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Open Diffs are a drag and aftermarket Limit Slip
Units can be outrageously expensive. There is hope for any non-LSD
equipped 240SX. Factory limit slip diffs are available from many
different Nissan offerings. The 300zx, LSD equipped 240's, Q45's
and J30's to name a few. In most cases, the only extra parts
necessary are 240SX VLSD diff outputs that can be picked up at your
local Nissan dealer.
I picked up a '90 300ZX non-turbo diff. This is the
R200V that is recommended. It has the same ratio as the 240 at
4.083. The turbo 300ZX has an R230V diff with a 3.69 final drive
ratio. Some say that that case will not fit in S13 240's. Plus,
the taller ratio will make for a more sluggish 240 unless you are
putting down serious power.
Below is the process to change the diff and the
Note: S13 and other notes from
240SX list members are at the bottom.
Additional information at the end of the page!
- socket set
- Combination wrenches (box wrench)
- Jack and Jack Stands
- Pry bar
- R200V differential (4.083 final drive ratio)
- Correct diff outputs if you don't have a 240 diff:
- 2 quarts of 80W-90 Gear oil (I used Pennzoil, Nissan's
- For S13's, you will need to obtain the correct rear cover.
Prepping The New Diff
Regardless of how new the diff is, it is a good idea to change
the fluid. Plus, if you have to change the diff outputs, you are
going to need to drain the fluid. Depending on which cover you
have, the drain plug will be on the bottom and the fill plug will be
on the driver's side of the diff. Either way, this is a much easier
process if the diff is not in the car. See images for details.
Once you have drained the oil, remove the outputs. Again, if you
have an VLSD from a 240, you will have the correct outputs and can
skip to refilling the diff with new fluid.
Here are a few pics comparing the diff outputs. You'll see that
the 300ZX outputs have ABS rings and a completely different bolt
Although the shafts look different, they will work fine.
Note: You cannot use the
300ZX half shafts. They are about 1-2 inches longer than the
240's half shafts and do not have the proper rings to protect the
wheel bearings. Jeff Callaway attempted to combine the
300ZX & 240SX half shafts with no luck. The 300ZX components
have a larger spline diameter preventing the combination.
Using a rubber mallet or a hammer and a piece of wood, tap in the
new diff outputs.
At this point, you can refill the diff with fluid. I chose to
prop the front of the diff with a piece of wood to make it level as
it would be in the car. The service manual calls for about 3.5
pints. Keep adding fluid until it runs out of the fill hole and
install the plug.
Installing the Diff
Raise the rear end of the car and support it with jack stands.
The best place to support the rear end of the car is by the front
subframe mounts. Although I didn't remove the sway bar (regrettably
so), it would make the process significantly easier. Support the
diff using a jack and a piece of wood. Be careful, the diff is well
over 70 lbs. Remove the drive shaft bolts and move it aside.
Remove the half shaft bolts and push them out of the way.
Ultimately, you can give yourself more room by removing the half
shafts, but that would take quite a bit more work. Remove the two
big bolts on the bottom of the diff and remove the two nuts on the
back of the diff.
Carefully lower the old diff. Once the old is out of the way,
load the new diff on the jack and slide it into place. Install the
two rear nuts (72-87 ft-lbs torque) replace the two bolts in front.
Then, reattach the half shafts and drive shaft and then the sway bar
if you removed it.
Normal driving situations the diff is completely invisible.
Corning under power is much more confidence inspiring. Power
sliding and drifting is much more predictable. Hard acceleration is
definitely improved on abnormal surfaces. As with the diff upgrade
on my civic, this is by far one of the best investments for serious
Complete Set of Pictures
Those swapping into an S13
S13 240's diff mounts differently than the S14 and pretty much
any other chassis where an R200V diff was standard. This requires a
different rear cover as well as a change to the front bushings.
Here is an explanation from 240SX chat list subscriber
I posted on freshalloy about the s14/j30/z32 diffs having
bushings on the
front that need to be replaced with metal spacers. The reasoning
this is that the s14/j30/z32 diffs are mounted by bushings to the
where as the s13 is metal on metal to the subframe. When replacing
rear cover the front points are bushing mounts while the back ones
small solid mounts. Also note the rear cover is aluminum and rather
If the front end of the diff is allowed to move then it puts stress
solid mounts on the rear of the diff. I will be getting metal
fabricated for this purpose to install my s14 Nismo diff in my s13
the s14 subframe won't swap over without special eccentric bushings.
The Infinity J30 uses an ABS sensor that attaches to the input of
the diff. If you have an ABS equipped 240, this will be the same
sensor ring. This sensor ring requires that you have a drive shaft
that is approximately .55" shorter than the non-ABS counterpart. If
you do not have ABS, you will have two options. First, you can buy
the ABS driveshaft. Second you can buy the non-abs diff input.
This information was provided by
Bill Redding, also a
240SX chat list subscriber.
Another important point to note, is that the
J30's final drive ratio is taller than the 4.083 found in 240's and
NA 300ZX's. The gear is approximately 3.9:1
Another alternative - Swapping
One other option that most people do not even
consider, in the case of obtaining a J30 diff, or trying to swap a
diff into an S13, is to swap the internals. Technically, the
only difference between an R200 and an R200V is the addition of the
VLSD unit. I would recommend having a shop do the work for the
purpose of getting the tolerances correct.
This idea will prevent you from having to
figure out how to properly swap any diff into an S13. Swapping
the VLSD unit into the original case will allow you to safely
install the differential.