Thread: Discovery 2 transmission remap

Just to try and answer the above questions in one go...

The V8 ECU sends different information to the TCU than what the TD5 does, so you will must likely be running lower pressure, that means all bets are off if using the V8 TCU with a TD5, irrespective of the converter... don't forget there is more that can slip in an auto than the converter.

So no guarantees with that mod.

And John... I've actually got a website setup, but realised I was too busy to actually advertise and leave people unhappy with my lack of ability to supply tunes on time, and also cause myself undue stress trying to do it... So it's on hold.

As regards the lockup mod, I'd just mention that whilst it may work, the auto runs different pressures between converter locked and converter unlocked, so again YMMV.

I'm not saying it's risky, just that it's an unknown and could cause damage, also you can actually stall the engine with the converter left locked, just like a manual.

Originally Posted by shack

Just to try and answer the above questions in one go...

The V8 ECU sends different information to the TCU than what the TD5 does, that means all bets are off if using the V8 TCU with a TD5, irrespective of the converter... don't forget there is more that can slip in an auto than the converter.

So no guarantees with that mod.

As regards the lockup mod, I'd just mention that whilst it may work, the auto runs different pressures between converter locked and converter unlocked, so again YMMV.

I'm not saying it's risky, just that it's an unknown and could cause damage, also you can actually stall the engine with the converter left locked, just like a manual.

So at the end of the day, and being lazy ie without doing my research, does this mean that for an auto TD5, there is no simple, relatively cheap long term way of having access to under 80 kmph lock-up, or any variations thereof?

Originally Posted by gavinwibrow

So at the end of the day, and being lazy ie without doing my research, does this mean that for an auto TD5, there is no simple, relatively cheap long term way of having access to under 80 kmph lock-up, or any variations thereof?

Depends what you mean by "relatively cheap" and if you can find someone to tune the TCU (probably me, and you'll need to be patient).

Originally Posted by gavinwibrow

So at the end of the day, and being lazy ie without doing my research, does this mean that for an auto TD5, there is no simple, relatively cheap long term way of having access to under 80 kmph lock-up, or any variations thereof?

I'm doing the research for all of you, by actually having it running in stop start traffic, very short runs to shops and longer 80km return runs to other side of city.

I don't have trans temp gauge so no help there, butt the bumometer isn't detecting any untoward trans behaviour/slip, up and down shift quality/operation seem same as Td5 trans controller.

What I do like is that the V8 trans controller doesn't keep the engine revving stupid in the lower gears with late upshifts to warm it up like the td5 one does on a cold morning. I always felt it was too revvy trying to warm itself up previously.

The V8 tcu does not allow any lockup at all unless engine temp is around 45 celsius last i checked with nanocom, it is a pleasure to drive with the upshifts happening a lot sooner and lazy pedal using that 1500-1900 rpm torque.

It does however still think it is in a revvy V8 so is a bit too quick to drop a cog and try and take off if I get too heavy on the pedal, this is actually ok when I run a power tune as the engine revs silly then, but with a stock tune it just drops a cog and revs more going nowhere unless I either put the boot in a lot more to get the revs up then back off to force an upshift, or back right off so the car slows a fraction to achieve the same.

It's 95 percent ok around town and fine on the highway at 110 but only if I don't try to overtake as it wants to rev the non existent V8 instead of using the torque of the diesel and holding gear.

But the early upshifts and the lockup at 60km/h I really really like, great for lazy plodding around in the traffic without the revvy behaviour. The V8 torque converter install also did have an additional calming effect , if I can call it that, on the around town driveability and made a significant difference in reducing the lag between putting the foot down and feeling the car follow through with movement instead of watching the revs jump up and then the little converter catching the vehicle up.

With my still limited experience on the vehicle and it's character (barely 10000 klicks driving if that, in 34 months of ownership) but taking in impressions of changes as I have played with tunes and torque converter swapout, and running both the td5 and V8 transmission controllers on each torque converter, I feel the real let down of the vehicle is the choice of transmission, not the tame factory tune of the engine, at least a 6 or preferably 8 speed tranny with their lower take off gearing would transform this thing into a far far more responsive vehicle.

Originally Posted by johnp38

I feel the real let down of the vehicle is the choice of transmission, not the tame factory tune of the engine, at least a 6 or preferably 8 speed tranny with their lower take off gearing would transform this thing into a far far more responsive vehicle.

Agreed, but for most of us, $15k to fit a better auto might stretch the car mods piggy bank!

So I decided to try make the best of what we have.

Has anyone investigated using the Compushift stand-alone TCU for the 4hp22/24?

That was my original thought before i stumbled across being able to use the V8 TCU or even getting the TCU reflashed! (where was this info 10 years ago!)

3rd Gear lockup @ 60Kph and 4th Gear Lockup somewhere between there and 80 would be my ideal, I would like to drive it in that config before committing to a TC Swap.


I think if I were going to drop 15K on a Gbox swap and its associated headaches, I would look at engine+Gbox swaps and get a proper headache lol

Originally Posted by CU55TM Disco

Has anyone investigated using the Compushift stand-alone TCU for the 4hp22/24?

I had a bit of a look a few years ago, probably set you back around $2k by the time you are finished, maybe a bit more if you get someone else to install.

At least that's the versions I was looking at.

I think they would be pretty good but I was recently told they take a bit of setting up to get it going right, which makes sense if you have to pick all of your own shift up and down points.

I don't know how they control/decide line pressure or if they have any adaptive shift patterns or low range settings.

Hi, I've been amazed at the progress James made working on dissecting and modifying the TCU, I thought I would crack it open and have a look.

My knowledge of mapping and how manufacturers lay out data onto PROMs to be interpreted by the software (If it is proprietary or following industry standards) is very lacking, and I barely know what I am looking at.

Fortunately, I know my way around the hot air station and a programmer, so here is a copy of mine for anyone wanting to see the TCU PROM.

I did try a few basic things to try and understand what was going on, but ended up running out of time to pursue it further. I last worked on this back in May after reading James' initial post.

What I tried:

- Opened file in a hex editor, and found strings relating to part numbers, but could not decipher any of the other data as I am not familiar with how it is encoded and laid out.

- Tried to see if there was any executable content using Ghidra, but that didn't go anywhere, assuming the generic 8051 instruction set shipped with the program was appropriate, and user error was not a factor.

Pretty sure the CPU is a Siemens 80C517. This is important as the 517 variant contains a mask ROM, which probably contains the actual program, and reads data on the factory-installed PROM. This makes sense as nothing "executable" stands out to me in the read PROM file, so I am sure the actual program is in mask ROM.

My next steps were to read the mask ROM from the CPU per the datasheet (Page attached). As long as the ROM is in unprotected mode, it should output data corresponding to the memory location I request. This test involves modifying the circuit significantly to facilitate reading and writing the data correctly, and I didn't get around to it. Maybe there was a better way?

Once I had copied over the mask ROM, I would have tried Ghidra again to see how the program read the PROM based on logic inputs from sensors and outputs to drivers, and make some uneducated guesses.

My ZIP file (Change extension!) contains:

- MODEL.TXT with all the writing located on the Bosch TCU front label.

- M27C1001-BACKUP.zip with three independent reads of the PROM. (All identical.)

- And M27C1001@PLCC32.BIN, another read of the PROM. (Identical again.)

Hope someone finds this helpful! Or at least James gets a laugh.

David.