A closed driveline is just that closed. Old chevy trucks are closed. commonly known as a torque tube. these have limited gear ratio choices. stock- and patrick's 3:55.1 is about it. the U joynts are on the small size. thus stock rear ends limit a trucks drivability to 50's (miles per hour) on the freeway.

Open drive lines have no enclosure drive tube, both U joynts are exposed allowing them to be serviced when needed. the rear end has many different gear ratios available and there is a cover that can be removed for changing gears and maintainance work. 10 and 12 bolt 5 and 6 lug rear ends are a common switch for 3100's learn to do a search on this web site as there is tons of info.

good luck and welcome to this site.

Jim & Caroline
The highway is for gamblers, better use your good sense."
Gooday-that's my 1¢ answer due to the lousy economy ~ cause I ain't got - no . mo . doe
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