TCM are separately flashable.

We discussed changing the ratio in another thread a while back, and the problem lies with input shaft v/s output shaft sensor discrepancies due to the unexpected rear end change. (Basically the trans thinks it's slipping internally). The biggest issue was the parameters weren't individually editable in IDS, and the sensors are both internal to the trans (so you can't modify the output shaft sensor signal).

BUT MAYBE.. just MAYBE. We could do the v6 rear end swap in combination with a TCM Flash to the v6 software (insert evil smile here).

The lincoln doesn't care what rear end you put into it because the ford transmission doesn't compare input shaft rotations v/s expected output shaft rotations in each gear (based on a software programmed rear axle ratio). So it doesn't throw the car into limp home mode.

Food for thought...

George

 

In case that doesn't work, it would be wise to have a spare tranny around! I guess - worst case - mechanical damage might occur

 

Well, in theory if the trans doesn't like the input - output shaft ratio it will throw the car into limp mode right? I can't see how you would cause mechanical damage unless you beat the heck out of it, and the shift points were wrong, but even then, you'd over rev the motor (or bounce off the rev limiter). Either way I don't see how you can break anything by changing the gear ratio.

The only thing is can you program the trans to play nice with the v6 rear with a v8 under the hood.

Take care,

George

 

George:
I like your idea about using the 6 cylinder programming. Sure sounds correct but I don't know how we could get that in the software? Brutal or another factory tech “might” be able to tell us if this is possible??

The LS transmission also monitors for incorrect gear ratios by comparing input shaft speed to output shaft speed and will set codes if things don't match. Because changing the rear end ratio does not change the gear ratio's in the transmission. So the ratio of input to output shaft speeds will not change. But it appears that Jaguar also monitors the shaft speeds of the drive shaft and the rear axle shafts because this will change when the rear end ratio is changed. The LS does not seem to worry about this measurement so no limp home problems.
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Actually I think we are both part right.
ZF monitors input shaft v/s output shaft speed. But that would only detect an internal trans fault, as you pointed out.

There is NO monitor for rear axle shaft speed But it's either using the wheel speed sensors, OR the calculated road speed. and figuring out that something is off, and throwing the car into limp home mode. I know the instrument cluster can be programmed based on tire size, and engine size as well.

Somewhere in the mix there is the programming for the car to play nice with the ZF trans, and the v6 3.31:1 rear end (which is physically the same except for the ring and pinion gear). Im wondering if it's independent of the programming for the engine PCM. I.e. can you use v8 engine software, but setup the car so the engine trans and v6 rear play nice together.

We need a Jag tech to chime in here.

Take care,

George

 

I did say worst case. I would hope for limp mode or even shutdown.

You could potentially get the V6 tranny code into the TCM by connecting a V6 PCM temporarily, then reconnecting the V8 PCM. I expect it's fairly easy to get PCMs from wreckers.

The TCM is shown in the diagrams with a different capacitor for V6 & V8 (and maybe other changes) but I don't know why or whether it matters.

Whether the ABS sensors are used to detect an issue - try it and see?

 

I am just working off deductive reasoning here, I dont know the intricacies of the operation of the S-Type THAT well yet.

What I do know.

All we are changing is the ring and pinion gearset in an otherwise identical differential.

The transmission's internal gear ratios remains the same (obviously), BUT the final drive ratio changes. The car is SOMEHOW able to detect this, and only a diff change will cause limp home mode. (As demonstrated by this swap accidentally being performed by a jaguar dealer).

The only thing that changes when you alter the final drive ratio, is road speed (and rear axle shaft rotations) relative to a specific engine RPM in any forward gear.

Shift points (relative to road speed) are also affected.

Now, I don't know exactly where the S-Type gets it's VSS information from. If indicated speed on the speedometer is calculated based on wheel rotations, or driveline rotations.

So the possible triggers of limp home mode are:

Incorrect relationship of engine rpm, current transmission gear, and axle rotations or vehicle speed. Or some combination of above.

When the SAME transmission and the V6 Rear, the V6 S-Type soldiers on, with no limp home mode. So, unless the TCM's are physically different, and each transmission is purpose built for its intended drivetain, chances are it's flash programmed.

Is this TCM Capacitor in the diagram in the ETM??

Thanks,

George

 

I expect the DSC/ABS module broadcasts the speed. (It'll also likely have messages for torque reduction etc.)

The caps are shown in the Elec Guide. Choose the Transmission section and look on the left of the TCM.

 

So I printed the TCM Page... I'm wondering if those capcitors are of different values. I wonder IF that's what tells the trans what motor is in front of it...

I doubt it's that simple. But that's definitely interesting.

Take care,

George

 

Er... wonder if a mod would like to split this stuff off under a new topic?

 

I concur that it's probably a good idea.

I can pm someone if you like...

George

 

For what its worth there is a shop in Dallas texas that specializes in ZF gearboxes and when I spoke with them they have a tool that they can change the final ratio in the TCM, which will cause the TCM to recalculate all of the shift points, and they have the ability to tap in and change the shift strategy maps.

I havent done it yet due to all the other stuff going on. But I need to find what gears Im going to throw in the diff along with what LSD I will be using.
So for now its on the back burner.

 

Mafioso, I'd like to give the dallas shop a chance to fix my lurch... what's their contact info, if you don't mind?

 

Furthermore if is the case, can this place in Dallas change the shift points/strategy to raise the 1-2,2-3 in a 03'?

Pete

 

http://www.freddiestransmissions.com/html/upgrades.html

Yes they claim to be able to alter the shift points if it's a zf gearbox

 

I called, they said they can't do anything as it's completely a software issue...

 

Dang!

 

This looks promising... https://www.jaguarforums.com/forum/x...e-59907/page2/

So is it safe to say no one who owns a 6HP26 equipped Jag has changed the shift points?