Replacing 5 gear Transmission with 6 gear Transmission

[srdan]

I have a chance to get 6 gear transmission (from CITROEN C5 2.2 HDI, around 70.000 miles) for my 2.2 HDI engine on P406, for a very small price.
Does any one has experience with replacing it?
Heard from some guys that 6 gear transmission for 2.2 HDI is just great, like born for it.

The main question is, will there be any problems with ecu? When I connect with Peugeot Planet 2000, ecu can determinate the gear you are driving in...
what will happen when I install 6 gear transmission.

For mechanical point of view there should not be a problem with wires? Should there be one more wire for 6th gear, or everything stays the same?

I apologise if my questions are dummy

Is the flywheel and clutch the same?

thx

[lozz]

Ive heard the 6speed gearboxs are like choclate,
and that came from a 'Gearbox specialists,
theres mention of this also on other forums,


id stick with the 5spd box if iwas you,

[srdan]

what does that mean?

[lozz]

What does that mean ?

from what ive heard there a weak box,
iblew a 406 hdi box up and had it rebuilt -ilooked into the 6spd and was told theyre shite,
5spd box is better stronger,
but is that true,? feck knows mate,

[jasper5]

My 6 speed transmission has been great so far, 60,000 miles now.

[srdan]

I think I will try and let you know how it goes...

[omega]

I think I will try and let you know how it goes...

good luck with the job and please let us know how it goes and what you have to change /swap

[srdan]

ok

[Doggy]

I'd love to do this myself, but have neither the time or opportunity. It seems the 6-speed has exactly the same ratios for 1st to 5th, just a taller 6th gear added on, which is exactly waht a remapped 2.2 is crying out for. Should give a useful fuel saving too.

I have considered the gear ratio detection issue and am fairly sure that it 'calculates' which gear is in use from the vehicle speed & crank sensor data. Recognising that cruise control is set up to engage only in 4th or 5th gear, above 30 mph, I worked out the following test method to determine if cruise will still work in 6th gear, without doing the job.......

1) Calculate the theoretical engine speed at say 100 kph / 62 mph in 6th.
2) Kidnap / bribe / threaten an assistant to drive, or monitor PP2000 while you drive.
3) On a level road, get the car to slightly above this speed, then put it in neutral.
4) As the road speed slowly decays past 62 mph, match the theoretical engine speed by operating the accelerator, (still in neutral).
5) Observe the 'calculated' gear ratio via PP2000 - (I think it will still say 5)
6) Carefully engage cruise - if it's going to work, it will increase the engine revs to try to maintain the road speed.

(You could possibly do it more easily at standstil, by jacking the front wheels off the ground).

Worth checking first - I'd hate to do it all & have no cruise in 6th.

Good luck.

[Busman]

Some one needs to do this as a test, for the good of the 406 comunity.

[Doggy]

Some one needs to do this as a test, for the good of the 406 comunity.

I'm guessing the number of forum members with PP2000 access, an ML5 'box and cruise might not be huge.

[srdan]

I think I have a new challenge

[steve_earwig]

Sounds like a big one I've been having a look, everything looks ok (driveshafts, clutch, but I have concerns about the gearchange, the mounting (which is completely different on the C5 and I have no way of comparing the three) and no idea at all about the BSI (didn't know it did that!) Also the ratios are the same up until 4th but 5th is slightly lower on the 6 speed (51x33 as opposed to 51x31) and obviously 6th is slightly higher.

Obviously it would be smart to check the BSI will be happy with the 6 speed, if the mounting is wildly different you might have to make one but also check that it will physically fit before spending anything else...

[steve_earwig]

Just as an afterthought I looked for the speedometer drive pinions - the C5 ML gearboxes have a blanking plate on the back of the differential housing - how does that work?

[mjb]

I have considered the gear ratio detection issue and am fairly sure that it 'calculates' which gear is in use from the vehicle speed & crank sensor data

That is correct.

1) Calculate the theoretical engine speed at say 100 kph / 62 mph in 6th.
2) Kidnap / bribe / threaten an assistant to drive, or monitor PP2000 while you drive.
3) On a level road, get the car to slightly above this speed, then put it in neutral.
4) As the road speed slowly decays past 62 mph, match the theoretical engine speed by operating the accelerator, (still in neutral).
5) Observe the 'calculated' gear ratio via PP2000 - (I think it will still say 5)
6) Carefully engage cruise - if it's going to work, it will increase the engine revs to try to maintain the road speed.

I was thinking taping the clutch switch up would work, but neutral's better I can do a slightly modified version of this on the way home tonight...

1) drive to 40mph in 5th
2) engage neutral
3) match revs to 5th
4) verify the cruise control still operates - should do
5) cancel cruise
6) hold revs at what I imagine 6th would be
7) see if cruise engages

No need to get the pp2000 out Mine is a petrol v6 with Bosch MP7.2 though...

The main thing to consider when swapping box is that the 6 speed is unlikely to be a 5 speed with an extra cog - all the ratios are likely to be different, so it will always have trouble calculating gear, or plain be unable to

I don't know if that will have any effect on the ECU's ability to run the engine properly in normal use though.