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