[Anatomius]

Hey Guys

This weekend i tried to installed a differnatial (3.08) on my N55 DCT. Just wanna try it, to see wheter it works

The ratio is now just perfect, but the ECU is not accepting the speed varriance. First try the shift behaviour was a mess, shifting a couple of times made everything better but still not good, as the actual RPMs arent fitting to the requested.

Does somebody now, wether the speed-calibration can be reseted on these car to make the shorter final drive run correctly

Thansk for help

[I35it]

interested to know as well!

[Unklejoe]

Curious as well. I'm in a slightly different position with my 6AT (I'm interested in swapping the 3.08 from a manual transmission car in), but the solution may be the same.

[snaimpally]

Not sure if this helps but I had an Mfactory LSD with a 3.46 final ratio installed on my 6MT and it worked fine after the diff swap. I didn't have to do anything else after getting the diff swapped.

[Unklejoe]

Originally Posted by snaimpally

Not sure if this helps but I had an Mfactory LSD with a 3.46 final ratio installed on my 6MT and it worked fine after the diff swap. I didn't have to do anything else after getting the diff swapped.

Makes sense. I'm curious if the 6AT will shift properly after though, since vehicle speed is one of the parameters. I actually expected it would since the car uses the ABS to determine speed, which is why I'm surprised it's causing issues with the DCT.

[Anatomius]

MT will work, no issue.. I changed the final drive ratio already on a car, absolutely no problem...

DCT is using the vehicle speed as a base reference, this makes it very difficult to adapt the 3.08 ratio. The problem is to get to the ECU tables were the ratio is stored, almost impossible for N55, it could be that N54 can be changed and it works. Unfortunately my one is N55. By logic the ECU should have included a tolerance, just bought a 2.81 unit, lets see whether it works

AT i do not have any experience...

[bjf66]

Hello, any updates on your gear swap?

I'm curious because I have a N54 DCT and am contemplating going to 3.08. You mentioned that it is easier to do this on N54, do you happen to know what is required for the proper modifications to the software?

It seems to me that there just might be a bit of trouble to get it working perfectly, and maybe I should just stick with 2.56.

Also, which LSD did you get?

[Ozzie335i]

Originally Posted by snaimpally

Not sure if this helps but I had an Mfactory LSD with a 3.46 final ratio installed on my 6MT and it worked fine after the diff swap. I didn't have to do anything else after getting the diff swapped.

Same setup and result as snaim. I looked into this before the ratio swap. Was told that the speed is done by the tire pressure system transducers, so a gear change on the tranny is not needed like hot rods of yesteryear to make the speedo register properly. I like the change and would do it again. It better keeps the turbo in the ready to go rpms.

[Unklejoe]

Originally Posted by Ozzie335i

Same setup and result as snaim. I looked into this before the ratio swap. Was told that the speed is done by the tire pressure system transducers, so a gear change on the tranny is not needed like hot rods of yesteryear to make the speedo register properly. I like the change and would do it again. It better keeps the turbo in the ready to go rpms.

Speed is more likely calculated by the ABS sensors on the wheel rather than the tire pressure sensors.

This is based on the fact that the speedometer still works when the TPM sensors are missing.

[katsooba]

hey Anatomius,

if you replaced the FD on the DCT it means you have also took out your pinion

what tool did you use to open the BIG 12 POINT nut securing the pinion in the case?

[MFactory]

Originally Posted by katsooba

hey Anatomius,

if you replaced the FD on the DCT it means you have also took out your pinion

what tool did you use to open the BIG 12 POINT nut securing the pinion in the case?

Around $400 from BMW, or you can use this aftermarket tool: http://www.bearingkits.co.uk/BMW-Dif...-tool/1028.htm

[katsooba]

MFactory,

actually the same tool costs less from bmw , its just that the entire toolset costs about 600$



but after you remove the diff from the car it is much harder working on that large nut,
i have found that using a 64mm 12 pt socket with a 3/4" drive and a huge impact wrench did the job for me, i just secured the pinion from inside the case, and took my time unscrewing\screwing the nut.
that nut had held on there untill the last turn! that is some locktite they used on it! heh

the only thing i was missing was a crush sleeve, which i reused the old one, and unfortunaly have some mild knock when going gas on/gas off/gas on at high speeds.

but i plan to order the new MFactory solid diff sleeve to fix that issue, i just think about redoing to pinion and i start to

[juld0zer]

DCT diff has an inserted type prop shaft. You unscrew the 6 sided nut then pull the shaft away to disconnect it.
You only need to disturb the pinion nut if you need to replace the seal or mess around inside. BMW has another special tool which fits onto the splines of the pinion and you brace that against the ground whilst wrestling the 12pt bigger nut off - which as you found out is held on with green threadlock. Very strong stuff which will indees fight you right til the end.

Before disturbing this nut, you must mark the nut relative to the pinion and measure the threaded section using a depth guage so you have two points of reference to restore the original preload.