What's wrong with my A343F Transmission? (4 Viewers)

[snorky18]

98 Lexus LX470 Transmission Symptoms

Intermittent Symptoms – Can’t always be repeated, but happens most of the
time under perfect conditions.

While driving up a steep hill in 2nd gear (shifter in D) and gradually decreasing
throttle input (like when there’s a stop sign at the top of the hill), it slows as
expected.

At the point where it has slowed enough that 2nd gear is too high, and you expect
it to shift down to first so you can keep going up the hill, instead it stays locked in
2nd and will shudder, clatter, and nearly stall as the RPMs drop off. (Same exact
symptoms as if it were a stick shift and you forgot to clutch when the RPM got too
low b/c your gear/load is too high.)

Generally if I come to a complete stop, it will shift down to first, then I can
proceed up the rest of the hill normally. Occasionally I have to stop, pull shifter
into L, and then it can be driven normally in first gear, and once up to a speed
appropriate for 2nd gear I shift back into D, and drive normally again.

This happens both when the transmission is warmed up after a 2 hour drive, and
when it is cold.

Second symptom: Just to the left of the gear shift is a PWR button and a 2nd gear
start button. This is highly inconsistent and difficult to repeat, but just as a test, I
have occasionally engaged that 2nd gear start button while in Park, then as soon as
I took the shifter to D (with my foot on the brake), it immediately stalls.

Any thoughts on what is wrong? 230K miles on it. It's been completely babied for almost all of those miles.

Changed all fluid (exchanged by disconnecting cooler line) about 3 weeks ago (after problem started), old fluid was a tiny shade darker red than the new fluid... nearly an indistinguishable difference. The old fluid didn't look bad at all.

I've been floating between needs a new torque converter vs needs a new shift solenoid.

The local transmission shop (who admits they don't like to do "partial" repairs, and prefer to rebuild the whole thing and give you a 3 year warranty on it all) says they pulled codes (but haven't specified which ones) and found some metal particles in the pan when they dropped it. $2900 for a full rebuild with unlimited mile 3 year warranty.

 

[flintknapper]

You need to do a bit of testing when you get time. Level surface, someplace without a lot of traffic (large school parking lot/other) on a weekend. MANUALLY shift between 1st and 2nd gear. See if the transmission will 'hold' 1st gear for as long you want when manually shifted to Low. Then take 1st up to about 2,000 rpm and manually upshift to 2nd. See if it makes the shift and you get a firm transfer of gears. Then while in second gear manually shift back to low/1st while slowing and see if the transmission makes the downshift and the engine will idle when you come to a stop. Lastly, take it out on the highway and use your OD button on the shifter to test whether or not the trans will reliably go between OD and OD OFF (torque converter lock up).

As for the 2nd start button, leave that damn thing alone unless you need it for starts on snow or ice.

'Metal Particles' in the pan can be perfectly normal (depending on how large and how many there were). If you drain your Tcase and strain it, you'll find small metal particles, if you inspect your front or rear diffs...you'll find small metal particles. So unless the trans shop said they found BIG metal particles, then they were just trying to alarm you.

The A343F trans is a pretty reliable and robust transmission. The most common issue with them being shift solenoids. With respect to the engine dying when placed in drive (2nd gear start), that sounds like the torque converter locked up instead. Also, if the TC doesn't unlock (when it is supposed to) it could be causing the issues you describe. But you need to first determine if the tranny is or isn't physically shifting between gears when 'manually' moved there. Let us know.

 

[codertimt]

Checked location and you are in the south...that's too much for a trans rebuild. Look for another shop. Of course, it has been quite a few years since I dealt with this, but still fell that a bit much. I've run the full course of transmission "dealing with" on the A343F, so will give advice based on that experience...you can decide whether it's good or bad....or what you want to deal with yourself. So, I will start will rebuild... I had my 4 speed rebuilt a few years ago in AR out the door just north of $2k. It failed in 70K miles...about 3 years later. At that time got a Toyota remanufactured in the upper 2 grand region...definitely under 2900, but I installed myself. I tried solenoids, tried to rebuild it myself, etc...ended up with the remanufactured...that being said...the behavior you are describing would lead me to check into solenoid replacement. I don't remember the solenoid pattern exactly for this trans, but there is definitely the possibility if one or more are sticking, then 2nd gear start would actually try to start in OD...and thus definitely stall...likewise if it doesn't open/close correctly downshifting it would hang in OD and cause those drivability issues...Since I like cheap and easy solutions, I would first buy some Lucas Oil trans fix that claims to fix sticking valves. If that doesn't work(probably won't since new fluid should also be really good to help old solenoid valves), I would get a set of solenoids...then if that doesn't work IMHO cut your loses and get a Toyota remanufactured...drive it for another 200K without worry....

 

[flintknapper]

Checked location and you are in the south...that's too much for a trans rebuild. Look for another shop.

OP didn't say....but most likely the $2900.00 figure is for a complete rebuild AND (labor to remove the trans and install), which is actually a pretty good price when you consider the unlimited mileage, 3 yr warranty. A Toyota 'reman' is likely a safer bet (if it comes to that) but you won't get that kind of warranty with it.

 

[sr5pickup]

I’d get a scan tool and pull the codes then go from there.

 

[Malleus]

FWIW, Toyota is advertising reman 100 series A343Fs for $2500, as do all the national reman outlets; of course that's just the gearbox. My 2000 LX470 has 1st, and sometimes 2nd gear, clutch problems and I have to use the 2nd start option to get the transmission to shift reliably from a stop. I'm rebuilding it later this year; I can't find anyone near me (that I'd trust) to rebuild it.

The transmission rebuild plants appear to be in the center of the country, which may account for the low prices in some places. They are certainly not that cheap here. I'd think $2900 with that kind of warranty is a good deal.

 

[snorky18]

You need to do a bit of testing when you get time. Level surface, someplace without a lot of traffic (large school parking lot/other) on a weekend. MANUALLY shift between 1st and 2nd gear. See if the transmission will 'hold' 1st gear for as long you want when manually shifted to Low. Then take 1st up to about 2,000 rpm and manually upshift to 2nd. See if it makes the shift and you get a firm transfer of gears. Then while in second gear manually shift back to low/1st while slowing and see if the transmission makes the downshift and the engine will idle when you come to a stop. Lastly, take it out on the highway and use your OD button on the shifter to test whether or not the trans will reliably go between OD and OD OFF (torque converter lock up).

As for the 2nd start button, leave that damn thing alone unless you need it for starts on snow or ice.

'Metal Particles' in the pan can be perfectly normal (depending on how large and how many there were). If you drain your Tcase and strain it, you'll find small metal particles, if you inspect your front or rear diffs...you'll find small metal particles. So unless the trans shop said they found BIG metal particles, then they were just trying to alarm you.

The A343F trans is a pretty reliable and robust transmission. The most common issue with them being shift solenoids. With respect to the engine dying when placed in drive (2nd gear start), that sounds like the torque converter locked up instead. Also, if the TC doesn't unlock (when it is supposed to) it could be causing the issues you describe. But you need to first determine if the tranny is or isn't physically shifting between gears when 'manually' moved there. Let us know.

I manually shifted through all the gears.
Every time I downshifted manually it executed the shift immediately with no shuddering under every condition I could think to throw at it.
It held gears as long as I wanted while I accelerated before I shifted up to allow a higher gear. Upshifts were crisp and correct.
O/D on and OD off cycled perfectly.

When I let it shift down on it's own under the headed uphill + low throttle coasting conditions I described originally, at the time it SHOULD shift down to a lower gear, I still get the shudder, like someone who forgets to clutch their manual at low speed. When I pull the shifter down manually into the next lowest gear, it immediately drops a gear, and the shudder. stop.

 

[snorky18]

I should have mentioned earlier, the $2900 for the transmission rebuild w/ 3 year unlimited mile warranty covers parts + labor, 2900 out the door.

 

[ramangain]

Shuddering points to a torque converter issue

 

[flintknapper]

Shuddering points to a torque converter issue

Or lack of input calling for TQ lock up or to unlock. OP's testing that I asked for demonstrates the transmission is physically capable of attaining and holding each gear. So....I suspect a shift solenoid issue OR a mis-signal to the T/C.

Valve body has pretty much been proven to be OK, since all up and downshifts (manually) were achieved.

IF I were the OP....I'd be inclined to replace all the solenoids (NOT FROM THE DEALER), refill with new fluid and go test drive it.

If it still continues to act up....contact another trans shop and see what they think.

 

[snorky18]

IF I were the OP....I'd be inclined to replace all the solenoids (NOT FROM THE DEALER), refill with new fluid and go test drive it.

Appreciate the input flintknapper. Do you have a preferred source or manufacturer of the solenoids? Do you avoid the dealer ones because of cost, or some other reason?

 

[flintknapper]

Appreciate the input flintknapper. Do you have a preferred source or manufacturer of the solenoids? Do you avoid the dealer ones because of cost, or some other reason?

Cost. Use the search function....I believe there are solenoids from an Isuzu (or something like that) that are exactly the same for a tremendous savings. Its been discussed here before, I just don't have the information readily at hand.

 

[pavlenti]

Was this ever resolved? I'm having very similar issues with my KZJ95 (A343F transmission). It actuates all shifts when told to via manual inputs, but intermittently and unpredictably misbehaves when left in D. Also, sometimes the 2nd start feature and dash light turn on seemingly randomly. ECT PWR overrides it.

I found that one solenoid wasn't actuating (applying 10.5 and 12v from power supply). It was the single solenoid (8542030220), not one of the two matching ones (8542030200). I replaced that shorted solenoid with a compatible one from Toyota (3525050030), but the problem persisted. I ordered the two other solenoids (8542021090), thinking that was the issue. BUT, after pulling the pan and testing, I found that the one that was bad before and I had replaced had gone bad again. It actuates rarely when tapping with the contacts and definitely heats up. When measuring resistance though, it matches the healthy solenoids. For context, it was working great before I installed it. I could throw it all back together with the two brand new and working solenoids alongside the seemingly shorted new one, but I am curious if anyone else has a different opinion.

Is my transmission frying the solenoid? What could be causing that? I've done all of the testing I can think of before I start digging further into electrical issues. For some context, this problem started happening a couple thousand miles after an engine rebuild, but immediately after the rebuild came the 2nd start issue. Any thoughts?

 

[SteveH]

For some context, this problem started happening a couple thousand miles after an engine rebuild, but immediately after the rebuild came the 2nd start issue. Any thoughts?

How about damaged transmission wiring during the engine re-install. Have you checked all wiring around the bell housing?

 

[pavlenti]

Visual inspection just now and many times in the past month haven't shown any worn wiring. I'd have to remove the harness and peel off the plastic sheathing to do more looking.

 

[baltistyle]

Visual inspection just now and many times in the past month haven't shown any worn wiring. I'd have to remove the harness and peel off the plastic sheathing to do more looking.

If you’re able. It might just be easier to do some continuity testing. Agreeing with others here that any problem that starts after a major repair like that, you should be looking into what they might’ve damaged.

 

[originalcruisey]

OP didn't say....but most likely the $2900.00 figure is for a complete rebuild AND (labor to remove the trans and install), which is actually a pretty good price when you consider the unlimited mileage, 3 yr warranty. A Toyota 'reman' is likely a safer bet (if it comes to that) but you won't get that kind of warranty with it.

Exactly, if you want something like a 3 year warranty they have to charge enough where they don’t loose their butt on a repair

 

[Malleus]

Was this ever resolved? I'm having very similar issues with my KZJ95 (A343F transmission). It actuates all shifts when told to via manual inputs, but intermittently and unpredictably misbehaves when left in D. Also, sometimes the 2nd start feature and dash light turn on seemingly randomly. ECT PWR overrides it.

I found that one solenoid wasn't actuating (applying 10.5 and 12v from power supply). It was the single solenoid (8542030220), not one of the two matching ones (8542030200). I replaced that shorted solenoid with a compatible one from Toyota (3525050030), but the problem persisted. I ordered the two other solenoids (8542021090), thinking that was the issue. BUT, after pulling the pan and testing, I found that the one that was bad before and I had replaced had gone bad again. It actuates rarely when tapping with the contacts and definitely heats up. When measuring resistance though, it matches the healthy solenoids. For context, it was working great before I installed it. I could throw it all back together with the two brand new and working solenoids alongside the seemingly shorted new one, but I am curious if anyone else has a different opinion.

Is my transmission frying the solenoid? What could be causing that? I've done all of the testing I can think of before I start digging further into electrical issues. For some context, this problem started happening a couple thousand miles after an engine rebuild, but immediately after the rebuild came the 2nd start issue. Any thoughts?

The transmission can't "fry" your solenoid. The solenoid operates a valve inside the transmission. Think of it like a remote door lock. The remote gets a signal and then moves the locking mechanism. The lock doesn't know or care anything about what's making it move. In the case of the solenoid, it isn't even touching anything; it's just moving a plunger into and out of a bore.

If you have a bad solenoid after replacing it, you either got a bad part, or something in the circuit is sending too much current. I would think that if the circuit was at fault, you'd have lost a fuse too.

FWIW, the single solenoid operates the torque lock up function, which doesn't happen until after you reach 50 mph. All of this is explained in the service manual for the A343F transmission (not unit repair), found in the general service manual. Any model with a A343F will operate (mostly) the same way (there are some programming differences within the transmission control unit).

As to your operating problem, I'd suggest having a look at the TCU board inside the ECM container. I'd bet you have a leaking capacitor on it.

 

[flintknapper]

 

[pavlenti]

Ok, so here's the update so far and the order in which I've done things. I figured the ECU problem might be the issue after malleus suggested it, but I wanted to check everything else first.

I tested continuity to the solenoids and couldn't find any damaged wiring anywhere near the transmission. So, this doesn't seem to be the root of the issue.

Then, I decided to see if there were any codes. I realized that I had never seen the check engine light in the life of the vehicle, so I didn't think this would do anything. I could not turn the diagnostic mode on (engine light should flash) on or turn the engine light on.

Some YouTube results showed that I should have seen the light turn on every time I started the car, but this has never been the case. So, I removed the instrument panel and checked for burned-out bulbs or nefarious previous owners. Nothing found.

Some googling about why dialogistic mode and/or the check engine light not working pointed potentially to the ECU and leaking capacitors.

So finally, I pulled out the ECU and found leaking capacitors (pictured, see the top right and bottom left). Now, I wait for a hopefully good second-hand ECU to show up and resume the repair.