280ZX Wierd Tranny Trouble HELP!

[danman_83]

Hey,

I got a 1980 280ZX about 5 years ago, and when I first got it, the transmission broke, so i took it to Aamco(mistake number 1) and they fixed it, and about 4 years later it broke again...

Whats happening is that when I drive it a little bit hard or if I drive it normal for about 3 weeks, I will turn the car off, leaving it in first gear.

Then when I start the car, I put it in Reverse, but the transmission gets stuck on the first gear rail. So Reverse locks up the tranny, won't let me go anywhere, and stalls the car. From there on out, neutral is first gear. The only way to fix the problem it seems is to pull out the transmission, and as soon as the mechanics get it on the bench and pull the tail housing off, the rails de-latch themselves. It has also happened before on the fourth gear rail. I've replaced all the parts in the tranny and gotten two seperate new(used) tranny's and it has happened to all of them within a few weeks. The car has been in and out of the shop for 8 months now because it keeps happening and it's absolutely baffled all the transmission guys i've taken it to.

Anyone heard of this problem or know how to fix it or anything? Any advice would be useful at this point.

P.S. Everything else on the car works great.

1980 Nissan\Datsun 280 ZX 5-speed manual

[260DET]

Is the clutch disengaging fully? Sometimes a clutch problem can appear to be gearbox related or cause gearbox problems.

[jmortensen]

This happened to my transmission on the track. My friend was driving my car, came around a corner and downshifted from 3rd to 2nd and got 2nd AND reverse at the same time. Needless to say that locked up the rear and the car slid off the track and past a brick corner workers' stand, misssing it by only 3' or so.

Same thing happened to a friend's Z. She came over to my house, and pulled off in the dirt. When she made her U-turn to park on the right side of the street, she peeled out, when she hit the asphalt the trans locked into 1st and reverse I think it was. Anyway, she didn't notice because she coasted across the street with the clutch in, but when she went to leave at about 12:00 AM she was stuck. Same thing happened to her again about 6 months later. Trans was pulled, rods pushed back and that was that.

When this happened to my car at the track my friend tried to put it into every gear, he wasn't able to really get all the way into any of them, but he kept monkeying with the stick and all of a sudden it fixed itself. When it happened to my friend's car the car we dropped the transmission and popped the covers off of the shift rail detent balls, then pushed them back in place from there.

Weird problem, and I still don't know the cause. I think you need a certain amount of vibration and a certain amount of luck to do this. Maybe increased spring pressure on the detent balls might help (???).

[Nigel1943]

Don't know what happened to my post yesterday but the gist of it was this.

Nissan changed the design of the gearstick on the later ZX to a spring loaded connecting pin. Could it be that Nissan recognized this problem and this was their answer? It has the effect of putting less load on the selector rod in all positions.

[jmortensen]

This guy and my friend both had this problem when the shifter was in 1st gear. I don't think the spring in the shifter would affect this problem at all, since the reverse rail isn't even engaged by the shifter at all when it moves. I brought this up on another forum and coincidentally the guy who responded was the one who was driving my car so many years ago. He said that this later happened to his 5 speed Roadster trans (same shift rail setup as the Z trans) and he said the solution was to shim the spring over the detent ball, or replace the spring. You can shim it by putting small washers on top to preload it, or just get a new one from Nissan, apparently he said they are available and cheap. You could do just the 5th/rev rail, but might as well do them all...

[Nigel1943]

As I read danman's post he says he has used other trannys and had the same problem with all of them which suggests to me that the problem is not with the tranny itself but something external. Agreed putting more pressure on the detents may cure the problem [ probably at the expense of a notchier shift ] but I wonder if he has used the same shifter on all the trannys.

[260DET]

The reverse gear teeth can get burred causing it to jam, usually the result of a poorly disengaging clutch, shifting into reverse while moving or rough treatment. Forcing it could result in a selector bending or some other gear engagement mechanism damage, which could then affect other gears I suppose.

Avatar car's gearbox jammed in reverse once, a burred gear was the cause as above. Dismantled the box and used an angle grinder to carefully smooth the leading edges of the gear teeth, in the best bush mechanic tradition