Mrspencer

Driving my 85 s3 5spd this am, still dark out on my way to wrk today, Decided to open her up a little ,so rolling at 80 MPh stomp on the throttle in 4th and the rear end has a very noticeable fishtail ,so I get out other gas and repeat and every time the same result I feel the rear end wander back and forth, have KONIS all the way around, afraid to drive her fast due to the uneasy feel ONLY under hard acceleration at 80 and above, if your reply is don't drive that fast pls don't reply, no time for the normal forum BS. ANY HELPFULL ADVISE GREATLY APPRECIATED, HAPPY HOLIDAYS TO ALL.

XS29L9B

How's tire pressure?
Road conditions?
Ambient temperature?

Drive fast!!

SeanR

Check the torque on the rear suspension pins.

Mrspencer

Thanks for the info I will check those in the am, car also sits on new tires, also doesn't seem to matter what the temp or time of day is it will squirm around, not so noticable with a passenger.

Ducman82

what sean said. I had that exact same issue, loose pins

jack up the car, stick blocks under the tires so you can torque the pins. 103 ft lb

dr bob

Both ends of each pin.

Verify that the cup and flat washers are in the right places and facing the right way.

jpitman2

What do you class as 'normal forum BS' ?
Anyway, has something changed recently that just might be relevant? Or have you never done this acceleration before? Dry road or wet? Even with LSD my car can do this in the wet quite easily, but almost never in the dry.

jp 83 Euro S AT 57k

Mrspencer

Just took possession of the car, put 700 miles on her so far, new,tires as stated earlier, don't drive her in the rain, I can only imagine , so let me get this straight your car when driven hard under acceleration, the rear end feels like it what's to step out, and no I don't mean breaking traction as if to do a burn out.its so noticeable you rollout of the throttle, thinking the car is going to snap to the left or right, more so to the left know that I think of it.85 us 5sp 154k porken chips pktensioner.

Mrspencer

Thanks for the info Ducman82, merry xmas.

jpitman2

I have LSD, and in the dry, accelerating away from stopped at a corner, I can feel one rear wheel go to spin, then the LSD come in and all is good. In the wet, straight line, too much power , a wheel spins, rear drifts sideways. Accelerating hard when already at speed, never an issue, but if you dont have LSD (Opt M220), ????
Check all the stuff mentioned above in the back end , and that nothing is loose or worn anywhere - shock mounts tight, pins, bushes, mounting bolts etc.

jp 83 Euro S AT 57k

Mrmerlin

I just corrected this issue with my 88 S4,
I replaced the 4 dog bone bushings ( rear upper control arm links)

and the bushing that anchors the lower control arm to the rear cross member,
this requires LCA removal and a fresh alignment.

From your info I would suggest to check the tightness of the link pin bolts as Sean has suggested,
AND the LCA eccentric bolts at the rear cross member,

NOTE if these LCA eccentrics are loose it will cause the rear to sway under loading.
NOTE proper torque is 140 ft lbs on the LCA to rear cross member eccentrics,

NOTE you can see the washers making marks on the mounting pads if they are sliding.

replacing the dog bone bushings will restore adjust-ability range of camber to the rear end.
the LCA eccentric bushings will stop the sway under hard acceleration.

NOTE I bought a 12 ton press from Harbor freight ($ 99.00) to swap these bushings out at home

Mrspencer

Thanks again for the info I will look into these bushings when I return to work, I have an industrial 75ton hydraulic press, merry xmas to all .

Randy V

Sure thing, Billy.

Slow down.

Crumpler

Saw that one coming!
​​

JWise

As previously mentioned, make sure the lower shock pins are properly torqued. BTDT

I've also encountered similar circumstances with excessive tire pressure. Had some Bridgestone S02 Pole Positions one time and just for fun, I aired them up to the factory recommendation which is 44psi rear IIRC. The back end yawed back and forth like it was on ball bearings under both acceleration and braking. I quickly dropped the pressure back to mid 30's and the handling returned to normal.