No O/D on '91 A4LD

The overdrive suddenly stopped working on my '91 Explorer with the A4LD auto
trans. From everything I've read it sounds like the O/D sprag broke. I
have only a vague idea of what a sprag is. The trans will not engage at all
if I put it in O/D. It seems to still work fine in D, R, 1, and 2. Is it
OK to continue to drive it in D or is it likely that it will suddenly fail
and not go at all? Will driving it make it worse, just in case I decide to
get it rebuilt?

Others have suggested getting a rebuilt A4LD that has a bunch of
modifications that will supposedly make the trans stronger and more
reliable. Anyone have any opinions on this? I want to keep my '91 but
these transmissions sure add up. This would be the third and the truck only
has 232K miles on it. If I could be fairly confident that a beefed-up trans
would go for 150K miles then I'd be willing to go for it, assuming it
doesn't cost too much more than a regular rebuilt. A used trans doesn't
seem to be an option because I figure 3/4 of the Explorers in the junk yards
are probably there because of the trans.

On Mon, 6 Jul 2009 08:24:04 -0700, "Ulysses"
> wrote:

>The overdrive suddenly stopped working on my '91 Explorer with the A4LD auto
>trans. From everything I've read it sounds like the O/D sprag broke. I
>have only a vague idea of what a sprag is. The trans will not engage at all
>if I put it in O/D. It seems to still work fine in D, R, 1, and 2. Is it
>OK to continue to drive it in D or is it likely that it will suddenly fail
>and not go at all? Will driving it make it worse, just in case I decide to
>get it rebuilt?
>
>Others have suggested getting a rebuilt A4LD that has a bunch of
>modifications that will supposedly make the trans stronger and more
>reliable. Anyone have any opinions on this? I want to keep my '91 but
>these transmissions sure add up. This would be the third and the truck only
>has 232K miles on it. If I could be fairly confident that a beefed-up trans
>would go for 150K miles then I'd be willing to go for it, assuming it
>doesn't cost too much more than a regular rebuilt. A used trans doesn't
>seem to be an option because I figure 3/4 of the Explorers in the junk yards
>are probably there because of the trans.
>

I think it's a crap shoot as to whether it's ok to keep driving it.
The pieces of the broken stuff might screw something else up. When
mine did what yours is doing the OD thrust bearing disintegrated
letting the drum move backward and taking some other part(s) of the OD
with it but the transmission didn't make any funny sounds, just no
overdrive and it freewheeled when coasting. I only drove it a few
hundred miles like that. They showed me the parts and from looking at
them it's not obvious to me that there is really anyway to make it
stronger. The thrust bearing is quite small and fragile looking. I
think the only way to get more life would be to not use OD unless you
were cruising on the freeway.

"Ashton Crusher" > wrote in message
...
> On Mon, 6 Jul 2009 08:24:04 -0700, "Ulysses"
> > wrote:
>
> >The overdrive suddenly stopped working on my '91 Explorer with the A4LD
auto
> >trans. From everything I've read it sounds like the O/D sprag broke. I
> >have only a vague idea of what a sprag is. The trans will not engage at
all
> >if I put it in O/D. It seems to still work fine in D, R, 1, and 2. Is
it
> >OK to continue to drive it in D or is it likely that it will suddenly
fail
> >and not go at all? Will driving it make it worse, just in case I decide
to
> >get it rebuilt?
> >
> >Others have suggested getting a rebuilt A4LD that has a bunch of
> >modifications that will supposedly make the trans stronger and more
> >reliable. Anyone have any opinions on this? I want to keep my '91 but
> >these transmissions sure add up. This would be the third and the truck
only
> >has 232K miles on it. If I could be fairly confident that a beefed-up
trans
> >would go for 150K miles then I'd be willing to go for it, assuming it
> >doesn't cost too much more than a regular rebuilt. A used trans doesn't
> >seem to be an option because I figure 3/4 of the Explorers in the junk
yards
> >are probably there because of the trans.
> >
>
> I think it's a crap shoot as to whether it's ok to keep driving it.
> The pieces of the broken stuff might screw something else up. When
> mine did what yours is doing the OD thrust bearing disintegrated
> letting the drum move backward and taking some other part(s) of the OD
> with it but the transmission didn't make any funny sounds, just no
> overdrive and it freewheeled when coasting. I only drove it a few
> hundred miles like that. They showed me the parts and from looking at
> them it's not obvious to me that there is really anyway to make it
> stronger. The thrust bearing is quite small and fragile looking. I
> think the only way to get more life would be to not use OD unless you
> were cruising on the freeway.

With my luck (I don't buy lottery tickets or go to Vegas) it'll mess up
everything if I keep driving it, from what you said. Since I don't know
what's inside the transmission and don't understand how they work it's a
mystery to me which parts others were talking about to replace to make it
stronger. I guess I'll try to find out it the thrust bearing was one of the
parts that can be replaced with a stronger version but it doesn't sound very
hopeful.