Transmission Problems (1 Viewer)

[Offroader93]

So I put another motor and trans in my rig after the original ones started to develop problems. 1Fz-fe/A343F. I am to the point in my project when I am ready to get it back on the road soon.

I am trying to figure out why it is barely moving in drive. The rpms go up high (3-4k), and it takes my foot to the floor to get it to move. Shift into low on the gear selector and it moves like normal in both drive and reverse. Shift the transfer case into low and it also moves normally.

If the transmission was completely bad, it would make sense......but to have it work in some ways and not in others is frustrating. What else do I need to be checking, or should I be putting in another transmission?

 

[ppc]

Need more info...

What year is your vehicle and what year was the donor?

 

[Malleus]

We need a little more info. The way the transmission works is that it always starts in 1st gear, unless you've engaged the "2nd start" feature, then, after sufficient pressure builds up, it upshifts to 2nd, and then again to 3rd (drive). Unless you have an LX450, then it starts in overdrive and immediately shifts to 1st.

So, when you say it barely moves in drive, do you mean you've selected drive and it won't move, or that it moves as expected through the 1st/2nd shifts, and then when it gets to drive it boggs down?

FWIW, there is a FSM for the transmission in the Resources section (80 series section). It has a troubleshooting matrix, as well as a well written explanation of the operation in it. I recommend downloading it. Don't download the unit repair manual.

All the 80 series A343F transmissions are the same, even the LX450. The Lexus difference is in the ECM/TCM.

 

[Offroader93]

We need a little more info. The way the transmission works is that it always starts in 1st gear, unless you've engaged the "2nd start" feature, then, after sufficient pressure builds up, it upshifts to 2nd, and then again to 3rd (drive). Unless you have an LX450, then it starts in overdrive and immediately shifts to 1st.

So, when you say it barely moves in drive, do you mean you've selected drive and it won't move, or that it moves as expected through the 1st/2nd shifts, and then when it gets to drive it boggs down?

FWIW, there is a FSM for the transmission in the Resources section (80 series section). It has a troubleshooting matrix, as well as a well written explanation of the operation in it. I recommend downloading it. Don't download the unit repair manual.

All the 80 series A343F transmissions are the same, even the LX450. The Lexus difference is in the ECM/TCM.

The donor motor and transmission were from a 95. My rig is a 97.
When I select drive, and press the gas, that is when it boggs down.
I will take a look at the FSM, thank you.

 

[Malleus]

So, here's the problem: regardless of whether you select D(rive) or L(ow), the transmission starts out in 1st gear. If it works as it should when you select 1st gear, but not when the TCM does it, there are a number of potential problems. The good news is that the transmission is probably OK.

Go through the troubleshooting matrix; it'll help you find the problem. LMK if you can't find it. Also, check to see if you have a transmission diagnostic trouble code; the FSM will tell you how, and tell you what the code means, if you do.

Report back and we'll try to get you back on the road.

 

[Offroader93]

So, here's the problem: regardless of whether you select D(rive) or L(ow), the transmission starts out in 1st gear. If it works as it should when you select 1st gear, but not when the TCM does it, there are a number of potential problems. The good news is that the transmission is probably OK.

Go through the troubleshooting matrix; it'll help you find the problem. LMK if you can't find it. Also, check to see if you have a transmission diagnostic trouble code; the FSM will tell you how, and tell you what the code means, if you do.

Report back and we'll try to get you back on the road.

So from what I have read, it could possibly be the solenoids, or valve body. I got the P0753, and P0758 codes which were electrical malfunctions. I actually have a 2nd transmission, so I cleared the codes, and swapped out the solenoids. The codes did not return, however the problems persisted. I can do more troubleshooting tomorrow, however this is where I am at.

 

[scottryana]

Truck was driving just fine before? Sounds like classic stripped drive flanges to me....

 

[Malleus]

Drive flanges? It shifts fine manually and not automatically. How is that drive flanges?

 

[scottryana]

Drive flanges? It shifts fine manually and not automatically. How is that drive flanges?

"I am trying to figure out why it is barely moving in drive. The rpms go up high (3-4k), and it takes my foot to the floor to get it to move. Shift into low on the gear selector and it moves like normal in both drive and reverse. Shift the transfer case into low and it also moves normally."

Barely moving in High range in drive, driving fine in Low range and moves normally. If you are saying the truck always moves fine but doesn't shift fine than I misread what you wrote.

 

[Offroader93]

So did more diagnosis just now. Got it up on the street in front of the house. I figured being on my driveway which is a hill won't be good to get a good test.
Backed out and put into drive. All the way down the street, 1500.2k constant rpms (not as high as previously stated) did not shift... Reversed and tried 2nd gear. Same thing. Low was normal.

 

[baldilocks]

What symptoms were you seeing that compelled you to replace both the engine and transmission?

Have you tried a test drive with the wire harness disconnected from the transmission where you shift through the gears manually starting off in low and progressing into 2 and then D?

 

[Offroader93]

What symptoms were you seeing that compelled you to replace both the engine and transmission?

Have you tried a test drive with the wire harness disconnected from the transmission where you shift through the gears manually starting off in low and progressing into 2 and then D?

The original motor developed a knock at over 300k so i sold it for parts, along with the transmission which would slip pretty bad in reverse.
And I have not. I can try that later however.

 

[93z]

I am having a similar issue.
93 LC - 4 new solenoids and soldered in 2 new capacitors in the ECT

Manually shifting works fine. When I put it in D it starts out in 2nd or 3rd. Sometimes when I put it in D it kills the motor like maybe the converter is locking up. Oddly it seems to get better after the trans heats up (10-20miles) and I can leave it in D.

Looking into checking for codes now.

 

[wpns4l]

"I am trying to figure out why it is barely moving in drive. The rpms go up high (3-4k), and it takes my foot to the floor to get it to move. Shift into low on the gear selector and it moves like normal in both drive and reverse. Shift the transfer case into low and it also moves normally."

Barely moving in High range in drive, driving fine in Low range and moves normally. If you are saying the truck always moves fine but doesn't shift fine than I misread what you wrote.

Unless I misread I agree. If it drives normal on low range but not high range check the drive flanges.

 

[mjosoba]

So the original transmission was also misbehaving? Would definitely lead me to look at the drive flanges. Try putting it in low, pulling the t-case fuse, then putting it back in high and see what happens.

The original motor developed a knock at over 300k so i sold it for parts, along with the transmission which would slip pretty bad in reverse.
And I have not. I can try that later however

 

[Malleus]

I am having a similar issue.
93 LC - 4 new solenoids and soldered in 2 new capacitors in the ECT

Manually shifting works fine. When I put it in D it starts out in 2nd or 3rd. Sometimes when I put it in D it kills the motor like maybe the converter is locking up. Oddly it seems to get better after the trans heats up (10-20miles) and I can leave it in D.

Looking into checking for codes now.

Your problem may not be the same as the OPs. He has a different transmission. Although the A442F you have is similar to the A343F, it's not the same. The A343F is controlled by a TCM which is integrated into the engine ECM. The A442F has a stand-alone TCM. The two are not programmed the same.

What makes you think the transmission is starting in 2nd or 3rd (drive)? Even if you manually start in transmission in 1st, it shifts into 2nd automatically at speed; it just won't shift into overdrive. You can check the operation against the A442F manual (RM360U); it's in the 80 series Resources section.

If you had the cover off to replace the solenoids, did you check the operation of the solenoid spools? They should all move freely without pressure.

 

[Malleus]

So did more diagnosis just now. Got it up on the street in front of the house. I figured being on my driveway which is a hill won't be good to get a good test.
Backed out and put into drive. All the way down the street, 1500.2k constant rpms (not as high as previously stated) did not shift... Reversed and tried 2nd gear. Same thing. Low was normal.

So, here's the rub, even if you select "L" (1st gear), the transmission is designed to shift into 2nd gear. If you select "2" (2nd gear) or "D" (3rd gear), the transmission starts in 1st gear, then shifts to 2nd, and then to 3rd (in "D", you also get O/D).
This excerpt is from the repair manual (RM479U), showing the normal operation:

When you say "Low was normal", does that mean the engine rpms seemed to match what you expected, AND the transmission shifted from 1st to 2nd, or just that you were able to get it rolling, and it didn't shift?

I apologize for being picky, but these problems are really hard to diagnose without specific faults. FWIW, this is why few people want to work on automatic transmissions. If a carb is wonky, you can watch it and sort of guess what's wrong. The transmission is a true black box.

From what you've shared so far, I'd look at the solenoid driven spools (the sliding shafts in the valve body the solenoids actually move) and the accumulator pistons, particularly the timing solenoid spool and accumulator. This is the "Shift solenoid valve SL circuit" fault from the problem solution matrix (pages AT-61 to AT-63).

Unfortunately, this requires removal of the cover to get to the spools and removal of the valve body to get at the pistons. If you have a spare gearbox, it might be helpful to take a look at these on that unit, before trying to get at them with the case bolted in the truck. The unit repair manual (RM479U) is the manual you need for information on all these parts (they are illustrated in the Repair Manual [RM432U], AT section, but not identified there).

Before you go to those extremes, however, it might be beneficial to perform the Mechanical and Hydraulic System Tests, described on pages AT-52 through AT-58; this assumes you still have no DTCs. If you do, definitely start there.

FWIW, if the transfer is in H (high gear range) and you can get the transmission to function differently just by moving the gear select lever, your problem isn't drive flanges. At least, if it is, it's a drive flange failure I haven't heard of (which is certainly possible); the drive flange observations above assume that when you describe "Low", you're indicating low range with respect to the transfer case, not 1st gear on the transmission select lever. The two operations are not connected.

 

[Malleus]

Just for general observation's sake, you can see the difference in operation between the A442F and the A343F from the operation tables above. The A343F in the Lexus LX450 is different still and the A343F programming in the LX470 is even more different - it'll get into drive with "L" selected (you just don't get O/D). Same transmission, just different programming.

 

[jonheld]

I have a 97 LX450. The auto transmission will NOT upshift to 2nd gear when the auto shift lever is in L. This is the case with the A440F and the A343F.
With the transmission shifter in 2, it will start in 1 and upshift to 2, unless the 2nd gear start button is pressed.
If I read your post incorrectly, I apologize.

 

[Malleus]

I had my doubts when I first read the operation description, but I tried it with my '95 A343F and it operates as the manual says it should. I haven't tried my '94 A442F.

I can only go by what I see personally, and what Toyota published. I'm all for new information, but there's not much published that I could find.