p.j.,
When I got my '57 Fire Truck it had a 7.17:1 single speed rear and had a top speed of about 53 mph. It has an 18,000 pound Eaton rear, so I found a 2-speed pumpkin (that fit my housing) that had a higher high ratio and a lower low 6.14/8.36:1. I added 10 mph on the top side and have a deeper low for pulling (Granny and 'Low Rear' will pull a house down). I drive it like a 6-speed, set the rear to 'low rear' and work up to 5th low then shift the rear to 'high'...I'm very happy with the results.
I was able to swap the pumpkins out without jacking the truck up or removing the wheels. I just slid the axles out, removed the drive shaft, removed the rear cover which drained the oil, removed the the pumpkin. To help align the new pumpkin I installed 2 long studs about 12" long into the bolt locations and slid the pumpkin in...found out the new ring gear was larger diameter then the old and I needed to cut a slot in the housing (about 1" wide by 1/2" deep). Once I got that done I installed the pumpkin, had a new drive shaft made to have it match the new U-joint size on the new rear and ran the electric lines to the gear shifter.
The 2-speed pumpkin and electric switch cost about $250. The drive shaft work was about $80. I didn't have to touch any of my brake stuff which was great!
Mike B
