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Passat CC B6 Gearbox replaced, cruise control now not working 4th,5th,6th gears

  • 22-07-2014 11:22pm
    #1
    1jcdub
    Registered Users, Registered Users 2 Posts: 960 ✭✭✭


    The gearbox on my 09 Passat CC tdi recently broke and needed to be replaced. I sourced another gearbox from a 2011 CC Bluemotion tdi which has slightly longer gearing in 4th, 5th and 6th. All went well with a new clutch and flywheel fitted also while the gearbox was out. Anyway. I got the car back today and when on the motorway i tried to activate the cruise control, but it wouldnt activate. Long story short cruise control works but only in 1st, 2nd and 3rd gear which have the same ratios as the original gearbox not month in 4th, 5th and 6th which are slight longer geared that the original box.Although it will activate briefly for a second of two in 4th before switching off.
    Any ideas on how I can be.t it working again for all gears? Can anything be recalibrated etc?
    Any help would be much appricated.


Comments

  • #2
    1jcdub
    Registered Users, Registered Users 2 Posts: 960 ✭✭✭1jcdub


    Correction. Cruise control will operate in 5th gear but not 4th or 6th


  • #3
    Chimaera
    Registered Users, Registered Users 2 Posts: 1,652 ✭✭✭Chimaera


    It sounds odd that it'd work in 5th but not 4th or 6th if it was an issue with the change in gearing (probably the most plausible explanation). I'd have a diagnostic scan done to see if there are any errors recorded by the cruise control system.


  • #4
    1jcdub
    Registered Users, Registered Users 2 Posts: 960 ✭✭✭1jcdub


    I received this response from Ross Tech:
    "My understanding is that the engine controller monitors the relationship between RPM and vehicle speed and when it detects too much of a deviation from known gear ratios, it doesn't allow cruise to operate. I am not aware of any way to use VCDS to get cruise working in your car. You may want to check with a chiptuner to see if it's possible to install the "wrong" chip file in your ECU but I have no idea if that is possible. "


  • #5
    dougie-lampkin
    Closed Accounts Posts: 677 ✭✭✭dougie-lampkin


    The ECU has a ratio for each forward gear (well, it has two ratios for each actually, a min and max to account for tyre sizes and wear). It compares RPM to speed to work out what gear you're in, rather than having 7 switches at the gearbox. Your new 5th gear is probably at the low end of your previous 6th gear, ratio wise. In 4th and 6th it doesn't have a matching ratio so it assumes you're in neutral. It should be logging errors to tell you there's a mismatch between speed and RPM, and I'm surprised it hasn't thrown the EML yet.

    As Ross-Tech have correctly said, it needs to have the ECU flashed with the ratios from a Bluemotion bin. It's a bit beyond the usual "chipping", so I'm not sure who you could bring it to. Joe Power is probably a good start, he might not be able to do it, but might at least advise someone who could. There's a lot of cowboys in this field, so be very cautious about who you bring it to. It's well beyond the remit of most "tuning" companies.

    I would have assumed VCDS would be able to modify these parameters, but judging by Ross-Tech's response, maybe not.


  • #6
    1jcdub
    Registered Users, Registered Users 2 Posts: 960 ✭✭✭1jcdub


    dougie-lampkin wrote: »
    The ECU has a ratio for each forward gear (well, it has two ratios for each actually, a min and max to account for tyre sizes and wear). It compares RPM to speed to work out what gear you're in, rather than having 7 switches at the gearbox. Your new 5th gear is probably at the low end of your previous 6th gear, ratio wise. In 4th and 6th it doesn't have a matching ratio so it assumes you're in neutral. It should be logging errors to tell you there's a mismatch between speed and RPM, and I'm surprised it hasn't thrown the EML yet.

    As Ross-Tech have correctly said, it needs to have the ECU flashed with the ratios from a Bluemotion bin. It's a bit beyond the usual "chipping", so I'm not sure who you could bring it to. Joe Power is probably a good start, he might not be able to do it, but might at least advise someone who could. There's a lot of cowboys in this field, so be very cautious about who you bring it to. It's well beyond the remit of most "tuning" companies.

    I would have assumed VCDS would be able to modify these parameters, but judging by Ross-Tech's response, maybe not.


    Thanks for the reply.
    I was in touch with Joe yesterday and he said he could do it, he's just to get a file from a blue motion and extract the data for 4th and 6th gear and place it into my map.

    I've checked vcds for faults but none are showing


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