Rear wheels still spin while in drive with foot brake depressed

[No disintegrations]

Yes need wheels on, or thread on some open face lug nuts.

 

[Chuck Leeper]

The reason the brakes don't hold when off the ground: Engine torque is multiplied x converter, x trans, x the diff ratio. Trying to hold that power w/ a skimpy drum brake doesn't work.
On the ground, the ft brakes come into play, as does the wt of the car, and the friction of the tire and the ground.

As for psi, SS Brake Corp, and others have instructions as to how to size m/c's what psi should be targeted.
As an example: my 55 has the Metric discs on the ft. 8" dual booster, 1.125" mc.
Engine vac at 18"= 800psi. This sob wouldn't stop in a football field.
Hyrdaboost installed: 2100psi. The sob stops, now.

http://ssbrakes.com/ft-1135-solutions-center.html

 

[The Granny]

Thank you Chuck, it makes sense now. I haven't gotten around to getting a pressure gauge yet, but last night I re did the entire bleeding process and took the car around the block and I'm still getting a mixture of a soft pedal 50% of the time I push the pedal, then a firm pedal the other 50% of the time. The brake light would come on occasionally too. Say I did have low brake pressure, what would I need to change to fix it? A new MC and/or accumulator?

I've been thinking more and more about going to manual brakes.. manualbrakes.com has a kit for g bodies and is only $200, seems too good to be true and I haven't seen many people on here saying they use that kit. I'll have to call them today to see what they're all about.


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[ttypewhite]

When ever I am putting in my tranny, I put it up on jack stands, put 4 liters of fluid in it, start the car and go through the gears to get the fluid into the converter. After running it in gear for awhile I step on the brake and it always stops the wheels from spinning, then I add the remainder of fluid, go through the gears again until the correct level is reached on the dipstick when the tranny is at operating temp. This is consistent with any of the Buick's I have ever worked on, and I have worked on many. Just my 2 cents.

 

[Chuck Leeper]

After running it in gear for awhile I step on the brake and it always stops the wheels from spinning, th

try it at stall/boost?

 

[The Granny]

I think I might've not been clear, I wasn't trying to hold any boost while in the air. I just had it drive and tried pushing the brakes to stop the wheels from spinning. And they would continue spinning. And on the road test around the neighborhood is when I tried holding boost on the footbrake and had no success. Wouldn't even get to 0psi


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[No disintegrations]

I think I might've not been clear, I wasn't trying to hold any boost while in the air. I just had it drive and tried pushing the brakes to stop the wheels from spinning. And they would continue spinning. And on the road test around the neighborhood is when I tried holding boost on the footbrake and had no success. Wouldn't even get to 0psi


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I knew what you meant. Some did not follow however.

 

[The Granny]

It looks like I'll be buying the manual conversion kit from manualbrakes.com. id love to have strange components for this conversion, and do their disc brakes on the front and back at the same time, but I just don't have the means for that at this time. Anyways, I called him just now and he seemed like an upfront, knowledgeable guy. I told him what I had, an 87 GN with stock PM brakes and a disc/drum set up and he assured me I could make it work. Aside from drilling my stock pedal and clearancing the firewall, it'd be pretty much bolt on. And he said he'd provide the instructions on where to drill my stock pedal and how big to drill it to.

Would an adjustable proportioning valve aid in me to achieve the proper pressure ratios? My car is mainly set up for the track but will see light street duty, so the I want to set up the braking for when I anticipate I'd need it the most, with skinnies (26x4.5x15) and slicks (28x10.5x15) on the car.


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[ttypewhite]

try it at stall/boost?

No arguments there Chuck, I agree 100%, but that is not what the OP was talking about. He said, "by stepping on the brakes it wouldn't stop the tires from spinning". Not brake torquing it while the tires are in the air.

 

[Wahoo]

Your probably needed to adjust the rear shoes. They were probably loose, but I also wouldn't be surprised if you damaged the rear wheel/brake cylinder being that the drum fell off and you probably were able to over extend it.

 

[Wahoo]

Im sorry but this makes no sense. If it cant hold a 30 pound wheel still how can it slow down a car?

chuck leepers response is basically what I was trying to say so I hope you understand it now.

 

[No disintegrations]

chuck leepers response is basically what I was trying to say so I hope you understand it now.

i did the first time, you and chuck went on the wrong trail and we were talking about different things.
I was talking about stopping a coasting wheel in the air and you referred to brake torquing it. No harm done.

 

[The Granny]

Your probably needed to adjust the rear shoes. They were probably loose, but I also wouldn't be surprised if you damaged the rear wheel/brake cylinder being that the drum fell off and you probably were able to over extend it.

I adjusted them prior to bleeding the brakes, they weren't going on or coming off loose at all. I made sure it was a snug fit to put on and take off


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