86 monty 200r4 ???

hello all

my monty ss  is stock all the way down to the rad  hoses..

when driving it there is a vibration at 55-65mph

checked tire/wheels/ect

took drive shaft to shop and was alittle bent...

had a new one made with 3" thickwall tube(incase I need it later)

new u joints...  but the viberations still there..

now if I excel to 70mph take the shifter put it in "N' then shift back into "D" at like 65-60 mph  the viberation goes bye bye..

till I slow down past 50mph and then excel again..

anybody got any idea's.....??????????????

The differental could have worn bearings.The transmission mount may be shot,the motor mounts may be worn.Also check that the bellhousing bolts have not loosened up.It really sucks to spend a bunch of money just to find you still have the problem.I would really lean twards the rear end .There is a way to check the backlash but I am not a expert on anything.  

thanks for the input 

but if it was the rear when I put the trains back into "d" at 60-65 mph the viberation would still be there  ..it isn't..

i'm thinking torq converter clutch or maybe  ?????????

Could be .Does it happen in 3rd gear?  

yes it does it in all gears at that  speed  unless you got you foot in it hard...

converter clutch free wheeling..

I've been told that if I unplug the 4 pin connect at trans that the conv. clutch will not ingage.. that way If it don't do it then.. it's the conv. clutch..

I really think it is the rear end.Anyway 2 of the plugs in the 4 pin connector go to the backup lights I think.Just dont want you to get a ticket for no b/u lights.

        Brian