What To Look For in Used Differentials (R200)

[Muzez]

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. 

[7tooZ]

What are you building that you need An R200?

[Muzez]

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

[7tooZ]

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, 2020 by 7tooZ

[Zed Head]

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, 2020 by Zed Head

[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.

[Dave WM]

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.

[Zed Head]

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.

[Muzez]

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.