91 Trans Reverse Problem

[wsu-nick]

Hi, I am new to this forum, so please bear with me. I recently bought a 91 EB 4wd 2dr with the auto A4ld trans and 111,000 miles on it.

The vehicle was sitting for about a year, but aside for some rust and minor mechanical problems it seems to be in pretty good shape. The previous owner said that periodically it would not shift into reverse.

I have been driving it for about two weeks and during the first week this only happened to me one or two times and then it would pop into gear for no obvious reason. During this last week it seems to be getting progressively worse and more reluctant to go into gear. There seems to be no real difference as to whether it matters if it is hot or cold.

I checked the fluid today and it is pretty dirty and way overfilled. Also, on a couple of real cold mornings the trans started to slip, but that quit when it warmed up. I am fairly mechanically inclined, but I am clueless when it comes to transmissions. Any suggestions would be greatly appreciated.

Thanks ahead of time.
Nick

 

[glfredrick]

If the transmission is not engaging reverse, then it likely has a low reverse servo problem. That is generally a hardened o-ring seal on the low reverse piston, which is fairly easily repaired at home - even by a beginner.

You can do this work yourself without having a lot of skills. You don't really have to know anything about rebuilding a transmission to drop the pan and check out the linkage. Just have a large drain pan, a small socket set, and a new gasket/filter set and, of course, the new low-reverse servo seal (you can pick one up at almost any transmission shop - just take the pics from this post with you so they get the right part) for your truck (before you start).

Begin loosening all the pan bolts - and leave the row across the front of the pan tight for now - remove all the bolts around 3 sides - and get the drain pan under there - then slowly start loosening the front side bolts. The pan will tilt down, and the oil will come out of the rear area into the pan. Continue to loosen the bolts until you have drained as much oil as possible out of the pan, then remove them and the pan entirely.

Then, you will need to look for this:

Originally posted by Glacier
Other than being right side up, this is what you will find under the Explorer if you remove the pan. One problem area that can be easily fixed with the transmission in the car is the low/reverse servo leakage problem - the delayed engagement in drive or reverse and the "jerk" on engagment. Here's the servo cover you need to remove:

Originally posted by Glacier
Here's the servo out of the bore. Replace the seals using a new version and your delayed engagement problem will be solved. Use vaseline lubricant (you know how to do THIS right ?) to carefully put it back in the bore.... make sure you first remove the gasket - it tends to stay on the valve body - put IT on the servo cover which goes on last after the servo body is in the bore.

The seals in question are the ones directly under Glacier's thumb - the rubber o-ring seals on the aluminum piston that comes out when you remove the servo cover.

Again, this is simple work - requires no expertise - and no special tools or parts, except for the pan gasket - a new filter (comes as a kit - and make sure you get the 4x4 version, which has an extended filter pickup as shown on the picture below (the white piece that sticks into the pan off the filter).

If the A4LD is popping into gear, then the adjustment for the shift mechanism is likely out of adjustment.

That could come from a couple things - including body sag from a rusting body - so I'd spend some time under there checking things out.

Do a visual on the external linkage - make sure that it is not pulling or anything (please block the tires!). Then, the next step would be to pull the pan and examine the way the internal linkage is working. The shifter operates an internal toothed plate that engages a roller (called a detent)(which holds it in "gear" - which is just a hydraulic valve moving in and out, by the way). It the roller is damaged or missing, that would allow the transmission to shift any time it wanted to - definately a dangerous condition.

The linkage runs alongside the driver's side of the tranny - and you will see the shifter linkage from where it crosses into the case. Check out this set of pictures for more details...

On the first picture, you can clearly see where the roller detent engages the shifter plate - the second picture is a detail of the shifter plate. If the roller is missing or damaged, that will be your problem, otherwise, it is an adjustment issue.

These pics and quotes come from this thread: http://www.explorerforum.com/forums/showthread.php?t=103582&highlight=A4LD+rebuild+diary

Hope this helps.

 

[wsu-nick]

Thanks

First of all, Wow and Thanks glfredrick. I never imagined I would get such an informative response. The thread is better than a shop manual. I am going to replace the servo on my next day off. Thanks for taking the time to respond to my problem. I really appreciate it. Nick

 

[glfredrick]

No problem - but the thanks is probably due to Glacier becsue he originated the info that helped me to my own repair as well... I just took a few miniutes to type something up for a beginning mechanic.

 

[Opera House]

Just want to add another thing. Don't buy another filter that looks like that! That is the older metal screen filter that really doesn't filter anything small. There is a newer Microfelt filter that also fits this transmission that might just keep your valve body from clogging.

The SPX MicroFelt filter is available from www.bulkpart.com for half the price of the auto parts store. This is Ford's OEM filter and it works for all the A4LD family through 5R55E. If buying local (about $23), ask for a filter for the 97 V6 OHV Explorer. You must use the new mounting hardware or the filter won't tighten up properly.

23921 Microfelt filter 4WD long pickup tube $10.35
23922 Microfelt filter 2WD short pickup tube $9.99

These must be ordered separately, you are buying bulk!
23270 filter O ring large $.29
23271 filter O ring small $.48
23141 pan gasket cork $.69

TMA4LD manual is $16 if you want to learn more about your transmission. They have the gasket/seal kit for about $30 that has the improved double lip low/reverse seal. The seal kit includes the above O-rings and pan gasket.

 

[ol_ben]

For about 4 years now I have been having problems with auto trans in my 93 explorer.

History:
This is the 3rd transmission in the car. The original went out at about 75k. Through a friend, I bought a rebuild ( Trans 2) from Jasper and swapped it out during warm weather. All was fine until the weather began to cool down. Then the trans would delay entering reverse in the mornings.

Since Jasper offers a 3 year replacement and labor guarantee I inquired about a fix. Jasper made myself and my friend jump through hoops before agreeing to replace the transmission.

Transmission #3 worked fine throughout the rest of that winter and following summer. When the weather began to cool down - same problem developed. Delayed reverse - sometimes up to 10 minutes - until everything warmed up. It was hard to beleive that 2 Jasper thansmissions would have the same exact problem.

Due to the amount of trouble and extra work put upon my friend I chose not to persue an additional replacement. I modified my driving habits - backing in or ensuring a grade to roll back out of whenever parking.

It has been about 3 years now and The reverse delay is continually worsening. Its a toss-up whether reverse will engage no matter how long the car has been running. The rest of the transmission performs well. Never a delay in first gear and shifts well in all others.

This reverse delay led me to the threads by Glacier991 and OperaHouse regarding the first/reverse servo and have ordered and received the following parts from www.bulkpart.com :

23031 "Overhaul kit, A4LD 85-95"
23921 Filter A4LD / 4R44E 4WD 86-up

The overhaul kit has so many so many "O" rings among other seals and gaskets that I am not sure I can locate the proper ones for the filter and servo. I am not sure I can recognize the "improved double lip low/reverse seal"

I have not removed the pan transmission yet and will probably not be able to do so for about 2 weeks.

3 questions:
1. Once disassembled will the proper o-rings/seals be evident?
2. Is it the opinoin of those knowledgeable of the A4LD that this will solve my delayed reverse problem?
3. Is it worthwhile to remove and clean the valve body while I have got the pan off?

Thanks,
Ben

 

[Glacier991]

Ben... some kits do not have the double lip seal.... whatever seals you have, the big one (the one that was doubled lip) will be about 2-1/2 - 3 inches in diameter and look different than an O-ring seal... and once you have the piston out the seals which go on it should be pretty evident by size. (And you may not have the double lip seal) But the reverse delay could also be other things... like a leaky pressure regulator valve (reverse gets a boosted line pressure), a cracked servo (unlikely), etc... While you have the valve body exposed, I would not think that it needs rebuilding since it supposedly recently overhauled, but I might suggest you add the Sonnax (or equivalent) O-ring sealed pressure regulator valve....(see the Rebuild Part of the A4LD rebuild thread in useful threads forum). As a matter of precaution I'd also consider the manual valve modification. There is an ongoing A4LD valve body rebuild thread, follow it closely. We are all ready to help.

(My kingdom for line pressure readings on Ben's tranny)

 

[hermitrl]

Just curious--kinda sounds like my problem Glacier? May be worthwhile to do anyways while I get the fluid changed?

 

[ol_ben]

I called Sonnax earlier today and found thay do not sell direct - only through distributors. I did talk the tech support peopls and explained my problem and asked if the O-ring sealed pressure regulator valve and the manual valve modification would solve the problem.

The tech said perhaps, but thought that I may already have the o-ring sealed regulator as he said Jasper was one of their biggest customers and that is commonly replaced component. He also said that the manual valve may help and suggested I disassemble first to see if either of those parts are present prior to purchasing them. He suggesed that a partially clogged trans cooler could cause the reverse problem, I countered with -wouldnot that affect the rest of the gears as well? We talked about the reverse servo sleeve kit as well.

I was ready to order, but I guess I will wait until I open it up first to see what it has and what it needs.

Also what is a good source for the Sonnax parts. The local distributor prices seemed kind of high especially considering I could buy a complete counter shaft for the manual transmission for less than the o-ring sealed boost kit costs.

The whole discussion with Sonnax left me wary that I may be in for more than replacing a couple of components on the valvebody. They suggested there could be some other significant leakage problem. I hope not. The goal is to fix it in a weekend.

Thanks,
Ben

 

[zebrex]

Im wanting to do the reverse servro piston seal upgrade to my 94 as well but I am very comfused on parts

1 can I buy the upgraded O ring/seals as a kit or do I need to buy a whole Gasket set?

2 If I buy the whole gasket set does it come with the filter or do I have to buy that seperate, also confused as to what filter to buy, filter for 94 or 96

A local trans shop priced the complete trans gasket seal kit for $65.00. This seems high to me.

 

[msmith65]

For anyone attempting this, I suggest buying two of each of the seals. I broke one of the new ones trying to install it. That left me with no source of a replacement part on the Saturday afternoon I had committed to fixing the problem, and I needed to drive the car Monday morning.

So I put on yesterday's underwear and toughed it out. :-(