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Discussion Starter · #1 ·
4bt has been in a Jeep Wrangler for 3 years and running fine. Today I took it out for a drive and it got a louder and louder knock and tick in the motor. I should have trailered it home but instead tried to limp it home on back roads and didn't make it very far before it finally gave out. The motor was still spinning with a loud grinding noise like crazy until it came to a stop but would not make power. Once it came to a stop it died. The starter will spin the motor and it sounds like it's kind of firing off but gears are grinding noise coming out of the motor and does not start. The motor is mated to a 47rh trans. It has a denny t fuel pin and hx30 turbo. Other than that it is stock. When it was making noise oil level was fine, oil pressure was fine, and Temps were normal. No external damage on the block and no oil leaking. Not sure where to start checking first. Any help is greatly appreciated.
 

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Any smoke when this happened?
Remove the oil fill and have someone crank the motor and see if it is puffing out the oil fill.
Remove the fan belt and see if there is any difference in the noise when cranking.
Maybe a compression test then drop the oil into a clean container and check for metal.
Steve
 
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Perhaps, the knocking and grinding is a sign that the 47RH has failed, plantaries, even converter coming apart internally sound like grinding gears, what does its fluid look like...drop its pan.
I had a 47RH that failed and locked up the rear wheels @ 60 mph.
Just a thought...
 

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Discussion Starter · #4 ·
Even if the trans went bad it should atleast start right? Seemed odd that it killed the motor. There wasn't any smoke. I checked for smoke and blowby when it was running and knocking but it was normal. Have not checked the oil yet and it has an electric fan.
 

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Discussion Starter · #5 ·
When the starter is turning the motor over the crank pully and belts on the front of the motor don't move right. They start to spin but then stop while the motor is turning over. Could it be the timing gears grinding or crankshaft broke? Oil on dipstick looks fine and coolant looks fine.
 

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Can you inspect the drive plate and torque converter?
Drive plate could be broken.
I have seen broken cranks on engines other than Cummins but not common.
Steve
 
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Even if the trans went bad it should atleast start right? Seemed odd that it killed the motor. There wasn't any smoke. I checked for smoke and blowby when it was running and knocking but it was normal. Have not checked the oil yet and it has an electric fan.
The converter could come apart along with the stator and broken parts jamming up in converter could prevent starting...did you bother to check inside the trans pan?
 

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Discussion Starter · #10 ·
Dropped the trans pan and no debris or anything out of ordinary. It sounds like grinding is coming from around front main when starter is turning over motor.
 

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Dropped the trans pan and no debris or anything out of ordinary. It sounds like grinding is coming from around front main when starter is turning over motor.
Well, looks like the gear cover is the next part to come off...
 

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My guess would be the old killer dowel pin or a gear housing bolt fell out into the gear train.
 

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Discussion Starter · #13 ·
Well I pulled the motor and found the flexplate broke off the motor. Now debating on complete teardown or putting a new plate on and seeing if it will run. Seems a bit odd to me that it would shear off like that without something else wrong. And why would that have killed the motor.
131386
 

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... it got a louder and louder knock and tick in the motor. I should have trailered it home but instead tried to limp it home on back roads and didn't make it very far before it finally gave out. The motor was still spinning with a loud grinding noise like crazy until it came to a stop...
I suspect that the flex plate was cracked and eventually tore loose form the crankshaft. Important to note that the 4bt did not seize. With a little luck, another flex plate will fix the problem. You might want to carefully check the alignment of the adapter and transmission bell housing, any misalignment would cause the flex plate t0wobble and eventually crack at the crankshaft.

Good luck <fingers crossed>.
 
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If you can hook it up to start you can check for noises before stripping, Will need the new flex plate first..
I just stuffed the garden hose into the water pump suction so I could run mine for a bit of time.
Guess some of the broken bits were jamming and with no flywheel effect from the torque converter mass it did not want to idle.
Cheers Steve
 

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Well I pulled the motor and found the flexplate broke off the motor. Now debating on complete teardown or putting a new plate on and seeing if it will run. Seems a bit odd to me that it would shear off like that without something else wrong. And why would that have killed the motor. View attachment 131386
When it broke the converter rocked because there was nothing but your stator and pump supporting it and the converter looks like it snagged on of the the plate bolts on the crank...while it is out, I would seriously check the pump gears too...lucky it is not your motor.
 

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Discussion Starter · #17 ·
Thanks for the advice! Couple of questions.

Russ, If the motor to adapter and adapter to trans is all bolted up tight without any gaps, does that mean the alignment is ok or is there some way to check the alignment?

SUBRUTUS, is there an easy way to check the pump without tearing down the trans? I had a friend rebuild the trans before I put it in the Jeep and am not really familiar with all the internals of the trans. I thought if you pull the pump you have to also have the clutches out to get it back in.
 

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...
Russ, If the motor to adapter and adapter to trans is all bolted up tight without any gaps, does that mean the alignment is ok or is there some way to check the alignment?
...
NO - The alignment I am referring to is the confirming that the engine crankshaft center, the adapter bore center and the transmission input center are all in a straight line. From a quick google definition search:
"Run-out

Run-out or runout is an inaccuracy of rotating mechanical systems, specifically that the tool or shaft does not rotate exactly in line with the main axis. For example; when drilling, run-out will result in a larger hole than the drill's nominal diameter due to the drill being rotated eccentrically. Wikipedia "

The wobble caused by run-out could have stress cracked your flexplate - NOTE that I said "could", there are other reasons for flexplates cracking. I am trying to make you aware of potential issues - DO NOT have the ability to stare at the pictures and give you an absolute answer.

Over the last 50+ years, I've done maybe 5 engine replacements (engine and transmission from the same manufacturer and design series) and 2 engine swaps requiring an adapter. Both engine swaps involved manual transmissions using the flywheel that came with the engine. I've never measured for run-out. Precision machine work (and precision mechanical measurements) are NOT in my skill set.

Russ
 
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Thanks for the advice! Couple of questions.

Russ, If the motor to adapter and adapter to trans is all bolted up tight without any gaps, does that mean the alignment is ok or is there some way to check the alignment?

SUBRUTUS, is there an easy way to check the pump without tearing down the trans? I had a friend rebuild the trans before I put it in the Jeep and am not really familiar with all the internals of the trans. I thought if you pull the pump you have to also have the clutches out to get it back in.
Look into the stator & input shaft 'that is the part the converter slides onto' w/flashlight see if pump ears are intact, damaged or missing...if intact perhaps still good, slide the converter on making sure pump ears are all the way into converter slots and rotate feeling for rough spots.

Not familiar w/trans, get a manual for your type of transmission and learn or find a shop to do it...
 

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