10 speed to 13 speed w/ 3.55 gears

http://www.vibratesoftware.com/html_help/2011/Eaton_Fuller/Transmissions/eaton_10speed_trans.htm

I went over to the web and checked on your tranny......it's too new to ID the gears set ( E ) but what he's selling you is a converted transmission. This means it came out as a 9 and was converted ( back half changed ) to a 13.

My concern is the torque output of that 435. She's no slouch so it's hard for me to believe they would hang a 1600 ft/lb tranny behind it. Get under yours and read that data plate on your tranny. The first 2 numbers are the torque rating of the tranny. If it's a 16 no problem, if it's 18 or higher your asking for trouble if you hang a 16 in it's place......and your mechanic knows this too.

If yours has a cooler and the 13 doesn't your getting shafted too.

Good luck

 

If its converted it will have a .87 or .84 final ratio not totally sure which one. If your ten speed is an RTLO or RTLX it should be a .73 overdrive. The third number in what you posted is a 6 that is the designation number. It will not be as smooth as your 10 speed early to mid 90's is when they quit making those. Some still didn't use tapered bearings. With that model of back box you also have to double work the OD button. Make a gear change with button in OD then move to direct before getting in throttle then let off hit OD and repeat. Instead of preselecting the OD shift. I would almost bet you have a 7 or 9 designation probably a 9. In my opinion it would be a step back. Sounds a little pricey for what it is as well.