D21 Drop spindles in a 73 620

[rand0m]

Hey guys

I have seen around that some people have managed to take the d21 A arms and spindles and install then into 620s. is it possible to install the whole lot into a 73 620 running kingpins. I pretty much want the lot if possible, so drop spindles and discs. Anyone done it and can offer a few pointers?

[wayno]

There is a lot more involved than just swapping parts, another guy is/was asking the same questions, he has been very quiet since I told him it was a failed disc brake conversion he bought and drove home, just read the thread link below, and then start asking your questions, as I have a hardbody conversion in my 521 work truck, so I can likely answer a lot of them, and I will say this again, and everytime, this is not the best avenue to take.

http://community.ratsun.net/topic/59092-620-lowering-issues/

[Farmer Joe]

gotta swap to balljoint suspension. 

 

im doing the same thing here soon. already got the front arms and spindle from a hardbody. im not going with drop spindles, but getting it converted to use balljoints is the main thing. 

 

upper control arms from the disk brake 620s are very different than the kingpin upper so it not just a bolt on. 

 

effectively, youll have to build or buy a set of upper control arms. the lower control arm from a 78-79 620, 80-86 720 and 86.5-97 D21 will work in the 620.

 

the stock torsion bars are still used, but youll also need the torsion keys that bolt to the LCAs. 

 

another point to bring up is the tension rod that goes to the front of the frame. ive seen 3 different ways to make these work. 

 

1st way was to wed a tab on the LCA like the stock kingpin arm has to mount the stock 620 tension rod. 

 

2nd way was to use D21 tension rods and drill and new hole on the LCA so the tension rod can swing out a little to match up withthe 620 tension rod mounts. 

 

3d way was to use the D21 tension rods, but to cut the tension rod mounts off the front of the frame, and reweld them on 2in more inward. this ive seen gives the best LCA geometry. 

 

it sounds like alot, but its really not that bad. 

[wayno]

I used a stock 620 disc brake tension rod with 620 bushings, it's been so long since I did the conversion that I cannot recall if I had to trim the bushings or not, I used a 620 lower arm, I am now using the hardbody spindle with the dual piston calipers, I don't recall which rotor I have as I bought this spindle/rotor/calipers from yellow620, but before converting over to the hardbody stuff, I was using the late 620, early 720 non-vented hardware.

I lengthened my upper 720 control arms 5/8ths of an inch, and I put the right UCA on the left side, and the left UCA on the right side, this gets the balljoint back where it needs to be.

This was all done to my 1971 datsun 521 work truck, most of it was done back in 2005.

[Farmer Joe]

wayno, what frame is the work truck on? 

[wayno]

wayno, what frame is the work truck on? 

 

It's on a 521 frame, it has been lengthened 24 inches.

Fact is I found a disc brake conversion at the boring wrecking yard, but it was a failed conversion and that is why it was there, but I took it to the next step and worked with it till I succeeded with the conversion, but it took me a few years to get all the bugs except one worked out, and now they are all worked out, but I added power steering to the conversion later, and that caused a couple more issues over time, but now they have been worked out also, I am sure more issues will show up from how I use this truck, but they would not be caused from the conversion, although the issues seem to effect the steering system.

I learned a lot about what works and what don't work, I haul a trailer behind this truck 90 percent of the time, so I have seen all the issues caused from not having the camber/castor/toe in the zone(safe areas of operation), most all of my problems were caused by caster, meaning the upper balljoint was to far forward, once I figured out that I needed to put the left UCA on the right, and the right one on the left to get that upper balljoint back far enough, then it was easy, it was like a different truck, it drove nice after that.

[Farmer Joe]

what kinda of control arms did you use? 

 

dod you end up cutting and adding anything to em, or were they left stock?

[wayno]

what kinda of control arms did you use? 

 

dod you end up cutting and adding anything to em, or were they left stock?

 

I used lower 620(late)/720(early) lower control arms from a non-vented rotor disc brake truck, I used 720 upper control arms, I had to buy 2 sets, as I added/lengthened them 5/8ths of an inch, sometimes I think if I did it again, I would add 3/4 of an inch, but I decided to use 720 frames instead, as they have disc brakes and power steering.

I actually made another set for the 520 project, but I went so low that I had to go back to the stock 720 upper control arm, and actually it needs to be shortened to tell you the truth.

Another thing I do is flip the upper control arms upside down, it helps keep the upper balljoint from binding, see how it is when lowered, it is binding.

 

While this way it is not binding.

Notice how the tension rod is almost touching the idler arm.

I also moved the tension rods to the back, I couldn't get it low because it was resting on the idler arm and pitman arm, you can see it connecting to the frame in the photo below if you look close.

 

[Farmer Joe]

ideas a brewing... 

 

i was thinking of doing an upper control arm like this guy did on DMT. 

 

http://datsunminitruckin.com/king-pin-to-ball-joint_topic231.html

 

just graft the end of a balljoint upper control arm to the kingpin arms. i figured this would be the easiest.. 

 

ive got the d21 lower control arms and loaded spindles. i went with the single pot caliper d21 brakes and they have the vented rotors. 

 

thanks for the pictures tho.. like i said, it gets my noodle runnin lol...

[wayno]

You don't want the upper balljoint straight out, you want it a little bit in back of the shock centerline, and you don't want to fix it using shims either, I went that route the first time, using shims to try and get that balljoint back, you have to tighten the UCA bolts real tight, and the head of the bolt bends and eventually breaks.

It's just easier to lengthen 720 arms, and put the  arm on so the balljoint is back(right side on left, left side on right), and not forward, the alignment guy said I had it within 2 degrees on everything by the time I was comfortable in believing it could be aligned, and I only felt good about it after I switched the upper control arms.

It was a dramatic change, driving it before switching the arms was a full time job, afterwards it was, so this is how it's supposed to drive, awesome!

[Farmer Joe]

do you have any pictures of the disk brake 620 or 720 arms on a 521/620 style frame? 

 

i know they have the non angled upper control arm mounts, and ive been curious how the arms end up being oriented. 

 

one way i know they end up making way too much positive castor. 

 

if one were to swap the arms left to right like you did, would it set the castor more in the negative? 

 

nevermind... 

 

i looked up mike klotz's attempt of using a stock upper control arm reversed. didnt work right. 

 

soooo im off to build upper arms. id like to build them like that guy on DMT, but with some more castor built in. im also not looking to shorten the lower control arms. id like to get some track width back 

[wayno]

Lets not get camber and castor mixed up, camber is when the top of the tire is tilted out(pos) or in(neg), negative camber is what happens when guys drop there car so far that the upper control arm is basically to short at that type of angle, and the top of the tires are tilted towards the engine.

Flipping the upper arms is the only reason I could get my 520 that low, as my UCA is at a dramatic angle now.

 

And I am also using a stud/stud type shock, it's the shortest shock out there, and it works great.

[Farmer Joe]

understand the castor/camber settings. 

 

im not worried about the camber settings. i need it to have a little more camber than acceptable, so the wheels clear the fenders. 

 

secondly, id like to built more castor into the upper arms to put the upper balljoint point more rearward than where the kingpin used to be. 

 

ive been looking at a few other arms that have been built and the norm seems to be about 1/2in set back from the centerline for the upper balljoint..