Strong pull under acceleration
 

So this car is driving me nuts. It pulls hard to the left but only under acceleration and when I let off the gas it twitches to the right and settles down. When I brake or let go of the steering wheel it stays straight. At speeds over 110mph the steering is extremely unstable. When I start to accelerate the steering wheel stays straight but the car turns (and I turn the steering wheel to keep it straight), then as I let off the car jerks to the right.

Info about the car:

Bad strut mounts (clunk when turning wheel)
Bad diff mount with a pinion snubber installed, almost no diff-snubber clearance
The problem started after I had 4 crappy used tires put on for a road trip, tread depth is pretty close but the brands are different.
Tire pressure is equal, 35F 38R.
Absolutely no lateral/longitudinal play in any of the wheels
The car has a steering wheel shimmy at 30mph+. Its almost timed, it vibrates and stops, on and off with ~5 seconds in between. The wheels werent balanced so I believe this is unrelated to the main issue.

I have no clue what it could be so I'd like to see what you all have to say in case it is something common (like DTSS bushings).

Fix the bushings and mounts, check ball joints, align the car.

wheels need to be balanced.

tires first...

Get the tired balanced, check your ball joints, get an alignment.

I don't see how the hell wheel balance, alignment, or even ball joints can cause this issue. The ball joints are fine either way, I'm suspecting either the PS rack bushings (tie rods have no play) or maybe the rear end distributing uneven torque (questionable JDM unit from Japan2LA)? The car only pulls under acceleration (moderate or full throttle).

Today I switched the front tires with the rear, no luck but it rules out some possible culprits. Please only reply with suggestions that have been thought through, not replace blah blah and see what happens, since I don't need you to help me play the guessing game.

um how did you check the ball joints? some times it takes more force then just beating on the wheel to see if they have play or not.

if the ball joints are bad, this can affect the angle of the steering knuckle to the tierod, if you move the bottom of the steering knuckle out, you get some toe in of the wheel. this would cause poor tire ware and pull.

Don't get an attitude because you're too lazy to properly diagnose the problem. The Haynes service manual and some common sense should successfully guide you through most of problems you're likely to encounter. Swapping front and rear tires was a good start.

If the ball joints are fine then its one of the PS rack bushings. Jack up the front end, remove the belly pan, have a friend jerk the wheel left and right while you lay under the car and watch the left and right steering rack links to the ball joints where they enter the steering rack. The bad one will make a clicking sound at the end of the steering rack as it moves around. This would also be a good time to double check the ball joints...

It sounds as if your problem is in the rear. Are you sure there is no play in your bushings? Worn bearing in the hub can give the same sympton. Have you checked the tire diameters? The same size in different brands can be different. Since you are only experiencing the pull when under acceleration it would indicate the problem to be in the rear. Front end problems would be constant and usually exhibit under accel and braking.

Get under the car and check your lateral links for either being bent or loose. IF you can shove up and down at the balljoint part of the lateral link.......ain't no darn good. Lateral links are shown in the Suspension section of the FSM.

Could be a number of things. That's just one.

You said that you had two different brand tires on the rear? Realize that different brands of tire have different rolling diameters, even if they are the "same size". That would explain your pull under acceleration.

If the problem started after you had the tires put on that would be a pretty good indication of where to start. Kumho ast tires are cheap, put some of those on. Check for any worn bushings or broken parts in the rear, that is where all the movement will come from on acceleration. I had an 8 with a bad balljoint back there that did what yours did. After everythingh is good get it aligned.

You can rule out the diff

Oh snap...

I vote for something loose/worn in the rear suspension. The thrust angle of the drive wheels is changing under load. Something is effecting the toe in the rear I bet.

I vote no. More like the front passenger side lower control arm ball joint...

i had a similar problem ended up having a snapped mount on the rear subframe

Why would this change under accel/decel?

If not the mis-matched tires , I'm voting rear - you may be having toe-changesunder load. One of the rear floating hubs is "floating" in unintended ways. My bet will be one of the DTSS bolts is loose (or missing, or broken). That's easy to check - it's on the front, inward and downward facing side of the rear floating hub. Had this happen myself a few weeks after installing my DTSS eliminators years ago - I failed to torque one side properly, and the one bolt backed out a few turns - leading to the car steering (withe the right rear) one way under accel, and the opposite way under decel/braking.

However, if that doesn't do it, your mismatched tires make diagnosis very difficult (if it's not the tires themselves, which it may well be - you may have to try swapping side-side as well). Even with matched tires (brand and model), even with the same tread depth, different ages and mileage will mean different levels of grip, which in turn leads to pulling, because different levels of lateral and longitudinal grip at different corners can't help but pull or push the car different ways . All the more so given these are apparently not even the same brand and model of tire (they should at least match in pairs at each end, if not all four corners.