A4LD Hard Shift issues (P,D & 1-2 ONLY)

tx_pwp5 · May 25, 2017

Hey guys,

I dug around a little but there is so much info on these it's a little overwhelming.

My truck pauses then engages very hard from Park to Reverse, Reverse to Drive, and Drive to reverse/ reverse to Park. Basically, any of these three gears = a big hard BANG and it goes into whatever gear that is.

Then, in 1st, the rpms climb and climb until it gets to about 3800-4KRMP then BANG it shifts into second very hard.

After that it drives great and seems to downshift with no issues.

I've read these can be simple solenoid or other fixes and it may not need a total rebuild so I'm hoping for that.

Any ideas? 160 ish K (I think) behind a 2.9. 4x4. 1987 supercab. Recently lifted it and drove it for about 4 days with the 2 piece driveshaft before it vibrated the rubber mount half to death and I swapped it for a 1 piece out of a sport trac. The trans issues started almost immediately after that so I'm sure they are related. (to the vibrating).

Shran · May 28, 2017

Fluid level OK? Did the vacuum modulator hose get unplugged or damaged during the lift or other maintenance, what about the electrical connectors and wiring to the transmission? Cooler lines in good shape, IE not crushed anywhere?

Simply swapping driveshafts or doing a lift wouldn't cause that issue, the first thing that comes to mind in this case is that something got bumped and unplugged or damaged... or just low on fluid.

RonD · May 28, 2017

2.9l is idling at 750-800 after warm up?

Yes, check vacuum modulator on side of transmission, check its vacuum hose for ATF

1987 should have the two solenoids
TCC, locks up torque converter once you reach a certain speed
3/4 Shift, operates the Overdrive shift from 3rd to 4th, and back to 3rd based on engine load and speed

So there are no 1st, 2nd, or 3rd gear solenoids like the 4R and 5R 1995 and up transmissions have.

A4LD shifts based on pressure and RPMs same as non-computer controlled automatics did

2002edgeplussupercab · May 29, 2017

I know not same tranny, but mine shifts hard if it is in LIMP mode.

mplummer08 · May 29, 2017

Fluid could cause all these problems.

However, from my understanding the delay could come from the pump going out and it taking excess time to build up the requisite pressure.

The high Rev from 1-2 could be fluid, a sticking governor, or a bad/disconnected vacuum modulator.

Sent from my SPH-L720T using Tapatalk

tx_pwp5 · May 31, 2017

Shran said:
Fluid level OK? Did the vacuum modulator hose get unplugged or damaged during the lift or other maintenance, what about the electrical connectors and wiring to the transmission? Cooler lines in good shape, IE not crushed anywhere?

Simply swapping driveshafts or doing a lift wouldn't cause that issue, the first thing that comes to mind in this case is that something got bumped and unplugged or damaged... or just low on fluid.

I was thinking more along the lines that the vibrating from before the drive shaft swap might have jangled something loose, which looks to be possible from everyone else's quotes. I'll crawl under there tonight and poke around and report back.

Thanks!

tx_pwp5 · Oct 11, 2017

New Vacuum Modulator- New problem

Hey everyone,

Took the CAT off to change the vacuum modulator, and the hose was disconnected. Not sure if I knocked it off taking the cat out or not, so I went ahead and changed the Vacuum Modulator anyway, and put a little hose clamp on the nipple side to keep it from sliding off again.

Now, the truck shifts smoothly into reverse, and from reverse into first gear. I believe it's shifting out of first and into second but it's definitely not shifting into 3rd or OD.

I drove it yesterday (old VM) and it was banging into reverse and first, and then climbing to 3500 and shifting hard into 2nd and was fine into 3rd and OD.

The new VM is adjustable, but without the little knob the old one had. I think I got it in all the way, I reused the pin from the old one, and the retainer clip mounted flush to the tranny, but I didn't feel the CLIP when I pushed it in. I tried to pull it out to make sure it was in there all the way and it was plenty snug.

What gives? If I need to adjust the VM, which way do I turn it?

Thanks

tx_pwp5 · Oct 24, 2017

mplummer08 · Oct 24, 2017

I know some problems can come from using the wrong modulator. Still fluid could be suspect.

Sent from my SPH-L720T using Tapatalk

tx_pwp5 · Oct 30, 2017

mplummer08 said:
I know some problems can come from using the wrong modulator. Still fluid could be suspect.

Sent from my SPH-L720T using Tapatalk

Nice thank you. The modulator definitely felt stiffer when I was installing it so I wonder if the pin isn't actuating as it should. I'll give this a whirl and see if that is the problem!

A4LD Hard Shift issues (P,D & 1-2 ONLY)

tx_pwp5

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Shran

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RonD

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2002edgeplussupercab

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