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JDM_240z

Sr20det 6speed conversion.

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Hy guys,

 

I've recently got my 240z up and going again and had it around the Perth hills today. Now the engine is a slightly worked l24, cam with triples and is very peaky power wise. Where I am going with this is that my current gearbox ratios are terrible and having the engine with little torque down low has amplified the issue. I think it's a standard 240z 5spd, you basically have to red line the engine in first to keep it in the power band for second and 3rd gear which isn't ideal.

 

Has any body on here put a 6spd behind there engines before? I was looking at the other threads showing how to swap the bell housings over etc, then looking into the ratios the 6spd are quite close together which is what I want/need. I figure now is the time to do it as my gbox mount is stuffed and my clutch I don't think will last too long once the car is tuned correctly.

 

Thoughts and opinions please  :D

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The ratios in the SR and Skyline boxes will also be just as horrible.

They are same as later 260z and pretty much all other Nissan boxes.

The better ratio box is the 2.9 first gear set as fitted to earlier 260z and 240z.

 

If you want to achieve a more spirty drive, ie close ratio gearset, i can supply you a new set, that can be fitted to the later L series four or six cylinder boxes, as well as the RB20/SR20/CA18/RB30 boxes.

 

Lets start with,

Confirm what box you have? Is it the original long 240Z box?

If so maybe stick with that, it has the 2.9 gearset fitted!

What diff ratio?

You say you redline the engine, but you arent happy with the car in the Perth hills!

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I just to be able to bang it through the gears and keep it in the power band so to speak (above 4000rpm). I dont really want to have to go to 7000rpm every time. The diff ratio is really tall and I will address at a later time. I think my car was 4spd then converted to 5spd. How much is a gear set? So your saying I wouldnt gain much looking at the ratios below?

 

SR20DET S15 Silvia R 3.626 2.200 1.541 1.213 1.000 0.767 3.382

 

 

240Z, 260Z R30 & 31 SKYLINE,

FS5C71B                 3.321 2.077 1.308 1.000 0.864 3.382

 

 

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if by 4 speed you mean auto then your dif will be the issue!! i would chuck in a 3.9 or something and see how you go!! Check your current dif ratio then report back  :)

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No 4 speed auto!

They were a NissanMatic 3 speed.

 

Will need to determine just what the box came from, and your diff ratio.

 

Have a bit of a guess, in 4th gear at 100 kmh, what engine rpm are you doing?

What is your tyre size/dimensions.?

Can work out diff ratio from that.

 

You say converted to a 5 speed, chances are it will be the 3.32 gearset, which has a big laggy engine rpm drop when you change up from 2nd to 3rd?

 

Close ratio sets are  2.42,  1.67,  1.25,(  1.0,  0.86 )

These are new sets and you get a local Perth gearbox shop to fit to your box, along with fresh bearings, seals, and other items, as needed.

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The 1st to 2nd and 2nd to 3rd lag is terrible, which is why I see the 6spd as a potential answer. Gain a gear and have them spaced closer together.

 

I think my diff would be around 3.4, I had it a roughly worked out a while ago.

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Might be a 3.54, I think thats the diff the autos run. I think with a manual you'd want to go with a 3.9 or 4.1, 3.9 is what I run

 

 

if it's 3.4 thats half your issue... before you do anything grab a 3.9... if top speed isnt your thing then grab a 4.1

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^^^ What they said. There really is no comparison in regard to how much better it drives with the 3.9 vs 3.54

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Go for a drive

On a freeway,

Put it in 4th gear,

Hold it at 100kmh, same as all other cars, if not sure on speedo accuracy.

Make note of engine RPM's.

 

Size f rear tyre?

Report rpm's and tyre size here, ie post on your thread.

Can calc your diff ratio.

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Changing your diff ratio will have no effect on the lag you are describing when changing gears, it will only change the vehicle speed that the lag occurs at.

 

According to the ratios you mentioned in your earlier post

SR20DET S15 Silvia R 3.626 2.200 1.541 1.213 1.000 0.767 3.382

 

240Z, 260Z R30 & 31 SKYLINE,

FS5C71B                 3.321 2.077 1.308 1.000 0.864 3.382

The change in revs between gears will be as follows and will be irrelevant of diff ratio

6 speed

1-2: 61%

2-3: 70%

3-4: 79%

4-5: 84%

5-6: 77%

 

5 speed

1-2: 63%

2-3: 63%

3-4: 76%

4-5: 86%

 

Therefore the 5 speed will be slightly closer between 1st and 2nd whereas the 6 speed will be quite a bit closer between 2nd and 3rd.

 

The close ratio gear set Jason mentioned

 

2.42,  1.67,  1.25,(  1.0,  0.86 )

 

Would be as follows

1-2: 69%

2-3: 75%

3-4: 80%

4-5: 86%

 

These are closer ratios than both the other boxes you mentioned in all gear changes.

 

If you were to use this gear set and you always wanted to be in the power band (above 4000 rpm) you would have to change up gears at the following rpm

 

1-2: 5797

2-3: 5333

3-4: 5000

4-5: 4651

 

Hope this helps

Mick

 

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Changing your diff ratio will have no effect on the lag you are describing when changing gears, it will only change the vehicle speed that the lag occurs at.

 

 

Thats not true, it will make the "lag" shorter and the diff is a torque multiplier at the wheels.

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Thats not true, it will make the "lag" shorter and the diff is a torque multiplier at the wheels.

 

Yes a higher ratio diff will act as a torque multiplier and will help you to accelerate quicker however, it will not change the rev difference between gear changes. That is directly related to the gear box ratios only.

 

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You currently have a 3.54 ratio diff fitted.

Just take single steps, try it out each time you change things.

 

Hunt around for  a 3.888 or a 4.111 diff. This will improve your off the line acceleration ability.

Worry about changing gearboxes or fitting close ratio sets later.

 

The S15 6 speed box, with a 3.6 first gear will be useless, the 2nd gear ratio of 2.2 will be a PITA getting the car off the line.

The lag/gap between 1-2 was done for the Turbo sr engine, doesn't suit a older L type atmo engine.

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You currently have a 3.54 ratio diff fitted.

Just take single steps, try it out each time you change things.

 

Hunt around for  a 3.888 or a 4.111 diff. This will improve your off the line acceleration ability.

Worry about changing gearboxes or fitting close ratio sets later.

 

The S15 6 speed box, with a 3.6 first gear will be useless, the 2nd gear ratio of 2.2 will be a PITA getting the car off the line.

The lag/gap between 1-2 was done for the Turbo sr engine, doesn't suit a older L type atmo engine.

 

 

^^ what he said

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I'm running a 6 speed behind the L18 in my 1600, its also fitted with a 4.44 diff.

 

1st gear is great ! For getting it on the trailer............

 

I don't do "standing starts" in the events I compete in, so for me I use 1st to get moving, then its strictly 2nd thru 5th on the track. Works really well as a cheap close ratio box. 6th is also fairly tall, ideally (one day) I'll fit the Toyota IS200 6th gearset I have at home to bring it up to .86 or thereabouts from the current .7-ish. Although, with only 100hp, I don't have that much of a need for using 6th on the track, I top out at 180-ish kph. If you are really keen, fit the Nismo 1st gearset (2.9 ratio) as well for a few hundred dollars. Or just buy the whole Nismo box brand new for $4K  :o

 

For me, it has worked out well - cheap-ish, good ratios, not too much work to fit and a ready supply of spares if I break it. Sure, there are better options, but it is an alternative if you're handy with an angle grinder and a welder to do a cut'n'shut bellhousing. It may also work out differently in a zed, with a higher top speed.

 

For anyone interested, here's the different ratios available for this box. Note that I haven't confirmed 100% that these are interchangeable, I guess I'll find out when I open mine up and try to fit the Toyota 6th gears......

 

And to whet your appetite -

- Fit an S15 box and you too could drive an old Datsun holding a Contour camera in your mouth  ;D

 

J160 6/MT found in the AS200 and RS200

First Gear: 3.874

Second Gear: 2.175

Third Gear: 1.484

Fourth Gear: 1.223

Fifth Gear: 1.000

Sixth Gear: 0.869

 

J160 6/MT found in the Nissan S15

First Gear: 3.626

Second Gear: 2.200

Third Gear: 1.541

Fourth Gear: 1.213

Fifth Gear: 1.000

Sixth Gear: 0.767

 

J160 6/MT found in the Mazda RX8

First Gear: 3.760

Second Gear: 2.269

Third Gear: 1.645

Fourth Gear: 1.187

Fifth Gear: 1.000

Sixth Gear: 0.843

 

J160 6/MT found in the Mazda MX5

First Gear: 3.760

Second Gear: 2.269

Third Gear: 1.645

Fourth Gear: 1.257

Fifth Gear: 1.000

Sixth Gear: 0.843

 

J160 6/MT TRD Gear Set (Part Numer: 33030-SE100)

First Gear: 3.106

Second Gear: 2.175

Third Gear: 1.585

Fourth Gear: 1.223

Fifth Gear: 1.000

Sixth Gear: 0.869

 

J160 6/MT Nismo Gear Set

First Gear: 2.9071

Second Gear: 1.9888

Third Gear: 1.5373

Fourth Gear: 1.2179

Fifth Gear: 1.0000

Sixth Gear: 0.8624

 

 

 

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The last one, the good one, the NISMO one,,,,,,

I can supply that!

Via my very nice friend at Nismo Japan.

If you have to ask, you cant afford it!

 

If i was permitted, i'd be running them!

 

Dave W, you reckon that 2.2 as a first gear on standing start is fun,

Try an original Option 3 Ultra Close Ratio box,

First gear is 1.858,,,,,,,,,,, need a 5.143 ratio diff for that one,,,, but geez, it's a nice super tight box!

BTW, my Ultra Close is for sale, if someone is a crazy as me,,,,,,,,

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Hi All,

 

I have now officially installed the 200sx 6 speed gearbox into my 240z. Another post I strongly recommend you review as well as this one is "S15 6 speed transmission on an L28". As Dave1600 has mentioned here and in several other posts, this is by far one of the best upgrades that I have done thus far. At the same time I have coupled it with a 4.44 Subaru wrx sti (mechanical/plated LSD).

 

Notes that I can add to this post, base upon my experience. (My experience being the fact I stripped, replaced every bearing, and syncho for new and modified and installed the worm drive gear so the speedo will also work, then put the jigsaw puzzle back together - which for the pros out there would have been an easy task but for myself having never done it before was a reasonable challenge).

 

The usual disclaimer - take everything I say with a grain of salt but the information I give here was relevant in my unique case.

 

BELL HOUSING

I had to remove 35mm from the front bell housing when it is welded. S15 (200sx bell housing size = 286mm prior to being modified, 251mm after the chop)

 

Depending upon what clutch plate you have (as they come in different sizes) - you will need to select an appropriate idler bearing carrier. For the record there are at least 3 difference sizes that I have found thus far. In my case I needed to use shortest one I could find (which was approximately 47mm).

The other 2 sizes I found were 53mm and 58mm (as measured based upon their entire length)

 

TAILSHAFT

You will need to modify the tailshaft by approximately 20mm (shorter). You can get a custom tailshaft made, using the front yoke from the 200sx..... The down side with this option is that by this model Nissan no longer made replaceable uni - joints. Therefore break the uni - joint need to make another custom tailshaft.

 

The option I went with was the front yoke from a Nissan R31 (automatic) will fit the 200sx gearbox, and it has replaceable uni - joints! You also need to remove the dust cover from the R31 yoke. Again I must stress it needs to come from an "AUTO" model.

 

MODIFY REAR MOUNT

Sorry I cannot offer much info here (as I did not do this part of the job) - but I wouldn't waste time buying the 200sx mount - modify the original Z one

 

BEARINGS & SYNCHROS

If you search online for a parts list you will find one for this model. The other thing to point out is that the bearings and synchros are interchangeable with a series one Mazda RX-8 (along with several other models). Nissan have discontinued some of these bearings hence I ended up at Mazda. In my case the Mazda parts were slightly cheaper but I honestly got great service from both companies.

 

GEARSTICK

I had to enlarge the floor hole approximately 15mm forwards and 5mm to the right - original rubber squeezed over the top. That said, my gearstick rubber is relatively new and still in good condition, older gear stick rubber may not take the strain. Also, as the tower which pokes up through the floor has it's own protective rubber to prevent anything getting into the gearbox. Thus you really only need rubber around the tower to block out road noise... Not sure if that makes sense.

 

WORM DRIVE GEAR

I have attached photos of this one. As Dave1600 outlined in another post (S15 6 speed transmission on an L28), you need to find an earlier model (2000 or earlier I think). You do need to find one which has the removable plug in place. Photos outline a Lexus IS200 worm drive compared with our Datsun worm drive gear (ours is the biggest one). All you need to do is trim the height and widen the hole of ours. You also need to source 5mm ball bearings as it is smaller than ours, and a little tweak of the worm drive where the bearing will sit.

 

MODIFICATION TO THE COUNTERSHAFT

These gearboxes have a bad rep - particularly as the cars were used for drifting. Once the power starts to head north of 250hp they can have issues where the forth gear pushes hard against its thrust washer, chips the teeth on the counter shaft and (from what I can gather) eventually it forth gear floats and ended up meeting with reverse. Therefore I also went to the extreme to modify the countershaft ready to handle a higher torque (possibly not required). In reality my countershaft was already chipped (photo included). There is a company in SA that gave excellent service and great advice and I cannot recommend them/him highly enough. Sam from Neat Gearboxes - was able to answer all the questions I threw at him throughout this process and also modifies these countershafts.

 

COST

Not for the feint hearted this one. If you were to do it minimal bare minimum you would be looking at around $1000. Costs (from what I can remember below) for myself ended up closer to $3100.

 

Gearbox - $500 (can get cheaper but will most likely have gears trashed. $700 general price from wreckers with a warranty)

Tailshaft - $350 (second hand R31 auto + make custom one)

Bearing Carrier - $15

Idler Bearing - $15

Bell Housing - $500 - $1500 (depending upon how lucky you are - just make sure its done properly)

New Bearings and Synchros - approx. $1000 (I cannot remember exactly for this one)

Countershaft Mod - $950 (approx. but this includes a new countershaft as well)

 

Hopefully this helps and please let me know if I can answer any further questions.

 

Again - these were the basics and how it worked out for me, costs and other things may vary but I have tried to be as accurate and descriptive as possible.

 

Cheers

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Edited by Roady

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