1) Diff gears drop your RPM's the same % in high and low range. Transfer case gears have 1 gearset for "high range" and another set for "4 wheel low". Why is this nice? Because you can "correct" for larger tires by reducing the high range by 18% or so (depending on your tire size and needs), but you can reduce the low range by 100% or more - which is REALLY nice!!!!

2) I kinda disagree with trail tough's perspective on things. I DO agree with him when we're talking about REALLY BIG tires (32"+). I totally disagree with him when it comes to smaller tires - stock sammi stuff can handle a little added stress. I have not seen a lot of driveline failures with more conservative sized tires.

3) It's $200 for ring and pinion gears, but it's $200 PER SIDE (need one set for front, and one set for rear).  You'll need 2 rebuild kits while you're in your diffs, and 2 bottles of gear oil. You'll only need 1 rebuild kit for the transfer case.

4) It's much easier to swap gears in a transfer case than in a diff.

So.... it really depends on what you're doing. But - if I made a short recommendation... 31" tires and smaller - do transfer case gears. 32"+ tires - do diffs.

That chart is a little misleading. By the way, the reduction (eg 4.9:1) is the high gear reduction only. To figure out the low range reduction, you need to bust out a little algebra:
Hi gear - where x is the percentage reduction   x*1.409/100+1.409="Gearing"
Low gear - where x is the percentage reduction   x*2.268/100+2.268="Gearing"

I'm doing the calculations now, and will be correcting that chart (which, by the way I got from here: http://www.zuwharrie.com/content/view/15/27/1/1/)

Stay tuned for a "corrected" chart that will be easier to use the gearing calculator with.

Okay - here's some numbers you can plug right into the gearing calculator (use the red numbers). I'm not really shure how they derive at their 8:1 or 4.9:1 numbers... "final drive" in one of the gears or something?

RRO      
8:1 Hi Reduction   24%   1.412
8:1 Lo Reduction   260%   2.327
       
6:1 Hi Reduction   24%   1.412
6:1 Lo Reduction   170%   2.307
       
4.16:1 Hi Reduction   12%   1.411
4.16:1 Lo Reduction   83%   2.287
       
Calmini      
6.5:1 Hi Reduction   20%   1.412
6.5:1 Lo Reduction   187%   2.31
       
5.14:1 Hi Reduction   18.30%   1.412
5.14:1 Lo Reduction   127%   2.297
       
4.16:1 Hi Reduction   12.20%   1.411
4.16:1 Lo Reduction   83.60%   2.287
       
Roadless Gear      
6.129:1 Hi Reduction   21%   1.412
6.129:1 Lo Reduction   170%   2.307
       
4.16:1 Hi Reduction   12%   1.411
4.16:1 Lo Reduction   84%   2.287
       
Petroworks      
4.89:1 Hi Reduction   18%   1.412
4.89:1 Lo Reduction   115%   2.294

Trail Tough      
6.4:1 Hi Reduction   17%   1.411
6.4:1 Lo Reduction   181%   2.309
      
4.9:1 Hi Reduction   16%   1.411
4.9:1 Lo Reduction   115%   2.294
      
4.16:1 Hi Reduction   12%   1.411
4.16:1 Lo Reduction   84%   2.287
      
AAPA      
6.4:1 Hi Reduction   21%   1.412
6.4:1 Lo Reduction   181%   2.309
      
4.9:1 Hi Reduction   18%   1.412
4.9:1 Lo Reduction   118%   2.295
      
4.1:1 Hi Reduction   12%   1.411
4.1:1 Lo Reduction   84%   2.287
      
DG Tuning (Netherlands)      
8:1 Hi Reduction   24%   1.412
8:1 Lo Reduction   260%   2.327
      
6:1 Hi Reduction   24%   1.412
6:1 Lo Reduction   170%   2.307
      
4.16:1 Hi Reduction   12%   1.411
4.16:1 Lo Reduction   83%   2.287

i learned a easy lesson. t-case gears + stock r/p + heavy foot +lots of mud + 31" tires= explode

Ok, but what exploded?  Was it your driveshafts or U-joints, or did you just blow up your CV shafts and/or axels?


Jeremiah - The 8:1 and 4.9:1 is the gearing of the low range.   I couldn't find that chart earlier, so I just drug up the high range drop (which is what you would use for calculating the tires size changes for highway driving) from an article.  You get your final drive ratio by calculating your 1st gear, transfer case, and diffs.

3.136 (Transmission) * 6.5 (Transfer Case) * 5.12 (Diff) = 104:1 in low range modified compared to
3.136 (Transmission) * 2.511 (Transfer Case) * 4.10 (Diff) = 32:1 stock for my SJ-410.

You can look up the transmission stats here.

Sweet - thanks for the heads up!

Would t-case gears be a better option than 5.83's?  What is the modified percentage in the high range? What is the price of t-case gears?

I wouldnt say better but alot easier for someone that can turn a wrench but doesnt know how to set lash or use a caliper!

im running 5:83 gears and a 4.16:1 t-case with 35" tires and can run about 60mph!

for driving on the road what is better? and whats better for offroad?

for driving on the road what is better? and whats better for offroad?

if you are lookin for a happy medium id go with a 4-1 t-case and do a track/kick 3rd member swap! 513 gears in the axles will get you low enough with the 4-1 and still be very streetable!

for driving on the road what is better? and whats better for offroad?

Depends on tire size. Anything below 31" t-case gears are best. Anything over 31" you should be using diff gears (and can mix/match diff gears and t-case).  Offroading - t-case gears WAY better 'cause it's the only way to reduce the low range below what it is stock.