Originally Posted by wrk101

On DT shifters, that's normal (index rear, friction front). Assuming your levers are Suntours, they do not index well with Shimano freewheels (different spacing). NOS Suntour freewheels are VERY expensive.

Give it a try, and if you don't like it, switch to friction mode.

I have one bike set up with Suntour indexing levers and rear derailleur, and a Shimano freewheel. Indexes OK, not great for sure.

From Sheldon's site, in my case, I wanted to keep my Superbe Pro RD, so changing the RD was not an option (I would rather go friction at that point):

Mixed Sun Tour/Shimano Indexing

Sun Tour indexed shifters pull less cable per shift than Shimano systems use. Thus, generally, you need to match Sun Tour indexed shifters with Sun Tour rear derailers. However, it turns out that Sun Tour 6-speed shifters index pretty well with 7-speed clusters if you replace the old Sun Tour rear derailer with a Shimano unit!
The mismatch in cable travel cancels out the mismatch between 6 and 7 speeds. There won't be a "click" for the lowest gear, but the derailer's low-gear limit stop will provide the "indexing" for that gear.