I've recently started driving my 87 Aerostar again and I suspect it's
not quite getting the fuel economy it once did. Everything seems to be
running fine but I do notice the transmission doesn't do the same
pattern of shifting when I go up a certain long hill. How can I tell
if the overdrive is kicking in? Count the number of times it shifts
during a long acceleration on a flat grade?
OBD = On Board Diagnostics. Your vehicle has a drivetrain scanning ability
built-in. In the case of FoMoCo vehicles from '84 thru (most) '95, it's called
EEC-IV, and a digital scanner is about $35. As far as knowing if you're in OD or
not, just listen to the engine. In OD at 60 mph, it shouldn't sound like more
than a warm-up (fast) idle.
Sure. Let me to take the opportunity to publicly thank Backyard
Mechanic for all his help. You're one of the bricks, if not _the_
brick of this newsgroup and there are a _lot_ of ford owners who've
benefited from your knowledge and willingness to help.
Shifting from OD to D while moving at 60 mph doesn't seem to produce
any noticeable difference in engine RPMs or speed. Once the car is
wamed up, it idles O.K. Starting up on cold mornings, it displays some
oscillation characteristics but nothing that hasn't been there in the
past few winters. Once it gets warmed up it sounds pretty much like it
I still haven't had any tangiable confirmation that 4th is kicking in.
I haven't had a chance to do the long straight level acceleration. My
impressions are, so far, I feel the changes up to 3rd then, when I'm
letting off the gas to maintain the 55 or 60 I choose to cruise at,
normally I'd feel that slight engagement of the clutch converter (this
is an A4LD transmission) and I don't think I'm getting that. I say
"don't think" because sometimes that engagement could be pretty subtle.
Now I don't know if it's happening at all.
I don't suppose there are any ways to use the OBD to tell what's
happening with the transmission?
Backyard Mechanic wrote:
With this transmission, letting off the throttle or any quick TIP in or
TIP out actually disengages the converter clutch. Tapping the brake
pedal will too, even w/ steady pressure on the accelerator pedal.
Reading through the posts it isn't clear - do you have a tach?
You should actually be able to detect 4 "shifts" including TC lockup on
normal, straight line level acceleration. When cold, the TC will not
lock up until a specified engine temp is reached - I think around 90-110
degrees recalling from memory. To confirm your "gear" status, a tach
would be the best tool.
Yes they did, it was the torque converter that didn't lock up until they
were warm. When the converter locks up it does feel like another gear. The
idea was to let the converter slippage help get the trans up to operating
The darn things run so slow that they'd stall under load in 4th when
cold.Or in third locked. Whether by design or by chance, both of mine
steadfastly refused to go into 4th for the first mile or so if I did
not warm the vehicle up before leaving (which I seldom did). And I DO
know the difference between lockup and overdrive(4th)
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