I know this is the probably one of the most asked about issues but I have a ranger that feels like it’s going to shake apart at 65+. Deep hum and vibration felt throughout the vehicle. I can put it in neutral drop the RPM’s to 800 and the sound remains the same so I know it’s speed dependent. At first I thought it was tires, so I was going to get them re balanced but they were pretty worn anyways so I replaced them. Didn’t fix it. I’m just not sure what to do for the next step. And the icing on the cake that really makes it weird is that the vibration completely goes away in 4wd. So now I’m really stumped. I’ve spent an hour under the truck looking at components with no obvious issues. Any ideas?

 

Welcome to the forum

Do you feel the vibration in your butt(rear axle) or in the steering wheel(front axle)?
And manual or auto trans?

If transfer case use(4WD) seems to dampen the vibration I would think rear drive line issue, have you ever serviced the slip joint?
Slip joint service seen here: https://www.ranger-forums.com/drivet...-sticky-73528/

I assume you looked at the u-joints
Also look at rear drive shaft closely for dents(off roading) or missing weights(light spots in patina)

 

Thank you for pointing me in the right direction!
Turns out the front driveshaft boot coming from the transfer case was torn and I somehow didn't see it. So I'm servicing the front drive shaft and while I'm working on it servicing the rear drive shaft as well! How often should I service the slip joint/driveshafts? Or is it more of an as needed thing?

 

Also, i was talking to a mechanic friend and he was telling me i should re gear my rear diff because i put larger tires on it. Stock it comes with 255/70-16 and i put 265/75-16's on it, is it that much of a difference that it needs re gearing?

Thanks again, this site is awesome!

 

You have a 4WD so BOTH front and rear differentials need to use the same ratios/gearing

Tire diameter effects ratio the most
255/70-16 = 30" diameter
265/75-16 = 31.6" diameter

Go here to find out what your ratio, front and rear, are now, Drivers door label: https://therangerstation.com/tech_li...le_codes.shtml

Then when you know the ratio go here: https://therangerstation.com/tech_li...ioChange.shtml

The 1.6" doesn't change things that much, so I wouldn't change anything, your speedometer will read a bit low, and of course odometer as well, so MPG calculations will be off if you used odometer for that
You can test it with mile markers or GPS on your phone, need reasonably level ground for GPS comparison

Speedometers/odometers are always +/- 5% so yours may be more accurate now, lol, or could be off 8-9%