How about some thoughts and opinions..

I am upgrading my L28 to a turbo and trying to decide on the transmission.

So for those that have tried both what cha like...

My 3:54 with a B type 4 speed is running 3000 rpm at 60 mph in 4th gear. I wouldn't want to run a 4 speed with a 3:90 .......go with a 5 speed. IMO

If you can get hold of a 71B out of a ZX would be a nice upgrade. The ZX 71B transmission is a close ratio where the 280Z is a wide ratio version.

For a stronger version you could go the 71C mod or try to find a Borg warner T5 from a turbo 280ZX

See my post here for the 71B ratio's http://www.classiczcars.com/forums/engine-drivetrain-s30/50294-time-diff-transmission-swap-what-more-change.html

Chas

81-83 ZX 5 Speed with a 3.9 is about perfect for spirited twisty's and interstate driving. At 60mph my tach drops under 3K and has a nice low growl in 5th gear. If you are not going to do much interstate driving go with the 3:54 and 4 speed.

3.90 R180's are tough to find - are you going with a R200 or a R180?

Word of advise - don't believe anybody when they claimed that they have rebuilt the manual transmission - have a shop open her up and give her a quick inspection - you can turn the bearings and if they don't roll very smooth - change them out before you install that transmission. They will have a gritty turn or wobbly feel if they are worn at all. Better to find that on the front end as to having to drop it back out.

Keep us posted

I really like my '82 ZX tranny. I have it with a 3.7 diff. As stated above, I rebuilt the tranny before putting it in because I knew the bearings were shot. The only reason I might consider running one without rebuilding is because on the Z's are pretty easy to drop out and install.

A Datsun Roadster is another story-There you have to pull the motor to get at the tranny.

Right now the car has a 3:90 R200 in it. I have a 4 speed and a 81-83 ZX 5 Speed(Which is close ratio).

I use the car for auto cross

a little road racing at Roebling Road Raceway

I did take the Z out for a spin this evening - 2200RPM @ 60 MPH in 5th gear.

The rear gear usually is matched to first gear since that's where you'll really notice it. And most of the replies here are about freeway cruising which is not really why you would modify to a turbo. Plus the fact that turbos aren't really known for being an autocross modification, as far as I know (I don't know much about autocross). Doesn't seem like you're any closer to an answer.

I've seen several posts on Hybridz about keeping a taller rear gear (like the 3.54 instead of 3.9) because the torque builds sooner with a turbo when you get in to boost and you get more time "on-boost" in first and second gear. But those guys are looking for raw acceleration. Seems like the close ratio might help your autocross and the 3.54 might help the road-racing, depending on what your top speed is. Trading off ease of leaving a stop light if you use the 5 speed with its 3.062 first gear.

I have 3:54 with 77 5 speed, but the rpms does not drop that much when driving with 5th gear. @ 60mph its about 2800rpms