The title says prop shaft bolts, but what I really meant was the flang nut on the diff side.

I've been dealing with the 75 mph phantom vibration for months now. Just came across posts mentioning a loose prop shaft flange nut that could be the culprit.

How can I tell if its loose? I'm about to drop the drive shaft to check, but wanted to ask first. It's a lock nut so I dont expect to be able to move it by hand. Should I check for play to determine if its loosened up? Or should I be checking the turning tq, with a low measurement signifying a loose nut?

Thanks!

 

Check out this video. Not sure if this is the same rattle. Also there is a sticky thread for finding sounds in general.
be prepared for prop shaft hex bolts to get stripped. Happens all the time. I got new ones from Fastenal for cheap, grade 12.9.

 

one of the comments on the vid:
had a vibration at 72-76 mph (in any gear, accel/decel/coast) and i have determined that the previous owner changed clutch and replaced 1 of the m10x1.25x62mm driveshaft bolts with an m10x1.25x60mm bolt. If i move the bolts around, it changes the vibration behavior. I just went and bought 12x 90182-s2a-a00 bolts from honda. my assumption is that these are hardened grade 10.9 or better (sae grade 8 or better) and corrosion resistant, so you dont want to replace with non-oem. black oxide hardened bolts will mess yo shittup. also, make sure you get the late model year bolts, since the have an 8mm hex drive instead of the 6mm hex drive i think early models had (not sure). torque spec is 24 ft lbs. i use hex bits with 3/8" drive, a 6 incvh wobble extension, and a 3/8" drive torque wrench to change them.

 

He is asking about the diff flange NUT, not the propshaft BOLTS. He worded tbe title very misleadingly, but text of thread indicates he means the single flange nut.

 

Correct. Unfortunetly I cant edit the title

 

you must be speaking of the pinion nut on the diff.

there's a specific torque procedure, and i don't know what it is.

you could try torquing until you feel resistance but it can still spin.

let us know what you find.