4R55E: Broken hard parts? | Ford Explorer Forums - Serious Explorations

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4R55E: Broken hard parts?


March 22, 2011
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Year, Model & Trim Level
97 XLT
Hello, everyone. My daughter's '95 XLT with 4.0/4R55E is misbehaving, and I think I'm gonna do my first automatic transmission rebuild. I have experience building engines, but no transmissions. Until now. The trans has no reverse and no 1st gear. In Drive the car starts off slowly, the engine revving higher than it should like it's slipping, accompanied by a light rattling sound from the trans. It doesn't do any discernible shifting until 30 mph or so. Shifting into reverse, nothing happens, in manual 1st gear the same. The car cannot be pushed backward even in Neutral, the wheels just lock up. Codes are: KOEO: 327; CM: 327, 645, 646. Researching the codes a bit turns up EGR circuit below min. value and improper gear ratios in 1st and 2nd. I haven't pulled the pan off, but I think some hard parts are busted, maybe the low/reverse band and/or a broken sprag. What do you guys think? Thanks in advance for any input.

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Yeah maybe that band. Or maybe that same servo tip. See what's in the pan when you pull it also.

Resurrecting this thread, I got busy with a bunch of other stuff and had to put this on the back burner. Anybody else have any input or educated guesses about what the problem may be? I'm getting ready to pull the trans out, it would be great to have a clue as to what to look for.

Since you are going to pull the trans, get a ATSG trans manual, lots of useful information. Remove the pan and look for broken metal parts. If there are small metal pieces or shavings in the pan the torque converter will have to be replaced, as these pieces will collect in it and they cannot be flushed out, but may come out later and ruin the trans. Also the cooling line and cooler should be flushed. Yes the low reverse band may be broken, the servo stem tip may be broken, none of which would cause the poor forward drive condition, unless the valve body is contaminated, or the pump is bad also look for blown valve body gaskets and low reverse servo gasket.

Thanks for the suggestions. Any ideas about why the car can't be pushed backward? Sprag, maybe?

One of the clutches could be melted or fused together, caused by trying to drive forward while slipping.

Back again. Thought I'd follow up on this and tell you all that there were indeed broken parts in the trans. The forward gear set was brokededed. The planet was gunny-bag, the ring gear was in three pieces, the sun gear was munched, and the shell looked like someone took a hammer to the inside. The drive lugs on the OD clutch drum were beat up, too. So I get to rebuild it on the cheep. Sourced some good used parts, we'll see how it goes. Thankfully there's some good rebuild threads here, between them and the ATSG manual I think it's doable. Will report back when it's driving (or not).

Haha I had the same exact thing happen to my exploder. Thank god for a manual transfer case. Just popped her in neutral to roll her backwards if needed. Nursed it as such for about a month then she self destructed in a mud hole while pullin my buddies Chevy out. Coated my truck in fluid, got his truck out, and still made it home.