Wheel hop

[SJAndrew]

I have a 98 GTP with 140k miles.

Upon acceleration (hard or soft) from a stop, the entire front end shakes violently. It has always felt like wheel-hop.

This has grown worse to the point where instead of being sporadic, it's persistent.

I had my wife drive it while I watched. I confirmed that the front wheels are hopping. They're acting as if they're torsional springs - they spool, release, hop, then regain traction. It can shift from L to R as it spools and then unloads.

I've replaced the front shocks with monroe quick struts, the front stabilizer with Dorman and moog poly inserts/links.

Is there anything I can do to stop this?

It seems to be worse now that my pass front tire is VERY bald (will be replaced soon).

Could it be something like a tranny mount?

I've checked the halfshafts and all other suspension/power components and I just don't see anything wrong. I've not looked for the tranny mount, so for all I know it could be shot (I presume it's a rubber/poly mount that could be rotted).

The cradle mounts are fine, and all other rubber components that I can see are also fine. I also checked the tranny etc - it works flawlessly (fluid just changed, no slipping etc).

Any ideas?

[Explicit_Spade]

What about wheel bearings?

[TheOtherNick]

Sounds like you have a bad cv shaft.

[SJAndrew]

I don't think it's a bearing. It makes no noise and I can't tilt the wheel when it's jacked.

The CV shaft makes more sense. But, I see no leaking.

How could have failed to produce this? Sheared splines?

[TheOtherNick]

See if you have a lot of movement in side the cups grab the center shaft and go up down and side to side. Just because they aren't leaking doesn't mean they are good.

[SJAndrew]

One thing I have noticed: I can rotate one tire 10* or so while the other one remains stationary. I always presumed this was slack in the tranny.

I'll wiggle the shafts tomorrow and see what I can report.

[SJAndrew]

I have the car on stands, front wheels off.

The shafts are rock solid side-side and up-down. There is a tiny amount of axial movement but this should be normal. Here's a video of me trying to move them side-side, then up-down, then axially.

Driver's side video

Passenger's side video

I think the CV's are fine - they make no noise when turning or otherwise.

I'm now checking the bearings. I have the rotors and caliper mounts off, and I'm wiggling the bearing flange trying to get movement. I get nothing - it's rock solid. I've only check the driver's side, I will check the passenger soon.

I'm pretty confident I've ruled out CV's. The ones I have are rock solid - I can't get ANY side-side/up-down movement as much as I try and yank on them.

I'm pretty close to ruling out bearings (one seems fine to me).

I also looked at the driver's side trans-mount, it seems fine (pic is here)

Any ideas? This is VERY frustrating...

I'm back top thinking this is just due to balding tires...

[matt5112]

LCA bushings?

[MoarkatsINmuhtrailer]

im with matt on this one. youll get a lot of movement from those suckers. look at the front most one (closest to nose of the car) and ill bet its tearing pretty good unless youve replaced the whole control arm with the dorman or moog. could be ball joints to

[matt5112]

My delco advantage LCA's were tearing after precisely 12 months.

[SJAndrew]

LCA bushing pics are below:






Are these shot? I assume they need to be pressed out at a shop?

[matt5112]

First one is shot.

Second one looks good.

Buy new LCA's.

Moog or Dorman.

[MoarkatsINmuhtrailer]

i got the dorman about a month ago, you can get rockautos price and pricematch em at advance, unless you get a dickhead in my company haha like 42 instead of the 92 we charge

[SJAndrew]

I assume I drop the LCA and have to have it pressed out?

I see that the first one is snot - you can see how the flange is missing.

I might as well replace the remainder of the busings too, correct?

If I need to drop the LCA to do this, should I also replace my BJ's?

[matt5112]

Which means you should buy a new lower control arm assembly and have a new everything and not have to worry about it.

[MoarkatsINmuhtrailer]

yeah lol dont hassle with everything separate, itll kill you in price, whole lca comes with bushings and ball joints

[SJAndrew]

It looks to me as if the MOOG front LCA bushing is a single flange design meaning it should more or less drop in.

I'm comfortable replacing all of the bushings and joints to save some cash.

Will I need a press to do this or am I missing something?

If I need a press, I will just get an entirely new LCA as you mentioned.

[matt5112]

They have to be pressed.

BJ rivets have to be drilled out.

Do this:

i got the dorman about a month ago, you can get rockautos price and pricematch em at advance, unless you get a dickhead in my company haha like 42 instead of the 92 we charge

[SJAndrew]

Thanks a lot for your help guys!

[MoarkatsINmuhtrailer]

and realize this, once you pay for all the bushings and ball joints separately, plus labor fees IF you need someone do press them for you. your looking at rockautos price for two new complete LCAs. so your getting the added security of whole new pieces