Vibration under load after engine replacement and transmission rebuild

[Sm1thson]

I have a 2002 UZJ100, 2UZ-FE 4.7 V8, A343F / 30-43LE, with about 280,000 miles.
The original engine had misfires and low compression in several cylinders. After disassembly, significant cylinder head damage was found, so the engine was replaced with another 2UZ-FE. The original flexplate was reused.
Before the engine replacement, the vehicle was test-driven. Despite the engine problems, the transmission shifted normally and there was no drivetrain vibration.
After the replacement engine was installed, the vehicle initially drove normally for over 60 miles, then developed a strong vibration under acceleration. Later, the transmission also developed a 1–2 shift problem/slip and occasional metallic noise.
The transmission was then professionally rebuilt, including friction plates, seals, hydraulic work and torque converter rebuild. After reinstalling it, the vehicle drove normally for about 20 miles, then the same vibration returned.

Current symptoms​

• Strong vibration under load, mainly around 1,200–2,000 rpm.
• If load is maintained around 2,000 rpm, the vibration continues.
• With very gentle acceleration, vibration is minimal or almost absent.
• Same behavior when starting in D, L or 2.
• No vibration in Reverse, even under stronger acceleration.
• Vibration disappears after shifting into higher gears.
• ATF level is correct; temperature was about 180°F when checked.
• ECU/TCM reset made no difference.

There is also a different, higher-frequency vibration during coasting/deceleration, noticeable around 25–28 mph. I am not sure whether this is related or a separate problem.
Both driveshafts have been rebuilt. The front driveshaft was removed and the vehicle was tested with the center differential locked and rear-wheel drive only — no change in the main vibration.
Engine mounts were checked and one was replaced. Torque converter bolts were also removed, inspected and reinstalled — again, no change.
The transmission rebuilder has test-driven the vehicle and believes the problem is most likely transmission-related.
My main questions:

1. What could cause a load-dependent vibration in the lower forward ranges, but not in Reverse, and disappear in higher gears?
2. Could a valve-body, pressure-control or solenoid problem cause a sustained vibration/shudder like this?
3. Could an electrical connection, internal harness or ground problem cause this?
4. Has anyone seen a similar A343F problem?

Any A343F-specific experience would be greatly appreciated.

 

[3_puppies]

when installing the flexplate, was the "red" bolt installed first? I think that is proper procedure

 

[Sm1thson]

when installing the flexplate, was the "red" bolt installed first? I think that is proper procedure

There was no red bolt... one blackish bolt was little bit different from others and this one went in first.

 

[Sm1thson]

got the rumble now on video aswell

 

[Malleus]

There was no red bolt... one blackish bolt was little bit different from others and this one went in first.

That's correct, one green the remainder are black (not yellow as per the list below; at least the ones we get in the states aren't). The lone bolt is for centering the torque converter on the flexplate.

I have some experience with the A343F, and from your description, I don't think the problem is in the transmission. Your shifting problem is likely in the valve body. If it wasn't cleaned well, there may be contamination in it. If the cooling circuit wasn't cleaned using kerosene and if the torque converter was reused, you could have the same problem, which, again based on your description, is what I would expect: the transmission operated well, until the trash in the cooling circuit/torque converter (or both) made its way to the valve spools and now you have delayed shifting. The good news is that flushing the fluid with at least a full load of new fluid, and then removing and cleaning the valve body thoroughly, will likely cure the problem.

I would, however, look very closely at the electrical connections between the engine harness and the transmission (they are on the top of the bell housing) and the connections between the transmission subharness and the transmission. Look very closely for damaged wiring or damaged terminals in the connector housings, before you tear into the case. Transmissions rarely "suddenly" fail.

As to your vibration problem, based on your description, I would not expect the problem to be in the transmission. Look at your harmonic balancer and both engine mount isolators, including the third one under the transmission, again, while driving if possible. Poor condition of either, or both, will tend to make an engine vibration seem larger than it would be on an engine stand. Bottom line: I'd look at the engine for the root cause of the vibration.

HTH

 

[3_puppies]

There was no red bolt... one blackish bolt was little bit different from others and this one went in first.

I couldn't remember the color, just that 1 "special" bolt needed to be installed first to get stuff in alignment

 

[Sm1thson]

That's correct, one green the remainder are black (not yellow as per the list below; at least the ones we get in the states aren't). The lone bolt is for centering the torque converter on the flexplate.
View attachment 4174222
I have some experience with the A343F, and from your description, I don't think the problem is in the transmission. Your shifting problem is likely in the valve body. If it wasn't cleaned well, there may be contamination in it. If the cooling circuit wasn't cleaned using kerosene and if the torque converter was reused, you could have the same problem, which, again based on your description, is what I would expect: the transmission operated well, until the trash in the cooling circuit/torque converter (or both) made its way to the valve spools and now you have delayed shifting. The good news is that flushing the fluid with at least a full load of new fluid, and then removing and cleaning the valve body thoroughly, will likely cure the problem.

I would, however, look very closely at the electrical connections between the engine harness and the transmission (they are on the top of the bell housing) and the connections between the transmission subharness and the transmission. Look very closely for damaged wiring or damaged terminals in the connector housings, before you tear into the case. Transmissions rarely "suddenly" fail.

As to your vibration problem, based on your description, I would not expect the problem to be in the transmission. Look at your harmonic balancer and both engine mount isolators, including the third one under the transmission, again, while driving if possible. Poor condition of either, or both, will tend to make an engine vibration seem larger than it would be on an engine stand. Bottom line: I'd look at the engine for the root cause of the vibration.

HTH

Thanks again for the detailed reply. I have now confirmed a few more details with the transmission shop.

The transmission was fully rebuilt. All clutch packs were reportedly replaced, while the torque converter and valve body were restored to as-new condition. The shop says all solenoids were either replaced or tested, and worn valve-body bores were reamed and fitted with oversized valves where necessary.
The metallic noise is gone, but the main vibration/slip is unchanged. When completely cold, the transmission works normally for the first 2–3 minutes. After that, the problem appears under load at around 1,500–2,000 rpm in D, 2 and L, including low range. Reverse remains completely smooth, even with more throttle.
During the vibration, engine speed seems to rise without a proportional increase in road speed, so it may actually be a clutch slipping and grabbing rather than a rotating imbalance.

Both driveshafts have been rebuilt, removing the front driveshaft made no difference, and reinstalling the torque-converter bolts in the correct Toyota sequence changed nothing.
The cooler and cooler lines were not flushed during the rebuild. The valve body is now being removed for another inspection.

Does this cold-versus-warm behaviour, together with normal Reverse operation, point more toward a forward-clutch hydraulic leak, a line-pressure/valve-body issue, or contamination from the cooler? Would comparing line pressure in D and Reverse, both cold and after the fault appears, help separate these possibilities?

 

[Sm1thson]

Quick update:

The valve body was checked again and no fault was found, so the transmission was removed and opened once more. This time the problem was finally found: the same clutch pack was burnt again, and the forward clutch drum had a micro-crack/leak around the welded section. The technician confirmed the leak with compressed air – bubbles appeared from the weld.

The drum was replaced with an OEM unit and the damaged clutch plates were replaced again. The transmission is now back in the truck and shifts extremely smoothly. The original strong vibration/slip under load at 1,500–2,000 rpm is completely gone.

There is still a separate intermittent vibration on coast, usually around 50–60 km/h. It remains if I shift to N, but disappears immediately with a little throttle or if I select 2nd and get engine braking. I have also felt it once around 120 km/h while coasting.

We are now replacing both complete front CV axles because they had a lot of play. During removal we found another interesting issue: the knuckle-side needle bearing supporting the CV shaft was damaged on one side, and on the other side there was basically nothing left of the bearing at all. The CV shaft bearing surface was also visibly worn. The bronze/brass guide bush will be replaced together with the needle bearing.

So at this point it looks like there were actually two separate problems: the cracked forward clutch drum caused the transmission slip/shudder, and the remaining coast vibration may be related to the badly worn front CV/needle-bearing support.

 

[3_puppies]

nice to see you most likely found the issues