Downshift when turning corners
02-28-2012, 02:31 PM
#1
MFz Lurker
Thread Starter
Join Date: Feb 2012
Location: Edom, Texas
Posts: 41
Downshift when turning corners
Weird problem happening. Sorry about posting alot of questions lately. My 92 sat up for 3 years and now it's back in the game.
Problem is not without many little nuances.
My new problem today is it automatically downshifts when turning corners (I have an automatic). Just started doing this today. Don't know if this is related but after a cold start in the mornings I put it in reverse and it rolls back about 15 ft. each time and then just sits there. I let off the gas and punch it and it jumps back into backing up.
Acts fine the rest of the day, except turning corners.
Wierd issue.
Anyone ever heard of this craziness?
Thanks
Problem is not without many little nuances.
My new problem today is it automatically downshifts when turning corners (I have an automatic). Just started doing this today. Don't know if this is related but after a cold start in the mornings I put it in reverse and it rolls back about 15 ft. each time and then just sits there. I let off the gas and punch it and it jumps back into backing up.
Acts fine the rest of the day, except turning corners.
Wierd issue.
Anyone ever heard of this craziness?
Thanks
02-28-2012, 06:29 PM
#4
Moderator
Join Date: Jul 2011
Location: Tampa, FL; Lake Jackson (Atlanta), GA
Posts: 1,902
Automatic transmissions sense manifold vacuum, input shaft speed (with the governor) and usually a cable attached to the throttle to measure its opening. Wide open throttle + low vacuum + low governor speed + downshift. Closed throttle + high vacuum + low governor speed = downshift, also. High governor speed = upshift (but upshift can be earlier or later due to vacuum).
Clear as mud?
Clear as mud?
02-29-2012, 09:12 AM
#6
MFz Lurker
Thread Starter
Join Date: Feb 2012
Location: Edom, Texas
Posts: 41
Automatic transmissions sense manifold vacuum, input shaft speed (with the governor) and usually a cable attached to the throttle to measure its opening. Wide open throttle + low vacuum + low governor speed + downshift. Closed throttle + high vacuum + low governor speed = downshift, also. High governor speed = upshift (but upshift can be earlier or later due to vacuum).
Clear as mud?
Clear as mud?
03-01-2012, 07:04 AM
#9
Moderator
Join Date: Jul 2011
Location: Tampa, FL; Lake Jackson (Atlanta), GA
Posts: 1,902
A vacuum leak could manifest itself in that fashion.
I was just throwing out some basics of automatic transmission shift modulation so that you could understand what outside elements act upon it and possibly decipher the root cause. A vacuum leak is an excellent thing to look for in this case. And it is easy/cheap to look for.
I was just throwing out some basics of automatic transmission shift modulation so that you could understand what outside elements act upon it and possibly decipher the root cause. A vacuum leak is an excellent thing to look for in this case. And it is easy/cheap to look for.
