My gear situation.

[xcracer48]

OK so here is the story. I bought my 6.0 about a year and a half ago. Was told it had arp head studs and egr delete and all the works done to it. Well it was just lagging in power, it was just not what I expected going from a 05 tundra to a diesel. It had edge cs, CAI, exhaust but it also had 6 inch lift and 37's and 22's. So I thought that the gears needed to be lower. So I had 4:56 ratio gears installed. It was better but still not where it needed to be.Well it started skipping, so I checked the FICM and of course it was below Voltage. I sent the ficm off to have it repaired and all and it was still skipping. So i finally found someone in my area that specializes in 6.0's in my area. I took it to him he ran his computer on it he said well its your #5 injector, you also dont have ARP headstuds, your turbo boot was torn on the underside, your stand pipe on one head was cracked, and you also need an ICP sensor. So he fixed all of that and I installed IDP tunes, and WOW!!!! Now the truck is just screaming! But now that it runs right I know that I dont need that low of a gear. So my question is do I need to go back to stock or do I need to just go up to 4:11 or something in that area? BTW I found out I had victor? or some kind of head bolts and I am currently having head studs, factory head gaskets, all injectors, new water pump installed and he is also changing the fuel pressure.

[PGreenSVT]

Keep the 4.56's and go to 39.5" or 40" tires. The optimum gear ratio for 37's is probably the 4.30 and it is not worth changing you 4.56's for that. When you get new tires just go a bit bigger.

[jerg_064]

4.56s are about perfect for a 37" tire, might be around 100rpms more out on the highway depending on actual circumference. Just go off your tach, if your sitting around or a little below 2000rpms at 65/70 in OD should be good to go.