Measurements/data for CJ to YJ brake swap -
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post #1 of 3 Old 02-19-2007, 10:35 PM Thread Starter
only in a jeep cj
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Measurements/data for CJ to YJ brake swap

For those looking for measurements on the differences in the CJ and YJ brake you go. I was lucky enough to secure 3 YJ tubs with the brake assembly in them. I'm putting in a new engine in my 86 CJ its all apart anyway. I compared 3 set ups. A stock 86 CJ power set up. Master, booster, bracket, swing arm bracket with manual clutch pedal. Next is a stock YJ power setup from a 1991 (all parts YJ). Last is a 83 CJ swing bracket/pedals but with YJ firewall bracket/booster and master. I also compared 87, and 94 YJ setups.
First, the YJ and CJ swing pedal assemblies are basically the same. The manual version has a small bracket welded on the left side for the clutch arm return spring. It also has a longer center pin for the clutch arm to mount on......the auto version lacks both of these. The YJ unit has an extra upper corner bolt for a support arm that goes out the firewall. Also, the brake switches are different and in different spots so the YJ brake pedal needs to stay in a YJ unit and the CJ pedal needs to stay in a CJ unit.

The brake pedals are roughly the same in size and length, but the "S" bend is spaced different as is the arm attachment pin. The CJs booster pin is closer to the arm pivot so it has less stroke, but more leverage. But the YJs will yield more booster movement per the same stoke length of the pedal.

The clutch pedal differences are in the clutch rod attachment locations and their pin size. The CJ uses a 1/2 inch pin while the later YJs uses a 5 /16. The CJ hydraulic pedal and bracket in the next pic came from an 81 GM 4 CYL version that I scored out of a junk yard years ago

Holding the CJ manual clutch arm on to the center pin is a washer and C clip. The hydraulic version uses a support bracket that attaches to the center pin and the firewall. The smaller one is used on the CJs and also early YJ tubs (my 87 tub), but my 91 and 94 tubs use the larger bracket. The mounting studs are 2.25 inches on the smaller one and 3.25 inches on the larger one...but the larger one sits .25 inches LOWER on the top stud given the constant of the center pin (pedal pivot main pin) So theyuse two different masters.My YJ tubs are all from autos, so I can only guess that the 87 used a bracket like pictured and a clutch pedal with a larger rod pin like pictured. Even the Auto tubs have a delete plate at this spot, but the holes under it are for that years style of master size. The manual YJ set -up pictured was bought off E bay.

With the stock YJ set up closest in the pic, you can see the pedal would be higher on the CJ pedals/YJ booster (background).

Next I pulled out the whole stock CJ set -up. Heres how a full YJ set up and a combo CJ pedals/yj booster stack up or compared. ( note the YJ booster arm pivot hole is offset to the arm centerline. It turns down on the YJ (stock) pedal and has to be rotated 180 to attach to the CJ maintain the same rod centerline,, but the distances traveled are still different due to the two pedals different booster rod attachment pin locations. THIS IS WHY FOLKS HAVE TO LENGTHEN THE YJ BOOSTER ARM WHEN USING CJ PEDALS. The CJ pedal doesn't give the same rod travel as its booster pin is closer to the main center shaft that the pedal swings on.
In stock form my CJ brake pedal is 1.75 inches lower than the clutch pedal.
In stock form, the YJ brake pedal is 1.25 inches lower than the same MANUAL clutch pedal.
In contrast, the COMBO unit had a brake pedal the same distance as the clutch pedal. (so if I just stuck the YJ booster on my 86 CJ, it would have pushed the brake pedal higher by 1.75 inches)
But wait, thats not all, the LENGTH the pedal travels is important. So combine this with needing to lengthen the YJ booster rod and it seems to put even more length to the pedal. This gets the pedal FIRMNESS off the floor.
All 3 boosters (two YJ and one CJ) fully extended gave 1.5 inches of master rod travel. The CJ unit is slightly smaller then the YJ units. When the pedals were pushed through the full range of the booster, the YJ pedal travel .75 inches more than the CJ and the COMBO unit traveled 3.25 inches more. Thats not good and why the pedal ends up in the floor without the YJ booster rod modification.
So you tell me (those that have done this), If I use a YJ booster/master on my CJ pedal unit, I have to extend the booster arm to get away from soft pedal and I will need to push the pedal from a higher starting point than my current CJ position...and get the "better" results at a lower point. OR use the YJ pedal unit and start out with a pedal only 1/2 higher and produces more booster rod stroke with less pedal distance......OK, HAS ANYONE DONE THE YJ SWAP WHERE THEY SWAPPED THE PEDAL UNIT TOO??? (SO IT WOULD BE ALL YJ STUFF) with new hard lines down to the CJ porp.valve.

This results in the next question.....WILL A YJ hydraulic master work well with a CJ slave????OR will I need to use the CJ hydraulic pedal and CJ hydraulic clutch master??? So the YJ slave is internal till what 93, then external from 94 and 95???? So I would use that one? Jeep in question will use a T-5 transmission. Either way, I will need to use the YJ brake pedal for the other part..I then can swap over a dual diaphragm booster if I don't see an improvement over my CJ power brakes. OK swap masters....please give feedback!!!!

1975 CJ-6 1983 CJ-8
1986 CJ-7 Laredo 1986 2003 Inca Gold TJ Rubicon

Last edited by only in a jeep cj; 02-21-2007 at 07:40 PM.
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post #2 of 3 Old 03-13-2007, 05:58 AM
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Hey did you end up doing the swap yet? What did you go with and what were the results?

1983 CJ7 - Project "Surf Jeep Restoration"
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post #3 of 3 Old 03-13-2007, 07:31 AM
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Originally Posted by only in a jeep cj
Yup. That's pretty much what I did, but I used XJ parts. I had to modify the brake pedal. Works good.

I always thought the XJ parts were interchangeable with the YJ parts, and probably some of them are, but after looking at the bracketry in your pics (Thanks) they are definitely different. The whole unit is shorter as the booster isn't mounted to that spacer.

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