L4N71B Transmission into Early 10-Series Car

[zerow]

[Note from author: This post originally started as a question regarding where the vacuum line to transmission on ANY automatic equipped Datsun. It has evolved into (what I feel is) an upgrade for my needs with my Datsun after my injury in Iraq. Should you need to do an upgrade like this for any reason, obtain all parts from the donor car first, and then proceed with the upgrade as necessary - zerow]

 

I need to see the pipes!

 

I *think* I have my manifold to transmission vacuum hardline, but, I am not sure... :mellow:

 

Any late 10 series owners with the 3N71B transmission, I need pics of the engine bay where the pipework comes up from under the car. And some extra credit points for those who can post pics of where the little bugger mounts to the car.

 

610s preferred, but a 710, late model 510, or 810 will also work. Thanks for the help in advance!!!

[datzenmike]

The hard line comes up over the auto bell housing and connects to the intake at the fitting that the brake booster gets it's vacuum from. This is for the '74 710 later years may be different but likely the 610 is the same. I have another vehicle where the hard line taps into the brake booster hose at the one way valve. As long as you have manifold vacuum on that line and it goes to the auto tranny it will work.

 

 

Here's another pic...

 

 

The hard line mounts to the left center portion of the transmission. Vacuum diaphragm on left (hose off) and electrical down shift solenoid to the right.

 

 

... how many points did I win?

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[zerow]

Datzenmike, I knew you would have the answer. And I will have an answer for everyone who has ever thought of the L4N71B trans in their older 10-series car. More to follow on that here in the next month or so.

 

50 points for the diagnosis and an additional 100 points for the very detailed pictures. You are living up to the KING RAT moniker everyday :thumbup:

 

I have the tap on the intake manifold. I'm good to go there. My only concern is that it is not the correct angle

(edit: I need to put another 1/2 turn on it for the "correct angle")

 

My car had automatic, and this part complexes the situation. If I did not remove the plumbing, and I was obviously keeping the auto, where did it go??? Does it mount to the pan, the firewall,...both???

[datzenmike]

In a pinch you could run arubber hose from the manifold to the auto tranny. A metal tube like a brake line would also work... be inventive. All you need is a vacuum supply, how it gets there is up to your imagination. It looks like in the picture there is a small support bracket on one of the top tranny mounting bolts that holds the hard line and in the bottom picture there is another just to the left of the diaphragm.

 

zerow did you say L4N71B??? I have one and am toying with the idea too! I also have the automatic from a turbo 280zx. I'm hoping to swap the main body from it behind the L4N71B or failing that swap the guts in. Why? Because the 280zx turbo had lower 1st and 2nd gears than the usual 3N71B for faster take offs to quickly spool the turbo.

 

280zx auto... 280zx turbo

1st.. 2.458............ 2.842

2nd. 1.458............ 1.542

3rd........... 1.000

 

 

Isn't the 4N71B an inch longer???

[zerow]

In a pinch you could run arubber hose from the manifold to the auto tranny. A metal tube like a brake line would also work... be inventive. All you need is a vacuum supply, how it gets there is up to your imagination. It looks like in the picture there is a small support bracket on one of the top tranny mounting bolts that holds the hard line and in the bottom picture there is another just to the left of the diaphragm.

 

zerow did you say L4N71B??? I have one and am toying with the idea too! ...

 

 

Isn't the 4N71B an inch longer???

I found my actual hard line for the transmission, so I am good there. There are some brackets on it (attached) but one has slid around on the line, so I had no idea where it attaches in relation to the rest of the car. I now know which direction it is meant to go based on the pics you posted.

 

Yes, I did say L4N71B! I have been sitting on one for the 610 for a year and a half now. Here is what I collected from the junkyard to make this thing work:

1) Transmission (sourced from an '83 Datsun/Nissan Maxima)

2) Flex plate and torque converter (same car) (funny story about that car: It had a low mileage used Japanese motor in it. The motor? An L20A. So I also got the 6 bolt correct flexplate FTW)

3) (The key ingredient) The driveshaft from said Maxima. The Maxima used both the 3N71B (standard automatic) and the L4N71B (optional automatic) I figured that since I would need the driveshaft to have one custom fabricated later, I might as well grab it from the donor car.

 

I brought all of this home and sat everybody side-by-side for comparision. Yes, the 3N71B is 1 inch shorter than the L4N71B, but the driveshafts that I have ('73 610 and the '83 Maxima) are also 1 inch (+/- 0.125") different. The 610 driveshaft is 1 inch longer than the Maxima, so I figured I'm good to go. The flange at the end of the driveshaft appears to match as well, so it seems to be even more painless than first thought. The only hitch has been the mounting. The Maxima has "halo" mounts that bolt to the sides of the trans tunnel whereas the 3N71B is bottom mount, and that is the development currently underway that should be completed by the end of the month :)

[MicroMachinery]

Keep this up to date Zerow. I'm starting to consider NOT changing my 610 from an auto to manual(keeps me more respectable ;) ). If I do leave it an auto, I'm going to want to upgrade the trans to something a little more fun. I'm interested to see how this turns out.

[datzenmike]

Shit! I got mine from an '84 Max Goon and don't have the drive shaft. Well crap, How was I to know I would own a 710 2 years later???? Hmmm the goon was a solid axle anyway and I think the drive shaft was two piece.... my 710 is one piece.

 

Wonder if 1" will matter. Maybe shove the motor ahead 1"?

[zerow]

Shit! I got mine from an '84 Max Goon and don't have the drive shaft. Well crap, How was I to know I would own a 710 2 years later???? Hmmm the goon was a solid axle anyway and I think the drive shaft was two piece.... my 710 is one piece.

 

Wonder if 1" will matter. Maybe shove the motor ahead 1"?

Don't move the motor forward the 1". Remember: the driveshaft is completely different between the two transmissions. The L4N71B has a meatier tail flange than the 3N71B. I figure the 1/8" give or take can be taken out at the tail of the transmission. The driveshaft slides past splines for almost 1 3/4 inches, what it going to hurt if it is only 1 5/8"?

 

Now, my only question, and I think the answer may be apparent: Are the ends at the differential different between the IRS diff in the 610 and 810 versus the live axle diff of the 710?

[datzenmike]

I'll bet they are the same.

[MicroMachinery]

 

280zx auto... 280zx turbo

1st.. 2.458............ 2.842

2nd. 1.458............ 1.542

3rd........... 1.000

 

 

Isn't the L4N71B a 4-speed? OD is 0.686 from what I've read.

[zerow]

Isn't the L4N71B a 4-speed? OD is 0.686 from what I've read.

Correct. The overdrive ratio is lower than the 5th gear in the 5 speed manual trans

[datzenmike]

I'm hoping to use the L4N71B but swap the lower 280zx turbo gears into it. It will still have the same 1 to 1 3rd gear and the insane high over drive for cruse. Here's a picture of the 3N71B auto in front and the L4N71B behind it. The 4th gear over drive is the small addition between the bell and the main body.

 

 

The turbo tranny also has several extra clutches and plates than the non turbo 3N71B and modified shift points. The pressure regulator and the pressure modifier valves can be shimmed to increase the firmness of the shifts. Chirp second anyone?

 

 

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[MicroMachinery]

I want that. There was a guy on here a while ago trying to sell one. Apparently the car didn't actually belong to him and it got towed before he could take it out.. :no:

[MicroMachinery]

... wait, so the 280zxt auto is still the 3N71B. That makes more sense now; I was confused about what Mike was saying about trying to swap the guts over into the L4N17B. I was under the impression that the ZX trans was a 4spd. Nooooow it's all starting to make sense :rolleyes:. As I haven't played with or even thought about getting into the autos, this is very interesting and educational.

Mike, do keep us posted on what becomes of trying to make the 2 into 1 trans. I may very well follow in your footsteps. :)

[datzenmike]

Yep all 280zx autos were 3N71Bs. The 280zx turbo was beefed up a bit with firmer shifts, lower gears to rev quicker for the turbo and a higher stall speed torque converter... again to get the revs up higher quicker. I don't have the torque converter with the turbo tranny but can't use it with the 4N71B anyway. The 4N71B has a unique converter that only works on it.

 

I'm hoping to combine the low speed take off and quick revving with a top 4 speed over drive capability.

[Skib]

... wait, so the 280zxt auto is still the 3N71B. That makes more sense now; I was confused about what Mike was saying about trying to swap the guts over into the L4N17B. I was under the impression that the ZX trans was a 4spd. Nooooow it's all starting to make sense :rolleyes:. As I haven't played with or even thought about getting into the autos, this is very interesting and educational.

Mike, do keep us posted on what becomes of trying to make the 2 into 1 trans. I may very well follow in your footsteps. :)

 

 

ya missed out :lol: I gave that ZXt trans to Mike at Canby...... saved me a trip to the scrappers :rofl:

[datzenmike]

I had heard of them and was hoping to get one from a KA or VG and put an L bell from an earlier 3N71B on it but at a glance I don't think the 4N71B bell is exactly the same. It looks slightly shorter front to back than the 3N71B. When I take them off I'll check. This leaves only one option... you would have to get the L4N71B from a Maxima in order to have the proper L bell. AFIC it's the only L series made after '83 when the L4N71B was introduced. Mine's from an '84 goon.

 

Maybe this weekend I'll pull then off and compare. Shure would be easier if they were the same. One other thing.... the flex plate it totally different to fit the very different torque converter. Don't loose that plate, earlier 3N71Bs and L3N71Bs with the torque converter lock up are different.

[datzenmike]

Well partially to mostly tore down the turbo auto for the internal parts. Had snap ring pliers but they worked the wrong way so used screwdriver. That and 10mm 12mm and 14mm sockets to do all this damage! Do not intend taking every part... apart just remove the oil pump, forward clutch, front planetary gears, sun gear, rear planetary gears. What I want are the lower gears and the 7 low/rev brake driven plates versus the 5 in the regular 3N71B and the and the 4 versus 3 in the front clutch. The rear clutch are 6. In comparison the 4 cyl or earlier 3N71Bs had low /rev 3, front clutch 3 and rear clutch 4.

 

 

 

 

 

 

 

 

 

 

 

 

 

Tail stock removed looking forward.

 

 

I may have much of tomorrow off so will pull the L4N out of storage and try to dismantle it.... maybe.

 

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[MicroMachinery]

Nice. Keep em comin

[datzenmike]

L4N71B teardown:

 

 

 

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[datzenmike]

Well, after comparing the gears in the L4N71B and the turbo 3N71B I have to say they are the same, with the lower 1st and 2nd. This 4 speed is from an L24 Maxima wagon with a 3.70 ratio so it could use a little help to get moving. Well no harm done and some interesting info learned.

 

I have it mostly assembled but for the control valve assy. which I am going to modify for firmer shifts and take some of the slush box feel out of it.

[zerow]

I came across this Level 10 upgrade for the L4N71B when I researching the transmission as a possible candidate for swap. While you're in there, and if you have the knowledge/confidence, you can make the upgrade:

[MicroMachinery]

Do you guys know if the Wagon driveline is the same length as the Sedan?

[zerow]

Do you guys know if the Wagon driveline is the same length as the Sedan?

For the 610?? Two different animals, my friend. The sedan and coupe have a single piece driveline, the wagon has a two piece with a center carrier bearing.

 

As for the Maxima, I do not know.

[datzenmike]

I came across this Level 10 upgrade for the L4N71B when I researching the transmission as a possible candidate for swap. While you're in there, and if you have the knowledge/confidence, you can make the upgrade:

 

Wahahaha I had that bookmarked!!!

 

 

Do you guys know if the Wagon driveline is the same length as the Sedan?

 

 

If you mean the Maxima, the goon and the sedan both have two pice d/s.