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89-92 vs 93-97 rear brakes and aftermarket axles Does anyone know what the differences are in terms of fitment? I've got to make a decision to go to an aftermarket axle or stay with the 9 bolt (another posi cone rebuild is in order), and finding a rear axle that uses third gen brakes is apparently impossible. oser, for example, sells an axle to fi the 93-02 rear brakes, but not one to fit thirdgen rear brakes, I cant imagine why. I recall these setups being nearly identical, but I've never actually looked at a 89-92 10 bolt disc brake setup, 89-92 9 bolt disc setup, and a 93-02 disc brake setup. I'm sure someone has posted something along these lines already, but my search skills just arent good enough. |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles I believe the 4th gen style is slightly larger size calipers of the same design(PBR) and use a larger rotor. I had the old 9 bolt diff and iirc the rotor size is 10.5, the newer size is 11.5. I personally like having the bigger rotors/calipers. The 4th gen stuff still has support for aftermarket axles and its why I choose to use it and retain my factory wheels.Im running the s60 rearend instead of the moser. Im not 100% sure thats the reason but the 3rdgen stuff vs 4th gen are not directly the same physically. |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles Pretty sure the difference between 89-92 and 93-97 rear discs is the diameter of the rotor, and the 4th gen calipers have the cooling/stiffening fins milled smooth across the top of the caliper. |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles 82-88 rear disc are not worth talking about imo. Heavy, prone to leaks, calipers freezing and on and on. 89 is the only year with the 9bolt, larger rotor and aluminum pbr caliper. Has 2 different caliper mounting brackets, early 2 piece (dust shield) and late 1 piece no dust shield. 90-92 have the same brakes as 89 but bracket for 10bolt. Somewhere in late 91 the calipers gained a round vibration dampener. It continued through 97 but sometime on the 4ths it changed and faced forward. 93-97 lost some of the fins on top of the caliper (for wheel clearance i'm thinking), have a couple different rotor designs but are same size. Also, the rotor and bracket have a specific offset in some years iirc. 98-02 got a thicker (larger diam?) rotor, different pbr caliper look, internal parking brake, more complex and more weight |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles
Originally Posted by 86White_T/A305
(Post 6346539)
I believe the 4th gen style is slightly larger size calipers of the same design(PBR) and use a larger rotor. I had the old 9 bolt diff and iirc the rotor size is 10.5, the newer size is 11.5. But it sounds like the reason they won’t work is the rotor is a different size on the 93+ cars. So I’m guessing there are no backing plates available for a ford 9” rear and the 89-92 brakes? https://cimg1.ibsrv.net/gimg/www.thi...2360d9dd2.jpeg https://cimg2.ibsrv.net/gimg/www.thi...51d70d6f2.jpeg |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles I have Bear backing plates on my big bearing ford 9" rear and 13" 2 piece rotors with my stock 89 formula calipers. I'm sure they make them for stock size rotors too but I used my stock 89 backing plates on the 9" with stock rotors. rear disc are the same diam for 89-97 but the offset is is different from 3rd to 4th gen rotor |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles My 9 bolt was original to my 86,probably why it had smaller rotors. So if the calipers are virtually the same minus the cooling fins, the only difference is the rotors offset from 3rd to 4th gen. Could a spacer to correct the offset be the solution. Assuming the offset is to bring the rotors further out? Chance are its not :P |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles It appears the 4th gen rears have 11.530 inch diameter rotors. 3rd gen PBR rears have 11.665" rear rotors. So the rotors are .165" smaller, and the calipers are ever so slightly clearanced as well. Probably to fit stock 15" wheels with the new 4th gen offset. Also was able to verify on Rock Auto that the caliper bracket is the same. So it looks like the only difference is .135" of rotor diameter. That probably means the caliper bracket mounting bracket holes are .0675" closer to axle centerline, so barely more than 1/16 of an inch. Not sure if the aftermarket axles come with backing plates, but I am guessing they do and that's the issue. The only other question is the rotor hat offset from the rotor surface... rock auto is showing some odd discrepancies, as usual, but it looks like all are in the 1.9-2 inch range. So I dont even think the offset of the rotor is different.I wonder if the 4th gen backing plates on an aftermarket axles could have their holes elongated just enough to fit... |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles I am doing something similar now, i just got a used 12 bolt from a 4th gen and i used to have the 9bolt from an 89 trans am. I took some pics to show the differences. I ordered 95 LT1 calipers, rotors and pads and they look almost identical to the 89 pbr's. https://cimg7.ibsrv.net/gimg/www.thi...ce6adee8c9.jpg new LT1 rotor on inside, old 89 pbr rotor on outside https://cimg0.ibsrv.net/gimg/www.thi...9d8d4bfa70.jpg old LT1 rotor on right, old 89 pbr rotor on left, notice the steep step in the LT1 rotor https://cimg8.ibsrv.net/gimg/www.thi...cea0e350a7.jpg LT1 rotor on right, 89 pbr rotor on left, notice the bolt holes in the LT1 rotor are larger and the machined lip on the 89 pbr rotor on the inside vs LT1 |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles
Originally Posted by InfernalVortex
(Post 6346681)
It appears the 4th gen rears have 11.530 inch diameter rotors. 3rd gen PBR rears have 11.665" rear rotors. So the rotors are .165" smaller, and the calipers are ever so slightly clearanced as well. Probably to fit stock 15" wheels with the new 4th gen offset. Also was able to verify on Rock Auto that the caliper bracket is the same. So it looks like the only difference is .165" of rotor diameter. That probably means the caliper bracket mounting bracket holes are .0825" closer to axle centerline, so between 1/16 of an inch and 3/32", not sure how much that matters. Not sure if the aftermarket axles come with backing plates, but I am guessing they do and that's the issue. The only other question is the rotor hat offset from the rotor surface... rock auto is showing some odd discrepancies, as usual, but it looks like all are in the 1.9-2 inch range. So I dont even think the offset of the rotor is different.I wonder if the 4th gen backing plates on an aftermarket axles could have their holes elongated just enough to fit... |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles If you look at the 3rdgen rotor, it has a lip on the outer edge of the pad surface not being used. My guess is that the smaller outer diam won't make a difference at all other than removing a bit of weight. |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles So perhaps the only thing that really needs to be changed to use a backing plate for 4th gen brakes is the rotor? This is interesting. 89GTA383, I cant see your linked pictures (probably my ancient computer), but you gotta try and mount up all the 3rd gen stuff and see if it fits! |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles I didn't link the pics I uploaded them to 3rd gen site. I still have the passenger side to bolt up, but from what I can tell, the calipers look to be the same. My backing plate on the 12 bolt is thicker so I had to get longer bolts for the caliper brackets. keep in mind I am using an aftermarket rear with the LT1 backing plates. If you look on the strange website they say the 3rd gen brakes wont work and you need to convert to Lt or Ls brakes but I don't think they researched that 89 to 97 calipers are the same. |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles
Originally Posted by 89gta383
(Post 6346925)
I didn't link the pics I uploaded them to 3rd gen site. I still have the passenger side to bolt up, but from what I can tell, the calipers look to be the same. My backing plate on the 12 bolt is thicker so I had to get longer bolts for the caliper brackets. keep in mind I am using an aftermarket rear with the LT1 backing plates. If you look on the strange website they say the 3rd gen brakes wont work and you need to convert to Lt or Ls brakes but I don't think they researched that 89 to 97 calipers are the same. |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles Instead of rebuilding the aweful cone type posi, get a Torsen for it. They work great. GD |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles I bolted the pbr caliper to the lt1 bracket, remember these are aftermarket brake backing plates. I put a small washer between the caliper bracket and backing plate to space the caliper out the correct distance. https://cimg7.ibsrv.net/gimg/www.thi...dd3817a69b.jpg 89 pbr caliper on backing plate https://cimg9.ibsrv.net/gimg/www.thi...1d6edb6536.jpg stange LT1 backing plate https://cimg3.ibsrv.net/gimg/www.thi...eb226866e0.jpg |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles A torsen for the 9-bolt? I've read that they exist, but do not fit 3rd gen axles, not convinced they fit the 3rd gen housing either. This is years old info, though, I havent look into it in a long while. Can you show me this? Edit: Found it on 9 bolt.com : http://9bolt.com/carriers.html What mods were needed to make it fit? |
Re: 89-92 vs 93-97 rear brakes and aftermarket axles They absolutely fit. Here's my post on the swap: https://www.thirdgen.org/forums/tran...rg-warner.html GD |
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