newbie p38 transfer box?

hi,
im new to the site and hoping u guys can shed some light on a few p 38 problems, i drive a 1997 4.0 manual with lpg conversion and 138,000 miles on the clock an live in harrogate north yorkshire work in the gas industry as a site instalation engineer and coded welder. i tend to do my own repairs on the rangie so far with sucess, had the old girl 3 years an replaced viscous coupling unit, both diffs,front half shafts, front prop shaft, front wheel bearings, 3 air springs and rear shocks, done the work my self so only cost in parts so far..... oh an most of the work has been done recently,
but i now have a nasty vibration at 25-30mph coming through the vehicle thats getting worse by the week,so with all the work done i recon only leaves the transfer box or gear box at fault. ive purchased a replacement transfer box thats only done 67,000 miles and am thinking ill change it my self, has anyone done this before succesfully? any advice would be greatfully recived.

cheers 46sooty

yes not too bad to do ,swap your viscous first if you have just fitted new one to your old unit

remove rear prop take for a drive see if it dissappears then try the same with the front prop,

yeah i will swap the viscous ive had it off road since i fitted it and the new unit worked beautifully,

an yeah ive tried the front an rear prop makes very little difference, i forgot to mention when i got the rangie the front prop was removed so was driving with the viscous engaged not sure how long it had been driven like that before so guessing it would put undue stress on the box an bearings.

front prop was removed as viscous was seized ,removing front prop would have removed wind up in transmission a seized v/c would give ,front diff usually sufferes first when v/c seizes