• Be careful not to unscrew the large nut on the top/driver side of the transmission. It's NOT an oil filler or inspection nut. It's actually the pivot bolt for the shifter arm that controls reverse. If you take it out it disconnects the arm and drops a circlip into the bottom of the trans. You have to completely open the trans case to reset everything.
  
  
• To open the case take off the shifter and drive a roll-pin out of the shifter rod. Then remove the 8 bolts around the housing to remove it. This lets you take the top cover off the transmission to expose the gears.

IMPORTANT NISSAN TIPS
The input shaft has a smaller pilot diameter and different spline count (24t) than Ford(10t) or GM(21t). This means it's not a straight bolt up to a V8 even with the proper bellhousing. You could swap out the input shaft for a V8 version but given the expense and time involved it's a lot easier sourcing a true V8 T5 if that's your path.

TAILSHAFT BUSHING
- the tailshaft yoke is a smaller diameter than other T5s. 1.3" versus 1.5". This means that you can't use a Ford or GM tailshaft bushing.
- the correct 1.3" tailshaft bushing was never sold by Nissan but I found one online at Driveline.com (as of 2015 I have been told there are no longer available).
- because of the smaller bushing diameter a standard T5 bushing removal tool is too large to fit into the Nissan tailshaft. So I took mine to a machine shop and had them replace it for $20.

REAR OIL SEAL
The correct replacement rear oil seal with the metal housing ring is the SKF brand #13958. I was able to get mine through Napa but it took them a few weeks to get it from a warehouse somewhere in the country. I suspect it's very scarce, the seal on mine was in new condition but the box looked very 1980s. Other brand seals will work but lack the metal ring.

MODIFYING THE NWC NISSAN T5

THE SHIFTER
The Nissan T5 came with a poor-quality shifter, it's simply a straight rod out of the top of the trans. This design makes rowing though the gears vague and notchy which I think is the main reason why some Nissan owners didn't like the T5. However, when a T5 was used in a Mustang with a standard shifter people praised it.

FORD SHIFTER: Over the years Ford perfected the T5 shifter coming up with an excellent one in late 90's. The dogleg angle greatly improved leverage and shifting feel. It also had a hard rubber damper that reduced buzziness. When used in 240-280Z in 1st, 3rd and 5th gears the shifter arm sits about 1 inch forward of the stock one which means you may need to modify the front of the console slightly. However, it improves shifting, smoothness, and overall drivability so much it's worth the trouble. To find a stock Mustang shifter go to Ebay. You can sometimes find people who have upgraded their Mustang and need to get rid of the old stock shifter.

THE BETTER SOLUTION: As good as the Mustang shifter is I recommend getting a true "short-throw" version. Make sure you get one with adjustable shift stops. This prevents you from stressing the aluminum shift forks in the trans and breaking them.

Be careful as there are several cheap knockoff T5 shifters on the internet, I believe the patent expired or went public. The B&M brand used to be the gold standard for T5 short throw shifters and theirs are still available. I decided to use the Summit Racing version shown below which had a nice fat arm with gated spring action and solid aluminum baseplate. My car felt like a Formula 1 car, very solid and fast, a major improvement over the excellent Mustang shifter. This Summit version is no longer available for some reason, too bad.

1983 Nissan T5 and 2000 Mustang T5 shifters

Summit T5 shifter

FRONT RETAINER
When using a heavy duty clutch the aluminum shaft under the throwout bearing collar has been known to wear and gall over time. The solution is to unbolt it and replace it with an aftermarket steel sleeved version, but as you would expect these retainers are easy to find for Mustangs but not for Nissan. I checked with the vendor and was told these were discontinued for the Nissan T5 a decade ago. The collar shaft OD of 1.30" is slightly smaller than the Ford or Jeep versions meaning that an aftermarket steel retainer from another T5 won't retrofit.

If you use a standard-strength clutch a steel sleeve may not be needed however. Below is my 29 year old retainer that had been dragraced and autocrossed on for the past decade and was pulled from a junkyard before that. The factory machining was still visible on the surface and showed no galling, the marks in the photo are grease.

stock aluminum retainer

MAIN/COUNTERSHAFT ENDPLAY
While most rotating engine parts specify some sort of shaft endplay the fore/aft endplay on a T5 mainshaft should be zero. Over the years as front and rear roller bearings wear down this endplay increases causing slop in the gearset, poorer shifting, and less available power to the wheels. The factory fix is to install different thickness shims (available in rebuild kits) behind the front retainer to precisely set the endplay. For new bearings the Nissan FSM lists mainshaft endplay as .13-.15mm (.0051-.0098") positive preload which should drop to zero after break-in. This was originally set at the factory but you can be sure that after three decades it's out of adjustment.

Countershaft front thrust bearing-worn and tired

On the countershaft, WORLD CLASS T5s have a rear removable retainer that also uses a shim to adjust preload. But because the NWC T5 uses a pressed-in rear bearing no shimming is possible. The preload is actually set by a thrust bearing on the front of the countershaft and rear compression by the tailhousing. The front thrust bearing (really a big washer) is 2mm thick and is made of seemingly low quality metal compared to the tool-steel parts used elsewhere in the T5. When I removed mine I found it badly worn and crushed.

CLUTCH
The T5 came with a Nissan turbo clutch and 240mm flywheel. Interestingly, while Zcar 225 and 240mm flywheels are identical in weight (23 lbs), the turbo clutch cover and plate are stouter and heavier. The weights listed by Perfection for their OEM clutches are: MU47732-1A (turbo 240mm) 18.72 LBS and MU47594-1A (coupe 225mm) 14.76 LBS. I believe the Nissan weights to be close if not identical which means if you are picky about weight you should stick with the 225mm couple flywheel and get a stronger clutch rather than use the heavier 2+2/turbo flywheel-clutch for more holding power.

The Perfection MU47594-1A coupe clutch had good reviews and I used one for 5 years in autocrossing with no issues. Interestingly there are two slave cylinders available from Nissan: one for the NA L28 and one for the Turbo L28. I have measured both and the bores/piston length between the NA and T5 are all identical even the rebuild kit is the same. The turbo slave does sit a couple of mm higher because of a thicker base however. I'm not sure why the T5 slave sits higher (for extra leverage?). NOTE: I have measured the clutch fork between NA and T5 and its the identical part.

LUBRICANT
There is a surprising amount of confusion over what oil to use in the NWC T5. The main reason is that much of the info online doesn't differentiate between the two T5s: the Non-World Class and World Class. The NWC T5 came with solid brass synchronizer rings, and when the WC T5 appeared in 1985 it received fiber-lined brass synchronizer rings. Gear oil delaminates these fiber linings and as a result the WC T5s came with a sticker that said "ATF Only". 20 years later well-intentioned people automatically state "ATF only!" without ever asking which version T5 it is.

The Nissan factory service manual states you can use 80/90w gear oil or "Dexron" ATF in the 280ZX NWC T5. In the early 1980s this would have been Dexron II ATF which is no longer made. Its replacement Dexron III is listed as backwards compatible with Dexron II and I have used Dexron III for a decade in my T5 with no issues. However in 2006 the GM license expired on Dexron III and it was upgraded to the lighter weight Dexron VI. While VI is said to be backward compatible with Dexron III I suspect that means for automatic transmissions. For a manual transmission I prefer to stay closer to the older ATF version.

Dexron III is still on the market but look for ATF labeled "Dex/Merc" which is the non-infringing name used. Of course without the GM guarantee of the name Dexron the no-name formulations could be anything in the bottle. So I went with Valvoline Dex/Merc because I trust their quality.

• - 80/90w has a lot of additives and cushions the gears and synchros well but is thicker in cold temperatures
• - ATF (10w) gives quicker shifting and gear engagement and makes cold weather shifting easier
  

An online rumor a few years ago was that Tremec recommended straight 50wt gear oil instead of Dexron III in the NWC. But according to the FAQ on their website:

"Q: What type of fluid does TREMEC recommended?
A: For all TKO 5-speed models, TREMEC recommends GM Synchromesh (GM Part #12345349). For all other aftermarket models we recommend Dexron III ATF."

I had just rebuilt my T5 and like to experiment so I decided to try 50wt, I could always drain it if I didn't like it. 50 wt gear oil is tricky to find though and is marketed for heavy-duty transmissions and being synthetic lacks the sulphur and phosphorus of standard gear oils. I decided if it could protect the gears of an 18-wheeler it should work great on my tiny 240Z. So I bought some Lucas 50wt synthetic. It was a clear light-yellow color with no discernible smell and the viscosity felt similar to a 10w-30. See my RESULTS section at the bottom of the page to see how it fared.

IMPORTANT NOTE: if you plan on using standard 80/90w gear oil in a Datsun transmission never use one labeled "GL-5", only use GL-4. GL-5 is meant for rear differentials and its additives will damage the brass components. Unfortunately GL-4 gear oil is hard to find nowadays.   

DRIVESHAFT (the tricky part in a 1st generation Z)

The Nissan T5 came with a special driveshaft to fit the 280ZX. It is stouter and fatter than other Z driveshafts, has a different spline count on the front end and a square flange on the rear. The front yoke is a special one for the Nissan T5 and has a 1.3" diameter versus the 1.5" used on the Ford and GM T5s. In other words the only driveshaft that will fit the Nissan T5 is the one that came with it. A 240/260/280 driveshaft cannot be modified to fit.

LENGTH: The T5 driveshaft is a couple of inces longer than a stock 1975-1978 Zcar driveshaft. This means if you use a Nissan T5 trans and T5 driveshaft in a first generation Z the driveshaft will be too long by about 2-3 inches. The solution is to have a custom driveshaft made or have the stock one shortened. Most driveshaft shops can fabricate one if you tell them what you want, about $300. A cheaper solution for us budget ZCAR people is to have the stock one shortened and rewelded, about $100. This gets tricky because driveshafts should be shortened only at the ends for balance reasons. And for some reason Nissan T5 driveshafts neck down to smaller diameters right at the flanges. This means that after cutting, the yoke and flange ends are too small to weld up to the center tube.

So I went down to the local racing machine shop that did my head work in Richmond, Va (Ballos Machine). The owner used to race and make his own driveshafts and said he would take a stab at it. Somehow he broke the law of physics and cut both ends, shortened it, and magically rewelded a perfect bead. It may not be perfect for a 500hp nitrous Z, but on a 6-cyl 2,200 lb car it works great.

New Powertrain Industries version on top, shortened stock one on the bottom. My measurements for both were 29 1/4" from tip of yoke to rear of flange.

In August 2007 I decided I wanted a new T5 driveshaft with replaceable u-joints. So I contacted Powertrain Industries who advertise themselves as Japanese driveshaft specialists. They were very helpful and using my simple length measurements fabricated an excellent driveshaft that fit perfectly into my T5/240Z. TIP: if your differential has a round differential flange, have a driveshaft fabricated with T5 front yoke and stock round rear flange.

Because of the new rear mount you will be fabricating you will need to check the the exact position of the tailshaft in relation to the driveshaft. Transmissions have to be indexed with the differential flange. You should have 2 degrees or less angle between the two.

I'm not going to get into the process here but search online using "driveshaft angle" to see how to adjust yours. A trans shop can do this for you but the easiest is to buy a cheap 'angle finder' with a self-leveling needle. Simply measure the angle on the face of the rear flange and the angle on the rear of the trans and use washers to raise/lower the rear of the trans.

REAR TRANS CROSSMEMBER
This is the rear crossmember that holds up the back of the transmission. The T5 uses the same rubber trans mount as the other Z transmissions, but the mount sits rearward about 2 inches making the crossmember boltup tricky but not hard. This is where you will need to do some fabrication.

There are 2 rear trans-crossmembers on 1st generation Z's.

To modify the earlier version I went to the hardware store, and found two thick (12 gauge) flat-steel angle-iron brackets (2"x6" long). By bolting one on each side facing rearward into the existing body holes, the crossmember now bolts to them rearward by 3 inches.

However, if you have later 240-280Z with the rubber-bushing syle mount you will need to fabricate something a bit different. I never tried creating a mount for the later Zs but the words "cutting" and "welding" come to mind.

REBUILDING & TOOLS
Of all the engine R&Ring I've done on Datsuns, rebuilding a T5 is the most satisfying and enjoyable one yet, no kidding. As scary as a transmission might seem the T5 is designed to come apart completely and easily, it almost ASKS you to rebuild it. If you can rebuild an engine you should have no problem here as parts kits are plentiful as well as online tutorials and forums.

Get it up on your workbench and spend a couple of evenings reading about the rebuild procedures first, and then simply start taking it apart. The important step to remember is that each gear hub synchro assembly needs to have a mark scribed on it so its teeth go back in the same splines to maintain smooth shifting. Other than that it's a matter of replacing things in the same order you took them out.

beadblasted case

REPAIR MANUALS
Most of the rebuilding folklore online deals with the World Class T5s. To get accurate info on the NWC versions you have to look in a few different locations. To start, search for the T5 rebuild...the Saga by Chris Neighbors. A really excellent pictorial which really shows you how to R&R a T5. Also do a search for the Nissan repair manual for the FS5R90A online. It's good reading although several of the procedures are vague and the photos unclear. It lists the Kent-Moore tools needed to rebuild the T5. Another source is the generic "t5rebuildmanual.pdf" found on several sites which has detailed WC/NMW diagrams but the text is dense to read. The Tremec manual available for download only covers WC models.

My favorite manual is actually the "T4 & T5 AMC Trans Rebuild Manual" available online. Excellent diagrams and descriptions that also apply to the Nissan T5 NWC. Don't let the different tailhousing design worry you, the procedures are all the same.

PHOTOS
At every step of dissassembly I took digital photos of the process, especially of the orientation of all the gears on the main shaft and case layout. I printed out a couple of 8x10 color prints of them to refer to on reassambly, much easier than squinting at the shop manual.

SHOP PRESS
Essential. Don't pry off the gears with screwdrivers or start hammering on them or you can damage things as well as becoming very frustrated when things don't move. Instead go and buy a "gear separator" and inexpensive shop press. This gives you total control and lets you quickly and easily press the things off/on at your leisure. My 12 ton press and separator cost about $130 at Harbor Freight tool and paid for themselves immediately as I will never have to run to a machine shop to get something pressed off again.

C-RING PLIERS
There are several "external spiral rings" that need to be removed and replaced. But these are not standard snap-rings that use needle-tip pliers, these are heavy rings with angled tips. While you may be able to work them off with snap-ring pliers (it broke my pair), getting them back on using them is very impossible on the 3rd/4th hub). The Stanley-Proto J250G lock ring plier is what you need, it has a special tip designed for this type of ring. You may never it after your T5 rebuild but it's a must for the rebuild.

Things come off like magic

New parts! Note the NWC countershaft bearings on the upper left

NWC BEARINGS
If you can hear your trans whirring at idle then your bearings are worn and the races no longer smooth. Close ups my races showed subtle scoring from 3 decades of dirt and minor pitting.

The NWC T5 rear countershaft bearing is pressed into the case instead of using a tapered roller bearing with a removable race as on the WC T5s. This means its more complicated to remove the countershaft because the rear bearing needs to be pressed out. To remove it simply use your drill-press to press against the first countershaft gear through the mainshaft hole in the front of the case. This uses the countershaft to easily push the bearing out of the rear of the case.

Re-installation of the rear bearing involves driving it in to sit precisely 3mm above the case afterwards. The Kent-Moore tool J-29895 made for T5s drives this bearing in to the preset height. I almost bought one but instead used my shop press to do it manually, stopping a couple of times to measure with a caliper, the whole operation took me about 2 minutes. Easy.

The NWC front countershaft bearing is a single piece needle-bearing in a cup. This is the the round disc you see from the front of the case that helps people denote NWC from WC. Hammering it can crack the case so I pressed the bearing in from the front. To reinstall it I pressed it back in from the inside using the old bearing on top to help drive it in. Standard specs say to "drive it flush" with the front of the case, but use extra care here. If it sits even a fraction of a MM above the case it can prevent the main-shaft bearing retainer from sealing fully causing an oil leak. Rather than use a large straight-edge I held a razor-blade across the front of the race to gauge its height.
NOTE: make sure to use a sealant on the case lip before pressing it in.

NWC front countershaft bearing and WC rear version

REPLACEMENT PARTS
In 2000 I was able to get a couple of internal parts (reverse circlip, shifter spring and ball) from my Nissan dealer but it appears that none of the T5 parts are available from them anymore. The Microfiche listed the parts as "US made" so I suspect once the Nissan warehouses were depleted of their 30 year stockpile that was it. Rather than scour the internet for the correct bearings, inserts, and circlips I strongly suggest you go to one of the websites that sell NWC rebuild kits.

Interestingly, because the Jeep used the NWC T5 for several years there is still an active community supporting it while the Mustang world has forgotten the NWC and moved on to the WC. So when looking for rebuilt kits for your Nissan T5, pretend its a Jeep T5 and find a 4x4 website that sells NWC T5 rebuild kits.

BEARINGS
My Borg Warner NWC used a mixture of "Koyo Hi-cap" (high capacity), Timkens, and Torrington bearings. Koyo has a slick brochure about their hi-caps I couldn't find a retail source for them so I went with all Timkens. Torrington bearing of Connecticut was bought by Timken in 2003 and my rebuild kit contained them. But searches for the two roller bearings show them to be very scarce in 2016. What will happen when those are gone is anybody's guess.

Here's what mine contained:

MAINSHAFT
FRONT- Koyo Hi-cap LM48548-N bearing & Koyo Hi-cap LM48510-N race (tapered)
REAR- Timken 25877 bearing & Timken 25821 race (tapered)

COUNTERSHAFT
FRONT- Torrington DK55836 (needle style)
REAR- Torrington DB43932 (needle style)

INPUT BEARING RETAINER SEAL
The input bearing seal on mine was an obsolete green "National" part # (forgot to write it down). The modern replacement is the Timken/National 7412S. But I found the metal shell on those to be thin and prone to damage upon pressing in. A good find was the alternative part SKF 12363 which has a stouter outer ring making pressing it easy.

ON THE ROAD
For my rebuild I installed new bearings, brass synchronizers, inserts/springs, snap-rings, shift fork pads, a new tailshaft bushing, as well as correcting the preload. On the road the shifting was much more precise and tight, very firm and smooth, a "new" feeling is the best description, no slop at all in the shifting action. The audible whirring I had at idle is now non-existent due to new bearings and at 70mph the vibration I used to get is gone which I believe is due to the new tailshaft bushing.

The effects of using 50wt oil surprised me. Shifting felt smooth and firm and driving it at 30°F (it was early spring) didn't pose any issues other than shifting being slightly tight for the first couple of blocks. But at operating temperature when upshifting 'out of order' (2nd to 4th or 1st to 3rd) I got some crunching when it went into the higher gear.It didn't do it during normal shifting (1,2,3,4,5) or at full power. Sometimes when I would downshift from 5th to 4th I would get a nasty crunch. I worried that I rebuilt it badly because my pre-rebuild T5 didn't act like this.

So as a test I drained the 50wt after the first 300 miles and replaced it with Dex/Merc and yes it made a difference. With the engine off action through the shifter felt snappier and sharper. On the road the action going into each gear is cleaner and crisper, no resistance versus the very slight engagement-feel like before. I got better feedback through my palm and found that skip-shifting didn't cause any of the clunking or crunching as before. Downshifting from 5th to 4th was predictable and quiet.

I don't expect perfection from a 30 year old transmission. But I can only conclude that 50wt is the wrong viscosity for a NWC T5, affecting the synchronizers, adding a slight 'cushion' to gear changes and blurring feedback from the gearbox. Nissan may have allowed 80/90w gear oil in their T5 but at this point I see no reason to use anything other than Dex/Merc.

these two 8-inch long shafts are the transmission, pretty simple eh?