Automatic transmission problem

SqerrNipz

SqerrNipz

Member
 Oxford
On my way to work this evening my Z4 developed a bit of an issue when changing gear. I was stuck in traffic and when I went to pull away the car lurched forward, almost like I'd let my foot off the clutch too rapidly in a manual. From then on, the gear changes were very off, almost going to the redline before changing gear at some points and then rapidly dropping down several gears, feeling like someone had just driven into the back of me!

I've never had any real issues prior to this and allegedly the box was serviced and transmission oil changed in 2020 with the previous owner. The only problem I've had before is the transmission light illuminating occasionally on first starting. A diagnostic check showed this to be the 'selector switch'. This has only happened about 3 times in 2 years though, has righted itself on turning the car off and on and never any issues with driving it.

I will plug Carly in when I got home, but just wondered if anyone had a similar issue before?
 
Rockhopper said:
Change the selector switch first, its a known problem and will only get worse.
Click to expand...

I concur!! Do this ^^.

I have a small fault with my auto also but it only occurs when the plug on the gearbox gets wet and the ECU doesn't know what speed and gear the car is in do throws that light. Your issue could also be electrical related if you have a faulty selector switch.

Other thing to check is to see if you have any leaks around the transmission cooler up front on the radiator, mine has a small weep and looses a little fluid. You dont want to run out of oil in your auto gearbox or you will cook all of your clutches.

What did the code reader say when you plugged it in?
 
Usel said:
Sorry I can't help with this but how was the trip home from work?
Click to expand...

Better than the journey in, thanks mate. Road closures meant a huge detour and gridlock traffic, plus the Z4 having a meltdown! Not a great start to the day. Typically it behaved impeccably on the run home! :roll: No kangarooing but I was taking it very steady. I should have known something would happen after I bought it some nice new brakes… :cry:
 
Rockhopper said:
Change the selector switch first, its a known problem and will only get worse.
Click to expand...

I’ve been putting it off, thinking it was just an intermittent issue, but obviously a lesson there! As luck would have it I’ve found an automatic transmission expert on an industrial estate about 3 minutes from me! I’m gonna get it booked in for a check.
 
Matty_Z4 said:
Rockhopper said:
Change the selector switch first, its a known problem and will only get worse.
Click to expand...

I concur!! Do this ^^.

I have a small fault with my auto also but it only occurs when the plug on the gearbox gets wet and the ECU doesn't know what speed and gear the car is in do throws that light. Your issue could also be electrical related if you have a faulty selector switch.

Other thing to check is to see if you have any leaks around the transmission cooler up front on the radiator, mine has a small weep and looses a little fluid. You dont want to run out of oil in your auto gearbox or you will cook all of your clutches.

What did the code reader say when you plugged it in?
Click to expand...

Code reader came up with -

000038 Hydraulic pressure / Symptom GLUE / Duty hydraulic unit

000039 CEMENT monitoring 2/3 / Abuse hydraulic unit / FGR / Sensor lateral acceleration

00003C Transmission switch

Some Googling required methinks… :?
 
SqerrNipz said:
Matty_Z4 said:
Rockhopper said:
Change the selector switch first, its a known problem and will only get worse.
Click to expand...

I concur!! Do this ^^.

I have a small fault with my auto also but it only occurs when the plug on the gearbox gets wet and the ECU doesn't know what speed and gear the car is in do throws that light. Your issue could also be electrical related if you have a faulty selector switch.

Other thing to check is to see if you have any leaks around the transmission cooler up front on the radiator, mine has a small weep and looses a little fluid. You dont want to run out of oil in your auto gearbox or you will cook all of your clutches.

What did the code reader say when you plugged it in?
Click to expand...

Code reader came up with -

000038 Hydraulic pressure / Symptom GLUE / Duty hydraulic unit

000039 CEMENT monitoring 2/3 / Abuse hydraulic unit / FGR / Sensor lateral acceleration

00003C Transmission switch

Some Googling required methinks… :?
Click to expand...


I should probably leave it to someone with a little more experiance to answer but these are where I would be looking based on those faults.

1) Replace the faulty selector as suggested by Rockhopper
2) Check for leaks around the drain pan and on the transmission coolers.
3) Check fluid level and top up as required.
4) If all else fails Panic and ask a transmission specialist to check/test/rebuild the mechatronic (Valve Body) unit.

Step 4 is probably quite expensive so do everything else first as the Valve Body rarely goes wrong unless the channels are clogged for some reason.
 
How many miles had it done when the fluid was changed? Perceived wisdom is on older boxes that have never had it done leave well alone.
 
Rockhopper said:
How many miles had it done when the fluid was changed? Perceived wisdom is on older boxes that have never had it done leave well alone.
Click to expand...

A tickle below 100k now and I think it was changed around 97k? Not much information on the invoice, literally just says 'gearbox fluid changed' for the princely sum of £55...

I have read varying schools of thought around the lifetime fluid', that the 'lifetime' can be anything from 60-100k. No previous issues though and was fine on the drive home last night. I did do a 'soft reset' procedure I read online, however I don't know if it's even relevant on transmissions this old. May be more of a placebo in my case!
 
bcolins said:
What are "cog the transmission" and "The clocks"
Click to expand...

An orange or yellow cog symbol between the rev counter and the speedo.

If you don't have that then this isn't your problem.
 
Thanks. Don't have that. My transmission works as it should in Automatic mode,....but I can only change gears manually in the first 30 seconds or so after start up,...then no manual mode from either the center console gear selector in the manual mode, or paddle shifters.
 
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