Automatic Transmission Problem

[BrentonW]

So I bought a 2008 3.0si Coupe 2 days ago with 91k miles. First 2 days were great, wasn’t having any issues besides a windshield washer pump which I replaced. Today, when I was driving for about 30 minutes, accelerating fairly hard, it started having problems when downshifting to accelerate. It started with being a bit jerky when downshifting, then started making strange noise after accelerating (almost like a grinding/slipping) then taking a second before it would actually downshift. I made this happen several times and then the transmission light came on and it locked into a gear and I couldn’t change it (4th I believe). I restarted the car and the light was gone and and not locked in 4th, but still making that noise and downshifting roughly on acceleration.

I took it to my local Indy mechanic who did the PPI to scan the codes but I forgot to have him give me the printout of the exact codes as we got to talking about what could be wrong. He cleared them and noted something about it mentioning something about 4/5th gear. He recommended a transmission service/flush, but the carfax shows this was done at 89k miles. He said I should call that BMW dealer to see what exactly was done, if it was a full flush or just a fill etc... he also noted it could be caused by other things such as a wheel speed sensor or a battery issue (it’s not the original battery in the car), maybe they didn’t add enough trans fluid. My current plan is to call the BMW dealer that did the trans service and see exactly what was done and take It from there, but I wanted to get some input/advice if anyone has any. I’m going to attempt to add a link to a video of what that sound was on acceleration before it shifts (this video was taken when it was stuck in 4th gear).

https://youtube.com/shorts/yNW2RjTkPM0?feature=share

Any input is greatly appreciated. I’m new to the forum and to Z4’s. Not super mechanical with cars but am wanting to learn and do as much as I can myself. Thanks so much!

[Rucky]

I would be thinking of taking it back after 2 days after purchase but sounds like you probably bought it privately - still worth talking to the vendor about it!
The fault codes are obviously the place to start - you really need to carry out the gearbox diagnosis again.
I would also contact BMW to find out why the car was brought to them for a gearbox oil check/change in the first instance at 89K.
Possibly the previous owner knew the gearbox was failing and sold it on before it got worse.

Going blind, before you pay another garage all you can do is drain down the gearbox, remove and replace the sump and filter then refill with the correct oil for your gearbox and give it another go.
The sump usually carries a sticker with the gearbox oil type but from memory its BMW ( Shell ) ATF M1375.4 for the 6 speed ZF.

There are plenty of posts on changing the gearbox oil - look for a positive DIY one.

I cant see the battery being responsible in any way, whilst it could / might be inked to a wheel speed sensor this would show up in a diagnostic check immediately. The fact that it is noisy implies an internal gearbox ssue rather than a control issue IMO.

IF you find significant debris/ finings on the sump magnets then you are looking at a gearbox repair / replacement .
I do hope not.

[BrentonW]

Just got off the phone with the BMW that did the trans service on it. Sounds like the previous owner was having the same issue, they didn't do a fluid flush, they replaced VANOS cylinders and inspected fluid and couldn't identify the issue and recommended a transmission replacement for $9,100
Any input? My thought would be to do a trans fluid flush, but BMW said it wouldn't make a difference. My indy mechanic did say to do a fluid flush though. No chance I'm spending $9k to get a trans replaced on a car a spent $15k on 2 days ago. Crazy. It doesn't slip or have any issues if I'm not accelerating hard, so I'm just gonna take it easy for now.

[Rucky]

Good luck with it. Suggest you buy a code reader if you are going to keep the car then at least you will be able to get an idea of faults before you need to visit a shop. I use a simple icarsoft but also bought inpa and loaded it to my laptop.
Well worth learning how to service yourself, oil, filters, brakes etc. Even a gbox oil change is not really difficult.
Hardest job is actually getting underneath the car to start with.
Enjoy they are great cars.

[mmm-five]

If you've got proof of an existing problem (as proved by the BMW service sheet), then I'd be going back to the seller (private or otherwise) for selling you a car with a known fault...you did ask them to declare any known faults, didn't you?

A full rebuild will cost you £2000 or $2600 - but you'd at least have some warranty.

You'll have the same/similar ZF 6HP gearbox (GA6HP19Z) as on lots of the less powerful (i.e. less than 400Nm) 1/3/5/6-series models of the same vintage...but the specific box may be slightly different to fit the Z4 chassis. RealOEM should allow you to do a cross-reference on other vehicles if you're considering buying a replacement, used gearbox. Used ones of these are available for less than £300/$450 over here.

The advice on BMW auto gearboxes seems to be that if they have never been opened, and have never caused problems, then leave them well alone.

The issues tend to accelerate once a worn box has its fluid, filters, controllers replaced during a major gearbox service, and then it's 50/50 whether you'll get a further 100,000 miles or 10,000 miles out of it.

[BrentonW]

If you've got proof of an existing problem (as proved by the BMW service sheet), then I'd be going back to the seller (private or otherwise) for selling you a car with a known fault...you did ask them to declare any known faults, didn't you?

Yes, but they say they didn’t know anything of it and that I bought it as is (private dealer) my guess is the previous owner didn’t disclose the info when he sold and no one at the dealer drove it hard enough to discover the issue.

A full rebuild will cost you £2000 or $2600 - but you'd at least have some warranty.

BMW quoted me $9k. Is that way over what it should be? Should I talk to a transmission shop instead? Is a rebuild the same thing as a replacement?

[mmm-five]

Sorry, I'm getting a bit lost.

Was it a PRIVATE sale or a DEALER/TRADER sale? It can't be PRIVATE + DEALER! (or are you using 'dealer' to mean a BMW Franchise, vs Private Dealer as an independent trader?)

If it was a private sale, from a non-trade seller, then what they tell you/claim in person & the advert forms part of the sale agreement between two private individuals. If they've knowingly sold it as 'good condition' when they know it's got gearbox issues then you need to take it up with them or go to Judge Judy.

If it's a dealer/trader sale (which it sounds like it is, and they say the previous owner didn't tell them about the fault), then you have your consumer rights against the dealer/trader...which should include some sort of warranty at the price you've paid. So go via that route. Don't you have 'lemon laws' which mean you can return the car & get a refund?

Yes, a brand new gearbox could be $9000...from BMW (it's £6000 in the UK)...but you may be able to find a good, used one on ebay/breaker and have it fitted for a 1/10th of that new gearbox....or a genuine one from somewhere like Turner Motorsport for $6000.

But that's the worst case...only after you've exhausted your options above, based on where you bought it.

BTW, if Carfax says the flush/service was done, yet there's no history of it in your paperwork or on BMW's systems, then where was it done? If the previous owner knew it was faulty, and BMW refused to do the service, then they must have taken it elsewhere to try to rectify the issue - so they can't claim they knew nothing about it.

[BrentonW]

Was it a PRIVATE sale or a DEALER/TRADER sale?

Sorry, I meant an independent non-BMW dealer. I called them today, he told me I bought it as-is and there’s really nothing they can do, which I figured. I’ll look into lemon laws/other options.

Carfax says the BMW did the flush but on the phone they said they didn’t. It was taken to another dealer later which I’m going to call tomorrow to get some more info.

[firebobby]

Hi, welcome to the forum and I'm sorry to read this story.
You bought it from a company/car dealer/garage for 15k, right ? Then you must have some come back from that business.
I googled your issues and found this

(Deceptive car ads or dealers — File a complaint with your state consumer protection agency and the Federal Trade Commission)

I would get in touch with someone in the legal system, very quickly, you must have protection as a consumer.
Don't take it laying down.

[Chippie]

I agree with firebobby, the dealer is just trying to fob you off in the hope you will go away, keep pursuing this, at the very least you should be able to return the car for a refund

[DPG]

In the Uk we’d reject it and ask the dealer for a full refund.

Not sure if the laws are the same in the US but I’d have thought you would have some protection (unless it was a trade /‘ sold as seen sale)

[BrentonW]

I purchased in Alabama, and to my understanding there’s a law that says that when purchasing a used car you’re purchasing it “as is” and that it’s my responsibility to look for any faults before purchasing. I do remember signing a paper saying I was purchasing the vehicle “as is”. So I’m not sure how much legal ground I’d have to stand on.

I think my next course of action will be to get an opinion from 1 or 2 other mechanics and see if they believe the tranny needs replaced. If so, hopefully I’ll take it easy on her for a while and she’ll be okay until I can have that done. I’m pretty bummed that I got screwed like this, but I’m trying to stay positive. The car was on consignment at the dealer, so I truly believe the dealer didn’t know of the issues, but the guy selling the car definitely did and didn’t disclose it to the dealer he was selling it through.

[caver69]

Brenton W - I bought an “as is” ‘08 3.0i last year w similar occasional issues that got worse. Finally left me in neutral in a passing lane with flashing tranny light.
Lots of research and an independent BMW specialist fixed my issue for $1100 incl parts. He replaced the valve body to transmission tubular seals (my push based on research), all six solenoids (one coded, others cheap insurance), flush and fill w new pan/filter. All smooth; no slips, no lights and no bump on 2-1 downshift at stops.
Hope yours turned out as simple (and cheap).