R180 Differential swap axle options in a 240Z

[chaztg]

I acquired a replacement R180 for my 73 240. It's a "K R180" later-type diff out of an 82 Maxima AT which was equipped with CV-joint halfshafts/axles and they do not interchange into the S30 for various reasons. Modern Motorsports offers companion flanges to use CV axles from a 280ZXt, but they only make flanges for 280Z style stub axles. Changing the wheel bearing stub axles to 280Z style means undoing the infamous axle nut...twice! And doing so, I'd better replace the bearings too. MM doesn't mention using other kinds of axles, like from the Maxima or maybe 200SX...? The 280ZXt axles are probably stouter...but the car's not a racer, so strength is not too critical as long as they fit. I measured the axles from the donor Maxima car and they appear to within 1/2" of the stock 240 halfshafts. It's a a big job to change those stub axles and I'm leaning toward just modifying the later diff to accept the 240 halfshafts, which means converting the K R180 to accept bolts (the CV axles are clip-in, not bolted). That means pulling the old & new differentials apart to swap over the threaded "buttons" and I'm thinking this is less labor & time overall (and less money). Another option is Beta Motorsport's modified axle flanges which require no diff dissasembly, just more money & down time for my vehicle. Any thoughts?

[Pop's Z]

I put a KA R180 w/ 4:11 gears from a 200sx in my '73. It involved taking my original diff apart and removing the "buttons", taking the KA apart and removing the pinned axle stuff and replacing them with the "buttons". Not very difficult and allows me to use my original half-shafts. I replaced the side and rear seals, but not the bearings...these diffys are pretty strong. It's been working fine for 5,000 miles...no problems. I recommend you go to hybrid z and look up the "sticky" on differentials by our own John Mortenson.

Cheers, Mike

[Carl Beck]

Or... Find a Shop that specializes in Differential Work. We have one or two here in Pinellas County, FL - - so I'm sure there will be one near you... Then take both diff's to them and let them do the swap. As mentioned above you might want to order the necessary seals, so you have them on hand to give the Shop that does the work. Really shouldn't be too expensive a job... You just want it done right the first time.

FWIW,

Carl B.

[chaztg]

Thanks guys. I already got the side seals & rear cover gasket, anticipating a full teardown of the diff. I'm thinking as long as it's put back together the same way, I won't experience any bearing issues. Carl, I'm just too proud to have a shop do it for me, so I'm trying it by myself. By the way Mike, how do you like the 4:11... Is it a noticeable rush to get that "hole shot" from the low gearing? I didn't get too extreme, so I went with a 3:7 ratio instead.

Tony

[Pop's Z]

Hi Tony, Yes it's a rush. First gear doesn't last too long, and second doesn't either. Third and fourth gears are really where the power band works...just a massive push in the butt. I use the car mostly for canyon carving here in Colorado so it works out fine with the 5 spd. I also have a cam, and head work (N42) and a header so it really revs. That being said, I am pondering a 3:90 R 180 from the front axle of a 4x4 pickup. At 75 mph I am currently turning near 3.5k rpms, and I'd like to lower that a bit. 3:70 will work real well for you. As I said before the swap isn't that difficult as long as you don't remove the front yoke for the driveshaft. That's where the spacing/backlash is done. I had never done anything like this before, but it was no big deal. Be sure to look at the sticky on hybridz.

Cheers, Mike

[chaztg]

Well I got the two diffs apart & was able to change out the buttons and refit them into the spider gears in the 3.7:1 differential unit.The ring gear needs to come off the carrier in order to do this to allow the shaft holding the spider gears to slide out. I thought I'd need a press, but not so because the shaft is held in place with a roll pin, not a press-fit. Everything fit back together really easy just like you said. I replaced the side seals and refit the rear cover using a gasket & sealant. I filled it with some pricey Amsoil synthetic 75w90 (couldn't find Redline)...hopefully the end result will be NO LEAKS and NO WHINE!! Fingers crossed! I took the opportunity to also clean 30+ years of crud, oil residue, grime & whatnot off the rear transverse link & diff crossmember, painted them in a few coats of semi-gloss black (looks almost as good as powder coat). All I need to do now is replace the transmission, which makes a noisy knocking in 5th gear only. Weird problem. I have no idea what is causing it. After all this, I can finally enjoy driving my car again with a rear end ratio change which I'll notice and a fully functioning transmission.

[Jarvo2]

I'm about to dive into switching from my '72 R180 (3.36) to a 200sx K-R180 (4.11), requiring the button swap.  Anyone have any spare buttons or a "bad" differential around that they want to get rid of?  Part of me wants to keep my original 3.36 in one piece in case I ever want to hot-swap it back into the car for extended highway use.  

 

For anyone else looking to do this swap, I found a great video on YouTube, below, as well as a great write up on several sites (http://forums.hybridz.org/index.php/topic/49194-differential-cv-lsd-hp-torque-r160-r180-r200-r230-diff-mount/)