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Jeep Wrangler YJ
YJ Build Threads & Member's Rides
8.8 rear end swap
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<blockquote data-quote="RangerRick" data-source="post: 431087" data-attributes="member: 19360"><p>If you read my post on "The Diesel Jeep Build" I am re-doing my front axle again this time installing the full-size knuckles out treatment. That includes full-size 1/2 or 3/4-ton modine single piston calipers, full size F-150 rotors and all the components that go with that. </p><p></p><p>On YJ wranglers that I've done this in the past to, I changed the MASTER CYLINDER ONLY to a mid 1970's to early 1980's Econoline E250 3/4-ton master cylinder ONLY when going to full size front brakes and Explorer or ZJ Grand rears together.</p><p></p><p>This firmed up the brakes and made everything work as it should with the Explorer 8.8 rear disc brakes out back. I could stand on the brakes and lock all four 35" or even 37" tires up on the highway in a hard panic stomp on the pedal.</p><p></p><p>Prior to changing the fronts out from the original CJ or YJ discs, I left everything the same with the original master from Jeep and the brakes all worked fine. Didn't bother removing "O" rings or anything in the proportioning valve. Only on one of the conversions we did for a friend that I went and snagged a ZJ Grand proportioning valve from a 4-wheel disc 1995+ ZJ. IT DIDN'T MAKE ANY DIFFERENCE that I could notice except for maybe decrease some rear residual pressure off the back calipers for the first 100 feet of driving after being at a stop or so. Not really noticeable difference at all. Didn't affect rear heat or fuel economy so everyone figured it was a waste of time to do that. </p><p></p><p>Finding the E250 van master for use in the 1995 power brakes YJ Wrangler took LOTS of trial and error with a parts house I worked with. We tried Corvette, F150, Cadillacs and all kinds of master cylinders until I found the Econoline van E250 master cylinder from a 1978 to 1986 E series van worked perfectly without any aftermarket pressure adjusters or "O" ring fiddly things etc.</p><p></p><p>It was a friends shop who had a good working relationship with his parts house that allowed us swapping some 15 different master cylinders until we found the correct combination on 4-wheel disc brakes (Explorer or ZJ Grand rears with full size GM, Ford or Jeep SJ front discs). We did the math on piston sizes and volume of fluid moved, we used caliper brake line pressure gauges and everything that sound engineering practice would expect. After all, this is your life and the lives of others around you on a safety item like brakes so it absolutely HAD to work correctly. No mickey-mouse playing around with safety!</p><p></p><p>With the Explorer or ZJ Grand rear discs and the stock YJ or CJ front brakes, the factory master worked just fine up to 35's and the factory power brake booster. Over 35's we start thinking of a hydro-boost system because the small calipers have a limit to clamping force against the larger diameter wheel. It's a physics thing at that point. You know, larger lever, more surface area required etc.....</p><p></p><p>RR</p></blockquote><p></p>
[QUOTE="RangerRick, post: 431087, member: 19360"] If you read my post on "The Diesel Jeep Build" I am re-doing my front axle again this time installing the full-size knuckles out treatment. That includes full-size 1/2 or 3/4-ton modine single piston calipers, full size F-150 rotors and all the components that go with that. On YJ wranglers that I've done this in the past to, I changed the MASTER CYLINDER ONLY to a mid 1970's to early 1980's Econoline E250 3/4-ton master cylinder ONLY when going to full size front brakes and Explorer or ZJ Grand rears together. This firmed up the brakes and made everything work as it should with the Explorer 8.8 rear disc brakes out back. I could stand on the brakes and lock all four 35" or even 37" tires up on the highway in a hard panic stomp on the pedal. Prior to changing the fronts out from the original CJ or YJ discs, I left everything the same with the original master from Jeep and the brakes all worked fine. Didn't bother removing "O" rings or anything in the proportioning valve. Only on one of the conversions we did for a friend that I went and snagged a ZJ Grand proportioning valve from a 4-wheel disc 1995+ ZJ. IT DIDN'T MAKE ANY DIFFERENCE that I could notice except for maybe decrease some rear residual pressure off the back calipers for the first 100 feet of driving after being at a stop or so. Not really noticeable difference at all. Didn't affect rear heat or fuel economy so everyone figured it was a waste of time to do that. Finding the E250 van master for use in the 1995 power brakes YJ Wrangler took LOTS of trial and error with a parts house I worked with. We tried Corvette, F150, Cadillacs and all kinds of master cylinders until I found the Econoline van E250 master cylinder from a 1978 to 1986 E series van worked perfectly without any aftermarket pressure adjusters or "O" ring fiddly things etc. It was a friends shop who had a good working relationship with his parts house that allowed us swapping some 15 different master cylinders until we found the correct combination on 4-wheel disc brakes (Explorer or ZJ Grand rears with full size GM, Ford or Jeep SJ front discs). We did the math on piston sizes and volume of fluid moved, we used caliper brake line pressure gauges and everything that sound engineering practice would expect. After all, this is your life and the lives of others around you on a safety item like brakes so it absolutely HAD to work correctly. No mickey-mouse playing around with safety! With the Explorer or ZJ Grand rear discs and the stock YJ or CJ front brakes, the factory master worked just fine up to 35's and the factory power brake booster. Over 35's we start thinking of a hydro-boost system because the small calipers have a limit to clamping force against the larger diameter wheel. It's a physics thing at that point. You know, larger lever, more surface area required etc..... RR [/QUOTE]
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Jeep Wrangler YJ
YJ Build Threads & Member's Rides
8.8 rear end swap
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