ABS Warning After 4.56 Installation

Durkin · July 8, 2004

Folks:

Have just installed 4.56 gears in a 2003 Tahoe Z71 and now ABS warning light is on and Service Brake System displays in the DIC after about 10 minutes driving time. It is not the brake system, but rather a PCM issue.

Does any one have a solution?

Regards,

Durkin

snoman · July 8, 2004

Have you changed tires sizes and/or have you reprogramed the ECM yet? It can mess up ABS if not properly programed for new ratio.

Durkin · July 8, 2004

snoman:

Lyndon Wester is working on it from the PCM side and I am just researcing some other alternatives such as: http://www.abbott-tach.com/era.htm

Regards,

Durkin

The SPEEDY · July 8, 2004

So is it caused by the gear change? Or did somone possibly disconnect the abs sensor mounted on the pumkin? Just thowing an idea out there.

My question is though, how why would the gear change effect the abs? Not questioning you, just trying to learn here.

Durkin · July 8, 2004

Folks:

Shortly after I posted the previous message, I got an email from Lyndon Wester as follows:

The problem is the EBCM {addedby me - Electronic Brake Control Module} (not PCM).

When the incorrect wheel speed from the rear wheel speed sensors is different than what is programmed into the EBCM (difference received at the trans VSS output), the code sets after a self test--right around 35 MPH.

Hang in there...

Lyndon

Me again: This is in the late evening in Canada - Fantastic Customer Service!!!!!!!!!!!!!!!!!!!!!!!Needless to say, I will wait for his solution.

Regards,

Durkin

July 8, 2004

Durkin,

I experienced the same problem when I changed the rear axle ratio in my truck from 3.42 to 4.10's. The error code is thrown because the computer is matching the wheel speeds of the front and rear wheels and since it thinks you still have the old gear ratio in your truck it believes the front and rear are turning at different speeds. The fix is easy, just have the programmer changed for the new gear ratio and the problem is gone. Your speedo should also be off. Hope this helps.

snoman · July 8, 2004

Durkin,

I experienced the same problem when I changed the rear axle ratio in my truck from 3.42 to 4.10's. The error code is thrown because the computer is matching the wheel speeds of the front and rear wheels and since it thinks you still have the old gear ratio in your truck it believes the front and rear are turning at different speeds. The fix is easy, just have the programmer changed for the new gear ratio and the problem is gone. Your speedo should also be off. Hope this helps.

Correct as the ABS monitors vehical speed data from drive shaft and compares it to speed data from wheel sensors. When it does not match correctly, you will get a error warning.

The SPEEDY · July 8, 2004

That makes sense, didn't realise it moniters tran output as well. Because of where the abs sensors are mounted a gear change will not cause it to see different wheel speeds.

tbyrne · July 25, 2004

I saw the same thing after going from 4.10 to 4.56 gears in my HD. I believe those lights will come on for anything over a 10% increase in gear. I talked to Lyndon this week, he thinks he has that taken care of now so I'll be seeing a new computer soon to check it out. Superlift has two boxes that are helpful. One can be used to calibrate the speedo while the other one will pretty much take care of the ABS and Brake lights. You will only see those lights when the truck is stopped in gear.

2002 8.1 Silverado HD - Full Throttle lift, 37" tires, Comp Cam, TOG headers, Volant induction plus more!

2002 8.1 Suburban -Intercooled Whipple supercharger, 22" wheels/tires + more - 407hp/558 ft-lb torque at the rear wheels - 13.93 @ 95.79 MPH

www.tbyrnemotorsports.com

Durkin · July 25, 2004

tbyrne:

Well you are still a bit faster than I am, but I am closing on you.

But first, the ABS thing. Lyndon programmed it out of coming on when the vehicle is moving, but every so often after the truck is started, the chimes go off and the ABS and brake lights come on; turn off the engine and restart and the no ABS warning for several more starts. Any ideas?

Just got back from the Carlsbad track and while I can stay neck and neck with a ZO6 6-speed though the 330 ft and and I am about 0.2 to 0.6 second slower at the 1/8th than the Z06. The best I could do today was 14.46 at 95.33 MPH. Gotta talk to Lyndon! Or maybe Yank! Or Yank and Lydon or... Tom, what is your recommendation with respect to Yank TruckThruster converters?

Regards,

Durkin

tbyrne · July 25, 2004

The ETs are coming down! I talked to Lyndon after my 4.56s went in. He reprogrammed to take care of the speedo and said to see what happens with the ABS because it would be close to what the computer could compensate for. The dash looked in a Christmas Tree! He was working on trying to get that taken care of. Just needed a truck up there to see what was going on and how to correct it. In the meantime I picked up the Superlift parts that I mentioned. The only time the lights come on now is when the truck is stopped. Lyndon thinks he has that taken care of now.

I would go with the Truck Thruster 3200 if you don't tow more than 4000lbs. Yank says that this will be good for a 5 tenth improvement. That should dip you into the 13s with good traction.

What size blower pulley are you running? Going down 1 or 2 sizes would be benefical if you still have the stock one on there.

Durkin · July 25, 2004

Tom:

Think I would need to use the TT3000 as I tow about 5,000 ponds occaisionaly and the mountains are not far away.

I have the stock pulley and am about to add Snow's water/alky injector. Do you think the stock 5.3 can handle more boost?

Regards,

Durkin

tbyrne · July 27, 2004

The ProTruck converters have a 7000lb tow rating. They are available in 3000, 3200 and 3400 stalls.

I'd feel safe with about 7-8# of boost. Some people run more but your changes of something happening are greater with higher levels of boost. The 3.1" pulley is good for about a 2# increase while the 3.0" will give you about 2.5-3#.