I noticed there is a different diff on my auto then on my 5speed. Witch one is better? both are 83's

 

83 auto = R200 3.54 gears
83 man = R200 3.90 gears

which one is 'better' is your opinion. 3.54 is better for fuel economy. 3.9 is better for more torque at the wheels.

 

are they inerchangeable?

 

yup... but make sure you get the speedo cog from the tranny that the diff is meant for, otherwise your speedo will be way off.

All 280zx's & Z31's had the R180 & R200 diffs... which are all the same body.

 

Nope... R180's are significantly different from R200's.

 

Well. I am pulling the 5 Speed trany out, droping the diff would be easyer if I drop it at the same time while I got the car in the air.

 

Didn't the 79 come w/ an R180??? or is the R180 the 240 - 280z?

 

240Z 70-73 MT (3.364) (R180)
240Z 70-73 MT 5spd. (3.900) (R180) - non US
240Z 71-73 Auto (3.545) (R180)

260Z 74 MT (3.364) (R180)
260Z 74 Auto (3.545) (R180)

280Z 75-76 (3.545) (R200)
280Z 77-78 MT (3.545) (R200)
280Z 77-78 Auto (3.545) (R180)

280ZX 79 MT,4 Spd,2 Seater (3.364) (R180)
280ZX 79 MT,5 Spd,2 Seater (3.364) (R180)
280ZX 79 All With Automatic(3.545) (R180)
280ZX 79 MT,4 Spd,4 Seater (3.364) (R200)
280ZX 79 MT,5 Spd,4 Seater (3.7) (R200)
280ZX-GL 79 (3.7) (R200)

280ZX 80 MT,2 Seater (3.545) (R180)
280ZX 80 Automatic 2/4Seat (3.545) (R180)
280ZX 80 MT,4 Seater (3.9) (R200)
280ZX-GL 80 (3.9) (R200)

280ZX 81-83 Automatic all (3.545) (R180)
280ZX 81-83 Turbo - all (3.545) (R200)
280ZX 81-83 MT (3.9) (R200)

 

so, will the 3.9 fit in the place of the 3.5?

 

The diff will fit in the other car. Just swap the axles and everything with it when you swap it. It's a bolt in deal, no mods needed. They just use different axles, that's all. I don't know if the drive shaft needs to be swapped though. I would doubt it though, but I could be wrong. So don't try swapping the gears, just swap the entire diff. You want the one from the manual trans car (input should be offset to one side, whereas the 180 input is right in the center (correct me if I'm wrong here, but thats how I remember it).

 

The input on the R200 is still centered on the car but the pumpkin sits offset to one side so don't mix up your axels!

It is a very straight forward swap, you'll also want the mustach bar from the car the R200 came out of.

 

Are the ring and pinion swapable? Not familiar with the R180's...anyone ever tried this?