A4LD No shifting

[mazdab40004x4]

Hoping you all can help me figure this out and sorry for the length. I've got a 94 B4000 with the A4LD trans and electronic shifting 4WD. Back about 6 weeks ago, the truck started to stall on me at random times while driving. In my attempt to resolve that issue, there were some other items I had been meaning to get to for awhile that I decided to do. I replaced the trans vacuum modulator because it was sending some fluid into the vacuum system for awhile. I also repaired my 4WD shift motor which the previous owner had left half done (meaning he put the new motor in place, but never de-pinned the two wires coming from the sensor and instead just zip tied the old motor to the crossmember with the sensor still attached to it )

In addition to above, the truck has a new TPS, IAC, CKP sensor and harness (the old harness was broken), fuel pump, fuel pressure regulator, evap solenoid/hoses/carbon canister, OEM battery cables, and every vacuum hose I could find. I also did and oil and filter change, cleaned every ground point, and cleaned the ignition module connector.

I finally got everything back together today and it started up no problem. YAY! Let it warm up in the driveway and idle seemed better than before at around 950. I won't say it was solid -- it surges just a tad between 900 and 1000 RPM which is probably a bit high. Disconnected the IAC to see if there might be vac leak and idle reduced down to 500 and stayed steady. Plugged the IAC back in and took it for a short drive -- NOT YAY! It shifts into reverse and drive OK, but will not shift out of first. I can get it to go to second if I drop the selector to 2 but as soon as I put it back in D it drops to first.

I'm guessing it has something to do with the vacuum modulator replacement since that's the only new thing on the trans. I was careful to reuse the little pin and topped up the fluid I lost when I pulled the old one out. Everything seemed to go back together fine so I'm not sure exactly where to start. Any advice would be appreciated.

 

[mplummer08]

Make sure the vacuum line was reconnected at the modulator. Also there is a pin and a shuttle for the modulator did you have both? And did you replace the modulator with the correct one?

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[mazdab40004x4]

It looked pretty much the same as the one that came out and the model number said it was the right one. I had a pin, but don't know what the shuttle is. Can you describe it or refer me to a picture? I put a brand new vacuum line on so it should be connected but I will double check that.

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[mplummer08]

Here is mine. The aluminum shuttle is the one I was referring to, it may have stayed in the tranny.

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[mplummer08]

And ignore the spring, it's from a shift kit

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[mazdab40004x4]

Hmm. Definitely didn't see a shuttle like that. Would that be used on all years of the a4ld?

I double checked that I got the right modulator and it is correct according to O'Reilly. http://m.oreillyauto.com/h5/r/www.oreillyauto.com/site/c/detail/PIO0/747008.oap?pt=03204&ppt=C0073

Hate to have to take it apart again but oh well.

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[mplummer08]

That part should be right. If you just ran a rubber vaccum line maybe melted near the exhaust?

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[mazdab40004x4]

I guess that's possible. I wasn't hearing any kind of hiss though and if it was a big vac leak it would have stalled when I disconnected the IAC. I will definitely check that line tomorrow.

I found an exploded view of the A4LD in my service manual (which is actually for the 94 Ranger) and that shuttle piece is shown. Ford calls it a Throttle Control Valve. So I guess it must be stuck in there. I couldn't really see what I was doing since there's only just enough space to get a hand in there from the access panel in the cab. I'm hoping I can get a pick or something in that bore to get it out.

Assuming I can retrieve it from the bore, do I just clean it up along with the inside of the bore and put it back in in front of the modulator and pin? Or is it supposed to attach somehow? I'm thinking that maybe there's some dirt in there. The top of the trans was coated in about 3 inches of 10-year-old caked on mud from the previous owner's off-roading escapades. I cleaned it off pretty good and let about a quart of fluid drain out of the hole but I wonder if some dirt got in when I went to push the new modulator in.

And thanks for your help BTW. Really appreciate it. That pic was especially helpful.

 

[mazdab40004x4]

I got it all apart and back together again today but unfortunately there was no change in symptoms. Still won't shift out of first unless I put it to 2 and then drops to first if I put it back in D.

Inspected the new vacuum hose on the modulator and all was good there. Removed the heat shield and then the modulator bracket and then pulled the modulator and pin out together. I felt around for the shuttle/control valve and it was seated in there. Grabbed my tweezers and got that out and it looked fine -- smooth on all sides. See pic.

Let some fluid drain to see if that would flush any dirt back in the bore a bit. Then took a clean cloth around a mini screwdriver and swabbed the inside of the bore gently. Seemed clean to me.

I decided to exchange the modulator for another new one just in case it was bad out of the box. Got the new one, placed the shuttle/control valve back in the bore with the dimple facing out, put some vaseline on the rod and placed it in the modulator, and then gently pushed the modulator into the bore to seat the o-ring. Put the bracket back on and tightened it to spec. Put the vacuum hose and heat shield back on and cleaned the area with brake cleaner. I'm pretty sure I did everything correctly.

I'm now back to square one. I think I've now eliminated the modulator as the problem, but I don't know what else it could be since it shifted fine before I started all this work. Unless the stalling was related to the trans somehow?

Any other ideas on how to diagnose this myself or am I bringing it to the trans shop next weekend?

 

[Transman304]

I would venture the governor is stuck. Google A4LD governor valve stuck for more info on repair.

 

[mazdab40004x4]

Thanks for the response. I googled that and I see what needs to be done. Not looking forward to dropping the transfer case -- mostly because I'm afraid I may actually drop it! That sucker looks heavy.

It's a little unclear -- will I lose fluid when I take the governor off? Just want to be prepared so I don't get a face full of fluid or contaminate my driveway.

I'm wondering if I should just change the fluid anyway. It's not been done in the 7 years I've owned the truck and I have no idea when it was done before that. The fluid is still reddish, but definitely has some grey/brown/black to it. Any advice there? Maybe I'll wait to see if I can get it shifting again first.

 

[mazdab40004x4]

OK folks. I wanted to circle back around on this and maybe save you all some headaches.

If you need a vacuum modulator for your A4LD, think twice about using the Pioneer part #747008 I linked above. It is listed as correct for both the Ranger and B4000 on multiple sites including O'Reilly and Rock Auto and on Pioneer's own site. But it's either not right for my 94 or I got two faulty ones out of the box or maybe both.

I finally gave up trying to solve this myself and brought it over to my local trans shop and told them what I had done so far. They know the A4LD well and I'm sure it has put meals on their plate for many years! They took a look at the modulator and said it didn't look right to them compared to what they use. Even though it fit just fine and looked similar to the old one I had in there before they were not convinced it was right. They ordered a different modulator from their supplier (I'll try to find out brand/model), installed it and now the trans shifts fine. No problems with the governor or anything else. This makes me both happy and annoyed at the same time.

 

[wildbill23c]

Glad its moving on its own again. These things aren't cheap to have rebuilt, and I'm hoping the rebuild on my A4LD holds up for many years, otherwise I hope a 3 speed auto from an 84 or 85 ranger or bronco 2 will work because if this A4LD fails again its getting tossed out permanently.

 

[mplummer08]

You know now that you mention it, the modulator I ordered from RockAuto was the incorrect one. They look nearly identical but I never installed it because I recognized it as being wrong thanks to some shift kit info I had during my rebuild. I ended up testing/using my old one instead.

I also can't find my English copy of these instructions lol.

Glad you got it running though!

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[mazdab40004x4]

Thanks guys. I was busy all week so I finally picked it up yesterday. Shifts perfectly now. Wasn't able to figure out what brand/model the shop used, but if I had to do it again I would just order the Motorcraft part. They did save me the bad one so at least I can get my $15 back from O'Reilly.

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