So, I have ford big bearing [3.150"] -small bolt [3/8th inch backing plate bolts] ends on my winters quick change axle tubes and I'm ready for rear brakes. I have my axle shafts with bearings and they fit ok. I was lurking around U-pull-it this afternoon looking at rear brakes and I made a discovery I didnt' expect. The 80s and early 90s ford 1/2 ton pickups with drum brakes [2.25-2.50 inch shoes] have the very same backing plate mount bolt pattern as my axle tubes. [3.5"X2"] My axles and brakes have a 2.5" offset. I can't help but wonder if the late backing plates, hardware and shoes will mount to my axle tubes and allow me to use new Speedway drums, which are also set up for 2.5" offset. Are the holes in the backing plates big enough for my bearings [3.150"] to p*** through? Has anybody tried using these late backing plates on ford 9" big bearing tubes?
Frank Oddo [I think] did an article on Ford 8" and 9" interchangeability in Street Rodder mag a few year back. I have a copy in my files and will look for it.
Just did a Quickchange for the pickup axles. The customer swore they were 2 3/8" offset. Moser confirmed that there was such a combination. I did not have the brakes, axle or backing plates. We'll see if it all comes together shortly. The nice thing is that these have the 5 on 5 1/2" bolt circle.
Could you look up the 80s/90s bearing diameter and compare it to yours? Worst case you could have someone with more expensive tools make the hole in the backing plate the correct size?
I found a 70 Montego with a 9 inch , in the yard sitting on it's wheels but damn! It's only about 18 inches from the cars on either side and sitting [flat tires] on soft spring-thaw mud.... I'm not looking forward to dissecting this heavy *** car for backing plates if some 85-85 pickup backing plates will work. The trucks are on firm ground. For 13 bucks apiece for loaded backing plates, I guess I can try the late model stuff.
Just brainstorming here....IF you had an axle housing that was a 2 1/2" offset.....and wanted to use backing plates designed for 2 3/8" offset, would it be feasible to use a 1/8" spacer between the backing plate and axle housing, reducing the spacing to 2 3/8" ? The spacer would have to be similar to the bearing retainer in shape, as it would be up against the bearing in place of the retainer. Am I missing something with that idea? Ray
Welp, the difference between 2.5 and 2 and 3/8ths is only 1/8th inch. I think I'd just grind the edges of the backing plates so they wouldn't contact the drums. But I don't know what the late model offset is...I'll have to measure it and the center hole tomorrow. Was hoping someone here had already tried this swap.
Who you callin' a "welp"? .......... 're the mental math..... Since I screwed up the first post....I'll try again. Wouldn't the 2 3/8" backing plate be farther from the drum on a 2 1/2" axle housing? Ray
Well, now I feel stupid....opened the speedway catalog to see all the dimensions of of backing plate bolt patterns and center holes on page 62! Guess I'll tackle that Monterey 9 inch tomorrow AM. I HATE rolling in the cold mud! Hope it's got the "new style" big ford plates/axles...or I could buy the Speedway 11" brake "kit" for .[gulp] $479 plus tax. Hell, the 11 and 1/4" disc brake kit is only $349
After a few hours sleep, I revisited this issue in my "minds eye". I still think the 2 3/8" backing plates could be adapted, but may not be as simple as a mere spacer. My "imagineering" suggests that since the backing plate center hole is the diameter of the axle bearing OD, the spacer would need to have the same diameter hole. That gets the backing plate out the needed 1/8", but also moves the bearing retainer outboard a like amount. That would result in the bearing not being tightly retained and that is not acceptable. So, some other means of moving the backing plate out 1/8" has to devised. Without having the parts in hand I can only speculate. One possibility that comes to mind, cut out the center of the backing plate (BP) in the shape of, but a bit larger, say 1/4", than the bearing retainer "footprint". Next, an 1/8" spacer plate is fabricated whose inside profile is the same as the outside edge of the retainer footprint ......and the outside profile is 1/2" larger. This would provide "overlap" for welding the spacer to the respective BP parts. The result would/should be ....original relationship of bearing retainer to bearing and axle housing and the BP being at 2 1/2" spacing. I can see (at least) two flies in this ointment. 1. There may not be enough "flat space" around the BP mounting surface to accommodate this modification....... 2. The amount of work involved making it happen could exceed the value of the result. Rocky, I hope you see this before you head out to "lay in the mud" this morning. Ray
Yup, I see it but with no lathe, I think I'll just scarf up the brakes off the 70 Merc this morning. Hope nobody else has beat me to it...gotta go! Thanks for the thoughts.
I don't believe the 70 brakes will work for you. I think 73 is the first year for the larger bearing with the 3/8 retaining bolts. 70 uses the older style pattern with 1/2 retaining bolts. Monterey should have the large bearing and Montego should have the small bearing (3/8 bolt) either way neither one will work. You mentioned both cars?
I make/sell the disk brake brackets that you can buy off the shelf rotors/calipers MUCH CHEAPER,,,, should you go that route
I got up at the stroke of 10 and loaded up for a morning of thrashing on the Merc. Long story short, I got the damned back brakes and backing plates. The drums were in good condition but I had to abuse them to get 'em off. Took a few hours to get the sum***** apart and I took a sizeable hunk of skin off the back of one hand and while prying the drums off, the pry bar slipped and I clacked myself in the face, just below my gl***es. Yup, they're big bearing/big bolt and my flanges are big bearing/small bolt. I'm planning to weld slugs in the big bolt holes and redrill them the correct size and bolt pattern. I mean, this was the only car or truck with a 9 inch in all of Omaha! Plus, they're the correct 2.5" offset and use 2.25" drums...Spent 52 bucks for everything and I can't justify spending almost 500 bucks for speedy Bill's brakes. If I continue to have problems I MAY go disc brakes but I doubt it.
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