Dear SDMB,
Lets say I’m driving in 5th gear at 65 mph and activate the cruise control. After slowing down to 35 mph and down shifting to 4th gear, I decide to use the “resume speed” function. Would the RPM’s over-rev in an attempt to achieve 65 mph in 4th gear? Does the “resume speed” function only work if you remain in the 5th gear?
I’m anxiously awaiting your reply.
Upperdeckfanly yours,
Don’t know if tihs is a general rule w/all cars or not, but my 5 Speed Audi will not engage the speed control unless I’m in 5th gear. If, at any point, I downshift to 4th, then resume, it will not resume. If I shift back into 5th gear, it still will not resume.
I can engage cruise in any gear in my Jeepm Cherokee (I haven’t tried 1st, but I have 3rd up) and it will attempt to go back to whatever speed it was set in when you resume.
I am pretty sure it won’t go past redline though… although I am not about to experiment for you 
Depressing the clutch (or the brakes) in my old Subaru would disengage cruise control, and ‘resume speed’ wouldn’t work. I would have to use the ‘set’ control again. I’m pretty sure that’s the case in other cars.
Peace,
mangeorge
My Chevy Lumina would do as you describe. I could set the speed at 60 in 5th, then shift down to 4th (using the clutch would cancel the cruise) then hit resume and it would resume at 60 with a higher RPM. I don’t know what it would have done if I’d set it to say 75 then tried to resume in 2nd. A funny cruise control story I heard once - this guy had some big Lincoln or Caddie or something with a huge engine and automatic transmission. He’d run it up to 100 and set the cruise. He’d then cancel the cruise and stop. Then from a dead stop with the car in drive he’d hit resume and do a big burn-out as the car tried to get back to 100 as fast as it could.
For some reason I thought you couldn’t get Cruise Control with a manual transmission until we got our '01 Civic last year, which has both.
I’ll experiment with mine sometime, but I won’t let it get to the redline if it tries, stop it at 6000 or so.
My Windstar (auto trans) also cancels CC below about 30mph. So, no burnouts here. 
Peace,
mangeorge
My '90 and '95 Civics both had manuals with cruise control.
Can’t speak for the '90, but the '95 would hit redline if I took the car out of gear with the cruise control engaged. Note: that’s taking out of gear without the use of the clutch Didn’t really hurt the car; as soon as redline hit, the engine would retard, then hit redline again, etc., etc., kind of neat when you think about it. Don’t buy a used, Black '95 Civic EX just in case you get my maltreated one…
Now I get it. You guys are trying to blow your engines.
Silly me, I thought you were trying not to.
Peace,
mangeorge
Fun and games in an auto transmission by activating cruise control and throwing it into neutral…
For even more fun, try “park”. Or even “reverse”.
Peace,
mangeorge
On my old 1984 Escort, I did BOTH of those a few times (no more than 10 times). All it did was stalled the motor. It didn’t seem to affect anything else, strangly enough. Finally died from the normal pre-Mazda Escort cause-of-death: cracked cylinder head.