Automatic Transmission Troubleshooting

[Sigmundr]

I have a 91 Ford Explorer and I am having a bear of a time trying to fix my transmission. I am on a very tight budget and can't afford to drop the truck off at AAMCO or any other shop to have them diagnose or repair. I have an A4LD transmission with about 120k on it.

Here are the symptoms.

For a while my truck would not up shift up while I was in OD. I could drop it into second and then back up to OD and it would work fine. The RPM had to be a little higher than normal for it to hit the high gear on the freeway, but was otherwise running normally. That behavior quit 2 weeks ago.

Now when I drive I have to place it into 2nd gear manually and keep it there. The OD is nonresponsive unless I hit the freeway. I still have to put it into OD, but it shifts when I start going ~65mph and at ~4k RPM. Then it drops back down into a lower gear again when I hit the 45mph mark.

While working under the truck on my fuel filter I noticed that the wiring harness that connects to my neutral start sensor and the converter solenoid was melted through on my exhaust manifold. I replaced that today and I am still having no luck. I also noticed that the retainer arm for the kick down cable is no longer there. I am going to replace that as soon as I can. I know I need to drop the pan and replace the filter; I don't think the previous owner ever did. I also checked all the major fuses and they all seem to be good.

From what I have read, it is most likely an electrical/sensor failure somewhere because the mechanical shifts all seem to work. Do you guys have any thoughts on what is going on or how best to fix this without dropping half a grand or more into it?

I included a drawing of the area I am working on.
http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/06/bc/67/medium/0900c1528006bc67.gif

 

[natenkiki2004]

Personally, I wouldn't worry too much about the filter. It's about as useful as window screen, it only keeps the big chunks out. Exchanging the fluid can be good but you don't have to drop the pan to do that, you can do it with the cooler lines.

I'm wondering if your whole issue is the kickdown retainer. Your transmission is almost behaving opposite of what it should be, it should allow OD to engage when throttle is light and then kick down a gear when you're heavy on the throttle. If you're 100% sure the wiring is fixed, I'd go after the kickdown retainer and doing a fluid exchange, very possible that one of those will fix the issues.

 

[BrooklynBay]

The filter could clog eventually so it's a good idea to replace it. Fix the kickdown retainer first. Don't use a power flush machine. They loosen the debis which is on the filter, then everything flies off to clog the transmission.

 

[the_don]

fix the kick down cable, and having 120k on it, i would drop the pan to clean out the bottom, change the fluid, and consider adjusting the bands.

 

[Sigmundr]

So...sounds like the kickdown is my biggest concern. Thankfully that is a cheap fix. One note about the cable, it has been partially frayed and melted due to the same issue of it resting against my exhaust manifold. it melted through partially with the wires that I mentioned in the first post.

what has me confused is the fact that I don't believe I've ever had the kickdown cable retainer since I purchased the vehicle almost 3 years ago. I didn't notice it was missing when I did my engine swap last summer. the only reason I realized it was missing was seeing one on the junk yard yesterday and finding that diagram I posted.

in regards to the wiring, I know the wiring has been fixed. However I don't know if there is a sensor or some other component of the electrical system that could cause these symptoms.

 

[natenkiki2004]

The A4LD is more mechanical than it is electronic. Start simple.

I didn't mean to say that you should forget the filter, just don't think too much into it. It's not going to get all clogged up, your transmission would die before it gives up that much large debris. Good idea to clean the pan out but if swapping fluid is a primary goal, I'd suggest doing it with the cooler lines. Pump old fluid out while you pour new fluid in, easy-peasy.

 

[FR-425]

Sticking governor is the issue with cold shifting:

Simple to fix and costs nothing to pull it and clean it.

Do NOT have to drop the trans just the transfer case.

http://www.explorerforum.com/forums/showthread.php?t=155582

 

[Sigmundr]

Well, I replaced my kickdown cable this morning and got the retainer arm back on there. Unfortunately there is no change in the behavior that I can see. Still doesn't shift unless I drop it down manually.

I'll try that governor next tonight. Any other thoughts on what could cause this behavior?

 

[natenkiki2004]

I could be wrong but the governor usually caused problems with a cold 1-2 shift. Either from debris or scoring on the valve. The faster the output is spinning, the more force on the governor and it'll slide easier, that's my logic anyway. It shouldn't cause a problem with OD.

However, re-reading your post, I'm not quite understanding what you're saying. You say you keep it in 2nd up until 65MPH? What about D? If you're talking about the final shift up around 50-55MPH, that should be torque converter lockup, maybe that's what you're missing? What's your process, can you tell us at what gear you start in (as shown on the indicator) and at what MPH you are at?

 

[Sigmundr]

So to clarify. On my dash I have OD D 2 1. If I leave it in OD and D my RPMs sky rocket to 5k plus before I can even hit 30mph and it will not shift up on its own. So, in order to prevent the RPM spike I start off in 2. I can drive around town as long as I keep it around 35mph and I wont go above 3k rpm. If I hit the freeway, I move it back into OD and it will shift once more on its own once I hit the 60mph and 4k rpm range. It drops back down at 45mph.

I basically skip the 1-2 shift by forcing it into 2nd to start. I can feel it do the 2-3 shift at the high rpm on the freeway. I don't know if I have or at least cant feel a 3-4 shift.

 

[natenkiki2004]

Then I think you have a couple of issues OR a super frozen governor.

To start simple... It might be worthwhile adjusting the kickdown cable and shift cable. To adjust the kickdown, locate the grey half-circle 'button' on the cable coming out of the firewall in the engine bay. There will be 2, they both go to a cable holder on top of the upper intake manifold. From there, one goes to the transmission and the other goes to the throttle. Once you've found it, press the button in and pull the cable towards the radiator. Then hop in the truck and floor the gas pedal.

As for adjusting the shift cable, there should be a post on this forum about it. If nobody can find it, I'll scan the page out of one of my manuals and post it here. I think the jist of it is that you put the shifter in D and then disconnect the cable at the trans, pull the adjuster all the way out, manually put the trans in D by manipulating the bracket then adjust the cable until the two line up. There's something about putting a weight on the shifter too.

When I had the 1-2 cold shift issue, a bottle of Seafoam Trans Tune and spin-on filter fixed it for me (see my signature). You don't have to go the spin-on filter route but you can get a 3/8" Magnefine filter that splices into the cooler line (hopefully you have the factory aux cooler). Then I'd suggest putting half a bottle of Trans Tune in and driving a few hundred miles. At worst, you've spent $25-$30 on helping clean up the inside of the transmission.


If this stuff doesn't work, it might be time to drop the transfer case and peek at the governor. I'm glad I didn't have to go that route though, there's different information on springs and weights, aftermarket parts and aside from the dealer, I don't know where you'd get one.