a4ld won't shift into overdrive

[Bob Weir]

Went for a drive and realized the Scorp wasn't shifting into OD. It still has tight, quick shifts through the lower gears as it always has, but doesn't get into OD.

The Trans Kickdown Solenoid holds 15 kPA vac as it should. The Trans Vac Switch slowly bleeds of vac from 15 kPa that I understand to mean it's ok. All the other related vac hoses are holding vac.

As a related note, sometimes it won't start in Park, but will start in Neutral. And when shifting from Drive to Reverse, sometimes the shift lever has to be pushed slightly forward to engage Reverse. I had my maniac check the linkage and couldn't determine a way to adjust the linkage. Although, he did mention there could be a missing bushing in the linkage that might be causing the shift linkage being slightly out of adjustment.

The Speed Control aka "cruise control" does work, indicating the Vehicle Speed Sensor aka "VSS" is ok.

Your thoughts are appreciated.

[Ed Lijewski]

Check the trans vac switch for clean On/Off modes? My understanding was that that switch just needs to close and send current to the trans solenoid for the 3rd to 4th gear shift.

Does the S.M. say otherwise?

YMMV

[Bob Weir]

Hi Ed

I'm very hesitant to fuss with the switch because the hose nipple is very fragile, but I'll probably remove the cap, inspect and clean per your suggestion.

SM doesn't say much about the "switch" that's mounted on the air box. But I have IMON 20 May 2004, "Scorpio Transmission Vacuum Switch Repair" from Jim Wirt and 20 Feb 2008 from Henry Walmsley "89 Scorpio a4ld problem diagnosis". My understanding is the switch unlocks the converter when manifold vac is 15 kPA, but doesn't affect the trans going into overdrive.

My go to a4ld guy retired. I stopped by the dealer that once upon a time sold Merkurs. I asked the service writers how much to change filter & fluid in a Merkur? One guy never heard of it and the other asked what kind of tranny was in it. I told him a4ld like a Bronco, Explorer, or Ranger. $100 to change or $200 to flush & change. The search continues to find another shop I can trust.

[Ed Lijewski]

The charge for trans flush is about on par with advertised prices. Watch for a promotion for fluid flush--prices may be around $125.

I'd just start with cleaning the switch/harness connections. Nothing more just now.

Lots of info re the torque converter lockup function in this thread on page 2...viewtopic.php?f=37&t=14991&hilit=Overdr ... p&start=15

YMMV

[scorpioaddict]

Hmm... transmission link rod is user-adjustable. Lift the
car from the driver's side and take a look. It's easy.

(deleted useless graphic)

[Bob Weir]

Ken
Scorpio doesn't have EEC pin 52. Thanks

[scorpioaddict]

Okay, there's only a million reasons why that flow chart
wouldn't apply to the Scorpio. One reason is it's from the
ATSG book on A4LDs. And our box isn't ECU controlled, etc.

The Scorpio FSM (if you don't have it) sez
- kickdown system damaged
- Vacuum line damaged
- Vacuum diaphragm damaged

Otherwise, it's internal problems.

The two times this has happened to me, I pulled the
transmissions and rebuilt them. The first I did in '05 and
it's still perkin', about $350 and 30k miles later.

[Bob Weir]

Although the Scorp still doesn’t shift into 4th OD, I did remove the slack from the solenoid cable and fix the shift linkage.

My Solenoid cable deftected about 1/4”. Two securing bolts loosened, a nudge to the solenoid = no slack.

The shift level had lost its positive feel. Often when shifting from Drive to Reverse, I had to move the shifter slightly forward to engage R. Where the shift linkage connects to the kickdown lever, it appeared to be missing a bushing. The hole in the arm was ≠ 1/8” larger than the pin of the kickdown lever. I used a 1/2” nut, increased diameter using 23/64” drill bit, rounded off the points of the nut. Because the pin is about 1/4” long before the indent for the securing clip and the rod is noticeable thinner, I used a drain plug washer to for a better fit. Not a perfect fit, but close enough for a Scorpio. Now the shift lever engages the gears as it should.

Larry Davis was very informative regarding the a4ld. The next step is find a shop that understands this a4ld version, drop the pan and take a serious look at its innards.

[Ed Lijewski]

I'd first get a transmission flush-even @ $150 (watch for sales on trans flushes for less). Trans flushes are worth the cost. They completely remove all old fluid including/Including from the torque converter, and filling with fresh fluid. I'm not saying that would resolve your 3-4 no shift issue, but note that that issue involves a mechanism and clutches within the converter...

A trans mechanic pulling the pan and draining that fluid only would refill with only the amount drained which leaves dirty fluid and crud within the torque converter untouched.

MTCW.

YMMV

[Bob Weir]

Ed
I'll have the tranny shop first drop the pan and check condition of internals. If ok, then I'll definitely have them flush it.

[milehighXR]

I wouldn't do the flush, I've heard horror stories of people getting their trannies flushed, and then the y need a rebuild. It seems like the converter kinda acts like a filter, and when you loosen that gunk, it mucks things up.

[Bob Weir]

Hi Johnny

Ironic that you mention the "trans flush" quandary. I was reading through my "all u need 2 know about A4LD notes" and read these cautioning comments. "To Do or Not To Do, that is the question."

I also read per Jake Delago [may his Scorpio rest in peace] that the Trans Vac Switch [located on air box] must be able to hold vac as well as the Vac Modulator. My Switch doesn't, but the Modulator does. Also read an article on "How to fix the switch." Fortunately, I have a couple of Vac Switches with broken nipples that I can practice.

[J.R.]

At the risk of sounding like a cheapskate... re. broken nipples on vacuum switches: sometimes repairs with a decent epoxy or JB Weld can be done by using a skinny wax 'birthday cake' candle shoved in as a temporary alignment device while the bond cures. Obviously the adhesive won't bond to the wax. On other occasions, inserting a thinwall brass or aluminum tube (permanently bonded in place) works better, especially if the switch's location subjects it to significant movement or vibration.

[Bob Weir]

I'm posting 2 pics due to a recent post on Facebook regarding an A4LD that won't shift into overdrive.
To best of my knowledge, this switch must function correctly for Overdrive to function.
The "Transmission Vacuum Switch is mounted on the side at bottom of the air cleaner box.
CAUTION The nipple of the switch for the hose is very fragile. I never found a glue to repair it. The cap should move. Obviously, check the other transmission related components, that they hold vacuum and test the PWR & GND circuits.
Hopefully, our favorite Merkur vendors have saved a few of these.
For more info go to posts in Scorpio forum titled; "Trans Vac Switch", "Transmission Switch"

[brokencase]

Bob - that vacuum switch releases torque converter lockup. It is not associated with overdrive. It should trip at 15 inches of vacuum.
As far as I am aware the torque converter can lockup in 3rd or OD. But here is the description from the EVTM...

The torque converter will lock up hydraulically
when vehicle speed exceeds 40 mph and power
is applied to the converter clutch solenoid. When
manifold vacuum exceeds 15 in-Hg. (decel, panic
stop), the transmission vacuum switch opens and
de-energizes the converter clutch solenoid, which
unlocks the torque converter.

Some people purposefully disable torque converter lockup for smoother around town driving by putting a switch in series with the vacuum switch.
When they get on the highway they flip the switch for better fuel economy. Prior to transmissions of the AL4D era, torque converters did not lock up. Instead there was always some slippage which reduced fuel economy slightly.

An aftermarket lockup vacuum switch is available for those missing or have damage to this switch. The aftermarket switch is adjustable and you need to connect a vacuum pump and gauge to it to make sure it opens at 15 in vacuum.