E46 M3 CSL 4th Gear SMG Problem......Any Ideas.

[Giles240]

I have a 2003 E46 M3 CSL trackday car, mileage is 13,000 but alot of that has been on track.

The car starts and runs fine, selects 1st, 2nd no problem. When driving around slowly all gears shift ok, but when driving hard i.e flatshifitng or changing gear at higher revs, it will not find 4th on the up change, resulting in either a bit of grinding noise then lots of revs as the gear has not engaged or more usually 4th just flashes on the dash while it takes ages to select the gear by which time the revs have dropped off. All other shifts seem fine, and when driving around at low speed 4th appears fine.

I originally thought it might be the box so replaced it with a second hand SMG box and having a clutch fitted at the same time, the salmon really was changed as was the SMG fluid.....nothing seems to have made a difference and the SMG light does not come on....does this mean no error codes have been lodged..??

Any ideas would be very much appreciated......

[Mr Bimmer]

That sounds like a classic case of a broken compression spring in the gearbox casing. The fact that you've changed the box might mean that both boxes have a broken spring. Do you still have your old box to check them?

Parts 6 and 9

http://www.realoem.com/bmw/showparts.do?model=BL96...

[Giles240]

Mr Bimmer said:

That sounds like a classic case of a broken compression spring in the gearbox casing. The fact that you've changed the box might mean that both boxes have a broken spring. Do you still have your old box to check them?

Parts 6 and 9

http://www.realoem.com/bmw/showparts.do?model=BL96...

Thanks I still have the old box so will check, have many people had the spring problem?

I assume its gearbox out to be able to check it..???

[Mr Bimmer]

Giles240 said:

Thanks I still have the old box so will check, have many people had the spring problem?

I assume its gearbox out to be able to check it..???

BMW usually just replace the box. It's far easier for them to charge £5k for a box than check a £2 spring.

It's happened to a lot of M3s, but not too many people know about the real problem. You can fit new springs in the fitted box, but it needs dropping. Best to practice on your spare.

Keep me informed as the whether it's broken

[Giles240]

Mr Bimmer said:

BMW usually just replace the box. It's far easier for them to charge £5k for a box than check a £2 spring.

It's happened to a lot of M3s, but not too many people know about the real problem. You can fit new springs in the fitted box, but it needs dropping. Best to practice on your spare.

Keep me informed as the whether it's broken

Well Mr Bimmer, unfortunately having dropped the gearbox down the spring was intact. As a result we bled the SMG system, set all the gear shift stuff on the Autologic (all fine, and no fault codes present at all) The SMG relay was also changed as for some reason the car had an ABS (orange) relay fitted......

Took it to Woodbridge on a Javelin trackday and the car was great, apart from 4th gear It will go in with a big lift 90% of the time, but at full revs or with the foot nailed, it just will not go in......given still no fault codes, all other shifts are perfect, no SMG light coming on.....do you think I am correct to assume that maybe 4th gear synchro is shagged...and change the box.....