During my recent clutch replacement job, I decided to replace my transmission's detent compression springs and locking pins. My transmission had 174,668 miles on it at the time of replacement, so the hardware was likely original and needed refreshing. All hardware removed was still functional and intact. This is not always the case, as the compression springs can break over time. After replacing all detent springs and pins, gear selection feels more precise and solid. Given that the information I researched and used was scattered, I figured this thread might help those considering tackling the job or wanting to learn more. Much thanks to George Hill for the advice and tidbits he provided in another thread.
List of resources I referenced for this DIY:
This is the RealOEM diagram and parts list for reference:
Since I was replacing the clutch, I removed the transmission from the car. This provided ample space to access all the detent springs and locking pins. I highly recommend this for ease of access, although I did read of others replacing these parts with the transmission still installed.
The detent spring and locking pins (sleeves) at the rear and right side (if looking from the rear) of the transmission have a metal retention cap held secure by two 10mm bolts. This is #17 if referencing the RealOEM diagram. Remove these bolts to access the springs. Use a small magnet to remove the detent springs and locking pins from holes 1, 3, and 5, leaving the larger pins in holes 2 and 4 (do not remove these pins). Replace the three detent springs and locking pins from the kit. A small amount of gear oil or similar lubricant is recommended on the parts before inserting. Install the new retention cap, 10mm bolts, and washers. Tighten down in an alternating pattern until snug. Torque to 10 Nm.
The detent spring and ball for parts #14, #15, and #16 in the RealOEM diagram are located at the rear and left side (if looking from the rear) of the transmission. The #16 locking device requires a 19mm socket to remove. Use a small magnet as necessary to remove the detent spring and ball from the slot. Replace them with the new detent spring and ball. A small amount of gear oil or similar lubricant is recommended on the parts before inserting. Add thread sealant to the locking device threads before replacing. Tighten until hand-tight (snug). Other DIYers suggest a torque value of 10 Nm.
The detent spring, thrust pin, and locking pin for parts #8, #9, and #10 in the RealOEM diagram are located behind the gear position switch (GPS). Before complete removal, the GPS cable connector needs to be unclipped and removed from its bracket; otherwise, the unscrewing action of the GPS will bind the cable and potentially damage it. A 22mm wrench is needed to remove the GPS from the transmission. Once removed, use a small magnet to retrieve the detent spring, thrust pin, and locking pin. Note the orientation of the locking pin when replacing. The roller needs to be in the vertical position (see picture for reference). A small amount of gear oil or similar lubricant is recommended on the parts before inserting. The assembly should slide into position without resistance. Add thread sealant to the GPS threads before replacing. Tighten until hand-tight (snug). Other DIYers suggest a torque value of 10 Nm.
Write-up IN PROGRESS
List of resources I referenced for this DIY:
- Getrag 420G secrets unveiled video: https://youtu.be/7iW1ECcfcm4?si=BOgYV4sehb62lr5Y
- Getrag 420G detent repair video: https://youtu.be/oDnoNxf_h2U?si=TFFT_JIfMWBaWtKg
- Getrag 420G compression springs thread: https://nam3forum.com/forums/forum/m...ession-springs
- Getrag 420G detent springs repair thread: https://nam3forum.com/forums/forum/m...nt-pins-repair
- Getrag 420G detent spring bolt tightening torque specs: https://nam3forum.com/forums/forum/m...ng-torque-spec
- Getrag 420G hard to get into reverse thread: https://forums.m3cutters.co.uk/threa...solved.250562/
- Getrag 420G shift pin replacement thread: https://www.m5board.com/threads/shif...t-info.491089/
- What else to consider when replacing clutch thread: https://nam3forum.com/forums/forum/m...i-do-my-clutch
- RealOEM parts list: https://www.realoem.com/bmw/enUS/sho...diagId=23_0887
This is the RealOEM diagram and parts list for reference:
Since I was replacing the clutch, I removed the transmission from the car. This provided ample space to access all the detent springs and locking pins. I highly recommend this for ease of access, although I did read of others replacing these parts with the transmission still installed.
The detent spring and locking pins (sleeves) at the rear and right side (if looking from the rear) of the transmission have a metal retention cap held secure by two 10mm bolts. This is #17 if referencing the RealOEM diagram. Remove these bolts to access the springs. Use a small magnet to remove the detent springs and locking pins from holes 1, 3, and 5, leaving the larger pins in holes 2 and 4 (do not remove these pins). Replace the three detent springs and locking pins from the kit. A small amount of gear oil or similar lubricant is recommended on the parts before inserting. Install the new retention cap, 10mm bolts, and washers. Tighten down in an alternating pattern until snug. Torque to 10 Nm.
The detent spring and ball for parts #14, #15, and #16 in the RealOEM diagram are located at the rear and left side (if looking from the rear) of the transmission. The #16 locking device requires a 19mm socket to remove. Use a small magnet as necessary to remove the detent spring and ball from the slot. Replace them with the new detent spring and ball. A small amount of gear oil or similar lubricant is recommended on the parts before inserting. Add thread sealant to the locking device threads before replacing. Tighten until hand-tight (snug). Other DIYers suggest a torque value of 10 Nm.
The detent spring, thrust pin, and locking pin for parts #8, #9, and #10 in the RealOEM diagram are located behind the gear position switch (GPS). Before complete removal, the GPS cable connector needs to be unclipped and removed from its bracket; otherwise, the unscrewing action of the GPS will bind the cable and potentially damage it. A 22mm wrench is needed to remove the GPS from the transmission. Once removed, use a small magnet to retrieve the detent spring, thrust pin, and locking pin. Note the orientation of the locking pin when replacing. The roller needs to be in the vertical position (see picture for reference). A small amount of gear oil or similar lubricant is recommended on the parts before inserting. The assembly should slide into position without resistance. Add thread sealant to the GPS threads before replacing. Tighten until hand-tight (snug). Other DIYers suggest a torque value of 10 Nm.
Write-up IN PROGRESS
Attached Files