456 steering responce and unstability...

One thing you might try is the 550/575 FHP Hydraulic Steering ECU, which takes a lot of slack out of the steering on any of the 456/550/575 cars. It is almost an overgrown relay, but has helped several owners enjoy more precise steering. Part # 175891.

Another possibility is that your steering ball joints (158016) are worn and introducing slop into the steering. A third is that the front suspension ball joints are worn.

Have you had a four wheel suspension alignment done recently? If not, poorly aligned suspension can also make tramlining worse. Probably the first thing I would check because it is the cheapest, even though fairly expensive on a Ferrari since ride height, camber and toe-in need to be adjusted. Caster is fixed. The V12s tend to be more susceptible to the suspension losing alignment because eccentrics are used instead of the shims on the V8s.

Taz
Terry Phillips

 

The ECU is an upgrade to the one fitted

Excess toe-in can wreck front tyres and cause symptoms as described - most tyre places and/or dealers should be able to check or if you are lucky have a computerised laser gizmo to give a printout evidencing the correction

 

Changing the front shocks and having the steering rack rebuilt made a huge difference for me. I have an extra front shock if someone needs it. I bought three new old stock ones for next to nothing and obviously only put two in. The place in South Carolina did the rack for a few hundred bucks, but the R and R on that is a big pain.

 

Check the pressure in your tires: if the pressure is low you are running on the tire shoulders and the car drives like you are describing when the road is uneven.

 

One good place to start is to have the alignment checked. Toe that is way off specification can lead to the symptoms you mention. Toe-out on the front wheels gives a quick left-or-right steering pull when respective wheel is pulled a bit by road conditions differing between the wheels (like a small road imperfection encountered at one wheel only). If the car was "curbed" or some other tap which altered the toe, then this can give a sudden change in steering. Camber and caster should be checked as well, but caster not changed unless compelling cause is found (sometimes caster is not measured right and it can be time-consuming to change). And rear wheel toe can contribute if it has been changed from specification by bump or otherwise.

Another contributor could be after-market wheels. You mention alloys but don't say if they are the original wheels. Deviating from manufacturer wheels can lead to sub-optimal steering results.

Personally, I don't go after other causes until alignment, tires, and wheels are in original specifications on a car. The 456 has wonderful steering when it is in specification.

 

Here's another possibility. The 456 has anti-dive front suspension which is controlled by a small switch in the brake fluid line. When the brakes are applied, the switch senses the pressure increase and hardens up the front shocks to stop dive. Occasionally that switch goes south and the shocks end up being hard constantly. The result is that the driving becomes very erratic. This situation is only apparent when driving. Stationary, the shocks will bounce just like they should so it does appear that they are OK. I've come across this before and it's a real hard thing to work out. The switch is not expensive and it's easy to replace. Many people don't even know it's there. Do a continuity test on it to verify it's integrity or not. Good luck.

 

Mark, where is this located please ?

have you got a part number, so we could see it on Eurospares or Ricambi please ?

 

Eurospares Ferrari 456M GT Mechanical section, Page 048, item 22, part no.154309.