Full Size Jeep Network

I snagged the hydroboost out of the 04 Yukon that provided the 5.3/4L60 and mocking it up this week.

I have a number of thoughts and many are addressed in various threads and conversions documented online but it never hurts to get more input.

The hydroboost provides much more assist, I don't recall the amount but I am curious what impact the length of the pedal assembly has on the brake "feel". If the distance from the brake pedal pivot point to the hydroboost rod attachment pin is close to the original booster assembly, say 2" center to center but the pedal length is 4" longer on the Yukon than the Cherokee, the brake should feel heavier when work = force * distance.

On the other hand, if the brake "feel" is similar in the example above, how about the sensitivity?

The shorter pedal assembly will require less total travel for full braking, is this a problem requiring a comparison between travel distance between the Yukon and Cherokee and relocation of the brake rod pen to account the the change in pedal overall length?

The brakes will be more touchy with the shorter brake pedal, for the reasons you state. But I am not sure if this would be a bad thing. GM's are notorious for having a spongy brake feel that requires a lot of travel to engage the brakes. Having a shorter pedal should get rid of some of this. So I would leave it as is until you get to drive it.

If that HB unit is anything like the one from the early 90s Astrovans, it will work wonderfully as is. I love the brakes in my truck, the pedal is *responsive* I like to think. If you put your foot on it, the brakes work. It's definitely different than before, but I definitely wouldn't change it.


aa

Thanks for the input, I payed attention driving home from the office because my 2500HD has hydroboost and the pedal only requires a small amount of travel for normal driving, I do like that.

Here is where I am at tonight:

I had hoped to not need a spacer so I mounted it with the Yukon backing plate, I like that it's flat or parallel to the ground but the proportioning valve is too low and probably close to exhaust manifold and the brake lines from the valve up to the mc are hitting the fender. The valve could be relocated and the lines bent to fit but there is more.







It may help the rod to pedal pin alignment if the assembly was tilted up a little. I believe I will try to use the Cherokee aluminum spacer that has some tilt built in.




And the snout of the hydroboost projects a bigly amount past the firewall.

Pedal up full travel,




Pedal down full travel,

I knew I would not sleep so I went back out to remove the hydroboost and as soon as I looked at the Jeep spacer I knew it would be easier than I expected to mock it up.

The fit is much better!

I may have to get a lower profile master cylinder.

What's that switch on your accelerator pedal arm? Is that a TPS?


aa

It’s the kick down for the transmission for WOT (wide open throttle). Cecil14

Oooohhhh, that makes sense. I've never seen one, as I've never had an auto FSJ.

And here I thought it was something cool and mysterious. ha


aa

High tech in the 70's

Cecil14 wrote:Oooohhhh, that makes sense. I've never seen one, as I've never had an auto FSJ.

And here I thought it was something cool and mysterious. ha


aa

I was just thinking the same thing. All of mine have been manuals. I was thinking cruise control related or something.

I didn't want a big spacer nor did I want to weld on the brake pedal. The hole on the MC rod ended up behind the pedal so I made a link that ties the pin on the pedal back to the hole in the MC rod. I think I shortened the rod some also.

Also moved the MC to the other side of the brake pedal.

SJTD wrote:I didn't want a big spacer nor did I want to weld on the brake pedal. The hole on the MC rod ended up behind the pedal so I made a link that ties the pin on the pedal back to the hole in the MC rod. I think I shortened the rod some also.

Also moved the MC to the other side of the brake pedal.

The pedal arm appears to be cast iron so I agree, I would not want to weld on it either.

Do you have a picture of your bracket to move the pin?

I was comparing the Yukon PV to the Jeep PV and the Yukon has only one output for front and rear, and the Jeep has three, one rear and two front, why is that?

Also, I bet the Yukon had rear disc brakes so I may need to plumb the lines to the factory PV and save the Yukon PV in case I convert to rear discs.

I thought I had uploaded some pics to PB but not so. I know I took some so I'll have to look on the camera. If they're gone I'll take some more.

243 wrote:I was comparing the Yukon PV to the Jeep PV and the Yukon has only one output for front and rear, and the Jeep has three, one rear and two front, why is that?

Because on the yukon, the brake line came out of the PV and went into the ABS unit/pump. That is where it splits off to each wheel. That way it can control each wheel separately.

Thank you!

I got some pics of the hydroboost up: http://www.ifsja.org/forums/vb/showthre ... 564&page=5

Thanks, that helps a lot and provides another option for mounting the rod.