Technical Muncie/quickchange pulsing noise only at cruise

Besides the suggestions already made it could be anything that can wear/fail. Trans mount. Tailshaft bushing. Ladder bar bushes. But u joints are the obvious starting point. Not sure about checking (uj) angles, other than it's an easy, no cost check, as, unless something else has changed, there's nothing that I can think of right now that would make the angle change.

Chris

 

Another question. Is the noise RPM dependent or road speed dependent? If you run it up in 3rd gear until the noise occurs (if it occurs), then shift into 4th does the noise level and frequency stay the same or drop with the RPM drop?

 

Question: Has the car always had this noise or was it OK for a while and then started ? Does it make the noise when sitting still with the car in neutral, or only when driven? I would put it on a 2 post lift and have someone shift thru the gears while listening underneath. Use some tall jackstands with the lift id you have any.

 

Let me preface this with: I don't think your noise is due to the Frankland, but

To eliminate the Quickchange from the equation:
1. Try a different set of change gears, or flip them. There is definitely a difference in 'good gears' as opposed to 'cheap gears' (There are no 'good cheap gears')
2. Measure the circumference of the rear tires. They should be veeerry close, + or - 1/4"
3. You don't specify what differential you are running, but Lockers can give some ratcheting vibes under certain conditions.

 

Road speed dependent….same noise in 3rd or 4th

 

I can’t quite say for sure if it’s gotten progressively louder or if my ears have become more in tune with the noise. No strange noises sitting still in neutral.

 

Not sure what kind of diff is in it…haven’t noticed any locker sounds…may very well be an open diff. I noticed a surprising (to me) amount of slop with gear backlash and spline fitment…maybe it’s normal…if the driveshaft checks out ok I may move on to a different set of gears

 

Where are you located?

 

@BryanR,
Many QC gearsets have too much clearance between the gears, but there should be no discernable movement between the shafts and the individual gears.
By changing the gears to a different set, you should be able to see if there is any change. It may not fix the problem, but you should see some difference if the gears are involved.
If you know anyone that races ovals in your area, I'm sure you can borrow a set of gears for diagnostic purposes. Most racers have a selection of ratios and most have 'good' and 'not so good' sets.