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Discussion Starter #1
The transmission in my '83 280 is an automatic 4 speed. 1, 2, and Drive has 2 speeds. My problem is that 'Drive low' only kicks in for about a half a second before kicking to 'Drive high'. I can find no vacume reference in the book that distinguises from dive high and drive low, only drive. Even the factory service book for that year only specifies 3 gears.

Is this quick shift in the upper gears normal?
 

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is it a shift or is it a torque converter automatically locking up?
 

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Possible vaccuum conections are split. Check your auto wiring loom and wire brush all clean. Also , if you haven't chanfed out your current auto filter and tranny fluid for new then its definetly time now to do that. You got dirt in 'er now. Goodluck.
 

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No, your automatic is a 3 speed. What is sounds like is it's slipping going into 3rd gear.
 

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Agree...

the tranny is a three speed, and either it's slipping before engaging, or some lockup device is coming online.

83 had a 3-speed, as did all Z's before...

The Maxima's had a 4-speed overdrive, and if you really DID have a 4 speed, your rpms would drop by about HALF when it kicked in... the Nissan 4-speed O.D. had a .67 O.D., or thereabouts.
 

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Discussion Starter #7
By all means, this is a shift. I say this because the car has down shifted to this mystery gear many times at lower speeds and up hills. I don't know the history of the car nor have i crawled under the car to take a look. But this is not a lockup, or a slip, but an actual gear the the car hits.
 

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If it really has had an overdrive auto installed, somewhere in the car a AT computer was also installed as all the OD auto trannies that could possibly fit were electronic controlled 4th gear.
 

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???

The Maxima Tranny is not electronically controlled, it is purely mechanical, just like the 3 speed it is based on.

Again, unless the engine is running HALF (or nearly half) the RPMS before the "downshift" you DO NOT have a four speed!
 

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Actually Tony, it's a 3 speed hydraulic trany with an electric solinoid controled overdrive on the front that -IS- computer controlled. It's a combination of both.

The later Z31 300ZX's and the RX-7's used this same gearbox. It's NOT "purely mechanical" and if you look, most have some sort of switch that turns the OD on and off that so the driver can decide if they want it to engage or not.
 

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So my thumb is the computer?

???
I do not see any overdrive computer on my Maxima, just a button to flick.

I don't see that as computer controlled.

Though the Z31 does have a tranny controller.
 

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It's an electric OD. It's controlled by an electric solinoid on the OD unit that's bolted to the front of the original jatco 3 speed unit. It's not "mechanically controlled" like the other 3 shifts are. There's a box somewhere in the car than controls the operation of the OD to make it power the soliniod into 4th only after the 3rd gear clutch pack has been engaged.
 

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Interesting...

I used a button.

Now I gotta go back to the junkyard and find the damnable box? Sh*t!

But the solenoid only controls hydraulic fluid to the OD Actuator, similar to all the other three. It just takes that solenoid to actuate it.

Now I gotta flick it when I'm not in top gear...

Waitaminit. I leave the button "on" when I drive, and after third, it shifts into O.D. automatically, hence my assumption it was a mechanical actuation. When I push the button "off", it drops into third.
Is that bod in the car somewhere, or on the transmission physically? Cause I know I didn't transfer anythign but the tranny.

How can this be working?

I'm gonna have to get the FSM back out to check on the circuitry.

I'm using an 83 Maxima Tranny. Is this controlled the same way? I don't have any box, I only have the button.
 

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Get a FSM and look. I can't imagine they would have designed a one year only tranny setup for that car but weirder things have happened.
 

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yeah....

but it was 82 to 84 I believe.
Why they used it only in sedans, and not the whole line is a mystery to me. Guess the response with that .67 OD on a stock engine was not that "sporty"...

Than again, the starion four speed for the turbo is internally much more beefy than the Maxima unit, similar to the turbo three-speed in the Z. So maybe they didn't go cross-platform due to having to build a stouter tranny for the turbo, so they kept it out of the line altogether.

But I pulled it, and outside of the reverse, N Safety, and traceable wires, I didn't trace anythign to any silver box modules. I will have to get out the FSM for the Maxima next time I get over to service garage, and check it out.
 

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You may be right, I always assumed the OD was totally electrically controlled but that solinoid may just turn the OD on or off and hydro valves control the shift point? The "computer" the Z31's use might have just been for emmisions/performance reasons? The 85's and up also had a lockup converter so needed a computer to control that.. I know those won't go into OD until a certain temp is seen etc. The tranny computer for the OD is conected to the main ECU computer and also uses a variable TPS sensor to get throttle reading etc.

Let me know (post a new thread) if you find out this is a full hydro with the OD soliniod just for kicking it out of OD. Like I said I always just assumed the OD was totally electronic and the other 3 speeds were hydro controlled.
 
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