Either the speedo cable isn't into one of the square drives properly or the teeth on one of the skew gears is lunched :shock:
Sisters Fiesta did that after about 180,000 miles, every time she took her foot of the gas the speedo hit the pin, would only work under acceleration :? Diff had moved sideways and eaten the gear, did the same to a new gear in about a week
Did you say lumps out of transfer box :-k