Still cant figure if i have a r180 or r200 differential on my 72 240z

[jalexquijano]

Cant seem to find any label pointing of my differential is r180 o r200.  My 1972 240z car has a 5 speed tranny from a 280z.

[Zed Head]

That is an R180.

[jalexquijano]

How do you know? Should i swap it with an r200 to get a faster response in first gear?

[Zed Head]

You can tell by the shape of the rear cover, and the bolts on the side flange that holds the axle bearings in.

R200's have the same gear ratios.  You need to know what the ratio of your R180 is.  The ratio is how many times the propeller shaft turns for how many times the wheels turn.  A 3.9 ratio will turn the propeller shaft 3.9 times for one rotation of both wheels.  Mark the tires and the propeller shaft and turn the propeller shaft.  Make sure that both wheels turn.  Cont how many times the propeller shaft runs to get one full rotation.

Or you can remove the rear cover and the ratio will be marked on the ring gear.

[wheee!]

Swapping an R200 in has a list of other mods that need to be done to support it. The R180 is a good diff for a stock powered 240...

[Jeff G 78]

On 8/4/2018 at 10:36 PM, wheee! said:

Swapping an R200 in has a list of other mods that need to be done to support it. The R180 is a good diff for a stock powered 240...

I broke an R180 during a 24 hour endurance race.  I converted it to an R200 and finished the race.  I even fabricated the R180 mustache bar to make it fit.  ☺️

[wheee!]

I broke an R180 during a 24 hour endurance race.  I converted it to an R200 and finished the race.  I even fabricated the R180 mustache bar to make it fit.  [emoji5]

Was it a stock engine?
But awesome for you to fab up a R200 moustache bar etc!

[Jeff G 78]

There was a very good reason the R180 failed.  Bought the car after it had been in a barn for 20 years and in 12 weeks, turned it into a caged race car.  We had about 100 items on the to-do list and the only item that never got crossed off was changing the diff fluid.  My teammates couldn't get the plugs out of the diff.  Once we ran out of time, a decision was made to not change the diff fluid.  There was no signs of leakage via dirt or stains.  4 hours into the race, the diff broke.  Upon teardown, we found no more than a few ounces of oil.  I was shocked it made it 4 hours!  I had to drive an hour to get a R200 diff and then engineer the mustache bar to fit and make the mods.  It was a long repair, but it got back on the track and ran the final 4 hours to take the checkered flag.  The mustache bar worked so well, that I left it in for another 14 hour race even though I had a R200 bar ready to swap in.  I didn't press my luck any further and the fabbed mount is now wall art.

[wheee!]

That... is.... awesome!