89gtwith3.55s

i don't know very much about trnsmission components so i figured i would ask on here since you have all been very helpful before. I was just curious if it is bad for your clutch/flywheel/tranny to leave your car in gear while slowing down. its an 89 gt 5speed king cobra clutch, aluminum flywheel, and rebuilt t5 thanks guys

Jfsram

Not bad for it if you speed match before you downshift.
On that note, in normal driving. I'd rather just coast in neutral and use my brakes.

89gtwith3.55s

im not talking about downshifting, im saying if im on a side street and im in second at 2500-3000 and theres a stop sign is it bad to leave it in second until i reach 1700 and then just shift to neutral before stopping?

67mustang302

No. And downshifting itself won't hurt anything unless you goobershift and pop the clutch as you downshift.

89gtwith3.55s

ok thank you i wasnt sure, and didnt want to do any damage =)

TrimDrip

hurts gas mileage. If it uses a lot of oil, it will use more oil too.

67mustang302

Gearing down will hardly affect mileage. There's barely any fuel at all going in during idle. But yeah, it can be an issue if you have bad ring seal, but that's not a downshifting issue, that's a ring seal issue.

Jfsram

Well not for a 89 Mustang but some newer cars actually kill all the fuel supply during decel.

TrimDrip

so they just run on compression

ah I see, the rest of the drivetrain keeps it running. The thing that kills mileage the most is backing out of the driveway. That gives 0 miles to gallon

67mustang302

Not really, reverse is like a bit taller than 1st in a lot of cars, so reverse gives you mileage about the same as driving in 1st gear...which is to say poor. But yeah, a lot of newer cars when the rpm is a certain point above idle and decreasing, fuel shuts off. It scrimps and saves a smidge on mileage, but also gives a slightly more effective decel since you don't have the idle combustion trying to keep the engine from slowing down as much.