'78 280Z auto trans-how reliable and durable

[carperson]

How reliable and durable are the '78 280Z auto transmissions? Anything special to check or look-out for?

[beandip]

I have a '73 with an auto and wondered the same thing . Acording to my trasmission man and several others the openion is that they are bullet proof . The fiest thing I was going to do when I bought my Z was pull the auto and go with a 5 speed. I have driven the car three years and have decided to no way , change. I have insted dropped in a moderatly built '82ZX engine. I personally like the auto tranny. Gary

[PrOxLaMuS©]

my automatic transmission lost 3rd gear at 120,000 miles...

I did "manually" shift it though.. so it probably didn't like it... which is why it completly lost 3rd gear..

so I swapped in a 5-speed.. best move I have made yet with my Z except for buying the car

[First Gen Z]

I've used both the 3n71b and the 4n71b and never had a problem with either. They are almost a clone of the Chevy THM350. The 4n71b is no more than a 3n71b with an overdrive added to it. I've added a larger boost valve to the 4n71b and it seems to shift a little better.

[chickenwafer]

auto tranys have always been a little weaker than manual ones, especially back in the '70's. But newer autos are just as strong.

First Gen Z- are you sure they're a clone of the Chevy Turbo 350 auto? Those transmissions are nearly bullet proof, and I know Datsun/Nissan doesn't use an american designs in there parts. In fact, Datsun/Nissan transmissions are nortiously weak.

Dave

[beandip]

There are two different automatics in the early Zs the A wich is in the '71 and the B that is in the later cars . My understanding is that parts for the A are no longer available, wile the B is still rebuildable. They will stand up to some abuse but are not unbrakeable.

[sblake01]

IIRC, the early auto trans was built by Borg Warner and the rest were built by Nissan. My ex had a 71 510 with a Borg Warner automatic trans and later had a 80 510 with a 'Nissanmatic' as it was reffered to in the literature.

[TomoHawk]

My 78 has the 3N71B transmission.

The 3N71B transmission was also used in the Nissan small trucks of the time. That would make me believe it is more durable than you'd think. I had mine rebuilt after 105,000 miles when I couldn't get any reverse gear.

1st Gen-

It's not that easy to swap in the 4N71B transmission. You need to use the bell housing and torque converter from a Maxima. (this info from Hybridz.org) http://forums.hybridz.org/showpost.php?p=368587&postcount=11

The oinly issue I have with mine is that it doesn't kick down every time when you put the pedal down to the floor, but somehow the L28 has enough torque to go anyway.

thx

[First Gen Z]

chickenwafer- I've been rebuilding auto trans for 30 years. All of the early non electronic trans are remarkably the same when you get them apart and compare the pieces. The 3n71b is not an exact clone but it is very much like a THM350.

TomoHawk- You are right about the 4n71b being a difficult swap. I've done it with great success, however. It's VERY labor intensive. Also requiring a knowledge of how transmissions work and how to wire the electric components. Fabrication skills are also required. The 3n71b and the 4n71b are built by JATCO. Japan Transmission Company. You may want to check for power at the kickdown switch. It's located on the accelerater pedal linkage inside the car. Also check the kickdown solenoid. You can apply 12v directly to it and listen for a click. No click- no good.

[TomoHawk]

Why did you mention electronic components?

The 4LN71B has hydraulic lockup, ans the 4EN71B has electronic. Do you know how to bypass all the sensors and stuff? I've been researching this swap since I got my 78, and I'd rather have the electronic lockup so I can turn it on when I get on the highway, and it shouldn't disengage everytime I pop the gas pedal, like the one in my Escort does.

I did check the kickdown switch some last summer. It clicks when you push it, and the switch does work, but I didn't know there was power going through it. I will have to measure the volts- probably not 12 (corroded connectors?) The solenoid will click sometimes, but not always. Not much info on the wiring for that. I asked the trans guy to check it and he thinks the modulator might need a tweek. (to get the shift points a little lower).

thx

[sblake01]

I had forgotten about 'JATCO'. I remember seeing that name somewhere when buying parts for the later 510(A10). Kind of off topic but what I remember is that the late 510 (78-81) was kind of like a '510ZX' when compared to the PL510 (68-73).

[First Gen Z]

In my 4n71b swap I specifically used the early version of that overdrive trans just for the reason of trying to eliminate the electronics. If you swap from a standard to an automatic you have to make wiring harnesses for the overdrive solenoid, the downshift solenoid and the inhibitor switch. The car in question was a 78 280 five speed. Bought from the original owner. It's a very nice unrestored original car. We (my Sweetie and I) have entered it in the last three years Central Florida Z Fests and won first place in our class. I wasn't real thrilled about changing from a five speed to an automatic but it wasn't a good road car. Sixty MPH=3000 RPM. Now it's sixty MPH=1200RPM. And Sweetie really didn't want to shift gears. So, she gets her car the way she wants it and when I get ready to build mine she can't say too much. I didn't use a lockup converter as overdrive does what I need. I did wire the overdrive solenoid to a rocker switch so I can shut down overdrive when I'm doing intown driving.