SMG issues: hesitation/stutter, missing gears

[big,JON]

Hey guys,

My SMG has started playing up recently. I first noticed it changing up to 3rd gear where it would flash '3' on the cluster but wouldn't go into gear. This was followed by a fairly savage hesitation changing into 3rd and had since developed into 2nd and 3rd and doesn't seem to coincide with changing up gears like I thought it did previously.

Today, it did the normal hesitation/stutter in 2nd but when I pulled up for 3rd it gave me a handful of neutrals and then decided 6th gear was good as well as giving me the transmission warning on the cluster. From that point I could only change down and not up. I had to stop at a set of lights and it reset to 1st, upon taking off it was fine in 1st but skipped 2nd and went straight to 3rd. It continued to keep skipping 2nd on up and down changes until I turned the car off then on and off went back to normal.

Video of issues here: https://youtu.be/nsl9_Zmuros

My initial research is leading me to think it's the gear position sensor, but I'm open to ideas, thoughts or theories. I haven't pulled codes yet because INPA was being a dick, hopefully I'll sort that out tomorrow.

Cheers!

[oceansize]

Without knowing the codes and assuming your pump seals, solenoids, motor, and accumulator are healthy then compression springs or GPS.

1. Pump prime time in seconds (from cold)?
2. Codes?
3. Accumulator test pass/fail?
4. At 145k any other known SMG service history?
5. Time elapsed for pressure to come down from max while motor running?

[Andy2424]

I do not know what it is called in English aisle detection sensor in germen Gangerkenungssensor!

Replace gear recognition sensor
Check wiring harness and plug connections

[sapote]

If gear recognition sensor or GPS detent pin (roller really) is bad causing 2nd gear shifting issue, then 4th and 6th should have the same problem as the shifting rod moving forward to engage 2nd and all the even gears.
I think you need to remove and check the detent pins (sleeves or balls) on the rear upper right side of the tranny as in pic, but don't pull out the 2 interlocking pins as this can lead to a nightmare.

[oceansize]

OP, the sleeves and rollers that sapote is referencing are in the video I posted here

[big,JON]

Without knowing the codes and assuming your pump seals, solenoids, motor, and accumulator are healthy then compression springs or GPS.

1. Pump prime time in seconds (from cold)?
2. Codes?
3. Accumulator test pass/fail?
4. At 145k any other known SMG service history?
5. Time elapsed for pressure to come down from max while motor running?

1. 7 seconds
2. Still working on this
3. 7 second prime, 11 shifts cold then 5 shifts and 3.5-4 second pump run time when at operating temp
4. No history of SMG errors or parts failures/replacement
5. Haven't been able to check this

If gear recognition sensor or GPS detent pin (roller really) is bad causing 2nd gear shifting issue, then 4th and 6th should have the same problem as the shifting rod moving forward to engage 2nd and all the even gears.
I think you need to remove and check the detent pins (sleeves or balls) on the rear upper right side of the tranny as in pic, but don't pull out the 2 interlocking pins as this can lead to a nightmare.

4th and 6th shift fine and haven't had the hesitation, the issue has been mostly in 3rd and more recently in 2nd

[big,JON]

OP, the sleeves and rollers that sapote is referencing are in the video I posted here

This is an excellent video, just to confirm that you're referring to the #9 and #15 compression springs? It seems like there is a heap of stuff in the kit that sapote linked/provided that won't be relevant to me?

[sapote]

Today, it did the normal hesitation/stutter in 2nd but when I pulled up for 3rd it gave me a handful of neutrals and then decided 6th gear was good as well as giving me the transmission warning on the cluster..

Cheers!

It seems the tail shifter actuator having problem of finding the gates (1/2, 3/4, ...) this means you might want to look for another actuator, but remove and check the 3 detent pin I suggested before as it is cheaper. The original stock parts are balls and springs and the new updated parts are sleeves and springs. After opened up the cover, there are 5 holes with things inside, but you only need to pull spring/ball (or spring/sleeve) from the odd number holes (counting from the end) and don't touch the two even number holes (these are holding the interlocking pins to prevent engaging 2 gears at one time). If they are balls then maybe it is the root cause (they can cock inside and causing high resistance to motion), as they need to be updated to sleeves (longer sleeve has less chance of cocked up in the cylinder) and springs. Also check the roller pin under the GPS on the left hand side, for good condition or broken.

[big,JON]

Thanks sapote, much appreciated.

I finally got around to pulling codes today, I've attached a picture of the results. From my research thus far, it seems like compression springs / detents are the culprit?

Cheers

[big,JON]

And finally got INPA kinda sorted (except for the language) so here's a video of SMG parameters at idle

[oceansize]

Your hydraulic pump looks to be in good health from the time to first prime to pressure decay when shifting and at idle. The SMG error code hex 31 is decimal 49 which points to the gear position sensor.

So in the end it is likely the gear position sensor or springs. Unfortunately I don't know how you can definitively identify which is the root cause. The SMG actuator does fail but it that is more rare.

[sapote]

Your hydraulic pump looks to be in good health from the time to first prime to pressure decay when shifting and at idle. The SMG error code hex 31 is decimal 49 which points to the gear position sensor.

So in the end it is likely the gear position sensor or springs. Unfortunately I don't know how you can definitively identify which is the root cause. The SMG actuator does fail but it that is more rare.

It's easier to remove the GPS plug or bolt, then pull out the pin with the roller and check its condition. If damaged then it is one of the root cause.

[big,JON]

Your hydraulic pump looks to be in good health from the time to first prime to pressure decay when shifting and at idle. The SMG error code hex 31 is decimal 49 which points to the gear position sensor.
So in the end it is likely the gear position sensor or springs. Unfortunately I don't know how you can definitively identify which is the root cause. The SMG actuator does fail but it that is more rare.

It seems that both have a similar process for replacement so I'll probably do both and the trans mounts while I'm in there.

Thank you to everyone who offered advice!

[sapote]

So in the end it is likely the gear position sensor or springs. Unfortunately I don't know how you can definitively identify which is the root cause. The SMG actuator does fail but it that is more rare.

Let's assume it is the detent spring load ball is the root cause, and it is 1st/2nd unit is bad (ball jammed causing very hard to internal shift rod to engage 1st or 2nd gear), then the symptom should help to narrow down.
* If we shift fast enough to skip 1st/2nd and engage 3rd or 4th, or 5th , or 6th with no issue, then this means the GPS pin is OK,
* If All of the odd gears have issue shifting but not the others, or vice versa, then the GPS pin is likely bad.

[big,JON]

Let's assume it is the detent spring load ball is the root cause, and it is 1st/2nd unit is bad (ball jammed causing very hard to internal shift rod to engage 1st or 2nd gear), then the symptom should help to narrow down.
* If we shift fast enough to skip 1st/2nd and engage 3rd or 4th, or 5th , or 6th with no issue, then this means the GPS pin is OK,
* If All of the odd gears have issue shifting but not the others, or vice versa, then the GPS pin is likely bad.

The only issue changing gears is 2nd into 3rd, all other shifts have been fine - changing up or down, there's not been an issue