brakes don't work going backwards?
Question:
Assuming the vehicle is a 1500 series, it does not have a hydraulic booster – is is vacuum, and it would have the most assist at lower rpms due to the lack of manfold vacuum at higher rpms. Your Safari has hydraulic assist due to the fact that everything is so cramped under the hood, there is no room for a vacuum booster, and the 6.5 has hydraulic assist because for one thing it is a more heavy duty vehicle (being a diesel), and also because diesel engines have no vacuum, unless it is equipped with a vacuum pump.
– Hide quoted text — Show quoted text -> some vehicles have hydraulic brake boosters. my 95 gmc safari has that (4.3L) and > so does my 97 tahoe (6.5TD) the hydraulic pressure is from the power steering > pump so low rpm = low boost. although on the silverado’s (99-present) they have a > vacuum brake booster > >How hot were your brakes?? Possible air in brake line (bleed brakes to fix) > >or problems with the booster not getting enough power from the engine at low > >RPM (I’d guess you didn’t have it hammered to roll backwards down the hill) > >or problems with the booster itself. Those would be my first 3 guesses. > The booster would actually get MORE power at idle. (there is little to no > manifold vaccum at high rpm’s). > Tony Kimmell > Normal, IL > 1986 Chevy C-10 "Midnight" > 1976 Ford F-150 "Big Nasty"
Response:
some vehicles have hydraulic brake boosters. my 95 gmc safari has that (4.3L) and so does my 97 tahoe (6.5TD) the hydraulic pressure is from the power steering pump so low rpm = low boost. although on the silverado’s (99-present) they have a vacuum brake booster – Hide quoted text — Show quoted text ->How hot were your brakes?? Possible air in brake line (bleed brakes to fix) >or problems with the booster not getting enough power from the engine at low >RPM (I’d guess you didn’t have it hammered to roll backwards down the hill) >or problems with the booster itself. Those would be my first 3 guesses. > The booster would actually get MORE power at idle. (there is little to no > manifold vaccum at high rpm’s). > Tony Kimmell > Normal, IL > 1986 Chevy C-10 "Midnight" > 1976 Ford F-150 "Big Nasty"
Response:
Just a quick note – Wheel speed sensors do not distinguish between forward and reverse – they are just an analog A/C voltage signal generated by the reluctor ring passing in close proximity to the sensor. ABS operates from these signals only by detecting a longer or shorter sine wave, longer wave indicating slow turning wheels, short wave indicating fast turning wheels, no wave indicating stopped wheels. In short, the signal is the same pattern, voltage, etc. going forward or backward.
– Hide quoted text — Show quoted text -> I would venture to guess here that with the transmission in a forward > gear(as recognized by the electronics), and the wheel speed sensors sending > an opposite signal indicating a reverse direction that the computer and ABS > system became confused. Anyway, I wouldn’t do this too often as rolling > backwards in a forward gear has to be hard on the transmission clutches and > planetary gear sets. > > Any help would be good. > > I was checking out my 1999 chevy silverado on a hill today climbing up > it I > > stopped and allowed it to roll backward in drive I then hit the brakes > and > > the truck would not slow down the pedal gave a weird pulse and that was > all. > > Then when I tried again I put the truck in reverse as it rolled backward > an > > everything was fine. > Pulsing brakes … ya got ABS? > …good reasons not to have computers in cars… 
> — > his ‘93 300ZX "Ishara" Alpine 1505/1214, JL Audio Evo XR/VR > hers ’00 Rodeo "Ramoth" and ‘92 Saturn SL2 "Sabrina" > truck ’74 K5 Blazer "Tank Grrl" 100% transistor-free and proud > projects ‘65 VW Type III Notchback and a ‘77 Chalet sans Blazer
Response:
I would venture to guess here that with the transmission in a forward gear(as recognized by the electronics), and the wheel speed sensors sending an opposite signal indicating a reverse direction that the computer and ABS system became confused. Anyway, I wouldn’t do this too often as rolling backwards in a forward gear has to be hard on the transmission clutches and planetary gear sets. – Hide quoted text — Show quoted text -> Any help would be good. > I was checking out my 1999 chevy silverado on a hill today climbing up it I > stopped and allowed it to roll backward in drive I then hit the brakes and > the truck would not slow down the pedal gave a weird pulse and that was all. > Then when I tried again I put the truck in reverse as it rolled backward an > everything was fine. > Pulsing brakes … ya got ABS? > …good reasons not to have computers in cars… > — > his ‘93 300ZX "Ishara" Alpine 1505/1214, JL Audio Evo XR/VR > hers ’00 Rodeo "Ramoth" and ‘92 Saturn SL2 "Sabrina" > truck ’74 K5 Blazer "Tank Grrl" 100% transistor-free and proud > projects ‘65 VW Type III Notchback and a ‘77 Chalet sans Blazer
Response:
Any help would be good. I was checking out my 1999 chevy silverado on a hill today climbing up it I stopped and allowed it to roll backward in drive I then hit the brakes and the truck would not slow down the pedal gave a weird pulse and that was all. Then when I tried again I put the truck in reverse as it rolled backward an everything was fine. Anybody seen this before?
Response:
>How hot were your brakes?? Possible air in brake line (bleed brakes to fix) >or problems with the booster not getting enough power from the engine at low >RPM (I’d guess you didn’t have it hammered to roll backwards down the hill) >or problems with the booster itself. Those would be my first 3 guesses.
The booster would actually get MORE power at idle. (there is little to no manifold vaccum at high rpm’s). Tony Kimmell Normal, IL 1986 Chevy C-10 "Midnight" 1976 Ford F-150 "Big Nasty"
Response:
How hot were your brakes?? Possible air in brake line (bleed brakes to fix) or problems with the booster not getting enough power from the engine at low RPM (I’d guess you didn’t have it hammered to roll backwards down the hill) or problems with the booster itself. Those would be my first 3 guesses. — Big Chris mrclm at yahoo dot com If God is good, and God gives us life, then life must be good even if we don’t particularly like it. -Rich Mullins
| Any help would be good. | I was checking out my 1999 chevy silverado on a hill today climbing up it I | stopped and allowed it to roll backward in drive I then hit the brakes and | the truck would not slow down the pedal gave a weird pulse and that was all. | Then when I tried again I put the truck in reverse as it rolled backward an | everything was fine. | Anybody seen this before? | |
Response:
> Any help would be good. > I was checking out my 1999 chevy silverado on a hill today climbing up it I > stopped and allowed it to roll backward in drive I then hit the brakes and > the truck would not slow down the pedal gave a weird pulse and that was all. > Then when I tried again I put the truck in reverse as it rolled backward an > everything was fine.
Pulsing brakes … ya got ABS? …good reasons not to have computers in cars… — his ‘93 300ZX "Ishara" Alpine 1505/1214, JL Audio Evo XR/VR hers ’00 Rodeo "Ramoth" and ‘92 Saturn SL2 "Sabrina" truck ’74 K5 Blazer "Tank Grrl" 100% transistor-free and proud projects ‘65 VW Type III Notchback and a ‘77 Chalet sans Blazer
