Moparts
Grand Cherokee Discs on 8 3/4 Rear?
Posted By: MCTPhoenix
Grand Cherokee Discs on 8 3/4 Rear? - 04/22/08 04:12 AM
I've heard of this being done but no one seems to have specifics. I do need a parking brake as the car is a stick and don't want a kit with the eldo calipers with integrated parking brake. Are the jeep parts the type with an internal drum e-brake? I hope someone can shed some light on this. Thanks !
Posted By: MCTPhoenix
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/23/08 01:30 AM
OK, I've confirmed that the 94-98 Jeep grand cherokee uses a drum style parking brake. Has anyone done this swap? Is the bolt pattern on the jeep axle flange the same as 8-3/4? Anyone?
Posted By: dogdays
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/23/08 01:53 PM
Calling DrDiff, calling DrDiff, we have a Code Blue at the rear braking area!
R.
Posted By: 340727dart
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/23/08 01:56 PM
I did the swap on my 8 1/4" rearend.
The caliper mounting brackets bolted right up.
I'm not familiar with the 8 3/4" mounting flange.
The 8 1/4" uses four bolts. I was told the 8 3/4" has five.
Posted By: Robbins
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/23/08 02:02 PM
I've done it on my 8 3/4. The fifth hole needs drilled, easy. I used the green bearings and I machined a step in the bracket so that the snap ring would sit in the bracket exactly the same distance of the old drum backing plate. The only thing that I didn't consider was the thickness of the rotor which was thicker than the drum, so.....the whole rearend is a little wider like 1/4 total so an 1/8 wider on both sides. Hope this makes since.
Posted By: moparman383
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/23/08 02:45 PM
I've heard about this before but didn't know if it was true. Also, someone told me that the master cylinder/brake booster from a Jeep will work on old Mopars...does anyone know if there is any truth to this?
Posted By: kick_the_reverb
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/23/08 05:17 PM
I got excuses up the yingyang as to why I have had all the parts for the conversion (for 2 years), but haven't done it yet. I will be using the 94-98 Jeep Grand Cherokee master cylinder in combination with F body front calipers. This will be on an A100 van, and a few people have done it with good results. They claim to have checked the piston volume on the F body as compared to the Jeep front calipers and found it close enough. So, take it as second hand information, but from people I trust.
Ran
Posted By: MCTPhoenix
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/24/08 12:34 AM
Quote:
I've done it on my 8 3/4. The fifth hole needs drilled, easy. I used the green bearings and I machined a step in the bracket so that the snap ring would sit in the bracket exactly the same distance of the old drum backing plate. The only thing that I didn't consider was the thickness of the rotor which was thicker than the drum, so.....the whole rearend is a little wider like 1/4 total so an 1/8 wider on both sides. Hope this makes since.
Lee, did you have to use the green bearings? It sounds too easy... drill the 5th hole and it all falls into place? You even used your original e-brake cables? Is the thickness of the bracket which replaces the drum backing plate the same as the drum backing plate. More details please and THANKS!
Posted By: Robbins
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/24/08 12:49 PM
Quote:
Lee, did you have to use the green bearings? Well, Dr. Diff thought that I should. I already them anyways.
It sounds too easy... drill the 5th hole and it all falls into place?
Well, sort of....but I machined a step in the caliper bracket so that the snap ring would sit inside the caliper bracket. The reason I did this is the caliper bracket is way thicker than the drum backing plate. Doing this I needed to make spacers to go on the outside of the snap ring so that it would be flush with the caliper bracket so that the green bearing flange would basically sandwich the snap ring inside the caliper bracket. Once you do this the axle flange is right where was with the drum brakes(another words the splines of you axles are seated just the way it was).
You even used your original e-brake cables?
I haven't got that hooked up yet. With an auto it really isn't need I don't think. But I've got a 4 speed so I'm going to hook that stuff up.
It's hard to explain. I need pictures of this and I don't have them where I can put them on my computer.
Posted By: BlakDak
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/24/08 10:39 PM
what did you guys do about the parking brake?
Posted By: BlakDak
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/25/08 12:16 AM
is this the right set up?
Posted By: 70Cuda383
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/25/08 02:44 AM
for those that have done this, let's get some GOOD pictures and crystal clear explanation as to what was done, and what the swap cost you.
seems like a cheap easy swap for rear discs using junk yard parts...but is it really cheaper than some of the kits on the market?
I've heard of this from several places, but a few years ago, I posted the question on here, and didn't get much response, if any. so I figured that if anyone had done it, it was NOT easy, and NOT cheaper than kits currently available.
Posted By: MCTPhoenix
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/25/08 03:52 AM
Lee, I'm lost on this snap ring thing? There are no snap rings I can recall anywhere on any of my 8-3/4's or Dana 60's for that matter.
Posted By: MCTPhoenix
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/25/08 04:11 AM
Quote:
is it really cheaper than some of the kits on the market?
I figured that if anyone had done it, it was NOT easy, and NOT cheaper than kits currently available.
Well, I tried cheap and got cheap with the scarybird crap. Long expensive story but the real problem is the integral parking brake on the GM calipers is a pain; combine that with the fact the brackets aren't perfect and don't allow the calipers to run parallel to the rotors yields uneven pad wear and that contributed to terrible pedal height and feel. So, I'd like a solution that eliminates calipers with an integral parking brake.. and uses an oem bracket for rigidity ( modified if needed )and off the shelf parts where I don't have to have rotors machined or drilled or any other nonsense. You can get cross drilled and slotted rotors for the Jeep for less than $100 bucks a pair; it seems to be a nice bolt on if it can truly be done with little trouble.
I'd like to see some pics or get some details. I've tried Dr. Diff and hope he has some of his kits at Spring Fling but he uses Ford calipers with integral parking brake and I don't know about the rotors etc.. off the shelf? The way things are now is the rear discs look cool but the system worked better with drums and right now I've got a 4500lb car putting 480hp to the rear wheels that doesnt wanna stop but I may go back to drums. UGH ! Thanks for the allowing the rant!
Posted By: BlakDak
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/25/08 04:21 AM
I think I'll attempt it, but it will be for a 8 1/4 rear.
The thing is I swear in 1995 I used 8 1/4 backing plates on a 8 3/4 I swapped into my duster.
Posted By: Robbins
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/25/08 11:13 AM
Quote:
Lee, I'm lost on this snap ring thing? There are no snap rings I can recall anywhere on any of my 8-3/4's or Dana 60's for that matter.
In this picture you can see the snap ring on the bottom side of the green bearing closet to the axle flange.
Posted By: Robbins
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/25/08 11:24 AM
Quote:
and what the swap cost you.
seems like a cheap easy swap for rear discs using junk yard parts...but is it really cheaper than some of the kits on the market?
I've heard of this from several places, but a few years ago, I posted the question on here, and didn't get much response, if any. so I figured that if anyone had done it, it was NOT easy, and NOT cheaper than kits currently available.
I've got $125 in mine with out the e-brake, which will change once I'm done with it. That's a lot better than a $500 dollar kit. Anyways that the cheapest kit I've seen. I can also go up to the parts house and buy parts.
Oh, and no welding required.
It's all in where your at when it comes to prices. My cousin up in K.C. got the same stuff cheaper than I got the stuff out of the salvage yard down in Branson, MO. So......I ended up with his stuff, cause he sold his car before putting them on. So now I have the e brake stuff.
As far as the 8 1/4 rear, it's too easy for that, cause the rear ends in the GC's are basically the same set up. They use the c-clip's to hold the axles in. So no need it drilling the fifth hole. Oh, you do need longer studs, which I went to the dealer ship and order some from a 2005 1/2 ton truck with rear disk brakes. Theses are the studs that hold the backing plate on the c-clip rears or the the same studs for the green or original bearings for the axles in the 8 3/4 rears.
Clear as mud?
Posted By: Robbins
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/25/08 11:29 AM
Quote:
I did the swap on my 8 1/4" rearend.
The caliper mounting brackets bolted right up.
I'm not familiar with the 8 3/4" mounting flange.
The 8 1/4" uses four bolts. I was told the 8 3/4" has five.
This guy can tell you how easy it is for the 8 1/4.
Also I forgot to mention when machining the step for the snap ring on the green bearing I also had the make the hole in the center of the caliper bracket a little bigger to go around the green bearing itself some. It wasn't much. Which for the 8 1/4 you don't have to machine the bracket at all. It truly is a bolt on deal.
The 7 1/4 and 9 1/4 rear with the 4.5 on 5 patterns with the 2 1/2 shoes can do this as easy an 8 1/4.
Posted By: MCTPhoenix
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/26/08 02:04 PM
Quote:
Also I forgot to mention when machining the step for the snap ring on the green bearing I also had the make the hole in the center of the caliper bracket a little bigger to go around the green bearing itself some.
Lee, If you didn't use the green bearing would you have to machine the step? I'm going to try to locate some used parts and try this. Sounds like if the standard bearings dont need the step for the snap ring I may only have to open the hole a little for the bearing clearance?
Posted By: DoctorDiff
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/26/08 05:26 PM
The Jeep caliper bracket would require extensive modifications to use A-7 adjustable wheel bearings.
Posted By: Robbins
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/28/08 12:26 PM
Quote:
Quote:
Also I forgot to mention when machining the step for the snap ring on the green bearing I also had the make the hole in the center of the caliper bracket a little bigger to go around the green bearing itself some.
Lee, If you didn't use the green bearing would you have to machine the step? I'm going to try to locate some used parts and try this. Sounds like if the standard bearings don't need the step for the snap ring I may only have to open the hole a little for the bearing clearance?
Well I haven't tried it with out the green bearings, but you need to be careful here. If you don't machine the caliper bracket to the thickness of the old drum backing plate then your axle may not be fare enough in the third member spline wise. The caliper bracket is really thick. Really for the 8 3/4, ideally you would want the housing narrow up so that once the caliper bracket was pushed on to the five studs on both sides you would have the exact width of a stock housing(what ever you working on, like A -body, B-body and so forth) as far as width is concerned.
That's why the 7 1/4, 8 1/4 and the 9 1/4 with the 5 on 4 1/2 pattern with 2 1/2 shoes work better cause these caliper bracket slide over the housing end and have nothing to do with the axle itself. As far having to bolt to the out side of the housing. They are held in with C clips.
Hope this makes sense. I realize that pictures are 1000 words, but I don't have any to be able to post.
Posted By: Von
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/28/08 02:28 PM
As far as cost, if you dont have core calipers this swap isnt much cheaper than some of the kits available.
I paid 115 for the brackets, most likely from the say place Robbins got his brackets in Branson.
The core charge on the calipers is around 75 a caliper plus the price of new calipers, around 60 a side. Rotors arent too bad, around 25 or so a side.
I havent used the brackets yet, because I didnt like the fact the brackets pulled the axles that much farther out of the housing. But, I can see with green bearings and by machining for the snap ring that issue should be taken care of.
Posted By: Robbins
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/28/08 02:35 PM
My cousin got all of it for like $60 in Branson. I got my stuff that's on the car now from two different places in Joplin. So.......ya, I'm running the used calipers that I bought in Joplin. I guess roundie rounders have been welding the brackets on dirt cars for awhile now on phord 9in's.
Posted By: 340727dart
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/28/08 02:48 PM
I've got less than $200 in my conversion. That includes the cost of rebuild kits for the calipers, along with new rotors, pads and brake hoses.
Posted By: Von
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/28/08 02:49 PM
Quote:
My cousin got all of it for like $60 in Branson. I got my stuff that's on the car now from two different places in Joplin. So.......ya, I'm running the used calipers that I bought in Joplin. I guess roundie rounders have been welding the brackets on dirt cars for awhile now on phord 9in's.
I sure wish I could have got all of the parts for even $100. I was referred to a Jeep place in Branson that had supposedly sold the parts for cheap. Well I didnt get the parts cheap. In fact they made sure and pull the backing plate and any parking brake parts off of the brackets. Jee whizz. 
I dont know why you would use the JGC brackets and dang sure cant see why you would weld them on a 9 inch for a dirt car. The cheap Afco weld on brackets are only 25 bucks and the calipers are dirt cheap, around 15 a side. At least that is what I and alot of other guys used on dirt cars with 9 inchers.
Posted By: Robbins
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/28/08 02:58 PM
Quote:
Quote:
My cousin got all of it for like $60 in Branson. I got my stuff that's on the car now from two different places in Joplin. So.......ya, I'm running the used calipers that I bought in Joplin. I guess roundie rounders have been welding the brackets on dirt cars for awhile now on phord 9in's.
I sure wish I could have got all of the parts for even $100. I was referred to a Jeep place in Branson that had supposedly sold the parts for cheap. Well I didnt get the parts cheap. In fact they made sure and pull the backing plate and any parking brake parts off of the brackets. Jee whizz.
I dont know why you would use the JGC brackets and dang sure cant see why you would weld them on a 9 inch for a dirt car. The cheap Afco weld on brackets are only 25 bucks and the calipers are dirt cheap, around 15 a side. At least that is what I and alot of other guys used on dirt cars with 9 inchers.
Don't know why they would do it. I was just repeating what the guys at the salvage yard was saying when I went and bought the calipers and the little rubber brake lines at the second place. I know what you mean by wish you could of got them that cheap. He got his stuff cheaper that I got mine, cause I didn't have the e-brake stuff.
As a matter of fact the first salvage yard didn't want to sell me just the brackets. They wanted to sell me the whole rearend. I was like I don't want the whole rearend. I'm retrofitting this on an old car.
When I said $125 in mine thats just with new rotors and pads. I reused the hoses and the calipers. I bought some pizza for the guys in the shop here at work to do the machining for the green bearings.
Posted By: wayfarer1
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/28/08 03:17 PM
I just bought a whole rearend from a 95 Grand Cherokee complete with suspension and disc brakes from a private owner for $100.00 in Ohio. I found the deal on Craigslist.
If the calipers look good I am going to use them as is and just replace the pads. I will have the rotors turned, so the cost will be relatively low.
With the green bearings, there is no need for the inner axle seal. If this seal is removed would that allow the axle to move into the housing further thus allowing more clearence for the backing plate and bracket?
I just talked to someone at Strange Engineering and the Green RP 400 bearing does not use the snap ring. The retaining plate is attached to the bearing which should allow the bearing to fit tighter into the housing.
Joe
Posted By: wayfarer1
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/30/08 12:26 PM
Moser also sells a bearing set without the snap ring and the part number is 9400RP. They are available from Summit for $67.99 a pair.
Using these bearings should eliminate the need to machine the step into the backing plate for the snap ring.
Joe
Posted By: DoctorDiff
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/30/08 01:05 PM
RP-400 Green wheel bearings (with the crimped on flange) would require extensive modifications to the caliper bracket.
Posted By: dogdays
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/30/08 01:47 PM
Listen to the Doc!
R.
Posted By: wayfarer1
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/30/08 05:11 PM
Quote:
RP-400 Green wheel bearings (with the crimped on flange) would require extensive modifications to the caliper bracket.
The Green bearing without the snap ring mounts the same and in the same location as the one with the snap ring so why would this bearing require so much modification to the caliper bracket where the snap ring type only requires the machining of a step for the snap ring and the enlarging of a hole in the bracket?
Posted By: DoctorDiff
Re: Grand Cherokee Discs on 8 3/4 Rear? - 04/30/08 07:03 PM
The MO-400/ST-400 snap ring is 0.050" thick and 3.125" in diameter. The RP-400 crimped on bearing retainer is 3/16" thick and about 4.375" in diameter.
Posted By: BlakDak
Re: Grand Cherokee Discs on 8 3/4 Rear? - 07/08/08 10:02 PM
I am curious as to what you guys did for a parking brake cable?
Posted By: Robbins
Re: Grand Cherokee Discs on 8 3/4 Rear? - 07/09/08 11:51 AM
I haven't done that part yet. My car is a standard and I really would like a parking brake. I've gotten all the stuff on the rear end for it, but haven't installed them yet.
Posted By: funkyjbp
Re: Grand Cherokee Discs on 8 3/4 Rear? - 07/09/08 12:39 PM
lee, jeff from parsons here. i met you at mopars invade mokan a while back. i go to joplin frequently. any chance i could come by and check out the disc swap in person? it would be awesome to see this up close and personal. i have several worthy disc swap candidates: 77 shortbed with 3.21 sure-grip 8 and 1/4, a few 8 & 3/4 SGs, and a 3.55 9 & 1/4 SG for my 92 truck. i will be sourcing a few GC rears systems in the meantime!
jprice@vikingnet.net or 620-820-3793. thanks and later, jP in KS.
Posted By: Robbins
Re: Grand Cherokee Discs on 8 3/4 Rear? - 07/09/08 12:48 PM
Both you & moparjamie are welcome to come over anytime. I do have an extra set also.