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Can a bad transmission replacement job cause harmonic balancer to fail

My Infiniti G20 with 200K miles on it recently had the transmission replaced with a rebuilt one (< 5k miles / 3 months ago). Now the harmonic balancer failed requiring replacement of the balancer / crankshaft / belts and possibly water pump.

How likely is it that a badly done transmission job could have caused the harmonic balancer to fail ? After the transmission replacement the car “felt” like it was running fine.

Or @200K miles, is the harmonic balancer failure just bad luck ?

Or worse, is it sign that the engine is on its last legs ?

The harmonic balancer and the transmission are at opposite ends of the engine. I see no connection.

If you’re replacing the crankshaft you might as well rebuild the entire engine. Or buy a rebuilt engine.

Personally, I’d say, “Goodbye, faithful G20.”

Are you sure you need to replace the “crankshaft”? If yes, I’d wonder about the future of the motor. It is possible they need to replace the balance shaft?

A balancer just spins and perhaps a bearing burned out, but that would not be related to a transmission replacemwnt.

unrelated, The harmonci balancer isn’t related to the trans.
I’d also agree that it’s time to buy a rebuilt engine and put it in, or have the motor rebuilt… it’s time for a 2nd water pump, 2nd timing belt and serp belt… (hopefully these have been done already kuz it’s time.)

The crankshaft must be rotated to access the mounting bolts for the torque converter. If the harmonic balancer bolt was turned counter clockwise it MIGHT have loosened it enough to cause the failure.

You’re suspicion about the crankshaft was well founded. I misunderstood what the garage told me on the phone. I cleared it up this morning in person.

The crankshaft is fine. The car is driveable for short distances, and engine itself seems fine. The outer section of the balancer separated from the composite material and inner section. So the balancer / belts need to be replaced, and since the radiator overflowed a little coolant, the garage suggested replacing the thermostat as well just to be on the safe side. The water pump also seems fine. Based on this, it seems reasonable to risk the cost of replacing the balancer/belts/thermostat.

Apologies for the incorrect initial information. I was a bit fried yesterday as the transmission in my MDX also decided to quit at pretty much the same time the G20 did. Not a good car day.

I think Rod Knox may be on to something here. It appears like the harmonic balancer bolt was loose allowing the balancer to slip on the crankshaft nose. It is unlikely that rotating the engine to gain access to the TC bolts would have loosened the crankshaft damper bolt as it is torqued to 108 - 112 ft-lbs. It is possible that the bolt was loosened if the flex plate was removed to replace the rear main seal. However the flex plate crankshaft bolts are only tightened to 61 - 69 ft-lbs.

When and at what mileage was the timing belt replaced most recently? It is possible that the harmonic balancer crankshaft bolt was not torqued to the correct specification at that time. A loose bolt would allow the balancer to slip on the crankshaft nose wallowing out the key and keyway until the balancer was so loose it started wobbling or came off entirely. If it has been a while since the crankshaft bolt was touched, it will be hard narrowing the liability to any one shop and then proving it. It could have just been bad mechanical luck.

Hope this helps.

Water pump has been replaced at least once. Major service was done recently. Timing belt was replaced. Not sure about serpentine belt. Also done recently (clutch, transmission … 8-()