Bad vibration in rear of 62 valiant

[62hypapak]

Questions again! Ok when I have 4 adults in the car I'm getting a bad vibration when I take off from a standing start. The harder I push the worse it is, it feels like I'm driving over a rumble strip. So the car has new shocks and new bushes in the leaf springs, a fully recon LSD borg warner diff with 3.5 gears, new uni, and ball and trunnion, tail shaft has been balanced. Recon stock 904 auto with transgo stage 2 shift, and a brand new 3000-3200 stall. I cant see any signs of wear or knocking under the car. The rear end isnt lowered and it dosnt look like that the bump stop on the diff is hitting he body Any clues what this may be?

[Mroldfart2u]

Sounds possibly like a pinion angle/driveshaft related problem to me, but i have been incorrect before.

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[Doc]

Was the cast outer housing changed when you serviced the B & T front joint?
This issue is usually caused by a worn spot in the B & T housing, not the rollers or cross-pin.
DD

[SlantSixDan]

+1 to what Doc says. This (pronounced vibration under loaded takeoff, eventually smooths out as you get up to speed) is classic worn ball and trunnion housing behaviour. Best way forward is described here.

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[62hypapak]

Thanks guys I have another tail shaft I'll try that one and see if it eliminates the problem, but I'm sure that you guys are right it makes sense.