L4N71B (OD AT, 1983-84)

#1

[For those just tuning in, Overdrive Cancel function is explained more fulling five pages downthread, in this post. You will want to keep that in mind as you read though the following pages of speculation. ALS]

GlenLloyd wrote: I was looking at the tranny section, do you have any idea off-hand what would be involved in adding the OD trans...electrically that is? I see that it has a disengage switch much like my dodge van. I wonder if that circuit is present in the 82 harness...my FSM for 82 has a very bad electrical layout and to be honest I haven't looked yet either. Also...is this the only item that you think would need to be added, since essentially it is just another 3 spd. auto?

The '82 harness definitely does not have provision for the OD Cancel switch or OD solenoid on the AT.

I am definitely confused about the function of the switch. In one diagram it looks like it needs to be ON to allow OD function, in another it looks like it's ON to cancel OD. I've never figured it out. I have an OD console switch from an '83 gasser out in the back of the wagon, and I think it just says "OD". And there's a light in it.

Reading the 1983 Owners Manual (pg 42), it says:

The overdrive control switch is located on the center console. To turn on the overdrive control switch, push the switch in. The light will go on when the transmission is upshifted to overdrive. When the vehicle is accelerated by operating the "ACCEL" set switch of the cruise control, the transmission is shifted down to 3rd gear even when the overdrive control switch is turned on.

That sure implies something, but I'm not sure what. Just because you push the OD switch to the "ON" position does not mean that it electrically provides power to the OD solenoid. I've run into that many times. In short, it's unclear to me the principle of operation, though I could draw you the circuit diagram in my sleep, it's not complex at all. I suppose I could go fetch the junkyard OD switch and do a continuity check of it to determine mode of operation, if you're really interested and if we need to know the answer definitively.

In any event, it would be very easy to add one wire to the OD Cancel solenoid and a switch somewhere, but it might not even be necessary, if it's a Cancel switch. Depending on your terrain, you might never need to manually cancel OD, and you could just wire the solenoid to switched 12v (if it's an enable solenoid, as in Ford A4LD OD, which I have in my daily driver and have had to extensively troubleshoot, including having to replace two driver transistors in my ECM!), or a disable solenoid (just leave it disconnected).

The larger problem is that I don't think that the OD trans can be backfit into the '82 and older chassis. I bought and own an '83 L4N71B from a gasser that I think will bolt up to the back of the LD28, but when I had my wagon up on a rack, I rolled the '83 AT under it, and took some measurements. The rear crossmember is in a different location but could be handled. The trans' overall length is quite close. But the back of the OD trans is fatter, and I don't think there's enough clearance in the trans tunnel.

There was, about four months ago, a fellow in Kansas who was quite rude in email, who was selling a "Nissan diesel AT" on eBay. Starting was $80 or so, quite reasonable, and I was all set to bid on it, the shipping was about $120 to me, but then I started asking him about details. I already have a gasser L4N71B; what I wanted was a real diesel version. I have the Nissan Parts Catalogue (as I know you do), and many parts are different part numbers, between the gasser and diesel versions. I'm pretty sure that the gasser version will bolt up, but will it shift right?

Anyway . . . when pressed, this eBayer insisted that he had had this L4N71B in an '82 Maxima. He also insisted that this was a "diesel" transmission, but couldn't cite its provenance and was rude when I pressed him on it. It didn't sell. I do not know if he knew what he was talking about, but I figure I'd better pass along the info, because you'll want to know both sides of this issue before you start.

If you pursue this angle (putting an L4N71B in your '82), I'll be quite interested to know how it fits. You pay shipping, I'll loan you my '83 gasser AT

. Shipping that bugger wouldn't be cheap though, so I'm just kidding. I don't need that trans for a couple of years yet at the earliest, and I'm still really looking for a diesel version, but externally the gasser & diesel versions of the L4N71B are the same.

I just added a few lines about transmissions in the FAQ.

#2

Al
Thanks for all the info, I'll have to do more checking before I take on this project, but I have found several candidate transmissions, one that's not too far from me too. I would like to get one without shipping because of the weight, and also because I would like to compare undercarriage items on the donor vehicle, as well as perhaps obtain the parts of the harness that I'm lacking. Certainly Like you I would rather not invest the money in a unit that didn't come from the LD28.

The OD switch issue sounds like my Dodge van in a sense. But in the case of the Dodge the OD is always on until you engage the switch, at which time the small like in the button says "OFF". I don't drive in town simply because I know that 1) the OD actually does engage or 2) the converter lock-up engages...not sure which. I have known too many of these Dodge OD trannies that have failed and so OD stays off until on the freeway.

I'll pass on more info as I become more familiar with the switch to OD situation, and solidfy a donor trans.

SA

#3

Al
I've been looking at both the 82 & 84 FSM and from the looks of it, and granted this is just from the visuals nissan provides, the difference between the two transmissions is the inclusion of the OD unit behind the bellhousing and a shorter tail housing. In essence what happens is the main body of the trans gets pushed further to the rear of the vehicle.

From your comparison on your car do you think this makes sense, or did it look to you like there was actually a difference between the main trans case on your two units?

Thanks
Steve A

#4

You've exactly nailed it: the OD unit is about 8" long, and Jatco shortened the extension housing by about that much. It didn't appear to be exact, but pretty darned close. The crossmember mounting is in a different place too. And the ass of the transmission gets larger from all this manoeuvring.

Oh. I just re-read your question. I really can't say if the main case is different or not, I wasn't looking at the same "side" of the transmission (bottom of the 82's trans vs the top of the '83).

If it's of great interest to you, I can pull the trans out of storage far enough to take better measurements of the case seams, and some pictures. It's on a piano dolly under a table in the very back of my storage unit, would take about fifteen minutes to get out far enough to work with. I can do that after the 29th or so.

#5

Hi: I am a new member, have too many maxi diesels to count. My experience with maxi transmissions is this: The overdrive transmission is weak and if you live in an area that has roads with truck passing (slow) lanes, you will come to regret having it. The 82 maxi automatic is the best for around town. The five speed is the best for highway. I took one of my five speed cars and put the 82 auto differential (3.36) in it and it is really "long legged". The five speed car has a 3.55 ratio and the OD auto has 3.73. One of my 83 OD auto's has been slipping since it had 105K and now has 157K. When the torque converter locks up at 38MPH it will slip if you have too much throttle on it, and when I slow down past 38 it will slip until I reach 35MPH when the torque converter unlocks, then I can speed back up above 38 if I need to. The OD torque converter is way more "freewheeling" than the 82. (much like an old Dynaflow Buick tranny was in the 50's)(Dynaflush they were nicknamed)

Being an auto mechanic I tend to see the shortcomings in cars, and they all have them, although if everyone had a Maxi diesel, I would be like the Maytag repairman...twiddling my thumbs.

I put oversize tires on everything I have. The Maxi's get 195/70r14 on the front, and on the rear 225/75r14 on the 82's and 215/70r14 on the 83 OD auto. With the large tires on the back it is like halfway towards the OD. In States that have annual inspections, they would probably not "allow" a tire on the back to be more than 2 sizes different than the front.

I "have" about 25 or so Maxi Diesels.

My Dad has 3, a customer has 3, My brother has 2 on the road and about 8 parts cars, I have 7 roadworthy and 5 parts cars. My first one came along in 1987 from an auto auction (maybe 5 or 6 total) and the rest from newspapers etc.

Hope some of my observations help!

#6

Hi, correct me if I'm wrong but do you also own a tractor repair business? I think I know who you are because I visited an owner of many Maxima diesels, along with two Datsun diesel pickups who lived in Elkton, MD. If you can't remember me, I was a young guy (19) that drove a 1982 Chevy LUV diesel pickup painted orange. I live in Glenville, PA and also own a 1982 Maxima diesel sedan. The main reason I came to visit was to check out your Datsun diesel pickup that was painted yellow and you let me test drive it. Anyway, welcome to the site and glad you joined. Hope to talk to you in the future.

Salvy

#7

Salvy:
Really close, My brother Dave has the yellow Nissan diesel, and has the tractor parts. He has the tractor show in September also. I live ten miles away and have my own little Maxi Fiefdom going on. I was just invited to this site today by ASAVAGE (saw me lurking around ebay buying up a Maxi diesel alternator). Yep, we got the Maxi diesel sickness real bad. I had a Nissan diesel pickup for about 3 weeks (got it from an auto auction) and sold it because it just didn't give me the "feel" I was looking for. I have a Maxi sedan 5 spd and it had plenty of "go" and would roll along at 75 if you felt like it. The pickup would go 60... but it just gave me the "feel" that it really only wanted to go 50. This same sedan has a 3.36 rear (came with a 3.55) and has 225/75r14 tires on it. It likes speed, got me a ticket,

on Interstate 68 towards Morgantown WV, going 86.1 MPH going down a long hill to get up the other side. Bear was hiding under the bridge.

"Rollscanardly" Rolls down and can 'ardly get up the other side.
I have a Nissan diesel pickup that has no cab roof. The guy I bought it from said his friend and he were at a shopping mall (having fun) putting the truck into a slide on the wet pavement, but hit a seam in the asphalt and it flipped over. (saw too many episodes of Dukes of Hazzard) Makes a great motorized wagon to go back in the woods to get firewood. (like my own oil well in the woods without drilling)
I saw your signature from near York and was wondering if you are "holding up your end" out there, grabbing up whatever comes along...
Wayne

#8

Wayne, at least I was close enough. When I took a visit to your brother's house he did tell me about you and did say you owned a diesel pickup with no roof. Actually, right now I'm looking for a used SD25 diesel engine to buy. Want to drop it in a Nissan 720 pickup with no engine or trans. Do you know of any diesel vehicles in junkyards local to you in Elkton? Not sure if you would recall them, but would you know where any 83-86 Nissan 720 cab and chassis dual wheel trucks are in MD/PA? Nissan came out with a cab and chassis back in the mid 80's that had a factory dually rear end. Bud wheel system with 4 rims in the rear. A nice looking little 1 ton truck is what you could call it. Also, right now I'm looking for a good, used radiator for my 82 Maxima diesel with automatic trans. Would you have a spare radiator that is used, but works almost like if it were new? Thanks for the reply.

Salvy

#9

diesel-man wrote:I put oversize tires on everything I have. The Maxi's get 195/70r14 on the front, and on the rear 225/75r14 on the 82's and 215/70r14 on the 83 OD auto.

Diesel-man, how do you get the 195/70r14s on the front not to scrape when climbing driveway entrances at steep steering angles?

#10

Salvy:
I've already bought most of the diesel cars up. I don't get around to many salvage yards anymore. There were never many of the SD25's around. Not that I dislike these trucks, but I just personally think a Dodge diesel pickup could do twice as much... I have a 1996 dually 5spd, 3.55 rear, 2wd, cap and I get 26.5MPG on a trip carrying about 1000 lbs driving up to 65 MPH. Done it a lot of times, not just freakish wind pushing me werever I go. Now if I had too much time....I would put a 3.9Turbo Cummins in a Dodge Dakota or a similar size truck. Anyhow, to each his own. There was a Nissan SD22 on ebay last week Item number: 8024795361

Dave has more parts cars over there than I have. Mine are all together yet. Are you sure that it is the radiator? My Dad's 83 wagon has most of the fins gone, with just the tubes left. The thermostat has a widget with a spring stuck to the bottom. My wifes car runs @ 3/4 all the time Summer/Winter. Changed the sensor, same thing. Fan clutch? If it freewheels all the time, my trick is to split it in half and center punch the shaft. (you have to keep it level so the fluid doen't run out.)

#11

Welcome to the fold!

diesel-man wrote:Hi: I am a new member, have too many maxi diesels
to count . . . . My Dad has 3, a customer has 3, My brother has 2 on the road and about 8 parts cars, I have 7 roadworthy and 5 parts cars.

Whew! That's a larger grouping of LD28s than I've ever heard of before. Out here on the Left Coast, I rarely see them. I searched for two years to find my '82 wagon, back in '97.

My experience with maxi transmissions is this: The overdrive transmission is weak . . .

Hmmm. There are so few of the '83s with OD around that I'd not had any feedback about them. I have an '85 Parts Catalog for the 910 (810) series, and it lists a lot of parts different internally for L4N71B for the LD28 than for the L24E. I haven't looked, but I assumed that the addition of the OD unit (between the bellhousing and the main case) didn't afffect the guts of the first three gears.

At some point, I'm planning on putting one of my LD28s and a L4N71B into an old wagon, probably a Ford Falcon, perhaps a Dart or Valiant wagon, or even a Rambler or Studebaker, if one comes along. The size of the LD28 + L4N71B makes it a nice swap.

When the torque converter locks up at 38MPH it will slip if you have too much throttle on it, and when I slow down past 38 it will slip until I reach 35MPH when the torque converter unlocks, then I can speed back up above 38 if I need to.

How odd. My L3N71B (82) locks the TC at 37 MPH too. The trans is quite solid shifting, though I liberally use the '2' position to be able to launch at full accel but not rev up so high for the 1-2 shift. Putting the trans in "snow mode" (manual '2') makes the upshift when I want it. Never any slippage here . . . but I have kept the AT oil changed, used to have a flushing machine and know how to use it.

The OD torque converter is way more "freewheeling" than the 82.

As in higher stall speed? Or less engine braking?

Again, welcome to the brethren, and with all those parts in your backyard, I definitely want to be your friend

#12

diesel-man wrote:The thermostat has a widget with a spring stuck to the bottom.

Bingo.
Salvy, check out Philip's excellent post on a similar issue with the SDxx diesels.

I just looked at NAPA online, and while their THM std and premium line of tstats are std construction (THM 536080 shown):

. . . take a look at the Beck-Arnley ones:
(BA 1430628)

(BA 1430354)

Because so many parts listings have the std construction thermostat listed, if the LD28 needs the bypass blocker (I do not know off the top of my head if it does for certain; the '82, '83, and Parts Catalog pics are inconclusive), then the lack of it will definitely impact circulation to the radiator.

HTH

[later]Member LD28 Owner states that he believes that the bypass blocker style thermostat is necessary.[/later]

#13

As in higher stall speed? Or less engine braking?

Higher stall speed. I have 3 '83 Maxi diesels w/OD. For flat ground they are wonderful, I'll never take another one much more than 50 miles West of Baltimore. Once the torque converter unlocks the engine speeds way up (a lot more than an 81 or 82) on a hill. I came back from Cincinnati OH (end of January of 2001) with a carload of stuff I bought off of ebay, on Interstate 68 which has a 7 mile hill (with a truck slow lane) and I was just rolling coal to keep speed up as long as possible on all the hills, otherwise it would come down to 25mph. I even could smell a little hot oil (transmission) from the torque converter slippage as well as the temp creaping up. (snow on the sides of the road) I think it was 20 hrs out, finding the place, loading up and coming back. In a pinch a crescent wrench (craftsman) makes a good hammer.

addition of the OD unit (between the bellhousing and the main case) didn't afffect the guts of the first three gears.

There is the problem. I think that they must not have beefed up the hydraulic pressure to the high gear clutch, yet it is under more of a load since it has the overdrive. Like having more horsepower and the manual clutch slipping on any type of car/truck.

Thanks for finding me on ebay and inviting me over!

#14

diesel-man wrote:Thanks for finding me on ebay and inviting me over!

You kiddin'? Who else could I find who can actually compare the difference in the torque converter on an '81, '82, and '83, because they own and drive all three, and know what a torque converter is??

Wayne, you are a find! Stick around, OK?

#15

asavage wrote:I am definitely confused about the function of the switch. In one diagram it looks like it needs to be ON to allow OD function, in another it looks like it's ON to cancel OD. I've never figured it out. I have an OD console switch from an '83 gasser out in the back of the wagon, and I think it just says "OD". And there's a light in it.

Reading the 1983 Owners Manual (pg 42), it says:
. . . The light will go on when the transmission is upshifted to overdrive. . . .

I still aren't driving mine, but I did find some better info on this, and I did ohm out the spare OD switch I've got.

First, a link to the original 1983 FSM page AT-13 & AT-14.

Those are wiring diagrams for the OD Control System, but they contain both the gasser & diesel diagrams married together with callouts, and you really need crayons to follow them. For ease of use, I PhotoShop'd out the gasser stuff in the copies below, and this makes it a whole lot easier to follow.

(click on diagrams for larger version)

It's clear now, both from the Owner's Manual description and the circuit diagram, that the OD console switch powers the OD "Cancel" solenoid when the switch is in the "ON" posistion. That really makes the OD "Cancel" solenoid an OD "Enable" solenoid, and without power to that solenoid, you get no overdrive.

The little light in the OD switch is grounded by the OD Indicator Switch in the trans, and if I read it correctly, only lights up when the trans has actually got hydraulic pressure to the OD unit (and at bulb-check time: key on, engine off). Can one of you who is driving an AT 1983 confirm that last?

================================================

Steve, I was down where my gasser '83 L4N71B is stored tonight, and I snapped a picture. I know, the lighting's bad (I was in there with a flashlight). If you want better pics & measurements, let me know and I'll drag it out from under the bench it's under and try to do a better job.

(click on any image for larger)

Compare it to a 1982 280Z turbo gasser 3N71B picture I happen to have (the picture, not the trans; this trans is for sale on seattle.craigslist.org/pts for $45 right now):

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