FS5W71C 240sx 5spd behind the L series (L16, L18, L20B)

[KlassicMotion]

I thought I would post this for anyone that has the same idea:

Notes to Newbies: The transmission behind the KA24DE (240sx) and the SR20DET (Silvia) have a different orientation to the engine than the L series (L16, L18, L20B, L28).

I have a 1971 510 2 door I'm putting an L20B in with a 5spd. I have a 1982 280zx 5spd I was going to put in the car, but after reviewing the gear ratios and feeling the shifter movements, I like the 240sx better. I bought two 240sx transmissions. Supposedly they were both for an S14. The had different looking front cases. One front case looked similar to my 280zx front case and the other looked to be later with a lot more structural ribbing. (I will try to ad some pictures when I get back from the Holidays). I also had lying around a 4spd from a late model 620, and that case again, looked similar to both the 280zx and early S14 trans. Because I've never opened up a transmission other than a Ford Model A, I first took the front cover off the 4spd to learn what would happen when I unbolted things... Easy-peasy. So I moved on to the EARLY S14 trans, because the shifter felt tighter than the later S14 trans I have. Plus I figured I can always go back and use the later model if this works out. With both front cases off, I could see that all the holes were in the correct places for the shafts and shifter rods. Good start. I also noticed that when removing the front case, the rear case becomes loose and will need to be sealed up properly. That is when I decided I did not want to learn how rebuild a 5spd right now. So, I took the front case from my 620 4spd trans, and the early s14 trans into my trusted machine shop. He finished it up today, here is what he said: First, I warned him that I had read that the counter shaft bearing may be a different size, Yes it is. He was able to match the bearing with an off-the-shelf metric bearing. He also found that one of the shift rod holes needed to be milled out a couple thousandths. And the inside of the front case had to be milled down to fit the bigger cluster of the 5spd (probably not an issue if you use a 280zx 5spd or the 200sx dogleg front case....This is my ASSUMPTION). The bearings also needed proper shimming. With that, he said it all fit together and everything seems to work nicely on the bench. The real test will be to drive it. (I will make some updates when I get it on the road).

Notes:
1971 automatic 510s and some random others have the transmission mount located further rearward compared to the standard 510s.

Preliminary mock up shows that the transmission cross member will not need to be moved for this conversion into a 1971 510 (I will verify this as I progress). I have an Experimental Engineering cross member on hand just in case (I was actually going to do this conversion on a '72, but the '71 was in better shape).

My cost in the transmission thus far: $100 for S14 5spd, $70 bearing and seal kit, $250 for machine work.

I read that the later S14 trans uses a synchronized reverse. The shop told me my reverse gear has taken some bad hits, but should be usable, this makes me wonder if these cars had issues with the reverse gear, and that is why they went to a synchro gear? Here are some transmission ratios I have dug up. I've also read that the 240sx S14 used a 4.06:1 rear diff. ratio.

My opinion: The 240sx 5spd will work better with the stock 3.90 rear diff, because of the lower first, second and overdrive. If your going to change the rear diff gear to 4.11 or lower, the 280zx trans will do just fine. Maybe someone else can testify to the usability of the 280zx gear set with a stock 3.90 rear diff...

510
1st- 3.382
2nd- 2.013
3rd- 1.312
4th- 1.00

510 optional:
1st- 3.657
2nd- 2.177
3rd- 1.419
4th- 1.00

280zx Early ('78-79)
1st- 3.321
2nd- 2.077
3rd- 1.308
4th- 1.00
5th- 0.864

280zx Late ('79-83)
1st- 3.062
2nd-1.858
3rd- 1.308
4th- 1.00
5th- 0.773 ('79-80)
5th- 0.745 ('80-83)

KA24DE (S13 & S14)
1st- 3.321
2nd- 1.902
3rd- 1.308
4th- 1.000
5th- 0.759

SR20DET (S15)
1st- 3.626
2nd- 2.20
3rd- 1.541
4th- 1.213
5th- 1.000
6th- 0.767


Here are two pics looking down into the front casings after the initial removal. Aside from sensors and fill plug holes, they look the same with the naked eye. (240sx trans has the extra sensor)

[Skib]

theres a dude on hybridz that makes an adapter to use the KA trans on an L series.

[datzenmike]

And the inside of the front case had to be milled down to fit the bigger cluster of the 5spd (probably not an issue if you use a 280zx 5spd or the 200sx dogleg front case....This is my ASSUMPTION).

 

Sorry the FS5W71B zx 5 speeds also need to be milled down in fact all 71B type will need this mod to take the later 71C gear cluster.

 

The FS5W63A 200sx dogleg is a totally different 5 speed case and nothing will swap to the 71B or 71C

 

Most 71B 5 speeds use the 56mm counter bearing but this was enlarged to 62mm around '85 just before the 71C came out.

 

 

510

1st- 3.382

2nd- 2.013

3rd- 1.312

4th- 1.00

 

510 optional:

1st- 3.657

2nd- 2.177

3rd- 1.419

4th- 1.00

 

 

The 510 'optional' gears are used on the 510 wagon. These same ratios are used on the 521 and early 620 trucks.

[KlassicMotion]

Good, thanks for the info. I'd like to compile as much info here for the swap, so the next person has all the info at hand. I've never seen the 200sx transmission. I'm pretty sure the same is true for the SR20DET 6spd, I believe it is a totally different transmission as well.

[DISLEXICDIME]

the 6 speed is crammed in to the same case as the 5 speed so you would think you could do a bell swap to make it work on a l.

[KlassicMotion]

Just to have all the info in the same thread, here are the other transmission ratio I have found:

 

Ratios for the '78 620 5spd L20B): also known as the Nismo truck wide ratio trans.

1st....2nd...3rd...4th.5th

3.321 2.077 1.308 1 0.864

 

Ratios for the '80 720 5spd (L20B 2wd):

1st....2nd...3rd...4th.5th

3.592 2.246 1.415 1 0.882

 

Ratios for the early 280Z 5spd: (wide ratio)see '78 truck above

1st....2nd...3rd...4th.5th

3.321 2.077 1.308 1 0.864

 

Ratios for the '77through '79 200sx 5spd (L20B): same ratios as the '68-'73 521 4spd but with a 5th o/d added on.

1st....2nd...3rd...4th.5th

3.382 2.013 1.312 1 0.854

[ggzilla]

By "milled down" are you talking about drilling out the bore holes larger?

[datzenmike]

By "milled down" are you talking about drilling out the bore holes larger?

 

Well you can bore the smaller, lower hole out to 62mm and use the larger 71C counter bearing. But the oil slinger and the counter driven gear are wider and will hit the case. If you look at the picture below, at the top hole you can see there is a shoulder around it that is missing on the bottom hole. Now look at the very bottom picture. You can see that on the 71B there is a shoulder around both holes. For the 71C gears to fit into a 71B case, that shoulder must be milled away.

 

 

 

If you have a keen eye, look at the smaller three shift rod holes. The top 71C hole is larger than the top 71B so the 71B must be drilled out to about 5/8" to allow for the larger 16mm 71C 1st/2nd shift rod.

[KlassicMotion]

I see it now, you can also see there is less material between the two bearing bores in the top 71C bellhousing.

[ggzilla]

Ah ok, so this is the traditional 71B front cover - to - 71C transmission modification. I never picked up on the shoulder milling step from previous explanations.

 

Good work!

[KlassicMotion]

That is correct, but both pictures are before machine work. The bottom 71B housing needs to be machined liked the top 71C housing.

[datzenmike]

You need about this much removed for the proper gear clearance. About a 3 1/2" diameter circle...

 

[Zendar]

All the info you need to do this can be found here

 

http://home.comcast....ransmission.htm or here http://zhome.com/ZCM...ransmission.htm

 

Also if you need to rebuild the FS5W71C you can get new bearings and synchros from here

 

http://www.drivetrain.com/parts_catalog/manual_transmission_overhaul_kits/nissan_f5w71_overhaul_kit.html#FS5W71C

 

DTS-BK133BWS $179.10

 

You will also need new main and counter shaft nut from nissan

[KlassicMotion]

Awesome! Thanks for the link. I guess I will have to go back and move the reverse switch. I'm happy there is a useful thread on Ratsun now with lots of good info. Thanks to everyone for pitching in.

[datzenmike]

It's probably here somewhere in past posts.

[KlassicMotion]

Well, not that I was able to find, but this will ensure the next person has better luck.

[datzenmike]

I guess I will have to go back and move the reverse switch.

 

Only if your L case has the reverse light mounted to the rear. I thought that only 4 speeds had this but it's not that common. If yours looks like this you're OK.

 

[KlassicMotion]

I pick my trans up tomorrow so I'm not sure right now. But looking at the pic I posted, I believe it looks like my housing has the switch mounted in the rearward position, it is the housing from the 4spd trans. Thanks Mike, I will make sure I check first.

[Mr.Dean_Yates]

so i can mount a ka24de trans to an l28? :w00t:

[Zendar]

with some work yes

[datzenmike]

One of which may be a change in driveshaft length.

[Stupid_fast]

My opinion: The 240sx 5spd will work better with the stock 3.90 rear diff, because of the lower first, second and overdrive. If your going to change the rear diff gear to 4.11 or lower, the 280zx trans will do just fine. Maybe someone else can testify to the usability of the 280zx gear set with a stock 3.90 rear diff...

 

280zx

1st- 3.062

2nd- 1.858

3rd- 1.308

4th- 1.00

5th- 0.864 ('78-79)

5th- 0.773 ('79-80)

5th- 0.745 ('80-83)

 

 

Personally, I ended up choosing the late close ratio ZX box over the 240sx box. I'm going with a 4.375 rear end to make the gears even closer. This ends up with more desirable gear spacing across the whole range, especially for Motorsport use.

 

Be noted, the ratio for the ZX you supplied is not completely correct. the 78-80 box has 3.321 1st, and 2.077 2nd. The LATE 80-83 'close ratio' box has the 3.062 1st and 1.858 2nd. The 5th gear ratios are correct.

 

I have one early ZX box, and with a cammed L20b its annoying. the 2nd-3rd shift is way too tall.

 

 

I'm curious how well the 240sx box performs in these cars, also the aftermarket short throw shifter options are a great bonus.

[KlassicMotion]

Yeah, I've noticed that depending on what source you find, the gear ratios are listed diffently for the 280zx. I will make the correction in my original posting.

 

I've got rear diffs in the stock 3.90, 4.11 and 4.44. I thought I would try each to see what difference it makes.

 

I just really like the feel of the positve engagement on the 240sx shifter over the "magic wand" feel of the 280zx shifter.