Transmission goes 'boing'

[Zeke3]

Kevin, I have a non-Ford car that had a squeak like noise that turned out to be the splined connection between the axle and a universal joint. I am thinking your noise might be the splined connector between the drive shaft and the pinion shaft at the differential. There was a picture on here not very long ago that showed excessive wear on a splined coupling. Good luck with your search.

[Fatheads4ever]

Interesting.. there is a splined connection from the tail shaft of the gearbox to the universal. I think that coupling is lubed from the gearbox. I might change the gearbox oil from ep90 to 600 and pack the universal's internal spline with a hard grease.
Thank you for your feedback.