ST gearbox change and ECU Coding

piglett

Active Member
Jul 23, 2018
9
0
Hello!
First time poster here.
I own a 2011 Exeo ST high milage one, aprox. 231k miles. Engine seems fine but the gearbox is too "long".
I did the math: 6'th gear @ 5000 revs = 314 km/h ( ~196 mph). It's a 3.3:1 differential with final ratio of 1.897:1.
I bought a second hand transmission HCK code. It has a 3.75:1 diff and a final ratio of 2.156:1. Top speed in final gear will be 276 km/h ( ~172 mph).
Wheel torque will be up by 13.6% except for 5'th gear witch will be 17.6 up.
I hope it will make my car more drivable since i find myself between gears quite often.

Here's my question:
Will i need some sort of ECU coding? It has gear suggestion in the MFD. Will it work ok after the replacement? How about vehicle speed? I hope it reads speed from the ABS sensors.

Thank you!
Sorry for the wall of text.
 

piglett

Active Member
Jul 23, 2018
9
0
No, it's CAGA engine code, 143 bhp. But i have a friend with and A4 B8 CAHA engine 170 bhp and that one has the close ratio gearbox. Go figure?!
His reaches 110 km/h in 6'th gear at 2000 revs, mine 125 km/h at 2000.
What's the logic here?

I know it's a manual, but is there a coding that will change the gear sugestion to the corect values given the different ratios?
 

piglett

Active Member
Jul 23, 2018
9
0
Nothing wrong with my driving. I like driving light to save fuel, and have a lead foot when needed or i'm in the mood for some hard cornering( i live close to some mountain passes). The ST is anything but efficient; it gets the same mileage as my 1990 80 Quattro with a 2 liter petrol engine. Last tank i got 6,15 L/100Km, 46 miles per gallon.
There's my problem, not many people know about gearboxes or just don't care. Same car, same engine, about 4 gearboxes fitted from factory. Today i spoke with a chap who owns a ST 2013, same engine, different gearbox. He gets 116 km/h at 2000 revs. I think that's a 3.55:1 diff.
I asked around witch gearbox i should get. Including some drifters and racing folk that build their own cars. None gave me an answer besides the low revs high speed crap.
The way i see it: shorter gears, higher ratio diff, more torque to the wheels, less load on the engine, faster acceleration, lower fuel consumption.
With a bit of luck i'll replace my gearbox this saturday and then we'll know.

Again, sorry for the wall of text, and thanks for being patient!
 

piglett

Active Member
Jul 23, 2018
9
0
Guys, i'm not a hypermiler, nor want to be one. My ST has 231k miles on it. The whole point is to tailor the car to my needs and my driving style.
While some mod their cars with stickers and bumpers, i mod it starting with suspension, geometry, gearbox ratios...
 

piglett

Active Member
Jul 23, 2018
9
0
I've replaced the gearbox yesterday. Had to replace the clutch assembly. The flywheel had both radial and axial play.
The gear suggestion on the MFD is not working properly. Just displays the gear i'm in after i engage it. Also the cruise control engages only if the MFD displays something, gear i'm in or gear change. Ex: at 90 km/h it suggests changing from 5th to 6th, but i'm already in 6'th, then it will engage the cruise control.
Seems i need some instruments coding to get it to display properly.
Any of you know how that is done?
 

Tom B

Active Member
Apr 2, 2002
4,710
16
Northampton
I've replaced the gearbox yesterday. Had to replace the clutch assembly. The flywheel had both radial and axial play.
The gear suggestion on the MFD is not working properly. Just displays the gear i'm in after i engage it. Also the cruise control engages only if the MFD displays something, gear i'm in or gear change. Ex: at 90 km/h it suggests changing from 5th to 6th, but i'm already in 6'th, then it will engage the cruise control.
Seems i need some instruments coding to get it to display properly.
Any of you know how that is done?

It could be a bad wiring connection to something like the clutch position switch. My cruise control only works & MFD only displays gear info when the clutch pedal is up.

As far as I'm aware there's no coding needed for a manual gearbox. Here's all the info for the A4 B7's control units http://wiki.ross-tech.com/wiki/index.php/Audi_A4/S4/RS4/Cabriolet_(8E/8H)
 

piglett

Active Member
Jul 23, 2018
9
0
There are no error codes stored on any module.
It suggests the gear based on vehicle speed and rpm. Since there are about four manual gearboxes fitted on this model for diesel, i'm guessing there must be some coding involved. Any VCDS modders around here?
 

piglett

Active Member
Jul 23, 2018
9
0
There's only the reverse lights switch on the gearbox. Vehicle speed is inputed via the ABS sensors.
 

piglett

Active Member
Jul 23, 2018
9
0
I agree. Since there are multiple gearboxes fitted to the same chassis and engine, i'm hoping the tables already exist and they only need to be switched to.
 

decadent

Active Member
Apr 1, 2012
421
1
Herts
Interesting topic. I have a 170 Exeo and I assume a close ratio box (iirc revs are circa 2.2k at 70mph). I find first gear quite short - when pulling away at traffic lights,normal driving with mechanical sympathy, I find other cars around me pulling away quicker but as soon as I select second I accelerate at faster rate with little change to throttle input. I had assumed it was configured like that to allow for towing? I usually change from 1st at around 1500-2000rpm & find reving to 2500 highlighs turbo lag generally pointless.

My other car (corrado 5 speed) is completely different where 1st gear accelerates away proportionally to 2nd and I keep with the traffic flow for normal driving. It's the only thing that bugs me with the Exeo but I've lived with it for 60k and will probably do the same again so it's not that bad.

Interested to hear how the OP's car is doing after 231k. You should post some pics and a readers ride type post :)
 

Dark Andrew

Active Member
Jan 25, 2011
324
0
Interesting topic. I have a 170 Exeo and I assume a close ratio box (iirc revs are circa 2.2k at 70mph). I find first gear quite short - when pulling away at traffic lights,normal driving with mechanical sympathy, I find other cars around me pulling away quicker but as soon as I select second I accelerate at faster rate with little change to throttle input. I had assumed it was configured like that to allow for towing? I usually change from 1st at around 1500-2000rpm & find reving to 2500 highlighs turbo lag generally pointless.

My other car (corrado 5 speed) is completely different where 1st gear accelerates away proportionally to 2nd and I keep with the traffic flow for normal driving. It's the only thing that bugs me with the Exeo but I've lived with it for 60k and will probably do the same again so it's not that bad.

Interested to hear how the OP's car is doing after 231k. You should post some pics and a readers ride type post :)

I know what you're saying: when I first test drove an Exeo I noticed how short the first gear was when compared to the Toyota Avensis that I was driving at the time (and also how wide the spacing on the gate was). I think they changed the gear ratios sometime in 2011 but unfortunately it wasn't tied in with the "face lift" of the same year, so you can't tell by just looking at the car. The 1st gear on my 143 saloon (May 2011, CAGA engine code) is quite useable and I don't find myself wanting to change up in middle of pulling out of junctions like I did on the older car that I test drove, so maybe the ratios were changed before mine was built or I've just subconsciously changed my driving style to compensate.

Edit: When I was driving today, I made a note of when I changed from first to second, and I must have forgotten how short first gear was - it really is quite short! Just as a matter of interest, what's your speed at 2000 rpm in sixth on the flat? Mine is just a little short of 80 mph.
 
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piglett

Active Member
Jul 23, 2018
9
0
@decadent
You have a very short gearbox. I think it's a JEM code, 3.55 diff. Your problem in first gear is with the torque limiter set in the ECU. Try reving it a little more of the line.
The car is fine, still drives like a new car. Very few and rare occurring rattling sounds mostly from things i deposit in the doors. Suspension is very stiff.
Replaced so far: gate wiper mechanism, gate opening switch and lock; boot storage lids on either sides; arm rest lid. And that's it.

@Dark Andrew
The 1'st to 3'rd gears are the same on all diesel gearboxes, but there are three diff ratios: 3.3 3.55 and 3.75.
You have a MPA gearbox, 3.3 diff, same as my original one. Very long ratios.
 

wes

Active Member
Sep 24, 2018
6
0
The coding will be in the cluster. It will need to know what gearbox is fitted so it can determine what gear you are in. Vcds will do this.
Or possible coding within abs module.


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