No O/D on '91 A4LD

- U
- Ulysses
  
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posted
14 years ago

Mon, Jul 6, 2009 3:24 PM

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.

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- Ashton Crusher
  
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posted
14 years ago

Tue, Jul 7, 2009 1:41 AM

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.

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- Ulysses
  
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posted
14 years ago

Tue, Jul 7, 2009 2:32 PM

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.