Diff Swap R200 for R180

Rob Gaskin

Rob Gaskin

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I'm sure someone out there can help me, suspect it might be Mike. I spent the weekend swapping my 240 diff for a 260 diff. Unfortunately I haven't been able to finish the job because the nearside driveshaft is too long. It wont quite fit but even if it did I suspect I would have a problem when the suspension was compressed. Are 260 driveshafts different lengths and if so does anybody have what I need?
 
Rob - all the 240Z, 260Z and early 280ZX manual driveshafts are the same as far as I am aware. There are different partnumbers, but these supercede one to the other. Your problem must lie elsewhere. Is the shaft too long even when fully compressed? Or perhaps something inside the sliding joint is obstructing full compression - broken roller ball or spacer?
 
Agree with Mike, you should not have a problem.  Changed my R180 for an R200 years ago.  Suggest you strip and check the bearings/spacers, etc.

Ken...
 
What year is your 240z?

If you have an early (1971) 240z then the diff is mounted slightly forward causeing the half-shafts to angle rearward and to the wheels (causes vibration and U-joint wear). Is it a 1971? The 1972 onward diff was moved rearward about 1-3/8". I have info on updating it if you need it.

I take it your staying with the R180 diff (the 180 refers to the diameter of the ring gear in mm)? An R-200 (most 280zs) diff will take more abuse... I don't know if its more readily available?

Cars with R-200 diffs have a different mustache bar than those with R-180s. You only need this new part which holds the rear of the diff in place.

Anyone know how much different again the 300zx diff is please? I know Darius runs a 300zx TT lsd 3:73 and it seems to work well, I'm trying to figure out the best bet. Mike???

If my information is dodgy please tell me, it's just what I've read.
 
If you've re-conditioned the internals then i suspect you may have over-loaded them with grease. The bearings need to be able to move in and out so go easy. Also about a teaspoon full in the bottom.
 
The driveshafts are still the same on the early cars.
I don't know of anyone who has used the Z31 differential - no real advantage unless you can find an import model with LSD.
The Z32 diff looks very strong (although I had a customer who had somehow broken the internals to release the viscous LSD fluid into the surrounding oil&#33<img src="http://www.zclub.net/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=';)'>. The diff mounts in the same way as the Z R180/R200, i.e. via rear studs in the back plate, so "only" requires redrilling of the moustache bar to hang in place, plus fabrication of a front mount. The problem would be with driveshafts where a custom / hybrid Z32 / Z shaft would have to be made. Ratios are 3.7:1 for TT and an interesting 4.08:1 for NA cars - a bit steep for low revving V8 conversions unless you are implementing a nice 6-speed manual conversion as well.......
 
Sorry for thread hijack,

Well I'm going for a Borgwarner T-56 6 speed, specifically the one with a .50:1 6th speed (not .62). which apparently works great with 3.54:1, I'm a bit green so I'm not sure how things would fare with a 3.7:1. Excuse my ignorance (as I know sweet fa&#33<img src="http://www.zclub.net/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=';)'> but could I use the moustache bar from a 300zx instead or is it mounted differently? Fabbing up the front mount and modding the driveshaft shouldn't be too much of an issue though. But if an R200 diff suffices (no doubt it will) I might be better off waiting till the R200 dies and then going for a Z32 LSD.

Interesting stuff <img src="http://www.zclub.net/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'>

Incase its useful

Gear - Ratio
1 - 2.66
2 - 1.78
3 - 1.30
4 - 1.00
5 - 0.78
6 - 0.50
 
With a 0.5:1 6th gear you could handle the 4.08:1 Z32 NA diff with ease and step up performance in the intermediate gears. Just make sure your Chevy can rev clean to 7000rpm and you'll outrun F1s and Koenigseggs (that looks wrong......). I calculate a theoretical top speed of 245mph with 24" diameter tyres. With the 3.54, 282mph should be possible!!!!! Even at 6000rpm in 6th you get 210 and 242mph respectively. Increase tyre diameter to get more speed and less acceleration, reduce diameter to increase acceleration and reduce speed.

The Z32 diff mounts in a rear sub-frame which bears no relation to a moustache bar - it just happens to mount through the back of the sub-frame in the same way a Z diff mounts to the moustache bar.
 
Thanks guys for your input. All I am doing is swapping the original standard 240 diff ( '73 240 car ) for a stronger 260 unit. It seems simple but I cannot get everything to line up. Now I know the driveshafts are the same length it must be the 260 moustace bar which is giving me the grief. I have had it in three different positions over the weekend ( now now ! ). The two holes appear to be offset slightly to one side. Zman ( Ken ? ) how did you position the bar, I think it has to go to the rear of the vertical transverse link supports i.e. next to the petrol tank with the rubber bush ends facing forward. This is not how the manuals show it but is confirmed with Geoff Gale who checked on a 260! Anywhere else and the diff sits too far forward so I can't connect the prop shaft. I have a couple of spare driveshafts by the way (but they look the same compressed length to me). Also my propshaft has never cleared the antiroll bar easily during a box change ( I have to lever it backwards with force ) is this normal? I have a 280ZX box now but it was the same with the 260 installed previously.
 
Rob - the orientation of the moustache bar is, as far as I can remember (and according to 260Z manual) correct as you describe. There is no difference between 2 seater and 2+2 moustache bars. The only different version is for automatic transmission and it is unlikely that you have one of those (?).

Is the situation the same if you swap your driveshafts from side to side? There is (I think) a slight increase in girth on the R200 at the driveshaft area. Maybe a driveshaft problem that was always there is showing as critical with the new configuration but was not apparent with the R180?

Confused - you will be.......
 
Sorry again for hijack,

N/A 4.08:1 diff
46.0mph
68.8mph
93.6mph
122.5mph
157.1mph
245.0mph
70mph @ 2000rpm

TT 3.7:1 diff
50.8mph
75.9mph
103.9mph
135.1mph
173.2mph
270.2mph
70mph @1800rpm

Mental... wonder if the windscreen would hold up at 270mph <img src="http://www.zclub.net/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt=':p'>
 
I wonder if you could build a streetable engine that would haul a 0.5:1 6th gear all the way up to 7000rpm? I think somewhere a tad under the 5th gear figures is more realistic, but nevertheless quite impressive.
 
I need to get an auto math book and find out the drag coefficient etc of the Z then can guestimate at what sort of performance this engine would need! I'm guessing 3000lb/ft <img src="http://www.zclub.net/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'>

To be honest though I have little fear of straighline speed, especially on motorbikes, but the thought of doing it on a 30yr old chassis (all be it with modern equipment attached) is pretty scary <img src="http://www.zclub.net/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'> But then the Z may inspire confidence.

Off to the Salt flats it is then! <img src="http://www.zclub.net/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'> Actually I'm gonna take it up against the Zonda for top speed on the top gear runway heh.
 
A VW Beetle has a better cd than a Zed (and yes, I mean the original bug).

G-nose would improve things a little, Nissan reckoned a 5mph increase in top speed with it.
 
Well <img src="http://www.zclub.net/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'> That's a bit of a worry, I was thinking headlight covers and a new front wing but not the G-nose...

Ah well, another 100bhp should counter it out <img src="http://www.zclub.net/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'>
 
Sadly the aftermarket G-noses available in the UK have a whacking great air-dam fitted in the lower half, so are unlikely to be as aerodynamically efficient as the original.........

Don't forget to remove side repeaters, wing mirrors, door handles and all emblems, shave gutter strip at edge of roof.....
 
Oh and a good clean and polish will help... <img src="http://www.zclub.net/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'>
 
Guys, The R200 diff is in and working!! Once I had confirmation which way the new moustace bar had to be, which is very different to the 240 position and not as shown in my 260 manuals, I went for it.

I was trying to fit the shafts without disconnecting from the hub, but this is not possible on the nearside because the distance is shorter. I unbolted from the hub ( checked its length with 2 others ) and fitted the shaft over the diff 'studs' first and then it was ok, but only just!

However all seems fine and it's lovely and quiet! As for the higher gearing, it still accelerates pretty strongly so my fears were unfounded. I intend going to Oulton Park for a track day on July 15th with 'Book-a-Track' so lets see then.
 
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