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77 620 Front Disc Brakes


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#1 NiMB

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Posted 10 June 2011 - 06:14 PM

Ok, so I am starting a new thread on this because it seems nobody has addressed this specific issue and the other related threads seem a bit old(2009 last post).

Specifically I want to upgrade my front drum brakes to disc (I know... imagine that, so original). I did my due diligence and searched the forums and found great info on how to do it with 02 Isuzu rotors, 79 280zx master cylinder, 92 D21 calipers, and Beebani's custom brackets; but I heard that some later 77 620s came with disc brakes... even my mechanic mentioned it.

I went onto Rockauto.com and looked up parts for a 1977 620 Disc brakes and loh and behold they are listed! You can go on and check for yourself. goto: http://www.rockauto....ramecatalog.php and search "1977 nissan 620" and select "brake/wheel hub" from there you will see caliper, rotor, etc.

So here are my questions:

If some 77s came with disc breaks could I just buy the calipers, rotors and master cylinder and then swap them out?

From what I understand the limitation to using 78 parts is the control arms and joints etc. Would this have the same issue even though they were made for a 77?

Lastly if I can just use the stock parts, what all would I need from the rockauto.com list?


Maybe this has been answered somewhere else already but I couldn't find it.

Please help me out here I would like to get original parts rather then piecing it together.

The thread I was going to follow prior to this revelation was this:
http://community.rat...isc-brake-swap/

#2 yello620

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Posted 10 June 2011 - 08:29 PM

Late 77 doesnt really matter. There was TWO 620 frame styles. Early(72-77) drum brake. And Late style(78/79). If you have a factory drum style frame then you need all the stuff, including the brackets from bee.

If you have a Late style frame then you have a factory ball joint frame and you already have disc brakes. Yet you still have room for improvement, cause the factory disc brakes of 78/79 suck.
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#3 mklotz70

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Posted 10 June 2011 - 08:40 PM

You'll have much better luck searching if you use google. Type in what you want and follow it with ";ratsun.net" (no quotes) to help isolate the search to just the ratsun site. There really is a ton of info out there about this, but it's getting buried since it's getting old(5yrs?) Most of it was probably posted on the old NWDE forum. Find the archive for that.

The control arms are completely different as are the shock towers...which is the real hang up. Beebani has control arms that will help you swap to balljoints, but it makes the track with about 2.5" wider.

If you're a master fabricator and have all the tools.....it's doable...if you're a novice with limited tools, it's going to be a lot more challenging.
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#4 NiMB

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Posted 10 June 2011 - 08:57 PM

Late 77 doesnt really matter. There was TWO 620 frame styles. Early(72-77) drum brake. And Late style(78/79). If you have a factory drum style frame then you need all the stuff, including the brackets from bee.

If you have a Late style frame then you have a factory ball joint frame and you already have disc brakes. Yet you still have room for improvement, cause the factory disc brakes of 78/79 suck.


Thanks so much, that explains a lot. Off to the Junk Yard for me to start putting this thing together.

#5 villegs

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Posted 15 June 2011 - 12:56 PM

either way has good and bad. As noted 77 and before were kingpin trucks and 78 after had ball joints. Swapping the whole suspension from a 78-79 is doable, the problem is find a donor truck, and the calipers and solid rotors are crap by design. The conversion is easier(hand tools only, took me about 2hours but I am OCD and cleaned every part I took off) and probably cheaper but your stuck with kingpins, which really isn't a bad thing. just getting hard to find repair parts.

#6 datzenmike

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Posted 15 June 2011 - 04:41 PM

No '77 had disc brakes early, late or in between. Only the '78 and up got them. The confusion with the '77 may be the build date on the door jam. The '77 model year ends July '77. The start of the '78 model year is Aug '77.

The disc brake parts from the '78 will not fit the '77. The lower control arms are different length and the mounting points on the frame are different to reflect that. I guess anything is possible but it would be easier to just cut the front off a '78 and weld it to a '77. Or swap the cab and bed onto a '78.

#7 jastrunk97

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Posted 30 June 2012 - 08:31 PM

So here is the case. My dad has a 79 Datsun 620 and a 77 datsun 620 so he can not just swap it over with out welding mountings point, etc?
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#8 Jersey

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Posted 30 June 2012 - 11:15 PM

If you mean take the '77 cab & bed and drop it onto the '79 frame(?)...yes you can do that, but, you will have to notch the front crossmember underneath the '77 bed for it to seat the gas tank (I believe...). The '79 has a frame mounted tank and the '77 does not. Other than that, you should have no problem swapping it over.
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#9 Jersey

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Posted 30 June 2012 - 11:19 PM

And yes all the body mounts should be the same, if you are dealing with the same body style: e.g., King Cab to King Cab, etc...
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#10 jastrunk97

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Posted 01 July 2012 - 09:32 AM

Well the 79 brakes onto the 77 frame.
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#11 Jersey

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Posted 02 July 2012 - 01:33 AM

Ok now I understand what you are asking. What Mike said!
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#12 mklotz70

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Posted 02 July 2012 - 05:25 AM

The big prob with trying to put the ball joint stuff on the kingpin frame is the upper shock tower. On the kingpin frame, the tower is straight with the frame. On the ball joint frame, the tower is at an angle and pushed out if I remember right. When you put the ball joint upper arm on the kingpin shock tower, the arm is way too short. Beebani makes upper arms to compensate for this, but as I mentioned above, your track width will widen by about 2.5". According to Steve Epperly(owner ZTherapy), back in the day, they used to just go to the dealer and get the ball joint tower and swap towers on the kingpin frame. But, because the lower control mounting points are different between the two frames, the track width would still be wider.

If you need bolt on, your options are limited. If you can fabricate.....you've got a lot more options.
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