240z rear differential re-gear or swap

[d-man]

Hi All,

 

I've been reading what seems like all the posts on rear differentials for the 240z (because I've found the conversations multiple times now). my question is because every forum post on the swap topic is a decade out of date and I wonder if there is new information now.

 

Here is my basic situation:

• The 4spd is leaking a bit  but works great
• the rear diff (datsun R180 1971)..  going by memory that is a 3.364 and it has a huge amount of backlash and needs new seals.

 

Instead of fixing all the leaks which could be done, I want to change to the 80s 5spd (close ratio) FS5W71B and a 3.90 rear.  The 5spd would be awful with the 3.364 rear. I understand that rebuilding the stock R180 3.364 is not possible with part availability. If I could rebuild the stock R180, I might keep the 4spd.  I still have the standard L24 / E88 engine but with weber carbs and it runs great.

 

OK, given that I could go with a few different 80's R200 from the 280zx or Subaru R180.  There is my question, all the Suba R180 articles are over a decade old and say that the Impreza WRX 04-05 is the way to go for the swap.  there is a lot of complexity about actual rear diff gearing on later Subs as they went to the transmission internal reduction gearing.

 

In my Suba research, I discovered that there are many newer imprezas that came in R180 with 3.90 gears well into the 2010's but those are listed in Suba service manuals as Hypoid type which as I understand is just a different gear interface design as all R180s appear to be offset pinon and ring (default on hypoid).

 

Does anyone know if the newer than 2005 Suba 3.90 rears can be swapped in?  assuming we still can use the half shafts adapters to adapt to the 240z axles. I'm not concerned about keeping this 240z stock or all datsun given other modifications.  for example, the 2011 STI service manual states the B2 identification rear differential is 3.90 for the 5spd with hypoid gears.

 

this might be a great topic to rekindle with all the changes in the suba side.

Edited January 6 by d-man

[jhm]

This might be helpful.  Also, there are a couple vendors left that produce the rear inner axles necessary for a Subie R180 swap...but they have been drying up the last few years.  Regarding backlash...that seems to be a forever issue with the R180.  I've had significant play in every R180 I've owned, both open and LSD versions.

 

 

[NewZed]

Make sure you get a 280Z mustache bar to use with that 280ZX R200, it's needed.  And the half-shafts if you don't have the clip-in style.  Not clear what you're starting with.

 

The other part of your "old posts" problem is parts availability.  They're not as plentiful as they used to be.  The 5 speeds and the R200's and the required mustache bar are getting harder to find.  You can go aftermarket on the mustache bar but it's expensive.

 

Finding parts might be your decision-maker.  A junker 280Z might be a good way to get the parts.  Good luck.

[madkaw]

Adapters for Subbie diffs are still plenty available . That’s  not  the cheapest but easiest option - plug and play . 3.54 is the most common but there are 3.9 clutch types around .