Car: 1990 Civic Si Hatch
The car has a B16 swap with an LS hydro trans and hydro-to-cable bracket.
New wheels and tires, new rack....car is lowered but not slammed...on K Sport Kontrol coilovers.
I have skunk2 upper front control arms/ball joints as well.

Recently, the car will feel like I have a bubble on one of the tires...the steering wheel will visibly turn while accelerating....like bump back and forth. This only happens during acceleration....off throttle or just cruising the car is smooth. Also, this only happens after hard acceleration or high speed interstate driving. When just starting a drive and going through the gears normally it's smooth.

What I've done so far:

1. rotated tires back to front
2. Replaced the driver's side axle
3. checked wheel bearings for play
4. checked ball joints....although boots are torn, no play....nice and tight.

What I've seen:

The passenger side axle where it goes into the transmission is loose....like I can grab the axle right where it going into the trans and wiggle it around in every direction...it doesn't move a whole lot but enough to make me uneasy. The driver's side wiggles a little in the intermediate shaft end. A fried who works at a local Honda shop says that the bearings in the diff or trans there is bad. Something is either pushing the axle into the hub or pulling the other side enough to move the wheel back and forth under accel. Has anyone had this happen? Bad trans? I know the LS trans aren't the strongest from what I've heard.

 

I've had a shimmy under acceleration on a couple of cars. Usually it's axles or engine mounts (bad mounts put a strange angle on the axles that the axles don't like so they shimmy). In your case, however, I suppose it could be a bearing that's deflecting inside the trans, since it would display the same symptoms as a bad axle. I've never seen it, but it's possible. Trouble is, there isn't an easy way to troubleshoot it, unless you have a shop that has a rolling road (basically an emissions testing dyno).

When I say I've never seen it, I mean i've never seen it cause those symptoms. I have loose bearings in the trans output flanges on my beetle, but that's a RWD car. I still don't get any vibration from the drivetrain though.

 

Maybe the passenger axle isn't seated into the trans properly? There's a ring on the end of the shaft that should help it hold position so you can't move it laterally.

 

check those front lower engine (torque) mounts.
drove me nuts til i figured it out.
filled all old mounts with window weld
(except for the rear, bought a new cheapie and filled it since it's a bitch to get at).
for a total of $30 (and some nightmarish torture on that rear bitch) the difference
is amazing. feels better than new lol. 8)
you'll need 2 tubes it's cheap as hell (my middle name).

2 Dow U-428Plus Automotive Urethane Adhesives | eBay

 

So....replaced both axles again....I bought a new trans from a 2000 Si...installed that...still does it. Replaced the intermediate shaft...still does it. Literally everything on either side of the hubs have been replaced or moved. Engine mounts are Innovate poly mounts being a B series swap and all...

 

Have you jacked up the car to see if there is any free play in the wheels? Are you missing a radius rod bushing from one side maybe?

 

Update: I swapped in some brand new axles and the problem was gone. We'd swapped in some used ones we had around the shop and the problem was still there. I feel like a dumbass.