[stanged1970]

Had my C-4 rebuilt a few weeks ago and got it back with a vibration at 2k and 4k rpm. I have an '87 5.0L HO and I know both have to have the 50oz balance. If either one of these are out of balance would there be a vibration throughout the whole rpm range or would it isolated to certain rpm values?

I need to know because the shop is getting ready to do some extra, non-warranty work and I'd like to prevent that if possible.

thanks

[The Greek]

If nothing else but the trans was worked on, I'd think that it would be, (the vibration), drive train related.

If you are getting the vibration when the trans is in neutral and the car is parked, then I'd say you have the wrong flexplate or one that is warped.

If you are getting the vib. while driving down the road, the cure may be as simple as rotating the driveshaft 180 deg. at the pinion yoke. Whoever did the work didn't mark the driveshaft when it was pulled for the trans work.

Ford pinion yokes have small locating tabs that lock the U-joint in position, so that it's centered, when you tighten the two U-bolts down.

It is possible to tighten down the U-joint off center if the tech isn't paying attention. That will give you a nice noticeable vibration.

[stanged1970]

Yeah, it does vibrate in park and neutral. When they rebuilt the tranny they put in a new torque converter and a new flexplate. They said it was a 50oz with a C4 bolt pattern so that should be ok, but I just remembered last week they told me they had matched the flexplate to the tranny and not the engine. That didn't make much sense to me.

The mechanic pointed out that the gasket(or whatever it is) in the dampner was coming out so that may be the cause of the vibration.

I paid a bunch of cash to get this tranny rebuilt and although the shop has been really good and taken the car back to look into it, I'm sure there is only so much they can do to find the vibration. Especially since I had a vibration before the rebuild but it was at 3k only.

[The Greek]

I now really think it's the wrong flexplate if they matched it to the transmission. There never was a production flexplate made for the C4 with 50 ounce imbalance. These flexplates are a specialty item which have to be ordered from a performance or specialty manufacturer. A regular parts house isn't going to stock a 157 tooth 50 oz flexplate for a C4. They're all going to be 28oz.