TSB-07-05-25-007B Calibration Letter

[Rail Jockey]

I also have an early 08 built third week of June, I haven't received it ether.
Just curious, has anyone that has had it done noticed any performance change besides the brakes good or bad.

[Bogie]

Originally Posted by Rail Jockey

I also have an early 08 built third week of June, I haven't received it ether.
Just curious, has anyone that has had it done noticed any performance change besides the brakes good or bad.

I've noticed no other performance changes other than much more responsive OHB brakes on start up.

The engineer in me is now very curious about the electro mechanical design of the brake "input" considering the system seems capable of brake deflection independent of vacuum compliance. This suggests a wee bit more linkage complexity than what one would normally encounter.

A normal brake vacuum system can basically have the mechanics hard connected to the vacuum diaphragm. When vacuum is present, the brake pedal is easy to push. When no vacuum is present, the brake pedal is hard to push.

An OHB system seems like it would need additional "gearing". I use the term "gearing" loosely to describe some kind of linkage that allows the brake pedal to drive two functions....one function being the normal vacuum initiation and the other function the OHB. The normal vacuum linkage will need to be designed to disconnect from the diaphragm on no vacuum start in order to allow the pedal to deflect. The brake pedal deflection would thus drive the OHB. Once vacuum builds, the reverse would occur. The system would need to back off the OHB function and allow the normal vacuum process to work.

The initial problems with the brakes suggest the transition to/from OHB and from/to vacuum had some programming issues. This is a very interesting process since it involves programming an electronic response (OHB), the need for which is determined by the feedback from a rapidly changing mechanical response (vacuum), when the input for BOTH responses is the same (user applied pressure on the brake pedal).

How does one use the SAME input (driver's force on the pedal) to drive two different processes (an electronic OHB and an mechanical vacuum assist), when the response of each process is dependent upon the response of the other process, which is dependent upon the driver's input on the brake pedal?

[SteveSky67]

Got my brakes done today, was in an out within 45 minutes....also, after they pulled my car out, they wanted to wash my car, all of a sudden the post the Celt03 posted about washing the car flashed in my mind, i said very nicely,
no thanks, i washed the car this past sunday and went on my way...Thanks Celt03 for posting that...

[HotRedPepper]

I had the work done to correct the braking issue about a month ago when I took my RL in for a oil change. I have noticed a difference in my startup in the morning. No need to wait as long anymore before taking off out of the driveway.

[JeffsSky]

I had them do this fix before the car even left the dealership (i noticed the brake issue on the test drive) and it is all but gone now. Thoroughly pleased with the fix.

[Wolfheart]

I had the work done on the brakes per the bulletin, I did and do notice a difference, the main difference is the car actually slows down and stops now when first put into gear when cold, brakes "crunchy" or not, previously it was iffy if the car would slow down significantly or not with the RPMs up so high at cold start. Yes, the brakes are still not normal at that time, but come on, how long does it take for the vacuum pressure to come up enough for the brakes to work normally? 1 minute, 1.5 minutes at most? All I cared about was the car actually slowing down and stopping during that time, now it does. In my opinion the fix works, not perfectly, but it works. Anybody who does not like the fix can sell their car to me for $50, about all a car with no brakes is worth. :P

[Wolfheart]

Originally Posted by samunoz1

I had this "upgrade" performed to little affect. Its less "spongy/crunchy", to keep inline with our nomenclature, but fact is its just plain old not right! This is the one thing that pisses me off about the car.

I can't convince the wife to let me get the Shelby Mustang GT KR. Probably has something to do with having an '08 Avalanche LTZ parked next to the '08 Sky RL. :-D

LOL Dump the wife and buy the Shelby, you can always pick up another wife with hot cars. LOL

[Mrbeanca]

For anyone looking to get TSB data on any vehicle they can go to ODI - Office of Defects Investigation and pull up the summary data. If you click on the safety recalls you can see those too. As a benefit this site is a government site and is free.

[mbeardsley]

I had the recalibration done Monday.

It has definiately improved the brake response at start-up. I no longer have the "crunchy" brakes first thing in the morning.

I never had as big a problem as some people reported, but it was a bit annoying. Now the brakes behave the same at start-up as any other time.

[Darkwing]

I have yet to receive the letter, but with a manual trans the problem isn't as apparent as it is on the auto trans cars.

[Jaysmith2000]

I'm not going to bother with the update, I'll just continue to let it warm up in the morning....

[Elff]

I pretty much do that without even thinking about it.
I sit down, Start the car, Put on my seat belt, shut the door, turn on the radio.
Decide between radio or iPod. Get my driving song, then put it in reverse.

[Bogie]

Originally Posted by Jaysmith2000

I'm not going to bother with the update, I'll just continue to let it warm up in the morning....

Saturn might update it anyway if you ever take it in for Service, even if you don't ask for it.

[jonahgirl]

I haven't receive a letter yet but will be making an appt. for the first oil change and will request it.