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Thread: Bellhousing cracked

  1. #1
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    Default Bellhousing cracked

    So I was reinstalling my 4r70w after jmod, with a new PI converter. The transmission mated up well, and the bolts were able to be threaded in most of the way by hand, including the top two (with intake removed). They were snugged with a ratchet. Going to torque the top two first to 50ft/lbs, there was little resistance until reaching the torque number. One of the top was torqued. On the second top bolt, the entire bellhousing snapped! I have no idea why.

    The TC was inserted and I felt two separate steps of it going in before bottoming out. This TC has no studs - it came with bolts to put through the flywheel.

    Anyone have any idea what the hell happened?! Should I find someone to weld the thing back together, or try to find another transmission? Mine is original, with only about 25k miles since it came new on a 2003 Mustang.

    Looking at the side of the bellhousing, the TC's...shaft thing sticks out just slightly from the bellhousing. I don't know how this is supposed to contact the crank or why, but it was a bit snug on removal, unlike the 12" unit that was stock (that one came right out). Lightly pressing with a prybar separated them though.

    Sucks! I was just about to finish buttoning it up - get the new exhaust on and drive!
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  2. #2
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    So I learned proper terminology - the "shaft thing" I mentioned earlier was the torque converter's pilot hub. Anyway, that thing was only partially was engaged in the crank. I didn't know where my spray greases were, so I smeared some engine oil on the pilot hub during installation. It wasn't close to bottoming out in the crank. I will go back and caliper this thing's outside diameter, but I would assume this wasn't the cause - especially since I had the thing already seated on all 6 bolts before I started torqueing! The inspection cover plate had no gaps on any side. Even the bolt holes for flexplate to converter were aligned beforehand to ease getting them installed. After putting the bottom 4 bolts in to keep the thing together, the top two threaded in by hand from the engine bay, until they couldn't go anymore.

    Took my damn time with getting this thing installed - checking everything! This is probably the 5th time I've put an AOD or 4r70w up in this car with no issues previously...

    That loud snap sound was terrifying, and a HUGE letdown...I really don't know what went wrong.

    The transmission was also on the jack the entire time, so one or two bolts shouldn't have had weird tension/stresses during installation.
    Last edited by Seek; 10-06-2014 at 12:47 PM.

  3. #3
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    Found one local welder that is mobile, and would come to my garage to repair this for under $200. I'm guessing that a proper weld would be stronger than the casting itself? Perhaps the ideal solution?

    I still would like to know what the hell happened. I can probably get a third set of eyes over here during installation to look it over as the two parts slide together (jrad). After all, mating them up only takes a couple minutes with a transmission jack!

  4. #4
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    Dang, I bet that did suck. I hate being almost done and having mechanical tragedies.

    I wish I had something helpful to say, but I don't. I just didn't want you to think nobody was listening, lol.
    CoogarXR

    1986 LTD Wagon
    1985 Cougar XR-7


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    I have a PI Stallion (AOD though). I don't remember if the pilot hub stuck out that much or not. I don't think it stuck out past the front of the bell housing. It was put in 4 years ago so my memory is a bit fuzzy.
    '88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, Edelbrock 70mm TB, 76mm C&L MAF, 30lb injectors, 2.5" exhaust, AOD with 2800 PI converter, 8.8 with 3.73 gears, 31 spline Traction-Lok, 31 spline Moser axles, 04 Cobra front arms, Maximum Motorsports extreme duty rear arms, subframes.
    '11 Focus, '12 Mustang 3.7, '17 Accord EX-L V6

  6. #6
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    Quote Originally Posted by thunderjet302 View Post
    I have a PI Stallion (AOD though). I don't remember if the pilot hub stuck out that much or not. I don't think it stuck out past the front of the bell housing. It was put in 4 years ago so my memory is a bit fuzzy.
    It doesn't seat any more than that. I know that is one of the things you need to check a dozen times to make sure it is in all the way - converter needs to pop in a couple times as you spin it. I think the first time I did an AOD, I didn't have it in all the way, and the bellhousing wouldn't slide onto the dowels/factory TC studs won't go through flywheel holes. Basically push in, spin, and wiggle, until the thing seats completely - normally two levels of "clunk" before it's completely seated. Even then, push more and wiggle to make sure it's in all the way. Not a difficult concept!

    I will be putting the factory one in today to see how it sits. I need to drain more fluid from that before mockups though - it keeps coming out!

    Also, I should mention that NOTHING was in between the block and bellhousing - all wires were tied up out of the way. I have the transmission wiring coming down from the firewall. The only things I had to watch when lifting was the linkage, one wire, one connector that comes out and goes back into the vehicle (?), and just mating up the two parts WITH a helper. Not much can go wrong, especially with no TC studs to worry about!

    I've run this by a few people and no one can give me a satisfactory answer. Everything I'm hearing to check, I've already checked many times during installation. We were at it for well over an hour, mating them up, and I kept checking all sides and transmission angles to make sure the thing slid on perfectly. I'm flabbergasted.

  7. #7
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    Stock 12" unit:
    Output shaft length: 2.1in
    Pilot Hub length: 0.73in
    Pilot Hub diameter: 1.378in
    Pilot Hub to Output Shaft length: 7 9/16in

    PI Converter:
    Output shaft length 2.55in
    Pilot Hub length: 0.72in
    Pilot Hub diameter: 1.377in
    Pilot Hub to Output Shaft length: 7 11/16in

    I don't have a way of measuring the thickness of the impeller and cover. The PI one is thinner, and has a longer output shaft.

    Basically, the PI converter is 1/8" deeper than the stock unit, making it stick out about 1/8" of an inch. While I didn't have a problem with what seemed to be perfect mating between the bellhousing and engine, this 1/8" thickness difference has me a bit concerned. The stock converter does not stick out past the bellhousing. Both were seated the same way, with a lot of pressure and wiggling. Perhaps just a fraction of this 1/8" during torquing is what caused the crack - if it went in even another 3/32 of an inch, but that last 1/32" put stress on the housing, the thing could snap. Everything would appear mated up near perfectly, but not quite. Cast aluminum doesn't bend like steel likely could.

    What is the difference for converters between AOD and AOD-E/4R70W? I'm curious if they sent me the wrong one? The paperwork references 4r70w though, including how to seat the converter into the transmission. PI's paperwork says I should have 1.030" +/0 0.050" of clearance between bellhousing and "converter pads"/bolt hole surface. No amount of wiggling and pressure will put the converter in any further to get it that close - I can't get clearance more than 0.90". Right there is 1/8" away from "1.030 inches". There is like a 1/3" difference between the second "set" feeling/pop in, and reaching 0.90" of clearance, so it seems to have slid into a 3rd section. I've been pulling it out and reinstalling quite a few times to see if I made any mistake, trying to find how to get it to go in any further. The TC came with plenty of lube on the output shaft, so I'm not having friction issues.

    I would THINK that it's not seating all the way with these numbers, but no amount of force will pop it in further. I haven't gone to the extreme and tried a hammer or anything - it should slide in all the way by hand.
    Last edited by Seek; 10-06-2014 at 05:35 PM.

  8. #8
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    I know nothing about it, just throwing it out there. Being that tranny came out of a 03 mustang, is there any possibility of the crank area being different on the 03 Stang that would accept that additional shaft sticking out????

    I really have no idea just thinking out loud for you, that kind of disappointment really sucks. Hope it is fixed quickly.
    Mike

  9. #9
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    Quote Originally Posted by mcb82gt View Post
    I know nothing about it, just throwing it out there. Being that tranny came out of a 03 mustang, is there any possibility of the crank area being different on the 03 Stang that would accept that additional shaft sticking out????

    I really have no idea just thinking out loud for you, that kind of disappointment really sucks. Hope it is fixed quickly.
    I have no idea - it shouldn't be. I've peaked at 4r70w threads for probably close to 10 years, both before, during, and after my install. I never saw such a problem. I assume converters with a cut pilot hub are done specifically for tolerance issues. In our cars it shouldn't matter though? After bolting everything up, the converter should pull out of the transmission slightly in order to bolt it to the flywheel, and connect the pilot hub. I didn't spin the crank to see if they were already contacting that much - a mistake on my part.

    I think I simply need to get the bellhousing fixed, using dye to see how far the crack actually went, then try again while verifying contact with the crank. Also pick up some more lithium grease and use that for lubrication of both the dowels and hub, instead of motor oil.
    Last edited by Seek; 10-06-2014 at 05:30 PM.

  10. #10
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    I would call PI. Just to verify that you got the proper converter.
    '88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, Edelbrock 70mm TB, 76mm C&L MAF, 30lb injectors, 2.5" exhaust, AOD with 2800 PI converter, 8.8 with 3.73 gears, 31 spline Traction-Lok, 31 spline Moser axles, 04 Cobra front arms, Maximum Motorsports extreme duty rear arms, subframes.
    '11 Focus, '12 Mustang 3.7, '17 Accord EX-L V6

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