CTS-V wheelhop fixed

[Bruce Nunnally]

Service Information Document ID# 1684809 2004 Cadillac CTS

Controlling Rear Axle or Wheel Hop on Full- Throttle Application from a Standstill and/or Full Throttle 1-2 Shift (Install Supplementary Rear Sub-Frame Bushings) #05-04-114-001A - (Jul 18, 2005)

Controlling Rear Axle or Wheel Hop on Full-Throttle Application From a Standstill and/or Full-Throttle 1-2 Shift (Install Supplementary Rear Sub-Frame Bushings)

2004-2005 Cadillac CTS-V The information presented in this bulletin is intended to inform, educate, and provide an effective means to further improve the outstanding high-performace handling qualities of the CTS-V for customers who value very aggressive driving capabilities. This bulletin is being revised to expand the title line, include additional information, and add a repair procedure.

Condition

Some customers may comment on rear wheel hop or rear suspension bounce under full throttle acceleration. This condition is not unsafe by itself and is the result of very aggressive driving practices. This condition is primarily confined to hard acceleration from a standstill with wide open throttle, though it may be possible to induce if the customer attempts a hurried wide open throttle or "Power-Shift" from 1st to 2nd gear.

Notice: Vehicle component durability is greatly influenced by these driver abuses. Driving in this manner is not recommended.

Customer Expectations and Real World Usage

The CTS-V is a very high performance vehicle capable of class-leading acceleration that, in most cases, exceeds even the capabilities of pure sport and muscle cars. The 5.7L V8 engine in the CTS-V provides outstanding reserves of power. This large available engine torque, coupled with a suspension system and

tire combination designed for maximum road adhesion, may result in wheel hop under certain conditions.

Cause

In the rear of the CTS-V, a sub-frame is mounted to the body structure at four rubber-isolated points. These mounts were carefully chosen to achieve an effective combination of excellent handling, while retaining effective damping of road shocks and bumps. The force of the suspension rapidly occillating vertically (hopping) provides enough weight transfer (up and down) that these bushings, which normally compress to help isolate passengers from irregular road surfaces, may deflect or compress in sympathy to wheel hop.

Correction

Improving High Performance Suspension Characteristics

For customers who value very aggressive driving capabilities, a revised set of firmer rear sub-frame bushings are available that may provide an incremental improvement in reducing the tendency of the rear suspension to wheel hop. This is an improvement that will further extend the handling capabilities of the CTS-V - it will not remove the possibility of wheel hop in all situations.

Important: Do NOT replace the rear sub-frame bushings unless the customer specifically has the concern of objectionable wheel hop.

[Scotty]

Nice! I am very happy they have addressed this. I like the way they phrased this:

"which normally compress to help isolate passengers from irregular road surfaces, may deflect or compress in sympathy to wheel hop"

[Bruce Nunnally]

Such a tricky line to take: Well, it wasn't broken, but it's fixed now.

Wonder how many transaxles Cadillac had to eat under warranty after they ejected themselves?

One happy CTS-V owner after-fix said he could now do 5,200 rpm clutch drops with no wheel hop. That sounds fixed to me.

[Scotty]

You know what I don't understand why didnt this 'problem' rear its head in Nurenberg? On the DVD I saw from Nurenberg the were pushing the CTS hard, no full throttle starts but pushing it. Do you think its because, your TYPICAL driver would not push the car to that point? Power Shifting?

[Bruce Nunnally]

I have wondered this as well.

Possible reasons:

a) to save development funds, and due to the need to test prior to production to 'dial-in' the best setups, the testing cars are prototypes, not off the line production models. Unless you test what you are shipping/about to ship, things change.

unique tires and possibly shocks / suspension setup for the Nurburgring cars in order to optimize track lap time

Why didn't GM see this during their acceleration testing in Lansing? I wonder if the test drivers are too good -- they were able to keep the car just below wheelhop and hit the numbers. But once real world drivers and magazines got the car and hammered it off the line the wheelhop was evident.

Does GM do actual 0-60 acceleration tests? Or is it all done via computer simulations?

Engineer/new owner conversation:

Owner: "Hey, if I just drop the clutch at redline the rear axle rips out!"

Engineer: "Well, ok, but why did you do that? When you detected wheel hop why didn't you back out of it?"

I'm not defending the factory setup. I don't want the car to break itself just accelerating out of a light either. And the real world and glossy magazine numbers for the CTS-V have not lived up to Cadillac's claims for it.

As I have mentioned, one of the local BMW M5 drivers destroyed his new tires. Put his buddies in the car to go to lunch, hit the freeway onramp and nailed it, the car squatted, and shredded the rear tires when they hit the inside of the rear fenders. Design problem? yes, sure. Avoidable? yes, sure, but BMW paid for the new tires, and one would assume considered different settings for the rear shocks to avoid a repeat.

[Scotty]

Hmm that is interesting about the M5, I did not know that.

[TDK]

Drove a CTS-V some months ago, what fun.

I can't say about wheel hop so much, because I did try to keep it from smoking (or applying traction control - which I wasn't sure about).

Anyhoo, every gear snick got rubber and more velocity. I recall the 4-5 change was at about 130 coming off the on ramp into I-80.

I can't recall what gear it was in when it ticked into 7,000rpm, but again I was anticipating a rev limiter (don't know if it had that either).

Me and a CTS-V would NOT be a good long-term combination. Even I figured that out after the blood returned to my brain.

I often meet this very same car on my drive to work, a gal who has never so much as chirpped the tires. Sigh... What a waste...

So, does it have traction control (as we know it), rev limiter, etc?

[danbuc]

They had alot of wheel hop when they test drove it on Top Gear. I'm happy to see they have finally made the effort to fix it. I've been saving money planning to get one when I get out of school, but wasn't sure since they hadn't fixed the problem yet. Now it looks like I can safely continue with my plan...hehe.

[WarrenJ]

Even I figured that out after the blood returned to my brain.