Trasmission HELP!!
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500, 472, 425, 368 Discussion, Trasmission HELP!! in Cadillac Engine Technical Discussion; Hey Guys, We all have stories about how we took our cars out when we were 16 and blew them ...
  1. #1
    leehern is offline Cadillac Owners Member
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    Trasmission HELP!!

    Hey Guys,

    We all have stories about how we took our cars out when we were 16 and blew them up right...? Well Im 16 and I now have one of those stores. Needless to say I thought it would be cool to down some ricer friends of mine in the big boat... now my Trasmissions leaking oil.. wow I showed them! I knew the trasmission was weak but now its leaking constantly.

    I want to rebuilt it or get a new one so I have a few questions. Concidre in want to do the following to my engine
    -Cam
    -Intake
    -Carb
    -exhause
    -and eventually a full rebuild...
    what should I look for in a new/rebuilt trasmission, my main question is what should I run for a stall converter? What RPM? Keeping in mind I do plan to race this car again (hopefully with more HPs under the hood)

    Im also concidering buying a trasmission thats already been rebuilt
    Is there anything specail about our "cadillac" trasmissions aposted to any other Turbo 400 GM unit? Im just wondering incase I find a deal kickin around... also then I need to know what RPM stall converter to run...?

    Thanks guys, Im walking till I get this going so please help a Young Cadillac Lover out!

    Keep em Smoking (the tires not the trasmissions)

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  3. #2
    davesdeville's Avatar
    davesdeville is offline Banned
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    Re: Trasmission HELP!!

    Find the leak, it could just be a gasket which is easier to fix. Or have a shop do it. If it's screwed up internally you can buy a new TH400 or maybe find a junkyard one, or have a shop rebuild yours. If you get another one, Cads use the Buick Olds Pontiac (BOP) bolt pattern instead of the Chevy one.

  4. #3
    bryan1970 is offline Cadillac Owners Fanatic
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    Re: Trasmission HELP!!

    a th400 is a th400 as far as internals goes. the only diffrence is the bolt pattern on the bell housing. it is what is called the BOP pattern. (Buick,Oldmobile,Pontiac) and a th400 converter is a th400 converter. the only diff with converters sit aht there are 2 bolt pattern spacing. but most aftermarket performace converters have both paterns drilled into the mounting ears on the converter if you wanted a performace th400 TCI makes a rebult tranny with i belive a shift kit installed and performance oriented clutches and bands for around $850. in picking a converteryou gotta know the specs of the cam. and what kind of racing are you planning on doing. like is the car only gonna be on the track or is it going to be a daily driver that you just occasionally race on the street? becasue race only cars have stall speeds into the 3000rpm range. and having a stall speed that high on the street is just gonna be a big headache. where is the oil leak coming from, cuz as davesdeville said if it is a pan gasket or a leaking modulator those are fairly easy to fix.

  5. #4
    davesdeville's Avatar
    davesdeville is offline Banned
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    Re: Trasmission HELP!!

    What year and model car is it anyway?

  6. #5
    leehern is offline Cadillac Owners Member
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    Re: Trasmission HELP!!

    Its a 1976 Cadillac Deville, (500ci) 4 door hard top.

    I looked under it last night and it was dripping from the bell housing. I cant see a blown pan gasket causing that eh? Its obvious what caused it, I did liek three breakstand launchs when racing my buddys... Im sure thats the first time that cars ever had that done to it... I dont know much about transmissions so I assume its something internal thats causing it leak out throught the stall converter...? would that make any secne at all?

    The worst part about this is a raced this kid in a ricy honda and we were so close. we agreed to run again to determin a winner... then im liek AHHHH oil!!!! NOOOOOOO

    thanks boys

  7. #6
    bryan1970 is offline Cadillac Owners Fanatic
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    Re: Trasmission HELP!!

    iono what exactly could casue it but it sounds like it is leaking out of the seal that the converter goes in.was the car sitting a while before you got it. becasue the seals could ahve dried up and gotten hard. if they did get hard sometimes you can put some brake fluid in the transmission to get them to seal again. it is a red neck way to try and get a quick fix to it can be driven but if it gets the job done then go for it. and i wouldn't recomend racing the Lac untill you get the tranny fixed. gotta keep in mind those old caddys aren't really made to drag race. evenb though they do have gobbs of torque, which can be better utilized for burn-outs . but burn-outs are even hrder on the tranny so if you want the Lac to last long enough to get money for repair i'd drive it just like a little old lady.

  8. #7
    BluEyes's Avatar
    BluEyes is offline Cadillac Owners Enthusiast
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    Re: Trasmission HELP!!

    sounds like the front main seal. Thing leaks like crazy because there is tranny fluid being pumped right behind it.

    Good news is that it is a $5 part. Bad news is you've gotta completley pull the tranny to get at it. It's not too hard if you've got some good tools and some experience, just plan on spending the better part of a weekend underneath the car unless you've done it before.
    Oh, and be sure you remove the tranny cooling lines before dropping the trans. Kinked or broken tranny cooling lines will kill it really fast.
    Untill then, make sure you keep it topped off (but not over-full) on tranny fluid or else you'll be rebuilding it for sure next!

  9. #8
    celeronpm is offline Cadillac Owners Member
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    Re: Trasmission HELP!!

    I remember racing ricers After I rebuilt my 472 with all kinds of goodies, I would usually win no problem. I first snapped the u joints on my driveshaft then completely rosted my primary clutch. Ps, I was 18 and had a 72 caddy, 4 door. Im now 19 and think the caddy is just too heavy, and having the finances to move on, I have.

  10. #9
    TeagueJT81's Avatar
    TeagueJT81 is offline Cadillac Owners Fanatic
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    Re: Trasmission HELP!!

    Try not to let those ricers tempt you. Remember what you drive is a classic with character and class, and they're just driving slightly modified grocery carriers. I'll race one every now and then in dad's '93 4.9L Deville, but when I start driving the '81 I'm gonna treat it like royalty. It doesn't matter if you can beat them or not, your car was an awesome symbol of prestige in its day (and for all I know still could be) and theirs was a mass produced, fuel efficient thing that still can't turn heads, so you should win by default .

    Anyway, as for trannies...

    The TH400 seems to be the choice of most people. It's a solid tranny and can take the extra stress of almost any engine modification.

    Hardcore drag racers still seem to like the Powerglide for some reason. Don't know too much about it, but I think it's a two-speed and, if it is, wouldn't recommend it for you if the car's your daily driver (for obvious reasons).

    The 4L60E has a good reputation among friends of mine. One has one one his Caprice, and the '93 I drive at the moment has the front-wheel drive equivalent. It's good and solid, has overdrive, and the computer control is nice, but I don't think they can take quite the beating the TH400 can.

    To wrap this lengthy post up, I'd recommend the TH400. Other people here seem to like it, and it has a good rep as both a racing and daily driver tranny.

    - Joe

  11. #10
    BluEyes's Avatar
    BluEyes is offline Cadillac Owners Enthusiast
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    Re: Trasmission HELP!!

    If you want an overdrive, find a 4L80E (not the 60E). It is the good old TH400, but electronically controlled, and with a 0.75:1 overdrive 4th gear.

    Just remember that this wouldn't be cheap - need an adapter for the tranny bellhousing bolt pattern, a controller for the tranny, adjust the driveshaft length, and change the rear axle ratio. The stock axle ratios would be too low for the engine with overdrive added in...

  12. #11
    Phantom&RedGoat2004's Avatar
    Phantom&RedGoat2004 is offline Cadillac Owners Fanatic
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    Re: Trasmission HELP!!

    I'm not positive, but I think that the tailshaft on the Cad is longer than the other BOP sisters (input from others here, please). I feel like you have pretty limited expereince, so I would recomend that you pull the trans yourself (it sounds intimidating, but it's pertty straight forward), and take it to a shop for a "bench repair". It's the best of both worlds when you can get your hands greasy, and leave the specialties to the specialists.

  13. #12
    BluEyes's Avatar
    BluEyes is offline Cadillac Owners Enthusiast
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    Re: Trasmission HELP!!

    I'm not sure how the Cad trannies fit in, but there are several different length tailshafts for TH400's (just like TH350's) I'm not sure if Caddies were the only ones that got tailshafts this long, but they certainly are long. You do need to find the right length tailshaft or else your driveshaft won't fit.
    The longer tailshaft keeps the driveshaft a bit shorter which increases it's critical speed - the RPM where it wants to shake itself apart...

  14. #13
    Benzilla's Avatar
    Benzilla is offline Cadillac Owners Connoisseur
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    Re: Trasmission HELP!!

    Quick question while we're on the subject of trannys, My '79 leaks transmission fluid at the front of the transmission, I'm getting it fixed soon, and I'm checking the fluid, but I just wanted to confirm what my mechanic told me - it's the main seal right?

  15. #14
    BluEyes's Avatar
    BluEyes is offline Cadillac Owners Enthusiast
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    Re: Trasmission HELP!!

    Most likely.

  16. #15
    Benzilla's Avatar
    Benzilla is offline Cadillac Owners Connoisseur
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    Re: Trasmission HELP!!

    Thanks, just thought I'd check.

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