Vibration through gears until it goes into overdrive - aod

[Sean D 31]

Hi All - I have been trying to figured out a vibration I have since replacing the c6 with aod, new stock torque convertor, new aluminum drive shaft and u joints, new strange truetrac differential and new axles. Used same flexplate. Seems like vibration is present through first 3 gears, most noticeable in 3rd at 35 to 45 mph. All vibration goes away as soon as trans goes into overdrive either manually or automatically. Also under normal and light acceleration, it seems like vibration is a bit less in first part of each gear range. And again goes away in OD. 351 cleveland. Thoughts?

[Sean D 31]

One more note: we reused the flexplate that was behind the c6 trans. Also seems I can get the vibration in neutral sitting in the garage.

[Midlife 814]

Have you checked the drivetrain angle?  That's the tranny drop, the rear end rise, and the driveshaft angle.  Unless those angles are within a narrow tolerance, you can get all sorts of vibrations that won't go away. 

[1969_Mach1 333]

If you are certain is does it in neutral, I wonder if there is a balance issue with the torque converter.  You mention the vibration stops when the trans is in overdrive.  I've only tinkered with the AODE and 4R70W which are later versions of the AOD.  I think the AOD has a lock-up torque converter.  Pay attention to when the torque converter locks up, overdrive only, third gear and again in overdrive.  That might help to isolate the issue.  You know, is the vibration stopping related to when the torque converter locks up or not?

[bigmal 225]

Not sure how the torque converter locks on a Mustang but vibration was a common problem in Australian Holden Commodores that were fitted with the Nissan in line 6. The cheap fix was to disconnect the lock up wires. It's been a while so my memory is scracthy but may be worth trying it either locked or unlocked and see if there is a difference. Of course this suggestion is no use if it's not electrically operated.

[Sean D 31]

11 hours ago, 1969_Mach1 said:

If you are certain is does it in neutral, I wonder if there is a balance issue with the torque converter.  You mention the vibration stops when the trans is in overdrive.  I've only tinkered with the AODE and 4R70W which are later versions of the AOD.  I think the AOD has a lock-up torque converter.  Pay attention to when the torque converter locks up, overdrive only, third gear and again in overdrive.  That might help to isolate the issue.  You know, is the vibration stopping related to when the torque converter locks up or not?

I have done this test to go from overdrive only, third gear and again in overdrive, and the vibration stops as soon as I get into overdrive, as start when I downshift into 3rd. BTW - how can you tell if I am running a lock-up torque converter and if so how to tell if/when it is locking up?

[det0326 179]

An AOD does not have a clutch pack in the converter to lock, it is locked  by the  direct clutch in the transmission thru the small internal input shaft.  I too think that it sounds like a converter issue. 

[1969_Mach1 333]

Thanks det0326.  I wasn't certain if torque converter in an AOD locked up by using a clutch inside like the later AODE and 4R70W.  Still seems like an issue with the converter.  At least that is a straight forward repair.

[det0326 179]

Yes I am with you on the converter issue, 1969_Mach1 but not sure what it could be tho. The way Sean D described the issue anyway.  Don't know the state of the AOD whether it is a rebuild or used when put in the Mustang but possibly a pump bearing/bushing.  Assuming everything on the engine is the same and has not been changed.

[Sean D 31]

On 11/6/2017 at 1:42 PM, det0326 said:

Yes I am with you on the converter issue, 1969_Mach1 but not sure what it could be tho. The way Sean D described the issue anyway.  Don't know the state of the AOD whether it is a rebuild or used when put in the Mustang but possibly a pump bearing/bushing.  Assuming everything on the engine is the same and has not been changed.

Everything in the engine is the same, and the aod was rebuilt with a shift kit (hard shifts). I am know not 100% sure if all the vibration goes away in neutral (hard to tell) but most of it does. However, I am 100% sure that the vibration is present in all gear until it shifts into overdrive. But when not in overdrive the vibration seems to get worse as speed increases through each gear, so more vibration at the top of each gear. Then bam, goes away once it goes into overdrive. 

[det0326 179]

Sean 

Check your transmission and pinion angles if you haven't done so .  I don't think the drive angle would have changed that much from just swapping the C6 out for the AOD but u never know.   The thing that makes it confusing tho is the vibration stops when in OD. The small input shaft would still be turning in neutral so may produce a little vibration so maybe something associated with it. Sorry u are having problems with tranny there not fun to remove and install. I had mine out twice now and still need to drop the valve body out one more time to correct another problem. It was recommended to leave one of the balls out of the VB by a well know AOD mechanic as an upgrade to 3-4 downshift but it didn't work on mine so I need to install the ball sometime. It works ok just sometime as a hard downshift.   

Dave