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GM auto box issues, far from home edition

720 Views 26 Replies 9 Participants Last post by  Sapote
I'm in Oregon visiting my mom, getting ready to head home and two days ago had a ! gear indicator pop up and it went into limp mode. This isn't that uncommon, as it's been happening every once in a while for some time and it usually clears after shutting off for a minute and restarting. I haven't been super concerned with it as I have a 6MT swap waiting to go in the car ('03 325i wagon, MS45.1, GM automatic). This time though, after limping me to an offramp and then around the corner, it revved like mad and had almost no drive to get around the second corner and off the main street. Got it into a parking lot and called AAA and got it back to mom's house. Since then, it's been very intermittent - sometimes having reverse but no forward, sometimes nothing, and sometimes seeming fine - leading me to believe that it's an electrical issue. Of course my K+DCAN cable is 2700mi away.

Ordered a cable and got to play with it today.
INPA showed no notable stored faults - only two, which would have coincided with previous mentioned events back at home - and I had drive, so I cleared the faults and took it for a test drive, where it failed on me less than half a mile away. Get it back and check for codes and there are none, but I start getting repeated "lost connection with TCM" faults, which kind of leads me to believe a failed TCM. Thoughts?

Seems like a fault between the TCM and trans would still allow comms between the TCM and the OBD II port and connection with INPA, right?
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I'm hoping to get this fixed enough to make the drive home with as small an investment as possible, given that I have a complete 6MT swap once I get there. Would super suck to have to rebuild a trans just to yank it back out in less than 3k miles
Even with no electronic control you should still get R and D. Those are controlled hydraulically with the manual selector valve. Any signs of leakage? Could be low fluid and need a topup.

Have you tried running with the TCM disconnected completely?

Manual selected D will be 4th gear but w no converter lockup. Shouldn’t be too bad if you’re cruising on the highway
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Even with no electronic control you should still get R and D. Those are controlled hydraulically with the manual selector valve. Any signs of leakage? Could be low fluid and need a topup.

Have you tried running with the TCM disconnected completely?
Have not.

No major leaks, just the usual minor Bimmer puddles and did the o-ring and bronze bearing trick to slow the drip at the selector shaft seal.
Low fluid should exhibit more when cold rather than after you've been rolling a while and the fluid expands, no?
Have not.

No major leaks, just the usual minor Bimmer puddles and did the o-ring and bronze bearing trick to slow the drip at the selector shaft seal.
Low fluid should exhibit more when cold rather than after you've been rolling a while and the fluid expands, no?
You’d think so but the one time I had low fluid was worse when warm (but it was a ZF box). Things work mysteriously sometimes…

Worth checking the level and dumping a quart of cheap dex 6 in
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In answer to the "have you tried it with TCM disconnected?" question - car won't even start without seeing the neutral safety switch, so I can't answer anything that way.

Got the ramps out to put the front of the car up so that I can check fluid and had drive. Got it up to the top (I thought) only to find myself only halfway up. Put car back in drive and proceed to roll backwards. D'oh!
Will try again in a little bit, otherwise may have to wait until my brother gets off of work so that all three of us can push it up, then jack up the rear.
Seems like a fault between the TCM and trans would still allow comms between the TCM and the OBD II port and connection with INPA, right?
Can you access TCM (to read the codes) with INPA? If not then there is issue with the can-bus from DME to TCM.
unfortunately it doesn't seem like electrical issue as it is then the issue should appear all the time with a bad connection.
You’d think so but the one time I had low fluid was worse when warm (but it was a ZF box). Things work mysteriously sometimes…

Worth checking the level and dumping a quart of cheap dex 6 in
Fwiw, when I underfilled my GM transmission once, things got worse the more I drove also. Going up steep hills made it worse, and I was about 35 miles away when I realized I had to head home. No limp mode though, and no gear cog on the dash.
Put it u[p in the air to check fluid level, which was fine. Because I was under there with the car running I was able to hear some pretty bad noises coming from the box, which gave me a sinking feeling. Drained fluid - very dark given that it was changed somewhat recently, and could see some sparkles in it - and dropped the pan. A prospector would be thrilled to see so much metal in their pan!

Looks like it's toast.
:cry:
Can you swap in a good used AT sourced locally?
Can you swap in a good used AT sourced locally?
That's the plan now.
I got on car-part and found the yard nearby has four in stock for $200-250, so I've got a bunch of work ahead of me but won't be out much cash since I should be able to resell a working automatic for about that when I finally do my swap.

I had planned on leaving this morning, so I'm actually pretty lucky that this happened now and not somewhere in Wyoming with a trailer behind the car.
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Must be clutch/brake set wear down to metal, not the gears.
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Must be clutch/brake set wear down to metal, not the gears.
This.
No big pieces, just filings.

Made it 250k, just wish that it could have made it 253k!
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That's the plan now.
I got on car-part and found the yard nearby has four in stock for $200-250, so I've got a bunch of work ahead of me but won't be out much cash since I should be able to resell a working automatic for about that when I finally do my swap.

I had planned on leaving this morning, so I'm actually pretty lucky that this happened now and not somewhere in Wyoming with a trailer behind the car.
I've no idea, but what would a u-haul truck and car trailer combo cost you to one-way hire? If it saves you having to do a tranny swap on your mum's drive. Though of course you couldn't recoup the cost later though like you could by reselling the temporary trans. (BTW I admire your spirit in not letting this get you down and instead focussing on finding a solution!)
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Good luck with the trans, Vick! I think I know what you'll be doing pretty shortly after getting home. If you can get a trans for that little $$ it definitely seems like the best course of action.
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I've no idea, but what would a u-haul truck and car trailer combo cost you to one-way hire? If it saves you having to do a tranny swap on your mum's drive. Though of course you couldn't recoup the cost later though like you could by reselling the temporary trans. (BTW I admire your spirit in not letting this get you down and instead focussing on finding a solution!)
My dad passed away shortly after I got here and I've got a couple of old motorcycles as inheritance that I have to get home, so had been looking at a U-Haul trailer a couple of weeks ago and it was a pretty reasonable $240. Went to book it the morning before the trans failed and it had shot up to $519. U-Haul can be very hit or miss on price depending on how many people are moving where at any given time, as they adjust prices to compensate so that they don't end up with all of their fleet in one place. Charlotte is an in-demand destination and will make truck/trailer rental prohibitively expensive, not to mention the complication of having brought my cats with me and them having gotten about as comfortable as can be expected in the car, but would be freaked out by three or four days in a noisy ass truck that they can't see out of.
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Sorry for your loss. Hope you and your family find solace and closure.

Doug
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2
Last Week -


I got headed out a week late, but still headed home.
Ogden Utah here, on the second morning.


Battery light came on briefly in Wyoming so I started watching the temp gauge in case the serpentine belt had been thrown, but all good. Light went back out so I decided to just monitor it and see how it shook out, since I really wasn't anywhere where I might have done anything about it anyway - there's a whole lot of nothing in Eastern Wyoming and Western Nebraska!

Plan had been to spend that night in Lincoln, NE, and I was on track to roll in about quarter to eleven. At some point the low coolant light came on, but the car was too warm to check it and it tends to give a lot of false alarms anyway, so I didn't think too much about it, check it before heading out in the morning.

Half an hour West of Lincoln the dash starts lighting up, the trans cog right among the first. I was still driving, but now locked in fourth gear, more lights coming on and I figured out that this was low voltage and that I'd lost the alternator. When the headlights cut out I had to make it to the shoulder.

Called AAA at 10:10 and didn't hear from a local dispatcher until 1:30, was after two when she told me that they weren't going to be able to send a truck for me and that I could either find my own tow and submit for reimbursement, or Uber or something into town and they'd pick it up unattended at some later time. I talked to a guy who wouldn't be able to get anyone there until morning, so I made enough room in the back to get a little bit comfortable and get some sleep until then.

He was supposed to call me at 8 (he didn't) but I figured I'd give AAA another go and called again at 7:30. This time got a guy who had me all set up in just a few minutes, even accounting for the trailer. I found European Auto Tech on Google and decided that a good indy shop was going to be a better bet for me than the dealer, so called as soon as they opened and let them know that I was on my way. Corey and Ben there took care of me (and my cats!) and got an alternator from a NAPA that was in town (lucky, since the next closest was in Kansas City) and I was back under way around 1, hoping to make it 7 hours to St. Louis for the night, leaving an 11 hour drive home from there.

I made it less than five miles.

I'd noticed the temp creeping up leaving red lights pretty quickly, and the low coolant light came back on despite having just been topped up, and thought that perhaps the harness to the cooling fan had been forgotten, but when I pulled in to gas up and look at it I saw expansion tank spewing at the top seam. I turned around and started trying to make it back to European Auto Tech, but by now the temp gauge was starting to get dangerously high, so stopped and bought 3 gallons of water and fought for about an hour to get rid of the air bubbly that had by now gotten into the engine.

Did eventually get back and Corey happened to have an expansion tank on the shelf and Ben popped it in for me and filled up the system in no time.
...and then saw the crack in the radiator end tank.

I spent two days in Lincoln waiting on the part, then the bypass assembly on the Nissens unit wouldn't seal and it dumped all the coolant straight out onto the floor.
Ben happened to have one from a genuine radiator that fit somehow and that solved the problem and finally got me back under way.

I made it to Nashville last night, and finally home this afternoon. Finally.

The trans that I had put in learned some weird trick during my stay in Lincoln, and now it stumbles and sometimes stalls when put into reverse. Not really sure what's up with that, but it really made for a tense two days wondering whether it was going to hold up and get me home or not. I think I'm going to be doing this manual swap that I've been meaning to get to sooner rather than later.

All in all, it was a pretty hellish trip this time, but glad to have met Corey and Ben at European Auto Tech. If you happen to be in Lincoln, NE and need help I can't recommend them enough.
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Auto transmissions are a labor of hate…

glad you made it home!
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Sorry to hear such an eventful trip.
Battery light came on briefly in Wyoming so I started watching the temp gauge in case the serpentine belt had been thrown, but all good.
People should take the batt warning light serious. In this case, I would at least buy a charger to charge up the batt overnight on the road. Did you measure the batt with hidden display or voltmeter after the batt light came on a brief moment? I think the carbon brushes were worn short.
Half an hour West of Lincoln the dash starts lighting up, the trans cog right among the first. I was still driving, but now locked in fourth gear, more lights coming on and I figured out that this was low voltage and that I'd lost the alternator. When the headlights cut out I had to make it to the shoulder.
Emergency: For over 150K miles cars, the best thing to do at the moment is to remove the regulator with brushes, then try to stress the copper wires on the brushes to max length to force the brushes out a millimeter longer and it would be ok to get home. Always have a voltmeter in the tool box on a trip.

At some point the low coolant light came on, but the car was too warm to check it and it tends to give a lot of false alarms anyway, so I didn't think too much about it, check it before heading out in the morning.
What did you find the next morning in the tank?
and then saw the crack in the radiator end tank.
What is radiator end tank? The long vertical black plastic end caps at both end of the radiator? Or the neck where it connected to the upper hose?
the bypass assembly on the Nissens unit wouldn't seal and it dumped all the coolant straight out onto the floor.
The drain plug assembly? Could be manual vs auto version?

Too many parts failed on the car at the wrong time.
Yes, carry spare parts on the long trip: If car over 140K miles, replace the alternator brushes or have spare; spare tank; extra ignition coil; empty can for water or with water; extra coolant top hose; engine belt. Those part are needed for maintenance anyway so it's not a waste.
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