reversed batteries

what is likely to be fried when the 12Vdc batteries are installed backwards.
I am not getting 12 VDC to the starter selenoid and the transmission controller will not work.

 

Thanks for your feedback.

The batteries were installed applying -12 vdc to the wiring, all wiring coming to the batteries. (+post to gnd and -post to +wiring).
The Cummings engine starts and runs after I apply 12 volts to the solenoid directly, where this ignition switch would normally. I get 12 volts out of the switch in the dashboard, but nothing at the solenoid. Whatever is between these 2 points, I cannot find. The wires go into a bundle along with many other bundles. This is a Dutch Star coach on a freightliner chassis.

Also, there is a transmission shift panel beside the drivers seat. It is not lite either, which means the transmission can be operated, can't move the coach. Some fuses were changed, all that I could find were checked, these were under the dash or under the hood out front.

I'm thinking there is an electronic box between ignition switch and the solenoid, and the same is involved with the transmission.

This all started with a change out of the alternator. Where might the voltage regulator located?

Exhausted!

 

OK, we were lucky. One alternator and blown fuses were the major issue. I got to say Shaun Bridges at Frieghtliner was a savior when the wiring diagrams arrived by email. After that, finding the different "boxes" took a little while, but found that final fuse in the VIM box, back in the engine area.
Thanks to all who provided info, but Shaun Bridges you were my hero today!!