Qyota

Howdy all, I'm a T4R.org member, and thought I'd come tap the minds of the Yotatech crowd for a bit. I know there's some overlap, so for those of you who've heard this story, I'm sorry!

Anyway, I have a 1999 4x4 Limited with about 138,000 miles. I bought it with 133K miles last January.

In March, I had to replace the ECM since the one that was in there failed. I replaced with a factory unit from a donor 4runner of the same year. Once I got my transponder keys programmed in, everything was hunky dory.

Then one day this summer we're driving back into town from a road trip, and coasting to a stop light. The light turns green as we're slowing to about 10-15 mph...so I get back on the gas gently. Nothing really happens other than the revs climb. Then, about 2 seconds later, it BANGS into gear very loudly and violently. It scared the crap out of both of us. It did this once again (similar circumstance, coming down from highway speed to a stop) a few days later, and then the problem changed. More on that in a minute.

I check the fluid and it doesn't look good. Doesn't smell burned, but it's not bright red by any means. More of a murky brown. So I drain and fill the fluid with fresh Dex3 a couple times. The shifting improves, but now the problem is slightly different. After driving at highway speeds for a while (say, 20-30 minutes or more...sometimes less), and I come to a stop, the transmission ends up in a neutral state, probably between 2nd and 1st gears (hard to tell). Sometimes it'll engage on it's own if I wait a few seconds, other times I have to manually shift down to L to get it to bump into gear. Then I can take off and shift up into D.

I took it into a quality independent transmission shop and they drained and replaced the fluid and filter (which appeared to be the STOCK filter from 1999....grrrr). They test drove it and OF COURSE it didn't happen to them (it never does, right?). They hooked up their scan tool and found nothing wrong. It has never thrown a DTC for any of this. The only code it's every thrown is for something related to the original ECM dying (MAF sensor). So, he put in some LubeGaurd with the new fluid, to help free up any sticking valves or solenoids in the valve body.

Now, 99% of the time it shifts GREAT! Up and down through the gears in town is a dream, mostly. Coming to a stop, I can now feel 1st gear engaging with a slight bump (at about 5mph). Not a big deal, at least it's going into gear on it's own! BUT, I still get the intermittent neutral state after driving at highway speeds and coming to a stop.

SO, what's going on here? I have 3 theories, each can be "proven wrong" so to speak...so I'm basically at square one.

1. ECM. Somehow it's not telling the transmission to shift down into first...sometimes, only after highway speeds for a while. But, works great every other time.

2. Shift or lock-up solenoid. This probably is the most reasonable thing to check, but as I said, there have NEVER been any CELs or codes for this problem.

3. Throttle Position Sensor or kick-down cable. Cable is adjusted properly (1mm of rubber showing out the cable boot), but I haven't checked the TPS. Here's my logic on the TPS: When I'm at highway speed, I'm usually in cruise, or holding the throttle very steady (I don't pass very much, and like to keep her in the sweet spot for good fuel efficiency). So if the throttle is in the same or nearly the same position for a LONG time, maybe the TPS gets confused and doesn't send the downshift signal to the ECM. Possible? Again, since this only happens after highway speeds and not ALL the time, it's doubtful.

Anything else I can check? Toyota dealer in town says they could flash the ECM with possibly updated firmware (or something)...but that might not do anything (and still cost $150). But, they do seem to think it's an electronic problem.

What are your thoughts? I'm ready to really love this truck...just gotta get this sorted out!

Thanks much

mt_goat

I'm guessing #2.

BTW welcome to YT.

Qyota

Thanks for the response (and welcome!). Does the solenoid explain the problem if it works fine 99% of the time? Seems to me, if the solenoid was bad, not only would it throw a code, but it would also not work more often than it does. The fact that this only happens after driving on the highway for a while (trans temps around 150F), suggests that heat may be playing a factor. Although, in town, ATF temps are higher, and it doesn't have a problem shifting down to 1st.

TPS seems to be working, according to my ScanGaugeII.

R.DesJardin

iTrader: (1)

Sounds like the ECM doesn't know you've stopped, this could be related to a VSS sensor being bad.
The kick-down cable as you call it is for trans line pressure not kick down, the TPS is a different item, but worth checking with a Volt-Ohm meter. Other than that nothing come to mind to check.

mt_goat

Maybe its just a sticky solenoid valve and only sticks every now and then. I think the codes are thrown from electrical failure, rather than mechanical valve problems (sticking valve). But I could be wrong on that

Qyota

Yup, sticky solenoid is high on the list, but it's not exactly intermittent. It's pretty likely to happen after driving on the highway for a while and coming to a stop. If it happened ANY other time, I'd buy the argument that it's just sticky.

ALSO, by shifting manually down into Low (1st gear), it engages right away. What's different about letting the ECM decide to shift, and me manually selecting it? Maybe that points more to the ECM?

Ugh....

Qyota

Forgot about this thread.

Toyota and my trans tech both agreed it was a shift sprag that had gone "bad", but not completely bad. So, the options were to rebuild the transmission (139K miles) for about $2200, or find a donor tranny from a wrecked 4runner. I went for the donor. Found one with 78K miles with a one year parts and labor warranty for $660. Installation was another $600 including everything (fluid, filter, etc.).

I'm back in biznass! Shifting has never been better. So, I'm a happy camper to get this solved for ~$1300.

mt_goat

Great, thanks for the update.

BigBallsMcFalls

wow I have the exact same issue. It drives perfect around town. ONLY after getting off the highway, if I have to come to a stop right away, I am likely stuck in neutral until it decides to give me 1st. if i wait 30 secs, thump, I can go.

I am gonna see what is out there for a used a340f

J2F42C

Big Balls,

Did you have this occur before the milkshake?

http://www.car-part.com/

Qyota

I believe this is fallout from milkshake. Mine almost certainly had the milkshake before I bought it. That's why the fluid looked murky brown when I checked it first. If I was a smart car buyer, I would have checked that in the lot before buying it. My guess is, it had the milkshake, but they just drained the fluid in the pan, swapped in a new radiator and called it a day...Leaving the rest of the contaminated fluid in the transmission...for me to discover how many months later.

Sorry for the bad news, Balls. I found my used a340F on car-part.com, as J2 has suggested.

BigBallsMcFalls

never. about 10,000 after the milkshake


yes my atf goes brown fast post-milkshake. it is gonna die someday. I think
those who get the milkshake and report zero issues later must only drive around town a lot.

it never slips or anything....just seems slow to lock up in drive
after a 15 minute 65mph run....around town, flawless at all times all gears.

oh well. I will save up some monies to get tranny replaced this summer
and see how far it goes until then.

In the meantime when I don't need 4wd I use the car.

J2F42C

Big Balls,

I wonder if it has to do with the sudden increase in the ATF temp once one pulls off the highway. I've seen mine increase in temp 20+ degrees once off the beltway or highway before....

At least this time you can inspect the inside of the pan before buying the 340F. If not, find another one.

BTW, it was your post that got me off the fence to ditch the old radiator for the Koyo A1998 last year. I know it does not help your situation, but thanks for the heads up.

BigBallsMcFalls

spoke to a guy at a transmission shop. This guy is recommended and is a 100% no bull.

he gave me a driving and shifting pattern to try, and then he will know more about the
issue.

anyhow, I know I found the right shop. Now to do some driving and shifting patterns to see how it behaves. and then maybe I only need a few parts and not a whole tranny. I am saving my coin for all outcomes (rebuild 2 grand, find a used one, 500 to 1500, fix a single part or two , 100-400) the thing that bums me out about a used one is I have a 98 built 99 limited with multimatic AWD, and not just any a340f
from the same era will exactly match the tranny ecu. and 5/99 and above is different yet again. the awd is in the transfer case but there may be a requirement to get only another a340f from the same year and model limited. I don't know those answers...

????

I will post up any updates. he did say right off that...oh man those coolant mixes are never good.

Qyota

Yeah, my entire tranny wasn't shot, it was the 1st gear "shift sprag" that wouldn't engage after highway speed (for whatever reason). But, to get to the sprag and change it would have meant more work/time/money than just replacing the thing. So, that's what I did.

Good luck finding the replacement!

x2468

Sucks that you couldn't save it in the end.