My friend has a Tacoma that oscillates violently at highway speed. It makes you feel like a bobble head. Starts at about 60 and gets real scary around 65. She has replaced rear shocks and leaf springs and it hasn’t helped. This is what a mechanic recommended what else should she look at?
Do you mean left to right, or front to back?
Right to left
First of all I am not sure the correct mechanic was involved. She needs a good alignment and wheel balance as a starting point. Also check lug nuts on all wheels just in case it is that simple.
I have recommend an alignment place hopefully they will see the problem
Probably some kind of tire, wheels, steering, or suspension problem. An experienced shop should be able to figure it out by putting it on the left and levering here and there looking for too much play. They’ll also do some tests on the wheels looking for bent rims and side to side run out, tread wear problems, loose wheel bearings, missing lug nuts, etc. I presume the shocks and springs were replaced b/c it was clear from inspection they were no good, so had to be replaced in any event. My guess, either the steering rack has developed too much play, or there’s something loose in the suspension system, worn out bushing, front strut mount, etc.
If you want to do something yourself, look carefully at all the tires. See any indication of the rubber cracking, bulges in the side wall, tread separation? Plenty of good tread left? Are they inflated properly? Weird tread wear patterns?
It sounds like a real safety concern . I would take it in to a trusted mechanic to get it checked out. I really enjoying doing the work myself whenever possible but sometimes it’s worth it to take it in.
Does it have non-standard wheels and tires, bigger than original? I once test drove a Toyota truck that had had that modification, and it felt like a bucking bronco on the highway - dangerous. Modifications like that add to the stresses put on the steering and suspension systems.
First check would be for a tire that has a bulge or broken belt. Swapping tires front to rear could discern that in case it’s not visibly obvious.
2WD or 4WD?
How has the truck been used? Has it towed?
The wheels and tires can be checked well on a balancing machine that does “road force balancing” It tests them by applying a spinning drum to the tread to simulate road forces while spinning the wheels to balance them. It can detect defects and irregularities that a regular balance cannot.
With a pickup, you also have universal joints (U-joints) in the “propeller shaft (Toyota’s term)” that can become worn and cause vibrations. These can be checked with the truck on a lift, and should be.
If it’s a crew cab, it might also have a “carrier bearing” in the center (I don’t know for certain if Toyota uses these on their 2000 Tacoma crew cabs, but longer trucks generally do).
If it’s 4WD, it might also have a “steering stabilizer”. That’s sort of a horizontal shock absorber that absorbs lateral movement in the front end. These, like shock absorbers, wear out and need to be replaced.
I think your friend needs a way better shop. There are too many possibilities to have someone who’d suggest replacing the rear springs without some very specific reason.