anyone feel like learing me about this, (keep it simple: ya know, layman terms so the marines on the board can follow along also) [img]/wwwthreads_images/icons/smile.gif[/img]

maybe some links?......
and no i didn't do a search....

<font color=red>3/4tonYJ</font color=red>

http://www.geocities.com/yj3qtr_ton
"Sept 11th 2001" will not be forgotten

I know someone will read this or reply that has a site up about this. I really hope that they will submit the link to SWB.com. We could really use this mod on there. Or even email me with the link to it.

[email protected]

[img]/wwwthreads_images/icons/smile.gif[/img] Here is the scoop:[img]/wwwthreads_images/icons/crazy.gif[/img] "Hydro-Boost" means that the brake ASSIST is derived from hydraulic pressure rather than atmospheric pressure. In most power brake systems, intake manifold vacuum evacuates both sides of the diaphram of a vacuum pot and holds the diaphram "suspended". When you press the pedal, a valve opens and lets atmospheric pressure into the rear chamber and that pressure pushes the diaphram forward and helps you set the brakes. Using the suspended system makes the action of the vacuum booster very quick and it's a simple mechanism. There are, however, some disadvantages: FIRST of all, the amount of PUSH that can be generated is the diameter of the diaphram TIMES ATMOSPHERIC PRESURE....(about 14.7 PSI). That's ALL you would have to work with AT SEA LEVEL.....14.7 PSI; at 7,000 feet it would be a LOT less. SECOND of all, what if you have a diesel? There IS no intake manifold vacuum on a diesel[img]/wwwthreads_images/icons/crazy.gif[/img], so you're screwed completely.[img]/wwwthreads_images/icons/frown.gif[/img] THIRD, as you pedal the brake, and the vacuum that is behind the diaphram is broken, the intake vacuum must restore it and that lets the engine go THAT MUCH FASTER, just when you needed engine braking, you have the opposite.[img]/wwwthreads_images/icons/crazy.gif[/img] FINALLY, if you had enourmous tires and needed a crapload of braking effort, you could only get it by increasing the diaphram diameter; and soon it would be so big that the hood could not close; OR....use dual diaphrams like GM did. Today's modern cars have such low cruise vacuum to get the mileage up that control vacuum for heaters and so forth is too low to work, so the dual diaphram setup was the fix for the brakes and an electric vacuum pump for the controls.[img]/wwwthreads_images/icons/tongue.gif[/img] HYDRO-BOOST uses the power steering system as a fluid power source and the pump pressure is used to help you push that brake pedal down. That system is independent of engine vacuum, and the power needed to crank that power steering pump and boost those brakes actually HELPS the engine braking effect as well, so it's a win-win. The hydro-boost is capable of one heck of a lot of boost since it isn't limited by altitude, engine vacuum, and diaphram diameter.[img]/wwwthreads_images/icons/crazy.gif[/img]

CJDave
A moonguy-operated Jeep Skunkworks in the "Heartland" building the Ultimate SNOJEEP.

thanks alot CJDave, (long time no talky) my real problem stopping is when i'm in double low range and the engine is still on hi idle,,,,,it won't come to a complete stop just really really slow....i'm current using a stock YJ booster and a 1-ton ford master cylinder (it just made my pedal travel less) which kind of give me a warm fuzzy feeling.

also here's a link to Pyro's page (it's a really good write-up, i thought he swapped them on his CJ, http://www.members.tripod.com/surfmac/21.html
i got a chance to buy a system off a 86 chevy truck for $60, i'm talking to him and hopefully getting it by this weekend..........

<font color=red>3/4tonYJ</font color=red>

http://www.geocities.com/yj3qtr_ton
"Sept 11th 2001" will not be forgotten

[img]/wwwthreads_images/icons/tongue.gif[/img] I'm suspectin' that the Ferd master cylinder has a larger bore and would normally require a LARGER DIAMETER vacuum diaphram to push it.[img]/wwwthreads_images/icons/crazy.gif[/img] Your braking pressure, therefore, is LESS than it was before.[img]/wwwthreads_images/icons/tongue.gif[/img] In "Double Under" it takes so little torque to move the Jeep that the drag from the clutch is moving it forward.[img]/wwwthreads_images/icons/smile.gif[/img].......Er....ah....[img]/wwwthreads_images/icons/blush.gif[/img] make that "converter" drag.[img]/wwwthreads_images/icons/blush.gif[/img]

CJDave
A moonguy-operated Jeep Skunkworks in the "Heartland" building the Ultimate SNOJEEP.

Hey Gregg, You sayin' bad things happen when you can't stop[img]/wwwthreads_images/icons/wink.gif[/img]

"It's not accident damage,
it's poseur trail damage"

Thanks Gregg, I got Pyro's link up. I also got your ram assist one up too.

[email protected]

Downside to hydroboost is that your braking systems and steering systems are now linked. When one fails, they both fail. We have a 98/99/00? gmc 1ton at work and the hydro boost is dying. Its a $1600 fix, and when it periodically goes out now, you lose braking AND steering. not good with 4 tons of sand in back. Brendan

Proud owner of the world's best running Carter BBD

-snip-Downside to hydroboost is that your braking systems and steering systems are now linked. When one fails, they both fail-snip-

So, if you where driving this truck and the brakes failed but the steering still worked, you'd keep driving? Or the steering failed but the brakes still worked you'd not stop right there?
The only way both would stop working, is a pump failure, in which case, you'd still be able to steer and stop(as easy as any powered brake or steering system without the power on) in a vehicle as light as a Jeep.

BTW, at 1600 bucks to fix the brakes,,,,,,???,,,,,,,,your getting ripped.

Wayne @ Big Island RockCrawlers
"PYRO" The Rock Crawler
Web Site: http://www.members.tripod.com/surfmac/Index.html

The system is just starting to fail, and what will happen is if you are really working the steering or pump the brakes hard afew times, there is not enough pressure left for full assist for the other system. The pressure jumps back up quickly, the pump seems fine, but for that moment there is no assist.

I hear you--stop driving the damn truck. This problem pops up so infrequently and usually in backing up situations, so we're riding it out till spring.

1600 is what the dealer wants for the hydroboost unit, not for the repair. Me, I'd dump the truck. GM is building crap 1 tons these days.

Proud owner of the world's best running Carter BBD