I have a T-5, and was wondering if it's possible to get a custom 5th gear, so that i could have 4.10's in the back, and be able to cruise on the highway with low RPM's... is it possible

 

anyone? mostly sponsors please.

 

You might get a better response if gave a range of ratios you want. But to answer the original Q: You can make a custom 5th ratio. It would take both drive and driven gear manufacture . aiat would be limited by what you could fit into the castings and by the driven gear cross-section. That is ,the gear is pressed on the mainshaft so it would have to have enough"meat" to assemble without distorting.

 

.59 is do-able, depending on what gearset you have currently.
There were a LOT of different T5 boxes made with different gear tooth counts.

 

With a 2.95 ratio gear kit, you can get down in the .59 area.