Interpreting Automatic Transmission Symptoms + Caution & Care

[IdeaNerd]

Our first Weekender came with a new timing chain and rebuilt transmission (German Transaxle of America), GTA-installed cooler, and related transmission warranty in our name. We've had it a little over a year, drive it everywhere, and have had no mechanical trouble of any kind in that time.

Yesterday, we took it through the Sierra into a deep river canyon, with quite a few hours of varied mountain driving and only one stop along the way. Everything performed fine up until the end of the day, as we were climbing back over the mountains again to come home.

We drive in the mountains often, so putting the shifter into 3 is a fairly common practice "when the transmission shifts frequently between third and fourth gears in position D," as the owner's manual puts it. Ditto (though less common) for putting it in 2 when really climbing or descending steep inclines. Having driven T2s and Vanagons in days past, I always smile at how easily our late-model Weekender climbs hills.

Yesterday, though, it really bogged down coming up that hill. Didn't want to do more the 25 MPH, and it seemed like it was either A) refusing to shift into 2nd, or (more what it seemed like) that 2nd was a "mush ball" -- with no real power transferring. If I slowed down enough, I could put the shifter to 1 to force it into 1st, wind it up, and there was plenty of power and torque. The engine seemed to be running fine.

I basically resigned to that -- winding it up in 1st, and/or then shifting it to 2 or 3 and bogging along at sub-3K RPM, around 25 MPH. A few of those up and down shifts ended up being hard ones.

We got over the hill (last big one of the day fortunately), and descended.

My perception during descent was that when shifting into 2 for engine braking coming down the hill, it wasn't as "brake-y" as it normally would be -- kind of the inverse of what it felt like going up the hill.

While we got home fine, during the remainder of the journey, the transmission vaguely didn't feel like it was running as well as it normally does.

On the flatland highways, I tried a few things, and it basically ran OK, just didn't feel as solid or smooth. That could just be my own hypersensitivity after the hill-climb episode, though. I did test kick-down shifting with the throttle at a few different speeds, and it seemed to work fine.

Scanned it today, and no codes show.

The shift lockout relay seems a little louder today than I remember it being, as I mentioned in my ABS/scanner-related thread.

Transmission fluid and filter were changed a couple months ago (per the warranty requirements).

I've read through the three threads linked here, and plan to spend much of today learning the conceptual basics of automatic transmissions (they've always been a "black box" to me). (I expect I'll see quite a few 3D animation videos in the process.)

Questions:

1) Is it possible the transmission just got too hot? (It was in the low- mid-90s I think where we were driving at the time).

2) Should I minimize and/or avoid driving it currently to avoid doing any, or further, damage?

3) If I do keep driving it, what should I pay attention to, to gather better symptom information? (Or, does that even matter? e.g. we're likely headed into some variation of a rebuild scenario, and the better information will only come from tearing it apart?)

4) Any recommended "next steps" to address the problem?


I know we get a lot of transmission-related posts here, and I hate to be "that guy" posting yet another one. That said, I'm an eager learner, and any and all pointers or useful advice would be appreciated.

[Abscate]

Drive it on the flats for a few days to see if you really have a problem.

The first thing I would do is drop the 3 liters or so from the pan using the overflow tube and see what the fluid looks like, then replace it.
_________________
.ssS!

[jjvincent]

That's a hard one to figure out because you are hyper sensitive right now (you can tell because of the shifter lock is louder).

I'd pull the pan and filter. Break the filter apart, unfold the filter and make sure there are no goodies hiding in there. Again, the EV transmission filter is the best ever invented and it does it's job keeping all of the garbage out of the pan and in the transmission. As for the fluid, it should not smell burnt (really stinky) or be clack and thick. It should come out like water.

If the fluid looks fine and the filter is not hiding anything, then new filter and fluid.

If that doesn't fix it then I'd find out if the valve body was rebuilt and if it had new solenoids.

[IdeaNerd]

@Abscate & @jjvincent, thanks very much for the advice!

[Abscate]

We are both somewhat less risk adverse than most, to be fair ( at least , that's the impression I get of jj, who is a careful thinker here)

I did win lottery twice , though.
_________________
.ssS!

[jjvincent]

[Abscate]

[jjvincent]

I think we should sticky this thread because it will serve as a general PSA of the knowledge base from just two posters. We can answer anything.

[Abscate]

I think, deeply buried in the cryptic TOS of the Samba, that accurate answers are desired....
_________________
.ssS!

[jjvincent]

[Abscate]

[IdeaNerd]

You guys have superpowers. Skills are optional.


Diagnosis sleuthing on this is still in progress (van is at the shop), but the transmission seems to be behaving itself perfectly currently, even under close live monitoring (via VCDS or similar, it sounds like).

I'm still learning about automatic transmissions, but one thing that keeps coming up in my online reading and research is "limp mode" -- yet it's almost always explained in some pathetically vague, general way. It also sometimes sounds like "limp mode" can affect either the engine, the transmission, or both, and also that it varies (as one might expect) from one car manufacturer to another.

What EXACTLY does "limp mode" do on a 2001-2003 Eurovan, what causes it, and is there more than one "limp mode" on these vehicles (e.g. engine vs. transmission)? I'd love to know the solid specifics of its causes and effects.

@jjvincent, I found this post of yours very informative -- a beautiful example of the kind of the specific, useful information I'm looking for (thanks for posting it on that thread). It's exactly the opposite of what I keep finding when looking for information online about how "limp mode" affects a 2002 Eurovan, what kicks it in, etc.: "Most modern vehicles have a special mode that protects the mechanical bits when the car gets confused or doesn't like you.... symptoms vary from car to car, but... "


Thanks in advance...

[cc-91tech]

Hello, I just read the post.
Very interesting.
Previously sorry for my english I come from Germany.
If I may say something to this,
The oil temperature is most likely if the error does not occur.
Electrical error should be saved. How was read out system?
If it occurs opener it is likely that there is a mechanical problem.
Greeting Andy

[Abscate]

I don't know the specifics on the EV, and that may be buried in proprietary ECU code, but if you want the general picture, under certain conditions of fault, the ECU limits fuel delivery to cylinders , spark advance, turbo boost ( where applicable) to keep the rpm at about 2000 or less. This can be triggered by a transmission or engine fault.

Both engines and transmissions have separate limp modes. An AT will stick it in third gear which will give you a slow start but let you roll home at 20-30 mph.

I looked for VR6 specifics but couldn't find it on the web, either.

Hope that helps
_________________
.ssS!

[jjvincent]

Every car has different limp modes. We run into this in racing when we use a stock ECU. I can tell you that even APR had a hell of a time with their GTI's in Grand-Am because they could go a few laps and all of a sudden a loss of power. You had to do an inflight reset. Their Audi S4 was a complete disaster.

Same for my BMW 330. If I ran a lighter flywheel and at places like Daytona before going into turn 1 or before the bus stop, the car would drop either cylinder #3 or #4. The injector would shut off because it thought we had a misfire. What it was reading was the speed of the toothed wheel on the crankshaft. In a misfire, the crank rotates slower on that power pulse, thus it thinks a bad coil pack and shuts off the injector so you are not dumping raw fuel in the CAT. In my case, running at exactly 6800 rpm, the crank was twisting and fooling the crank sensor. It was another inflight reset.

Just like with the Subaru. The variable cam timing would shut off for no reason.

Usually most ECU's have limp mode for many different scenarios it's that some engines rear one of those issues better than others and thus, limp mode.

Like with the EV and the TCU. Just unhooking it will give you the built in manual override limp mode.

[swsl]

This discussion is timely as I had a similar experience two days ago and I've wondered the same things.

I bought my 2002 weekender this Thursday with 134k miles. It had the transmission overhauled by a supposedly respected Seattle transmission shop (Rons) 13 months and 9 k miles ago. Seller says they added the tranny cooler.

It drove perfectly smoothly coming back from CO into NM but the second.day I was on some sketchy mountain roads running 20-40 mph climbing dropping, hitting some of the potholes here and there. I was driving it like any car, neither beating on it nor babying it much.

After a about :45 min I accelerated out of a climbing curve and it responded strangely- it just revved up and didnt move forward much for the rpms nor did it shift. I.backed off the.throttle and it did shift and move. High rpm but felt a.little like a clutch slipping. I kept going more carefully and noted.some continued vague wierdness and two more times it wound up past 4000 before shifting or else I backed off and it shifted. Sometimes I thought it was slipping and sometimes I thought the shifting program was fighting me or just tweaking. It was maybe 80 degrees and 6-7000ft.

Hitting the highway again it was normal except one slightly pronounced shift. I stopped the vehicle and let it sit five minutes off then got going again. It then did fine the last two hours of the trip and fine around town last couple days. Hitting the road tomorrow for a few days.of highway travel and hoping it stays good!

I.would like to drop the pan but no time and no parts here in the boonies. Thiinking maybe to have the dealer or a.recommended mechanic do that Thursday in Boulder when I get there...

i hope this post is not jacking the thread...so.similar are the two experiences. I wonder if it was the tranny or the program that was acting up. I understand the ecu will choose from two or more shifting programs depending on driving input. Or maybe something loosened up or broke free with the jarring? Wiring? Valve body crud that was.missed?. I dont know hardly anything about auto transmission myself either.

Steve

[IdeaNerd]

@swlsl: not jacking the thread at all IMO. Glad my "very odd to me" hill-climbing episode at least sounds familiar to someone else. It was so strange to experience -- like our van had a "body snatcher" experience for a brief bit. Your description sounds similar to mind -- the "felt a little like a clutch slipping" and "vague weirdness" in particular. It was the "disconnect" sense of interacting with it that was the oddest part.

One thing I didn't mention in my earlier post is that I did pull over at one point, while we were mostly still heading downhill on the backside. I turned off the van for a bit then -- mostly just to enjoy the peace and quiet (one of my favorite parts about being out in the middle of nowhere). Later (during the searches noted above), I learned that it can sometimes reset "limp mode" if you turn the vehicle off and back on.

On that note, @jjvincent, I don't envy your "Surprise! Limp mode!" racing experiences at all. Seems like that would be very frustrating!

For our case: my mechanic checked the fluid levels and looked at the fluid itself, and all looked good. He ran it on a reasonably long hill-including drive while live monitoring w/VCDS, and all shifted as and when it was supposed to. We did end up finding an occasional misfire as part of that, and that led to replacing a coil on one cylinder. All seems OK now (so far anyway). I still plan to take it on non-critical, still-inside-our-cellphone-coverage-area, fairly intensive hill drive sometime this week or weekend just as an additional "before we go deep into the backwoods" test, but it's driving fine on flatland.

I also called GTA and had my mechanic call them too, and it sounded like they were on the same page as far as sequence of diagnosis steps, etc.

Limp mode's darker secrets and triggers remain a mystery.

...and @jjvincent, you were right: I was being hypersensitive when hearing the lockout relay.

I hope it goes well for you, @swsl!

I'll update this thread if anything further happens w/our situation. I'm hoping to have no further updates though.

[IdeaNerd]

P.S. Thanks for the help and advice, everyone -- greatly appreciated!

[IdeaNerd]

Took this van up to the mountains and down into another deep canyon this weekend, and it ran like a champ. No power/drivetrain-wimpiness (that's the technical term, I think) problems at all.

[gakali]

Generally if an engine or tranny goes into limp-in mode a fault code will be set as a malfunction has been recognised by the control module.

Transmission fluid getting too hot would very likely cause an emergency mode to be activated (emergency running modes can be different than a true limp-in mode). The torque converter clutch would be activated and a perceived lack of power would definitely be noticed especially at lower speeds. I would think that in this case a fluid temp. overheat fault would be stored but this code could be cleared out eventually. Some scanners don't "see" all fault codes so keep that in mind too.
_________________
Why do it? Because you can.

1999 Eurovan
2003 A4 Avant 1.8T Quattro
1992 W201 190e 2.3 Mercedes
2006 W220 S600 V12 Twin Turbo 5.5 Mercedes