Can't identfy vibration

mhjo

Founding Member
Nov 9, 2000
490
0
17
Oslo, Norway
After AOD swap (from c4) I experince vibration at a certain rpm. It is noticable at 50 mph in 3d and 80 mph in OD. Wheels have been balanced, axle too. Vibration can be felt in the shifter stick.

What can this be?
 
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is your driveshaft a slip yoke style or a 2 piece?

if it is a 2 piece have you checked that your driveshaft is in phase? its very common to get the driveshaft 180* rotated and that will cause vibration and the more the angle of the drive shaft the worse it gets

or since your trans is new, does your pinion angle and trans output angle angle match, if not that will cause vibration too, a cvd driveshaft or axle shims can fix this
 
What flexplate did you use? The swap requires a conversion type flexplate because the 5.0 that the AOD came from and your 289 are not balanced the same. The C4 flexplate won't bolt up to the AOD converter. The AOD flexplate will bolt right up to your 289 crank, BUT will cause vibration due to the balance differnce.
 
What flexplate did you use? The swap requires a conversion type flexplate because the 5.0 that the AOD came from and your 289 are not balanced the same. The C4 flexplate won't bolt up to the AOD converter. The AOD flexplate will bolt right up to your 289 crank, BUT will cause vibration due to the balance differnce.

that was my first thought, until i realized that he had the vibration at a couple of rpm points rather than through the whole rpm range.
 
I'm having the exact same problem with my 67 aod conversion. Your post said you had your axles balanced. I didn't know that was possible.:shrug: Who did you take it to?
 

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I'm having the exact same problem with my 67 aod conversion. Your post said you had your axles balanced. I didn't know that was possible.:shrug: Who did you take it to?

Don't balance your axles unless you're sure that's the problem. Did you swap axles right before you got the vibration? If you changed the trans and then got the vibration, why not start at the trans when looking to cure the vibration problem?
 
mhjo,
You haven't answered the implied question about whether/how you dealt with the flex plate imbalance issue. If it is a stock flex plate from a late model 5.0 it will be balanced incorrectly for your 289 and WILL cause a vibration that may be worse at different RPM's.
HTH,
Gene
 
Sorry for "lost in translation" When I say axle I mean drive shaft.
The people that sold me the flex plate insist it is the right one (they are a specialized Classic Mustang supplier i Norway who get their stock from NPD and Summit).
However, I will call the today and ask for product name/number and post here.
 
mhjo,
You haven't answered the implied question about whether/how you dealt with the flex plate imbalance issue. If it is a stock flex plate from a late model 5.0 it will be balanced incorrectly for your 289 and WILL cause a vibration that may be worse at different RPM's.
HTH,
Gene

actually yes he did.

mhjo said:
I only have vibration at a certain rpm

if the flexplate was the wrong one it would have a bad vibration through out the rpm range, and not just a couple of specific rpm points, which is why i think that he has a bad output yoke bushing, or the U-joint was improperly assembled.