280z 5-speed into a 240?

[Dave WM]

Garm, make sure you know the diff in the various ones, the 280z has final OD of like .83 iirc vs a .75 on a 280zx, it will matter as far as the diff you want. the key is a wide ratio vs a close ratio transmission.

[Zed Head]

You should check your diff for sure.  If it has an L28 it might also have an R200.

I never know for sure what's going on with the 240Z diffs.  The FSM seems to show certain things and people find different on their cars.  The 1973 FSM shows a 3.364 ratio diff in your car combined with a 3.592 first gear.  But that still leaves a 3.364 final ratio in 4th gear, which is "tall" and should not leave you grabbing for 5th on the freeway.  A 280Z with a 5 speed would have a .864 x 3.54 final ratio >>> 3.06.  But the 280Z's came with 4 speeds for three years, a 3.54 final ratio in top gear.  So your stock 73 240Z should have a nice cruising RPM in top gear.

Anyway, in short, know what you have before you buy replacement parts.  You can determine your diff ratio by turning the wheels and counting propeller shaft revolutions.  Take a picture and post it and we'll tell you if its been replaced in the past.

Edited May 16, 2019 by Zed Head
got my 280Z 5th ratio wrong. Right now.

[Garm]

Great info guys, thank you very much.

I will get under there and take some pictures; also rotate the wheels/shaft and report what I have.

Garm

[cgsheen1]

5th gear in the early 5-speeds is definitely an overdrive gear - for lowering RPM and getting better fuel economy at cruise. Spirited driving (and probably top speed) will be done in the lower 4 gears. Sounds like your differential will be stock which would be a 3.36 R180. My 260Z came equipped with the same differential and I used it for years behind my L28ET and ZX close ratio 5-speed before swapping to a 3.54 R200. The L-series engines used in the 240Z, 260Z, 280Z, and 280ZX (1970-1983) had a similar block config and any transmission mounted to one can be mounted to any other. 

[7tooZ]

@Garm  here is my 2 cents dashed on your initial post. Sounds like you are new to this car and possibly Zcars. If that is right my recommendation would be get as much seat time to find out what you like/dislike about it. Make some notes. Hiway speed at what RPM. Think about how much and how often you would actually do that kind of driving. Most stock 240s will run all day long at      70 MPH and capable of pushing out over to 100 MPH.  If you get to a point that you are serious about a transmission swap consider so things that come to my mind having put a 83 close ratio in an early 72. 

How much money is available to commit?

A rebuilt wide ratio trans will run $1200+. A close ratio us to1600+. used one a a gamble.

Then new clutch? fly wheel? Throw out bearing? Rear seal?

Adapting a shift lever to fit your particular car.

then there is the diff. can you live with the one you have? My thinking is A 3.70 or 3.90 is needed. hard to find in R180 form. a close ratio could go to a 4:11.

Put your car on a jack or stands. Put piece of tape a wheel and one on your driveline. Rotate the wheel and note if both wheels turn in the same direction and count the number full turn you make and how Many turns the drive shaft turns. The more turns you make the better and in multiples of 10. shoot photos of your current diff from side and back .

Post what what you get and where you want to go and you will find tons of help here. it’s what these guys do best.q

Ps nice car these cars a fun ride in multiple ways.

Edited May 16, 2019 by 7tooZ

[Garm]

@7tooZ  thanks, that's a good post. 

I have a lot of experience with sports cars in general,  seat time at the track, and a 2L Roadster that I built up as well. That car was converted to 5-speed with LSD; at the least it's a cousin to the 240. That 5-speed swap was a GREAT change.

My other cars include a 911, a 914 converted to a 2.7L sixer and a little Honda N600 hoonigan with a mid-engine CBR1000RR motor.

I'm not going to feel guilty about saying that money isn't the most important thing  --  the driving experience is.
I'm going to figure the diff ratio this afternoon. Should have done that before my first post. Keep the opinions coming, they are always helpful.

[Zed Head]

The $1200 -1600 must be for a completely rebuilt transmission using Nissan parts, at a spendy shop.  That is a very very high price.  The other comments are on though.  I put a 5 speed in my 76 and after I got the engine running right, smoothly, I often found that I was still in 4th on the freeway.

The other end is 1st gear.  Taking off from a stop.  If you live in the hills, a 13:1 overall ratio in first might be appropriate.   3.9 X 3.321 (Z or KA/71C), for example.  If you're on the flat lands, maybe a 3.54 and a 3.062 (1980+ ZX), 10.8.

[7tooZ]

1 hour ago, Garm said:

@7tooZ  thanks, that's a good post. 

I have a lot of experience with sports cars in general,  seat time at the track, and a 2L Roadster that I built up as well. That car was converted to 5-speed with LSD; at the least it's a cousin to the 240. That 5-speed swap was a GREAT change.

My other cars include a 911, a 914 converted to a 2.7L sixer and a little Honda N600 hoonigan with a mid-engine CBR1000RR motor.

I'm not going to feel guilty about saying that money isn't the most important thing  --  the driving experience is.
I'm going to figure the diff ratio this afternoon. Should have done that before my first post. Keep the opinions coming, they are always helpful.

@Garm thanks for responding . Knowing your experience certainly helps when offering feedback. Those are some great cars . Welcome to the club your experiences will be helpful to others.

ps I have done the Subaru R180 conversion and the R200 with a new Quaife also if you want to consider that. 

 

[Garm]

It's 3.7. I didn't get it any more accurate than that 

[Zed Head]

That's an odd number for a 73 240Z.  Is it still the R180?

It's still a good ratio for any of the 5 speeds.  The 71C front case swap is a nice option if you get a later model 240SX transmission.  Synchros in reverse and some have double synchros on second gear.  Plus wider gears, physically, than the early 5 speeds.

[Terrapin Z]

A very nice looking Z indeed, Congrats!!

Many questions like this are answered with "What do you want to do with the car?" Cruise, race, show, rally, tour, some of two or three......more?

The cool thing about these cars is mix and match. Any "B" trans should fit you car 73 just fine, no real mods. It's going from "A" to "B" or "A, B to C" thats the extra work. "B to B" is bolt up.

R180 to R180 with different ratios is easy, as is R200 to R200. R180 to R200 needs a few more parts. 

An easy upgrade, IMO. The thing is to tune it to how you drive it. 

These are not all the options, but popular ones.

Enjoy that new Z........

[Garm]

I don't know if this site resizes pics, I'll just try loading a couple of the diff off my phone