transmission identification

[porscha356]

Good Day all!

 

Trying to identify the 5 speed in a 71 510.

 

I paid to have a 5 speed put in in 1992.  Installed used all those years ago, and  200k miles---no trouble.  Now, the car is being updated with new suspension and drivetrain and I have been on the search for a 81-83 zx 5 speed to replace it, thinking it was from a 200sx.  

 

The issue though is the current 5 speed is not a dog leg.  It has a "normal" shift pattern of reverse being to the right and down.  The ratios are comfortably close and it seems to handle my tired 1800 with a single weber quite well in fifth at freeway speeds.  There seems to be enough torque to push it along even though that engine can't be producing more than a 100hp.

 

There were no drive shaft modifications done in 1992, the tranny bolted right in, with only what the receipt said: "fabricate two plates for mounting".  Speedometer hooked up with no problem, at least none that I've noticed over the years.

 

Could this transmission be a short tail piece FS5W71B?  Possibly some other transmission?  If it is a 71B short, then I don't need to search for a long tail piece model, just rebuild this one and be merrily on my way. It should handle the hp of the new motor, around 200.

 

Anyone have an opinion on this, I would appreciate it.

 

 

[datzenmike]

A picture of it wouldn't hurt.  

 

If the driveshaft wasn't modified then the  first 5 speed must be a 26" length and a dogleg from a '77-'79 200sx or the optional 5 speed from a '78-'79 A10.

 

If the new five speed has the reverse under 5th, then it can only be an FS5W71B from a '83?-'86 720. The front case would have to have been removed and an earlier 4 or 5 speed front case swapped on... unless you now have a KA engine in which case the front case swap isn't needed. As it has a speedometer drive it must be from a 2wd and the gear ratios would be similar to the dogleg which were identical to the original 4 speed (again I assume you have a sedan?)  

[porscha356]

Hi Datzenmike,

 

Thanks for your response.

 

I wish I had a picture as the car is now in Tracy having suspension work done.  Long story short, I was tasked by the builders to acquire an 81-83 zx box and a lsd (Subaru?) for this 510.  I am trying to stay relatively original and tasteful during this update, as this is a very clean, uncut, no rust, second owner car.  I was told the box is definitely not a 200sx but probably out of a Datsun truck from the early eighties.

 

The conundrum:  is it worthwhile to rebuild the truck box with the lower ratios and not go to all the trouble of finding, then rebuilding, a zx tranny with a more ideal ratio set up?  Next question: can the truck box gear ratios be changed cost effectively?

 

I really don't want to do a complete transmission change that involves cutting the driveshaft, relocating the transmission mount, etc., etc., down the line when the car is undergoing an upgrade now.

I,m sure that when we pull it out during the drivetrain rework it will reveal itself.  But, it was my job to locate a box and if I don't have it to install, then we have a longer delay to completion.

 

Any thoughts?

[porscha356]

Hi Datzenmike,

 

More info.....  I am looking to buy a long tail fs5w71b at a yard.  However, according to one of your previous posts, the bolt hole on the bell housing is one inch to the left.  Indicating an L series tranny....does that mean a truck with lower gearing in first?  I am looking for the higher ratio fifth of the 81-83 zx tranny and the one at the yard indicates the L series.

 

The speedo cable bolt is at the 6 o'clock position...does that mean manufactured after 1980 and would it have the higher ratio fifth?

 

When the zx trans is put into a 5 ten, does the shifter need to be modified to fit into the middle of the transmission hump?

 

Confused............  I am pretty sure I have a short tailpiece truck tranny already in the car!

[datzenmike]

 200hp is a lot from an L series. You haven't said but IS IT an L or a later KA engine.  

 

 

 

Just measure it. 26" or 31.5"

 

If 26" is has to be from a 720 truck with an earlier L series front casw swapped on. The ratio for first is likely 3.321 and is what I call a mid ratio transmissiomn.

 

The zx after '79 has a 3.062 first and the gears closer together (close ratio) with a 24% or 25.5% overdrive depending on the year. All L series transmissions were originally long 31.5. As far as strength the 'truck' and the zx (non turbo) are identical. If going to the zx for the big over drive you will need the driveshaft shortened.

 

Speedo hold down bolt at 6 o'clock made '80 or ater.

 

You may have to trim the rear of the shifter hole to fit the longer tail transmission. If you want I can measure the shifter position difference betweem long and short (if any) when I get home.

[datzenmike]

The difference in shifter location is 11.3cm or 113mm or just a hair under 4.5". If you have a shorty 5 speed, the long 5 speed shifter will be 4.5" more to the rear.

[porscha356]

Hi Datzenmike,

 

A couple of more questions have cropped up since the last post.  I was shown dyno work ups on several engines at the shop in Antioch where an L20 is being prepared for my 510.  The higher ratio transmission was recommended as better suited for me, personally, and the street in general.  That is why I am searching for the 81-83 fs5w71b.

 

I am trying to identify two separate transmissions;  the 5 speed in my 510 which, unfortunately, is two hours away in Tracy being suspension upgraded.  And a 5 speed at a yard, from which, I was told, was pulled from an 83 MT, non-turbo, 280 zx.  

 

I will probably find out for certain next week on the identity of the box in my car.  So instead of putting you through this quess work when I can't provide any pictures or even look at the car myself, is

asking too much.  However, do you know offhand, whether the gearsets from an actual 81-83 fs5w71b long tailpiece zx box will interchange into the short tailpiece version?  That would be very beneficial if, in fact, I had a short tail truck tranny in the car now.

 

The yard sent pictures of the "zx" transmission and, according to one of your previous posts, the bolt hole at the top of the bell housing is to the left of the center rib, thus indicating an L series box.  Yet it does have the speedo bolt down hole in the 6 o'clock position, indicating a post 1980 manufacture.  I have repeatedly asked the yard guy to estimate the first and fifth gear ratios by rotating the input shaft and counting the revolutions but so far, he's not giving it to me.  My instructions were:  rotate the output shaft 10 times and count the revolutions at the input shaft.  If they count 30 + 1/3 in first, good.  If they count 7.5 in fifth, good.  It takes two guys to make the count easy but methinks I wish for the 49ers to win the superbowl.  Probably too much to ask for a $300 part.........

 

Your input would be greatly appreciated.

[datzenmike]

The zx transmission should have a 3.062 first gear. It's the only transmission with this ratio first gear. Every 3.062 turns will give one output turn. So 20 input turns divided by 3.062 means the output will turn 6.53167 or 6.5 times.

 

A mid ratio 5 speed with a 3.321 first will turn 6.02228 or 6 times

 

A wide ratio 5 speed with 3.592 first will turn 5.56792 or 5.5 times

 

 

 

You may be able to swap all the zx internals into the short box but cheaper to shorten the driveshaft. This way the car is converted and any 71B that you want to swap in later will fit right in.

[porscha356]

Hi Datzenmike,

 

You work overtime for us.  Thanks for all you do!