Automatic transmission?

[dieselhund]

Is this OEM auto trans. on the '81 Maxima diesel, LD28, interchangeable with other auto trannys for the L28 or is it significantly different?
Curious,
dieselhund

1981 Nissan Maxima diesel stn. wagon
1981 Nissan 720 diesel kingcab
1989 Iveco 15-14 tow truck
1980 DB 300 TD non-turbo

[asavage]

You can probably bolt up any gasser or diesel trans to any L/LD engine.

The 1981 AT is the least-desireable of the three ATs available. Read why at the Transmission section of the FAQ.

A cheap retrofit would be the '82 L3N71b -- I *think* it's a bolt-in all around, but that is merely a semi-educated guess, as there are not a lot of '81s around, but lots and lots of '82s. The '83 L4N71b won't fit in the '81-82 chassis without moderate mods (read: chop up the floor pan. Read also the L4N71b thread for good AT info. on that trans.).

[philip]

SNIP The 1981 AT is the least-desireable of the three ATs available. Read why at the Transmission section of the FAQ.

So...

Every year had a different model AT:

1981: 3N71B = conventional 3-spd AT*
1982: L3N71B = 3-spd w/lockup converter
1983: L4N71B = 3-spd w/lockup converter + OD

The L4N71b has an additional planetary gearset ... making it a 4-spd plus converter lockup that requires electronic support to locj the torque converter? Will this transmission also lock the torque converter in 3rd gear under predetermined circumstances or if OD is blocked?

The L3N71b is a conventional 3-spd but ... is torque converter lockup controlled electronically or not? (If all hydraulic, only 3rd gear and vehicle speed above 'x' to lock converter).

On the net, I find many references to Mazda B2200 having the L4N71b.

[asavage]

Every year had a different model AT:

1981: 3N71B = conventional 3-spd AT*
1982: L3N71B = 3-spd w/lockup converter
1983: L4N71B = 3-spd w/lockup converter + OD

The L4N71b has an additional planetary gearset ... making it a 4-spd plus converter lockup . . .

So far, so good . . .

. . . that requires electronic support to locj the torque converter?

As I understand it, it's all hydraulic. On the Maxima (AFAIK) there is a single solenoid that allows one to cancel the OD function. It isn't necessary to have it connected.

Will this transmission also lock the torque converter in 3rd gear under predetermined circumstances or if OD is blocked?

I don't know.

On the net, I find many references to Mazda B2200 having the L4N71b.

And the MPV as well. Actually, there's a whole bunch of vehicles that used it. However, the later ones are electronically controlled to a greater extent and probably do require support electronics. Somewhere, DaveHoos expounded on the function of the later ones. Did you read the L4N71b thread?

[philip]

As I understand it, it's all hydraulic. On the Maxima (AFAIK) there is a single solenoid that allows one to cancel the OD function. It isn't necessary to have it connected.

So ... this non-electronic trans shifts 1,2,3,4, with lockup occuring at a fixed vehicle speed once in 4th.

The OD blocker button prevents BOTH converter lockup AND 4th gear engagement? Then it seems there should also be no converter lockup in 3rd when the blocker button is pressed. ??

Interesting thing in those early non-electronic 4-spd days is that when you let off the throttle, the converter stayed locked while in the subsequent electronic 4-spds, the converter unlocks the moment the throttle is released ... an effort to cushion drive line slop.

[philip]

SNIP Somewhere, DaveHoos expounded on the function of the later ones. Did you read the L4N71b thread?

I tried to follow DaveHoos' L4N71b post. He did not address the normal shift order of the non-electronic and electronic versions.

In my '03 Corolla, the upshift order goes (assuming level ground and <3000 rpm shift rpm)... 1,2,3,4,Lock

If assending a 2% or greater grade and throttling more so that shifts are >than 3500 rpm ... 1,2,3, 3/lock, unlock-4, 4-lock {if engine load lessens).

Interesting feature is the transmission "learns" repeated 4-3 downs shifts in close time proximity result in holding 3rd gear longer ... even while coasting for up to 10 seconds instead of immediately upshifting.

The other electronic behavior is automatic downshifts (grade logic) while applying the brakes moderately (vehicle in 4th gear, above 45 mph). After you release the brake pedal (car now in 3rd), it will stay in 3rd so long as vehicle speed remains the same or increases from the speed at which the brake pedal was released. If the vehicle coasts up to 65 mph, it will then uphift to 4th/lockup. But if the vehicle continues to lose speed after brake pedal release, the transmission upshifts to 4th/lockup.

The whole thing works very well in the mountains!

[HowlerMonkey]

It won't go into overdrive or lockup if you have no vacuum to the modulator.

Mine is a turbocharged gasser and the boost finally killed the modulator to the tune of huge clouds of smoke.

To drive home, I disconnected the modulator and got the behavior explained above.

If you're going to boost, you need the "white dot" turbo modulators.