A and M body disc brake spindles

Are the spindles from a mid 80's Diplomat/5th Avenue interchangeable with 76 Duster?

Yes.IIRC they are taller than the A bodys.I used both on my 65 conversion.Took the A bodys off and used the taller ones.The taller ones gave a better alingnment.Been on for 15 years and no problems.Rocky

Thanks, I heard they might be a bit taller, do you remember the difference?

About 1/2 inch taller.

I used the F body (F, M, J are all the same) . . . on my 70 Sport Satellite - has not been an issue at all !!! Just had to make sure that I got the correct calipers that are mounted on the rear with the bleeder screw on the TOP of the caliper . . . M body calipers. And getting stainless steel braided brake hoses (Dr.Diff) . . .

Thank for the help. I called local yards but nothing. Found a set in Texas, they should be here Tuesday. The fellow has a yard full of clean parts, very kind and helpful, his name is Ralph 800-572-8109 if anybody needs parts.

What did you have to pay for them?

Saying taller it means the car would sit lower on same circunstances.... just in case


More info, here:

https://www.allpar.com/history/mopar/brakes/disc-main.html


About the caliper indexing... I think spindle could be switched from L to R if needed?

Actually no, these do not lower the car at all compared to other equivilent OEM mopar spindles. They only have an additional 3/8" of material on the top of the spindle that creates slightly altered geometry to the upper control arm. They do not provide any built in drop because the bearing shaft center line relative to the lower joint has not changed dimensionaly. They also weight about a pound and a half less than the pre '76 disc spindles as well, so there is that benefit as well.

Now, with that said, there is a one year only C body spindle that does have a 1" drop built into it. But its lower ball joint bolt pattern is not bolt in compatible with the ABE ball joint pattern.

i have stood the taller spindles side by side, and at most, there may be 7/16" difference, depending on the casting. with the upper balljoint taper machining depth done, it likely would amount to a height difference of around 5/16-3/8" difference, depending on casting length and how the casting was fixtured for machining. add in the tolerance stacking allowed back in those days, plus tire size used in your application, if there is any one contributing thing that would create a visible/measurable height difference, i would say it would be the tire itself.
the reason i say this. pick three identical size tires from three different manufacturers. these can have up to one inch difference in height, tread width, and section width, and still meet the manufacturers quality specifications when mounted on the same size [width] wheel.
hard to believe, but try it some time. seeing is believing. just my real world experience of way over 50yrs.
so, in my opinion, i don't believe the spindles themselves would contribute anything with regards to "lowering" the vehicle ride height by any significant/measurable amount that would be visible to the eye.

Oh Ok!!! so the diff being on just top side will make a diff ratious action on UCA. Interesting! I allways have thought the spindle location was diff with both control arms. Sounds logic the diff just on UCA end being the frame rail higher due the isolation!

thanks!

yes, the isolators were the reason for the height difference. that said, when the taller spindles are used on the earlier cars, this introduces a different camber curve into the geometry, which will produce arguments and opinions on both sides of good and bad characteristics using this spindle. for 99.999% of the users, this is of no concern, as a good alignment allows them to work perfectly. the other .001% seem to want or need what they want or need.
over the years i have done countless conversions using these spindles for myself and others, and by now, i'm sure there are millions and millions of miles traveled without issues. i have never heard, or seen any.

X2 . . . . certainly the engineering side can be argued til all are blue in the face . . . but real world experience, well, it shows real world experience.

I wouldn;t say that.

the isolators have no bearing on the relationship between the UCA and the LCA. All they do is isolate the entire front suspension, UCA included, from the frame rails.

there was a mopar muscle article about the spindle swaps and the height difference you guys talk about---they mounted up a car with both types of spindles then put the car on a chassis machine that moved the suspension in all the movements that you would see in driving the car---they found the taller spindles stayed within specs better than the stock height spindles--so they figured the taller ones were better....

You are probably thinking of the Bigblockdart article

I have used the taller spindles AND the offset bushings together on many builds and there was never a problem with the alignment. But stock spindles and stock UCA bushings often will not come in.

So just to be sure and get it clear!

The distance between the shaft/bearing ( center of wheel ) and LCA is the same between earliers and laters spindles while te distance difference is actually located between shaft/bearing and UCA.

And of course this just affects aligment specs but not the ride height which actually will remain the same being still the same on bottom section of spindle.


Now I have a question. Phisically is posible to swap the spindles L to R, but... could this be done to change the calipers indexing for convenience? Visually it seems this is posible without affect anything on geometry or axles distance.

Sorry the highjack to the OP, but this could be interesting!

Ok sorry, i jumped out unintentionally this reply... good to know.

The RH article says not to swap side to side spindles but making mention just to hose and sway bar deal, however this could still be done for any custom convenience ( by owners decision ) without affect anything on geometry including axle distance on car! Right?

Talking about this!

Locally all mopars have REALLY bad reputation about front end weakness and aligment troubles. So bad, that ppl tends to remove the stock K frame and modify everything needed to install CHEBBY subframes down stock frame rails ( usually 70s Novas &/or small Malibus on A bodies at least )

Some ppl however use to cut the UCA and elongate them by an inch or so get them outer just right an offset bushing.

Some ppl have changed the LCA bushing using brass pieces or even BEARINGS on them due premature failures. I have think this deal is related to oil leaks on engine which damages the rubber &/or tighten up the LCA pivot nut before set the ride height, breaking the bushing out when seting the ride height after tight the nut.

Whatever, the question on this is, if have somebody found some problem on frame rails being bent or twisted after all these years causing the aligment issues being the UCA attached to frame rail? Meaning this due the offset bushing existance and now you mention having a similar problem.

Need to say locally Mopars have allways abused after all these years. And has being like that since ever!

Once again sorry the highjack, but since has being floated out somehow, maybe is time to ask

Dosent matter which side the spindles are on.Just as long as the bleeders are up and no interference.I have/had mine mounted both ways.Calipars are just swapped side to side also so they have as said bleeder up.Rocky

I'm aware of that! thanks!

I don't need it, since my car is factory disc, but just for infomation.

Wow, but I'm not surprised.

The mopar design of the muscle car era has always had limitations on caster/camber changes. Other than that. it actually has very good geometry. The frame, upper control arm, alignment angles, and geometry curves are all interrelated. But, a tweak any one of this combination and it will impact all the others. The lack of adjustment range combined with the interdependancy of all the parts could lead some people to thinking that similar year chevy design could be better (geometrically, it isn't, it just has a broader range of adjustment). Ironically, for all the work of swapping in a chevy stub, you could easily to a fraction of the work to add adjustment range to the mopar set up. Most aftermarket upper arms already provide more range. Offset bushing add range. If you really want chevy style range, convert the upper arms to mount on studs and use a chevy upper arm. Add two holes for studs, ream the spindle for the chevy ball joint and a pack of shims and you have a significantly broader range of adjustment. That is much easier than swapping an entire front stub.

totally agreed but not enough brain for anything like that LOL. PPl doesn't think, just go for it.

Anyway I'm not even talking about some custom requirement for some specific car use, is just about constant fails on front end with regular use.... is not uncommon to see the fronts wheels like this / \ ( on a front view ) on a local old and abused Mopar

I don't mind the hijack...lol. The discussion is good. I'm building my 68 Hemi Dart for Power Tour, its not your average build so your answers help a lot. If anyone is interested in more info? I'm using the HDK Torsion Bar eliminator kit with M body spindles, modified K frame, stock strut bars and looking and 6 piston Wilwood brakes. That brings another question to mind, Wilwood lists a 6 piston 12.8 rotor kit that says its for Magnum Force drop spindles, has anyone tried to put this kit on the M body spindles?

I'm 57 years old, build hi performance cars for a living at my own shop. I learn something new EVERY day. Being able to ask questions and share info helps in many ways. At this point the info helps me choose parts before I buy instead of buying / sending stuff back prolonging the process. Thank you all and I hope this discussion helps others too.

The Magnumforce drop spindles are designed to use the large bearing ,uni-cast (1 pc ) rotors, so yes, the Wilwood discs would swap on to the M body spindles.

my mind remembers a dropped spindle from years ago, that was a fabbed piece of plate steel with a pressed in hub spindle and a welded on tapered bung for the upper ball joint stud.
who made those ? it was during the time aspen/volare front K member swaps were invented for 60's pickups.

If you want an impressive brake system that bolts on to the FMJ knuckle and works then skip the Wilwood stuff and put a Viper based system on there. Here is what I have on my Duster.

Andy, Looks great! can you elaborate on the individual parts, source of hubs, rotors caliper brackets and mods you did to get the parts to fit? How well does it stop and what are you using in the rear?
Thanks

Fatman Fabrications. Yes, they looked like a high school shop project that got a D. Primary market for them was the rod builders and showground cruisers, who used to bolt the FJM subframes into early iron.

Fatman makes those.

that's the deal ! i wasn't impressed with those at all. if done correctly, i'm not afraid of welded components, but those looked sketchy at best, and a pressed in spindle did not make me feel good at all.
back in the early 70's, ramblers [AMC] had a bolt on spindle disc brake setup that used a 4 1/2"bc. if i wanted to make a dropped spindle, i would look at that setup and see what my mind could think up.

The circle track guys adopted the Mopar style crew - in upper ball joint a few years ago. Cool thing is that they make the ball joint with various pin lengths, so if you have shorter spindles and want the advantage of tall spindles to improve suspension geometry, swap in a set of longer ball joints! Wa La... check any circle track supplier, Speedway, Motor State for parts.

Wa la..
Do you mean Voila ??

That irritates me too

that's pronounced vee OH la ..........