1985 720 Transmission options

[Airplanedoc]

I've got a 1985 720 2WD automatic that I just purchased and I'd like to convert it to 5 speed manual. What would be the easiest transmission to install with the least amount of modifications?  I have tried to locate a 5 speed out of the same year model with no luck, any information would be appreciated.  

[datzenmike]

Confirm that the automatic is 31.5" from front to back. It should be. Any FS5W71B 5speed from any Z series equipped car or truck* will work. '81 and '82 had 4 speeds with optional 5 speeds so know what you are looking for. (*measure or ask the seller to measure any truck transmission length, as some are 26")

 

'81-'86 720  For the most part are mid ratio.

'80-'83 S110 200sc car. All long transmissions. '80-'81 are mid ratio and '82-'83 are wide ratio.

 

You'll need a flywheel. The Z24 uses one capable of bolting a 240mm diameter pressure plate and clutch disc. All Z24s and the Z20 engine used in the 720 truck had the correct flywheel for the 240mm clutch. The later D21 Hardbody with Z24i and KA series engines also used them.

 

A clutch master cylinder and pedal box as well as the clutch slave (it might come with the transmission) and the joining hydraulic hard and flex line. Also the push rod to the clutch fork.

 

Transmission may come with the clutch fork and dust boot.

 

 

There is a torque converter pilot on the end of the crankshaft. This has to be easily pried off to fit a flywheel.

 

 

 

 

The end of the crankshaft needs a pilot bushing tapped in to support the transmission nose.

 

The automatic has a vacuum line from the intake. It can be removed but must be sealed.

 

Gas pedal has a kick down switch above it. Remove or not.

 

[Airplanedoc]

It is a 31.5 with the speedometer drive on the right, the D21 has the speedometer cable drive on the left will it still work and does the gear selector lineup in the cutout? I have found some 90’s D21’s locally. 

[datzenmike]

The reference to the D21 Hardbody was only about the 240mm flywheel. The FS5W71B as only used till the end of the 720 in '86 1/2. The FS5W71C used in the Hardbody was somewhat shorter so the driveshaft would need to be lengthened. you would like to avoid that.

[Airplanedoc]

I would like to avoid lengthening the driveshaft but if I can’t find a FS5W71B will the FS5W71C work?

[datzenmike]

The 71C on the Z24i and the KA series engines are interchangeable. Length is around 30", I've never measured one.

[Airplanedoc]

Do you know if the speedometer cable will work being the drive will be on the left instead of the right?

[datzenmike]

Sure will just run it down the left side. My 710 had the short 26" 4 speed with speedo on the left like that. I went to a zx 5 speed that is 5.5" longer and on the right and it fit.

[Airplanedoc]

Thanks for all the information datzenmike, I'll be visiting the salvage yards this weekend.  I've had no luck locating an FS5W71B so I will try and located a FS5W71C transmission.

 

[NC85ST]

If you find a C transmission from the same body style as yours, ie if yours is a short bed and you find a transmission from a short bed, grab the driveshaft also. It’s a good possibility that you won’t have to have a driveshaft made. I did a 5-speed swap on a 521 many years ago and ended up using an unmodified driveshaft out of a 620. Worked perfect. 
I also did the same swap you’re wanting to do, years ago, parts trucks were plentiful then, you will need both the clutch and brake pedals to make it work. The automatic brake pedal is to wide to work with the clutch pedal.

[Airplanedoc]

I have a 1984 Nissan King Cab 4X4 5 speed I bought as a parts truck so I have everything except the transmission and driveshaft being the 4X4 transmission doesn't have the speedometer drive.

[datzenmike]

Excellent. You'll need a speedometer sleeve and pinion to match your differential ratio. I tried to make automatic ones work in standards but they seem different.

[Airplanedoc]

Do you know what gear ratio I need with the 5 speed it has a HF38 (3.88) now?

[datzenmike]

Any ratio, close mid or wide will work just fine. Some are more desirable than others and depends on intended use. The 2wd Z24 engine used the mid ratio for easier crawl speeds. Only the 280zx (non turbo) use the close ratio but it was a lighter car with more powerful engine. 

[iceman510]

I have an '81  2wd 5 speed if interested.  Would need shipping of course.  I also have a flywheel from a Z22, but I would have to check the clutch diameter.

 

[Airplanedoc]

I'm going to try and locate one closer to me but I'll keep it in mind, thanks iceman510

[Airplanedoc]

I was referring to the gear ratio in the differential datzenmike  

[datzenmike]

Your 3.875 is fine with any transmission. It's what the factory selected for mileage and utility carrying loads.