I’ve been working on the is 79 SR5 for a bit, and I have it mostly buttoned up to drive, except for this really bad/sketchy steering wheel shake above 40 mph. On inspection things look in working order, the hub bearings have been completely re-packed, and the wheels/tires balanced, and no play in any of the wheels from what I can tell.
Can’t figure out what is causing this aggressive shaking.
Any insight on what to inspect and/or what specifically to do to inspect and test .
Any and all advice is welcome, thanks in advance.
Cheers.

 

Flat spots on the tyres, has it been sitting around for a while? They are hard to spot with a visual inspection.

 

thanks for the reply.
That is possible it was sitting for about 5 years before I got it. Even though I balanced and fully inflated the tires, would I feel this above 40 mph only?

 

At lower speeds, it can feel like a bumpy road, if both tyres have flat spots the shaking can change depending if the flats are synchronised or offset. Delaminated tyres can also do the same thing.
have a look at this video

 

its probably the tires. I had an old tire delaminate on the freeway, i'll never drive on a old crusty tire if i can help it no matter of its balanced and inflated.

Check tie rods, ball joints, pitman and idler arms.

 

Rotate the tires and see if it changes

 

I've already tried that. I've been trying to source a set of wheels and tires and I can temporary tryout, to see if this solves the issue. don't have the cash to upgrade the wheels and tires yet. I wish I knew for sure if flat spots on the tires is the issue or its something more.

 

Well if there was no change then it’s not likely the problem. It could be a steering component or suspension bushing, but you usually would hear a noise at low speeds if that was the case.
Try airing the tires up to 50psi and see if it improves.
If you let go of the wheel does it shake/pull to one side?
After a quick drive, feel each wheel with your bare hand to check temperature, (obviously don’t grab and hold the wheel, but pat it lightly to gauge how hot it is before actually feeling it) if one is hotter than the other you may have brake drag causing the vibration.
Other than that you may need to go old-school and stick your head out the window at speed to see if you can visibly see a wheel shaking, of course this should be done with a helper to steer, etc…but it may be isolated to one wheel, so you need to check both.

 

UPDATE: You were all right, it was the 20+ year old tires and flat spots. I replaced the wheels and tires and it drives awesome now. Thanks

 

Dude yea 20 year old tires! I wouldnt have even tried driving any faster than 20mph!