I just caught this thread... I have '82 civilian K5 Blazer with 6.2, 700,208.
Stock axles were 3.08, tires.. 31's.
The setup SUCKED! If you went to 33 with 3.08, it would suck even worse. No power, no grunt with 31's, I could just imagine how gutless it would be with 33's!!
I just got my truck back this past Monday, the rear pinion bearings were toasted from the day I got it, and it finally chipped a few teeth from the ring gear...
$1,400 later I got it back re-geared to 4.11.
So, the current setup is 4.11 and 31's, with future plans of 33's.
I can say, 4.11 is a fantastic setup, with the 31's even... a LOT of grunt, and the 3-4-3 gear hunt is GONE, FINALLY! Now when it goes into overdrive, it STAYS in overdrive and its a pure joy to drive!
The "ideal" setup for the 6.2l diesel is NOT anywhere close to what a gasser would be setup for.
My highest suggestion is:
31" tire = 3.73
33" tire = 4.11
35" tire = 4.56
The reason being, as the tire size goes up, the gearing goes down, but the RPMs at the various stages of the transmission shift will be...
wait for it....
about the SAME as 31" and 3.73...
So, whats so special about 31" and 3.73?
Both were factory options. Therefore the above suggestions keep in trend with the RPMs that the TC and 700 are expecting for PROPER shifting AND good grunt, while maintaining decent economy.
Please bear in mind, the TC and 700 for a diesel and a gas are NOT the same... small differences, but not the same! The TC & trans for a diesel are setup specifically for the 6.2/6.5's power band.
If this is your first diesel, do yourself a favor and rely on those that currently have such a setup. TrustyK5 was a GREAT help to me throughout a lot of my work, you would do well to value his input also.
Any specific questions, shoot me a PM.
GL!
Andrew