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datzenmike

Datsun L series auto trans pix

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HF-38 IS 3.889 you are correct.

 

What can I say? I believe you. My info shows 17, 18, 19 and 20 tooth pinions used in the auto yet only one 3.70 rear ratio???? There were some optional tier sizes but not enough for that big a spread. Only 2wd gas engines got the automatic.

 

Well I found references to an auto using a 3.70 and a 3.889 so there are probably more. I haven't become perfect at reading the codes.

 

DSC01097.jpg

 

The K in the MODEL # is for automatic

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HF-38 IS 3.889 you are correct.

 

What can I say? I believe you. My info shows 17, 18, 19 and 20 tooth pinions used in the auto yet only one 3.70 rear ratio???? There were some optional tier sizes but not enough for that big a spread. Only 2wd gas engines got the automatic.

 

Well I found references to an auto using a 3.70 and a 3.889 so there are probably more. I haven't become perfect at reading the codes.

 

Mike I am trying to compile good information for these trucks. FSM Trucks 1976 4.375:1, 1980 & 1985 does not state raio that I can find.

 

Your information has been right on and who knows if these rear ends/transmissions have been swapped out over the years on these odities that I am finding. I know over the years I have swapped lots of parts. I have been told that the early 520 had 5.13's & 4.875's. My 520 FSM only shows 4.875 ratio & I have not personally come across the 5.13's in any thing.

 

As I personally verify or any of you info collected I will update as much info as I can on the numbers I PM'd you.

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The 720 trucks rear end ratios stretch from 3.364 through 4.625, incredible.

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The 720 trucks rear end ratios stretch from 3.364 through 4.625, incredible.

 

I need to go back to the JY and check the ratio on the rearend of the 1980 KC L20B L3N71B that I got the 21 tooth gear out of.

 

Mike you are like an encyclopedia when it comes to Datsuns.

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Would i be able to mate my 3 speed auto transmission to a honda b series motor?

is there a company that makes an adapter or some sort?

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The L4n71b from the 1983 and 1984 U.S. maxima (possibly the 1984 300zx as well) was 4 speed auto with lock-up convertor.

 

It is fully hydraulic shifted so it does not need the tranny controller that you would need if you used a E4n71b but it does have inputs for two simple switch circuits.

 

One is for kickdown and the other is to enable/disable OD.

 

They are available with two different torque convertors in the maxima which would be the 1983 diesel low stall speed and the standard gas engine stall speed.

 

I'm not sure if you can use the 300zx torque convertors (again two stall speed....non-turbo and turbo with higher stall) but it is posible that the only difference in dimensions is the flexplate between L engines and vg engines......still not sure.

 

The turbo transmissions will have more clutch frictions and steels in most, if not all clutch locations and some are seen with 4 planet gears rather than 3 in at least one of the gearsets.

 

If you have a high horsepower L engine, there are at least 4 good donor cars for the transmission.

 

1. the 1984 to 1989 300zx turbo (remember 1985 and later require electronic control unit)

 

2. the mitsubishi conquest/starion turbo (either tsi or esi)

 

3. the mid-80s rx7-turbos

 

4. some australian holdens or nissans with V8

 

Of course, you need to use the 1983 or 1984 nissan maxima bellhousing and most likely the flexplate and torque convertor but I would love to find out that the flex plate and bellhousing are the only thing different because that opens you up to many different stall speed convertors from the super high stall mazda rx7 to the super low stall speed Ld28 equipped 1983 maxima.

 

As far as 3n71b, the 280zx turbo 3n71b is sweet and has a pretty high stall speed convertor as well as a thicker output shaft.

 

The turbo car 3n71b have differences in the shafts inside the transmission with the turbo's sometimes having thicker output shafts as well as the short shaft between torque convertor and output shaft actually have a portion that slides within the other while the non-turbos don't have this.

 

Not sure if the 4n71b 4-speed has shafts mating or not.

 

280zx non turbo 3n71b have same output shaft diameter and outside diameter of the driveshaft yoke that slides in as the fs5w71b 5 speed manual but the 280zx turbo uses a larger diameter output shaft thickness while retaining the need for the same outside diameter of the yoke............outside diameter of this yoke is 35mm for both.

 

Some 4n71b have the same thicker output shaft as the turbo 3n71b but with a larger diameter yoke that slides in........outside diameter of this yoke was 38mm.

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I used an '88 maxima auto shift handle with the switch and cut it down to fit. The OD is activated when there is no power going to the solenoid.

 

The lock up occurs after a certain number of revolutions the driveshaft spins, about 40mph. 3.9 rearend but am going back to the 3.54. With the 3.54 and 3 spd auto I got 19mpg on a trip west, with the 3.9 and 4 spd auto I got 24mpg on another trip west.

 

 

 

ftm005.jpg

 

4spdauto.jpg

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I hope I got this right, from what I've heard here, I won't be able to put the 4spd. auto to a 1600 / 5bolt crank? I will ceck and measure, but if the old flex plate (3spd) is the same other than the holes for a 6 bolt crank, it should be good... anyone done this befor?!?!? help if you can, I really want a 4 spd auto!

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The 3 speed flex platess are different from the 4 speed (besides the 5/6 bolt holes) The 4 speed has a huge fat doughnut torque converter and the flex plate has a bulge in it for clearance.

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Can i use the first generation Maxima auto bellhousing to connect a 240sx 5 speed tranny to my L28?

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No.

 

The automatic has a true removable, bolt on bell housing while on the 4 and 5 speeds the bell housing is part of the front case half containing the gears. Afraid you're comparing apples and orages here.

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Just for reference, the Jatco 3N71B and 4N71B automatics are nearly indestructable torque-wise, with the addition of a shift kit. There is a guy on hybridZ who sells a kit he developed for his own 280ZX turbo, that currently puts down over 600HP and it's a stock transmission with his kit in it. He drag races this particular setup fairly often, and he's NOT easy on the car....

 

Given proper maintenance and a transmission cooler, these things can really handle the HP.

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Probably a Level 10 kit???

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Hello there,

 

My car is a nissan skyline with a L20b engine and 3N71B gearbox.

I'm busy replacing the gearbox but it seems to me the torque

converter sinks awfully deep into the gearbox.

I'm now worried that the torque converter might not reach

the inner axle when I mount the torque converter back to the

flex plate.

Could it be possible that the flex plate is the wrong way around?

 

Is there any way I can post a picture to explain my question?

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If the flex plate is flat it's maybe possible to put on backwards. Some later ones are dished slightly for a locking torque converter.

 

I would look at the starter ring teeth. The wear on the teeth will be to the front of the motor.

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Thanks for the quick reply,

 

It is slightly dished. My question is what side should be engine side?

Its also a second hand flex plate which has wear and slight damage on both sides of the starter ring, so no real clue there.

It looks very much like the one on the right hand side in your picture, where you say we are looking at the engine side.

Mine is mounted the other way around and I wonder if that is maybe the wrong way around?

It would explain a long history of starting problems to me.

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Turned flexplate around. All problems solved. It looks like it was the wrong way around for a while.

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Have read this thread from the beginning and still have a few questions. My 510 has the stock 3N71B transmission in it currently. Discovered today that I have no third gear so I need to swap out the trans. I have located two transmissions, reportedly in very good shape, a 3N71B out of a 280ZX Turbo and a L4N71B out of a Maxima. My preference is to modify as little as possible (mounts, drive-shaft, drive-shaft tunnel trimming, etc). Is there anybody out there that has successfully mated either of these two transmissions to an L16? If so what modifications did you need to make?

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The L4N71B is slightly longer than the 280zx 3N71B by about an inch. BOTH are longer than the 510 transmission by about 5 1/2".

 

The L16 powered 620 had the same length 3N71B as the 510.... about 26" long.

 

Most A series automatics are also 26". I suppose you might use one by swapping your L series bell onto the front of it..

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Thanks for the response. Will the additional length mean the shift lever will come through the tunnel further back for both transmissions or is the additional length in the tail shaft primarily? I really don't want to modify/cut the tunnel. I don't mind shortening the drive-shaft. Looks from the pictures like the L4N would definitely move the shift lever rearward. Not sure about the 3N out of a 280ZX Turbo. Also, I seem to recall that the Turbo trans has some other characteristics that would not make it a good swap for my L-16???

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The tail is stubby or long.

 

510 or early 620 3N71B

72510auto-1.jpg

 

Most other 3N71B autos (bottom) L4N71B at top...

(the shift rod for an L4N71B coulf be shortened to fit the floor hole.

transautotopL4N71B84Maximagoonand3N.jpg

 

The 3N71B turbo automatic was different for sure. It was extremely Heavy Duty, with extra clutches and plates a valve body with modified line pressure for firmer shifts and shift points. Don't forget that this transmission had to shift under full turbo power! The modulator valve was special also. Next was a high stall speed torque converter to allow the engine to rev higher under sudden load on take off and the 1st and second gears were lower allowing the motor to rev slightly higher. Third remained the same to preserve gas mileage. All this was to allow the motor to quickly rev to spool the turbo quickly.

 

My thoughts would be that this would also work well on a much smaller L16, allowing it to take off faster and rev quicker. If you find the shifts a bit abrupt you could always swap your modulator valve in to soften them.

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Looks like I will proceed with the 280ZX turbo trans option datzenmike. You mentioned that the torque converter was different. The torgue converter on the trans I'm looking at is missing so I'll have to source one separately. Long shot, but by chance do you know if the non-turbo ZX trans torque converter can be used with the turbo gear box? It will be much easier to find one than the turbo. I guess the other question is, can I use the torque converter from my failed 510 auto trans in the turbo trans? If so, I won't have to go looking for another one.

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Yes. The difference is stall speed. Use the original one, or for faster acceleration use the Turbo convertor.

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I suspect that it needs the turbo torque converter. This was a really heavy duty transmission and the input spline for the converter is probably larger. I forgot to mention that the out put spline is also larger and your 510 drive shaft is too small. Sorry about that. I had one of these once and the spline is larger for a special larger drive shaft on the turbo equipped cars.

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