manual sc300 rear diff into sc400

[GreenChevelleSS]

ive read that the 92 sc400 has a 3.92 rear end gear ratio, would installing the 4.08 sc300 diff help much? How much would it make my speedo off and would it kill my highway cruising much?
3.92 to 4.08 doesnt seem like much of a change.

 

[spf_lexus]

4.08 will yield 5% shorter gears. the auto sc300 diff's 4.27 yields 10% shorter. 5% or 10% shorter also means the speedo is off that same percentage as well. I have been told that if I swap speedo sensors from the donor vehcile that it will auto correct.. but I have not tried this yet.

I have the 4.27 on my sc400 and I love it. Forum member Blizzy estimated 3.5/tenths off your 0-60mph. Cruising on the freeway shows 3000rpm at 70mph. Its not too bad but that way I figure it, the car has a 155mph top speed and i might get there maybe once so why have top end capability thats never used?