Hi Guys, 

Going to look at a used differential this week to pair with a ZX transmission I just pulled. Was trying to think of things to check before buying. 

• Check Diff stamp on ring gears
• Internal welds
• Metal on the drain plug
• Damage to spider or ring gears
• Play in the pinions that hold the spider gears.
• Damage to the pinion seal or bearings.  

What else am I missing? Thanks to @Zed Head for some initial inspiration here. 

What are you building that you need An R200?

1 hour ago, 7tooZ said:

What are you building that you need An R200?

Switching to a 280zx 5 speed and am looking to get the 3.9 R200 since that appears to be the recommendation for best acceleration. Currently set up with a R200 3.54 and a 4 speed

Go on line and use a gearing calculator to speed the effects of different ratios entering the fifth gear ratio of which 5 speed you have. If you have a a .745 and driving on the street you may want a 4:11..

Have you considered a Subaru STI CLSD R180?

Edited December 1, 20204 yr by 7tooZ

I think that he already knows about the ratios and is planning to buy a 3.9 to match the 3.062 1st gear in the 5 speed.  Trying to figure out how to evaluate the quality of the 3.9 diff.

Here are some images of welded diffs.  Some people just do a few solid welds, some people go crazy and fill every crevice.

Here's a funny article about the "benefits" of welded diffs.  Those open diffs are unpredictable!

Edited December 1, 20204 yr by Zed Head

Pop out the axles and check the quality of the surface that rides inside the bearing.  They're hard to get out, take some tools to pry with.

39/10 is what you're looking for on the ring gear stamp.

16 minutes ago, Zed Head said:

I think that he already knows about the ratios and is planning to buy a 3.9 to match the 3.062 1st gear in the 5 speed.  Trying to figure out how to evaluate the quality of the 3.9 diff.

Here are some images of welded diffs.  Some people just do a few solid welds, some people go crazy and fill every crevice.

Here's a funny article about the "benefits" of welded diffs.  Those open diffs are unpredictable!

that looks like it would make turning very difficult. I guess if you  were drag racing this would be helpful. Would really scrub off rubber if you were to turn with a diff modified like this.

1 hour ago, Dave WM said:

 I guess if you  were drag racing this would be helpful. Would really scrub off rubber if you were to turn with a diff modified like this.

They do it for drifting.  It's just a cheap hack, just need a welder and some welding material.  I wonder if anyone has tried JB Weld.  That would be a great JB Weld ad.

20 hours ago, Zed Head said:

I think that he already knows about the ratios and is planning to buy a 3.9 to match the 3.062 1st gear in the 5 speed.  Trying to figure out how to evaluate the quality of the 3.9 diff.

Here are some images of welded diffs.  Some people just do a few solid welds, some people go crazy and fill every crevice.

Here's a funny article about the "benefits" of welded diffs.  Those open diffs are unpredictable!

Hugely helpful Zed, this is a perfect visual.