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Old 09-26-2013, 11:26 AM
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T-400 new whining noise

Hey guys. I rebuilt a good TH400 last year, and just started driving the truck that I put it in about a month ago. I've been tinkering with valve lash, timing, the vacuum modulator on the trans, and carb settings trying to dial it in just right.

Anyway, everything's been fine until yesterday, when the transmission started whining. It whines all the time in park and neutral, and when you put it in gear it seems to go away a little but gets louder as the RPM's go up. The whine is definitely dependent on the RPM's of the motor and not necessarily the driveline. For example, if I'm in neutral or park and rev the engine up, the noise gets louder as the RPM's increase. But if I'm cruising at 55mph and shift the trans into neutral allowing the engine RPM to drop to about 1000 the whine gets quieter.

I checked the fluid and it's full and looks and smells nice and new. I also removed the bolts which attach the flexplate to the torque converter to isolate the issue. With the transmission disconnected from the engine, the noise is non-existent.

Any ideas as to what's wrong, and what should I try next? This was the first transmission that I rebuilt so any number of things could have gone wrong, but I really do feel quite confident in it. I was meticulous with everything, and it's been functioning beautifully for about a month.
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Old 09-26-2013, 12:11 PM
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I'd be looking in the direction of a faulty torque converter. I've had many of em at the shop, after a rebuild, over the years do the same thing. I've changed converter company's a few times because of that problem. But normally,I might add,the noise would occur before it left the building.You should easily hear the noise from the converter if you were under the truck, with someone else goosing the gas pedal.

Last edited by rick 427; 09-26-2013 at 12:25 PM.
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Old 09-26-2013, 01:04 PM
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Thanks for the reply. It is a new TC but I didn't pay an outrageous amount for it so it's definitely suspect.

Is there any way I can rule the TC in and the front pump out? I did read online while I was researching that front pumps that are bad/going bad will whine in all gears PRND21 and respond negatively to engine RPM, and torque converters that are going bad make their most noise while in a forward or reverse gear with the vehicle stationary and not moving. Is this typically the case? When I'm in gear and not moving is the time the whine is the least pronounced.
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Old 09-26-2013, 01:28 PM
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All I can tell you at this point is,as long as the torque converter is spinning,if bad,it will make noise.And it will make more noise under a load,i.e. in gear. But at idle,in any gear,is when the noise will be the least. Generally,if the pump is going bad,it'll load the pan and filter with metal particles,eventually making the truck stop moving from a clogged filter.With a noisy converter,no metal particles are usually present,which sounds like is your case,since you say it still drives fine.Wouldn't hurt in your search to drop the pan and have a look anyways.

Last edited by rick 427; 09-26-2013 at 01:44 PM.
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Old 09-26-2013, 03:34 PM
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Sorry guys...wrong thread.
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