Axle hop - I have tried everything


New Member
Feb 1, 2001
Montverde, FL
I have been fighting axle hop on my 94 cobra for several months. No matter what I change it gets worse. I searched the threads and it seems I have covered everything. My problem is worst coming out of corners, even in 2nd gear. If I drop the clutch from a stop at 3000 the tires will spin but when the revs get back to around 4000 I will get some hop. The engine is stock so excess power isn't my problem.

I am slowly rebuilding the suspension since the car has 200000 miles and sees track events several times a year. I replaced the upper control arms, the lowers, the diff was rebuild (this is when the axle hop got worse). I checked all drive line and suspension bolts and nothing is loose.

The only thing that I haven't tried is the snubber. I replaced it a while ago but the style is from an earlier model. I don't know if they are the same size or not.

Has anyone had success with adjustable snubbers. How do these worK? Do I adjust it down or up to stop the hop?

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I used Steeda HD uppers (I think these are Ford Motorsports) and stock lowers. I heard too many pros and cons about aftermarket lowers with sperical and poly bushings. I figured that originals worked for the first 190000 miles then they should be fine.

I forgot to mention that I also replaced the Tokico Illumina shocks (thanks to a lifetime warranty) and put in Ford quad shocks. The car also has MM subframe connectors and realitively new Steeda Competition springs.

I never had any wheel hop before and I have owned the car and been doing track events since it was new. When this axle hop started I didn't even recognize what it was because I never had this problem.
You are using the stock rear control arms? Are you using the original rubber bushings in them? What did you do with the upper arm-to-axle housing bushing? Leave it, new rubber bushings, or poly?

The uppers have a harder rubber bushing installed, this is the FMS part that Steeda puts their name on. The lowers were replaced with OEM which contain new bushings.

I first had the problem with almost bald Kuhmo ECSTA 712s, I replaced them with the same tire and the problem didn't change. I thought about the tires but this is my 3th set of 712s and I never had the problem until the 2nd set was almost bald.
The bushing you describe sounds like to control arm-to-body bushing, the one that comes pre-pressed into the arm. I am wondering about the other end, the control arm-to-axle bushing. Is this bushing a 10 year old stocker? The Steeda kit comes with a replacement urethane bushing for the alxe. They want you to drill out the old rubber and replace it with urethane. I followed Maximum Motorsports advice and didn't use the urethane there and just put in some new OEM bushings.

Regardless, I'd bet that a decent set of lower control arms would solve your problem.

The Steeda comes with poly for the axle and rubber for the body. The uppers were installed at least six months before I started having problems so I don't suspect they are at fault.

I just recently changed the lowers when the axle hop got unbearable. The old ones were very worn, the bushings just dropped out. But the new OEMs didn't change the situation. Like I said before, I don't think that I need anything other than stock since the originals worked for so long (and were probably still working since replacing them didn't change anything).
Did you use the poly that came in the steeda kit or is that bushing still OEM? It seems that hop is usually (always?) caused by a sloppy rear axle location relative to the body. And that means control arms.

Is your housing tweaked? Have you hit anything or had a rear end collision? :shrug:

When installing the arms, did you tighten the bolts down with the car sitting on the suspension, with the arms at normal load and angle? Or did you have the frame on jackstands, and bolted it all down? :shrug:

I didn't do the work myself, I had it done by a local Orlando Mustang performance shop. But you got me thinking about the install of the arms. I can't remember whether the suspension was put at ride height when he tightened the arms. I guess I could loosen them and retighten, this takes some big tools I may not have though. I'll think about it this weekend. Maybe I will find another shop next week and get another opinion.

Perhaps I am misunderstanding, so please correct me... you are hopping at around 4000 RPM? I can't imagine a stock Cobra still spinning the tires at 4000 RPM, and I wouldn't expect you to be experiencing any hopping unless the tires are turning over. :shrug:

Perhaps I'm just being obtuse this evening, stranger things have happened....

Exactly. Its most noticable when I accelerate hard away from a stop and turn right. Then the hop starts at about 3500 in first gear.

I tried removing the pinion snubber just to test if the diff was bouncing on it. It made no difference. The hop was no worse or better. I sort of expected to have very loud noise if the diff was hitting the floor. I am glad that there wasn't that much movement down there!