Gangplank

My harsh 2-1 downshift aka "the coasting jolt" is back. :-(

Symptoms I have:

ENGINE COLD: (no warm up): delays the gear change from 1st to 2nd ONE TIME ONLY

ENGINE WARMS: No problem & all down and up shifts are good

ENGINE WARMER (15-20 min city driving or frequent short errands): I feel a "coasting jolt" when coming to a stop. It's like playing bumper cars w/ your big brother in the car behind you.

ENGINE WARMER (highway driving): NO problems at all, I could drive for hours with no issues UNTIL I get to a stop then get the hard down shift "coasting jolt" from 2nd to 1st.

The only other symptom I get is every once in a while when I shift from REVERSE to DRIVE the car will lurch forward. I've almost hit something 2x because of it. Might be unrelated. (Might be my floor mat creeping)

Possible solutions I'm considering:

1) new giubo disc. $
2) replace solenoids (need to find a shop willing to do it?). $$
3) replace mechatronics unit $$$
4) new/rebuilt transmission $,$$$

Of course #4 will fix the problem for a good 70,000+ miles but the cost is more than I can stomach right now.

I'm thinking of replacing the guibo disc & solenoids if I can find a shop that will do it. If not then the whole mechatronics unit.

sanjsanj

wtf is a giubo disc?

Anyway, you're describing exactly what I had (very delayed 1-2 shift when cold, and jolts when coming to a stop). The delayed 1-2 shift when cold (until at least the engine temp was 45 degrees) came in conjunction with my torque convertor wearing out (wobbly revs at steady speed on the motorway).

Long story short I had the torque convertor changed, oil changed (obviously) and gearbox software updated. This makes the gearox shift down at 10mph instead of (i think it used to be) 5mph, which has solved the problem. It's not an actual fix, it's a workaround bmw figured out to stop the jolt without having to rebuild everyone's transmissions.

The proper solution is to change the solenoids / mechatronics.

It's likely my box was low on oil, as are most cars older than 5 years, so this could have also had an effect on improving the symptoms too. You could try an oil change/level check and software update first, this would be the cheapest route. I've read some reports that the very latest gearbox software update brings the jolt back, so the right update is apparently one older than the very latest one? Don't quote me on that though, I know someone who had a whole software update on his car last week (took 1.5 days!) and he said the 2-1 jolt has gone.


Jaguar S-Type ZF Gearbox Lurch fault

Gangplank

I already changed the pan & fluid + did the most recent update. It fixed it for a bit but it came back.

I only have the 2-1 jolt. My RPMs hold steady driving on freeway far as I've noticed.

I'm thinking of doing a full mechatronics rebuild which is $1000 installed at a local shop + the guibo disc (u-joint disc?).

How much was the torque converter? New or rebuilt?

pcy

guibo is another name for flex disc that's mounted on the ends of driveshaft where the driveshaft mates with trans/trasnfercase/diff.

sanjsanj

Yeah, I do still detect the 2-1 jerk, but it's ever so sight since you're not at a standstill when it shifts. I have to stop really really abruptly to feel the jerk.

The TC was reconditioned with uprated parts, costs £230 for that to be done with a 48 hour turn around. There are faulty clutch packs in the TCs which cause premature wear, the company that does them over here do hundreds each week, it's a common problem for which they've developed an in house solution to strengthen.

You could do full mechatronics, or just the solenoids. Definitely get oil level checked out first though, highly likely it's low on oil.

Gangplank

I just had the pan and oil changed. Good Indy shop so it shouldn't be low. I'll get it checked tho.

Had the software updated and adaptations reset. That worked for a month then it came back. :-)

I found a local Indy that can get the mechatronics rebuilt. Total cost around $800-1000 installed which is cleaned, new solenoids, etc. thinking I'll do that + price the new torque converter.