i'm wondering if i gotta problem with my gears. first off, my 77 fj40 has a 4" lift, 1.5" shackles, shims on the front, 35x12.5 tires with 3.73 gears. when i'm on the highway, around 50 mph or 80 clicks, i get a slight vibration that robs me of acceleration, the vibration disappears when i go faster, but it's very consistent and always happens at that certain speed. is this because my of my gears matched up with the 35" tires?
i had the same problem that turned out to be unbalanced tires. there's alot of rubber in a 35X12.50. especially if it's on a 15 inch rim. some tire shops aren't clever enough to get it balanced right.
Gears don't cause vibration. There is no "Matching" of gears and tires in this sense.
35 inch tires are not large enough to cause balancing problems for any shop that has the smallest clue about things.
Dollars to donuts your problem is an out of phase driveshaft. Take a look and you'll probably see that the ends are not lined up. It's real easy to mistaken put them together a full 90 degrees out if you aren't paying atention.
EDIT... Check to see that the flanges at each end of the driveshaft(s) are parallel too. Mis-matched angles can cause this as well.
Not really. Depending on how far out of phase it is and what sort of angles you have on the shaft, the vibration can be BAD. It *can* sound like something is going to tear itself apart. But in other situations it is just a mildly irritating drone at specific speeds.
It is often most noticable in transition from engine driving wheels, to wheel overrunning engine. The momentary lack of load on the joints lets them make more of a fuss.
Mismatched ujoint angles from one end of the shaft to the other (usually due to a poorly designed lift...far too common) can produce similar vibrations. It's al due the pulsing delivery of power inherent to ujoints not being properly cancelled out between the two joints on the dhaft.
This is the best tip I've come across so far! My u-joints were, in fact, not aligned. 15 minutes including washing my hands and now I'm going 70 and it feels like a Lexus. Well, almost.
I sold off my wagon wheels and old tires and I'm getting steelys with newer tires, so I'm hoping that will help even more.
