L-series 6-speed Transmission Conversions

[Xnke]

Not sure if I need to post this in General Topics or here in For Sale, so here it is in For Sale.

 

I can convert the bellhousings on the S15 6-speed manual transmission, AKA Nissan FS6R92 to fit the L-series or KA series engines, and use standard L/KA clutch assemblies.

 

This transmission gets a bad rap as being a weak box...which simply isn't the case. At sustained torque levels of 350+ft-lbs, this transmission in unmodified condition can snap a circlip that retains the 4th countershaft gear, allowing it to crash into the reverse gear assembly. This generally fucks shit up pretty bad. This can be avoided by various "circlip mods" but that is not a service that I personally offer. I am still looking for a reputable shop that I can recommend for this service. Once this modification is made, the transmission can handle as 350ft-lbs on a regular basis without issues, according to those who have had this modification done.

 

That said, for any engine that puts down LESS than 300ft-lbs, you're within the safe zone and this box is a viable option for you. They are readily available from importers and due to the "weaksauce gearbox" rap they are going for a little less money than most other options for a 6-speed behind an L-series engine. The gear ratios are listed below:

 

3.6

2.2

1.5

1.3

1.0

0.76

 

This is a nice close ratio box, and is suitable for road racing as a 5-speed by ignoring 1st gear and using it as a dogleg-first gearbox. This means you leave the starting line in 2nd gear, and shift up into 3rd, using 3-4-5-6 in the standard 4-speed pattern to obtain a close approximation of the Nissan Competition close ratio gearbox.

 

To do this conversion, I need the front case from your S15 SR20 6-speed transmission, the front case from your L-series or KA24 transmission, and 375$. I will return to you a modified S15 6-speed front case, ready to be bolted back up to the transmission and fitted behind the engine.

 

If you require a speedometer drive, make sure your S15 transmission is machined for one. NOT ALL OF THEM ARE. The ones that are suitable will have a removable aluminum plug bolted into the usual location for the speedometer drive. This transmission does NOT have a drive cog inside on the tailshaft...so it's not just a bolt-it-in-and-go solution. I can machine your 5-speed speedo drive cog to fit, if you send it with your bellhousing. The cost for this is 45$, which includes machining your speedo cog, the ball bearing, and the two circlips to re-install it onto the tailshaft of the transmission.

 

If you are not comfortable dissasembling the transmission, then ship the entire transmission plus your bellhousing and speedometer cog, and I can do the bellhousing conversion for 430$, and the speedometer drive for 45$. It is totally understandable if you don't want to try to break one of these boxes down, as they are VERY tricky to reassemble properly. Very easy to lock them up when it comes time to put the bellhousing on...and then it all has to come apart to get it unlocked.

 

I can be reached by telephone or by PM here or on HybridZ, PM me for the phone number please, I won't be posting it on the internet.

 

Here are a few shots of the process; for those who are curious. Pardon the clutter, my former fab shop got condensed from a 4-car garage to a 12x16 machine shop due to leasing issues. It's a wreck right now.

 

Cutting the SR20 flange off the front case:

 

 

Getting the L24 flange bolted to the block, getting ready to align the welding jig:

 

 

Starting to weld the two bellhousings together along the outside:

 

 

Finished bellhousing, ready to be scrubbed down and reassembled onto the transmission:

 

 

Any questions, just ask. Everyone knows that 4 speeds is good, but 5 speeds is better...so 6 speeds must be best!

[MicroMachinery]

[datzenmike]

fapa fapa fapa fapa

[sssr20det510]

Do u have pics of the speedo mod

[metalmonkey47]

Nice. Guess I need to start looking for a 6 speed.

[Dawa]

nice. even though i have no personal experience with the s15 6speed, the first thing that came to mind was what ive read on zilvia (that theyre weak.) and was going to mention that, as well as if the z33 trans is a wiser decision and if it even fits readily/easily.

 

good stuff

[Xnke]

The Z33 conversion can be done as well, but since it requires a LOT more work and pretty much a fabricated bellhousing, I'd have to charge about 1500$ to do that one. It is a much larger transmission and will hold about 450-500HP, but I do not have torque figures on that yet. It also has synchronizer issues, similar to the Z32 transmissions, but worse. The synchro issues are bad enough that Nissan ran a TSB on them.

 

The 240SX *turbo* guys call them weak because they don't hold anymore power than the 5-speed they replaced, and when they fail they destroy the gearset, instead of destroying the bearings...they seem to think that destroyed gears means weak transmission, but destroyed bearings means weak bearings and a strong transmission...Both types of destruction start happening at 300HP/TQ, but since you can still beat on a C-box for a while at that level before it grenades "it's OK, just buy another 100$ transmission and put it in! It'll take it for a while and it's cheap!"

 

This is the same transmission used in the Altezza, IS200, Mazdaspeed MX5, the FR-S/BR-Z/GT86, and the RX8. Only the turbo SR20 guys running 350+ft-lbs whine about them breaking when (ab)used WELL past their ratings.

[Xnke]

I can get some photos of the speedometer modification shortly, mainly what to look for in picking a box that is machined for the speedometer. There isn't much to see other than that, the guts look the same as the 5-speed, just on a bigger output shaft.

[Farmer Joe]

ooooo!

 

this looks neat! 

 

dang, im still just trying to get a C type trans in my truck, and now we have an option for the 6 speed...

 

looks  good man. hope this has a little demand.

[bananahamuck]

How is the trans and bellhousing part aligned so it is in the correct position and depth before welding cuz i see a 1/2" board on saw horses??  You keeping that jig under wraps from the world is fine,,  just wondering..

 

 

 

 

 

 

That almost sounds like a personal attack but i couldn`t think of better phrasing at this hour..

:)

[Z-train]

3.6

 

2.2

 

1.5

 

1.3

 

1.0

 

0.76

 

Ill thought out box.the spread between 3rd & 5th is point-less.And with teh gearing MOST of us have,a 3.6 1st is over-kill.

And technically,it's a 5-speed OD,not a 6 -speed.But i digress.

[EricJB]

I was hoping 3rd would be closer to 1.7

[sssr20det510]

I can get some photos of the speedometer modification shortly, mainly what to look for in picking a box that is machined for the speedometer. There isn't much to see other than that, the guts look the same as the 5-speed, just on a bigger output shaft.

Ill have to look at mine i guess

[Xnke]

How is the trans and bellhousing part aligned so it is in the correct position and depth before welding cuz i see a 1/2" board on saw horses??  You keeping that jig under wraps from the world is fine,,  just wondering..

 

 

 

 

 

 

That almost sounds like a personal attack but i couldn`t think of better phrasing at this hour..

:)

 

The jig is installed in the main bearing caps of the engine block and is supporting the bellhousing in the proper alignment in all three planes.

 

 

Ill have to look at mine i guess

 

On the tailshaft housing, you'll see a little cover with a 10mm bolt holding it in place...it'll be tight pulling it out due to an O-ring fitting there. If you don't have the cover bolted on and it's just a casting hole, then that box is not convertable without having a milling machine to bore the tailshaft housing, and it also won't have the speeometer drive section machined into the tailshaft and will need to be broken down completely for machining.

 

If it DOES have the cover, then pull the cover and have a look with a flashlight in the hole as you slowly rotate the output shaft. You should see two circumferential grooves for C-clips and a machined divot between them that holds the ball bearing used to lock the speedo drive gear on the shaft.

[Xnke]

3.6

 

2.2

 

1.5

 

1.3

 

1.0

 

0.76

 

Ill thought out box.the spread between 3rd & 5th is point-less.And with teh gearing MOST of us have,a 3.6 1st is over-kill.

And technically,it's a 5-speed OD,not a 6 -speed.But i digress.

 

I agree, the 3.6 first is not great. However, I will direct you to the Nissan Competition Option boxes as to what the traditional options are...as I said, it's a close ratio box. For example, here's the Nissan Option transmission list:

 

These are all for the FS5W71B transmission:

 

32010-N3130 Gearbox ratios: 1st: 2.906, 2nd: 1.902, 3rd: 1.308, 4th: 1.000, 5th: 0.864

 

32010-N3030 Gearbox ratios: 1st: 3.321, 2nd: 2.077, 3rd: 1.308, 4th: 1.000, 5th: 0.864

 

32010-N3220 Gearbox ratios: 1st: 2.818, 2nd: 1.973, 3rd: 1.470, 4th: 1.292, 5th: 1.000

 

32010-N3221 Gearbox ratios: 1st: 2.348, 2nd: 1.601, 3rd: 1.296, 4th: 1.138, 5th: 1.000

 

32010-N3222 Gearbox ratios: 1st: 2.192, 2nd: 1.601, 3rd: 1.470, 4th: 1.138, 5th: 1.000

 

32010-N3201 Gearbox ratios: 1st: 3.321, 2nd: 2.270, 3rd: 1.601, 4th: 1.240, 5th: 1.000

 

OS Giken sells the following close ratio gearset for the FS5W71C transmission:

 

1st: 2.596, 2nd: 1.765, 3rd: 1.250, 4th: 1.000, 5th: 0.833

 

These gearbox ratios are all setup for competition use...thus I likened the gear ratios to the Nissan COMPETITION boxes. They're generally run with 3.90 or lower ratios in the rear, and the guys running 4.11 or 4.375 gears can use these VERY effectively for high-RPM, and thus high-horsepower usage. I'm not the one installing your rear end gears, so I don't get a say in that matter. In my opinion, the 6 speed would be GREAT with a 2.73 rear end...but I'm also running a supercharged engine with plenty of low-end grunt. The guy with the moderately cammed L16 in a 710 wagon might enjoy a 3.545 or 3.70 rear gear with these ratios, since it is low enough to keep the engine on the cam, but has a tall enough OD to return decent highway mileage.

 

For those out there who are using their cars for road race or other usage where a tight ratio box is desired, or if you have a big cam with a narrower power band, then this box is a much cheaper alternative to the Nissan Option boxes. The POINT of a close-ratio box is to keep the RPM's in a narrow power band, or in the OEM's case, the car is geared such that the close ratio box keeps the car in a nice, tightly-controlled RPM range that they can minimize fuel consumption and emissions without sacrificing much in ultimate power...instead of having to work a much wider range for the optimization and giving up power over a wider band.

 

For reference...the last time I saw a Nissan Option gearbox change hands the price paid for a used good transmission was 1400$. The new, never installed gearbox was 3200$.

 

 

Not trying to be a jerk here, just trying to answer questions on why the gearbox is layed out the way it is.

[datzenmike]

If it DOES have the cover, then pull the cover and have a look with a flashlight in the hole as you slowly rotate the output shaft. You should see two circumferential grooves for C-clips and a machined divot between them that holds the ball bearing used to lock the speedo drive gear on the shaft.

 

[sssr20det510]

Ya mine is just cast closed

[Xnke]

Thanks for the visual DatzenMike!

 

Yep, the boxes that are cast closed, I can't convert. You would have to break the whole gearbox down, take the shaft in to a machine shop, and have them cut the grooves for the circlips and the ball detent. Then you'd have to have the extension housing machined to accept the speedometer drive.

 

Or you could buy the Nismo 6-speed...it comes with the cable drive and the gear already installed for...4000$!

[sssr20det510]

F-that GPS speedo it is lol

[sssr20det510]

I almost bought a nismo one for 1400 but couldn't come up with the cash in time

[theguppiez]

Why not make an adaptor plate? I've seen people making adaptor plate for Z33.

[Xnke]

Because the the input shaft is WAYYYYY too short. The adaptor plate for the Z 33 is more expensive than my price for the bellhousing swap, and it adapts an auto-trans Z32 bellhousing into place by replacing the front half of the case with a billet section, which is then drilled for the nissan automatic bellhousing. No such part currently exists to put the Z33 trans behind an L-motor from one supplier...however you can do the following:

 

Buy JWT's Z33 to Z32 auto bellhousing adaptor

 

Buy Hoke Performance/Mazworks Custom Z32 to L adaptor plate

 

Machine the auto trans bellhousing to accept the Hoke Performance adaptor plate

 

Fit up the correct clutch and flywheel for the Z33 transmission

 

So far, I have not found any other solution currently offered for putting the Z33 transmission behind the L. Both the S15 and Z33 boxes are set up for a dual-mass flywheel, and the input shaft pilot bearings are moved nearly two inches further back into the bellhousing than the L and KA pilot bearings.

 

In other words, on the Z33/S15 6 speed boxes, your input shaft would be completely unsupported and you would have to run a large spacer between the crankshaft and the flywheel just to get the clutch in the right spot, BEFORE you account for the extra space needed to fit an adaptor plate into place.