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Troubleshooting a driveline vibration

So I've been tracking my car for the past year and started to get an intermittent driveline vibration. It was only noticeable to me in 4th gear and sometimes it was there and sometimes it wasn't, but it was getting worse as the year went on. For the rear suspension, having the 302S trailing arms and a Multimatic third link (both solid), the only rubber was the stock UCA bushing. The shop that put the car together originally told me that I should change this once a year. After going through the rear end, checking the pinion angle, I finally got to the UCA bushing. To make a long story short, the bushing was totally separated and the inside just fell out when we unbolted it. Lessons learned here is if you are tracking you car with a "race" type suspension, you need to be checking the UCA bushing or replace it frequently or swap it out with something a little more durable. After calling the race shop that originally did all the work, they corrected themselves and said they replaced the bushing every time the pulled the axle out, which turns out to be every race. Asked why they used the stock bushings, they said they get them for free from Ford. P/N for the stock bushing is BR3Z-5A638-B just in case you were curious. I replaced mine with a Prothane Polyeruthane Bushing, P/N: PT-6315BL.

Yes, this is the bushing on the top of the differential. The sleeve is reused. The shop just unbolted the shocks and removed the bolt going through the bushing and dropped the axle enough to do the work. I believe they burned what was left of the old rubber out of the sleeve, cleaned it up and then installed the Prothane Bushing without removing the sleeve from the car. Once you get the sleeve cleaned up and lubricate the pieces, no press is needed. The Prothane bushing is a three piece set, with two polyurethane pieces and the center metal crush tube. Hope this helps.

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