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Old 07-09-2010, 11:06 PM
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454 T-400 Questions.

So I have a 78 Caddy with a 425 and (I think) a TH400 3 speed auto trans.

The trans shifts very nice, and I have no problems with it. The 425 has a HUGE amount of blowby, and just needs a full rebuild. I plan on making a mild rod out of this car, and would like to put some nice after market performance parts on it, and I can't really do that with the 425.

I found a dirt cheap 454 for sale that is in pretty good shape. It also needs a rebuild. I'd like to drop a 454 in the car for the ease of adding performance parts, since the parts are everywhere.

My question is, will the 454 bolt up to the TH400 without dropping out a year or two down the road? I know the TH400 is a beast of a trans from reading up on it, and have read in several places that they can handle 500HP without issues. (Which is probably the max I would want.)

This car will not be a drag car, but it might make a few runs down the strip in it's life just for fun. I'm building it for a cruiser, so it will rack up the miles pretty quickly. I just need to know if it will bolt up without issues later, and if it's even worth it to keep it.

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Old 07-09-2010, 11:28 PM
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Also, if I'm wrong on what trans I have, please let me know. Everything I've found says it's a TH400.
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Old 07-10-2010, 06:42 AM
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Quote:
Originally Posted by Rodillac
Also, if I'm wrong on what trans I have, please let me know. Everything I've found says it's a TH400.
A BOP tranny can be easily bolted up to a Chevy engine like the 454 BBC. It takes an adapter plate like the one sold by TCI.
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Old 07-10-2010, 06:51 AM
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That's what I thought. I saw that on several forums, but I also saw that the tranny wouldn't last more than a year, as well as the rear end.

Now, I just need to figure out how to rebuild a BBC for super cheap. lol
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Old 07-10-2010, 06:56 AM
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Quote:
Originally Posted by Rodillac
That's what I thought. I saw that on several forums, but I also saw that the tranny wouldn't last more than a year, as well as the rear end.

Now, I just need to figure out how to rebuild a BBC for super cheap. lol

How long the trans and differential last is dependent on the weight of your throttle foot.

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Old 07-10-2010, 06:57 AM
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It gets pretty heavy at times, but normally it's average.
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Old 07-10-2010, 07:47 AM
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Quote:
Originally Posted by Rodillac
It gets pretty heavy at times, but normally it's average.
Your Cad may have a "corporate" 8.5" 10-bolt rear end (center, look for the squared-off "ears" on the bottom):



If so, it is a good, strong rear end. You may have either a 2.56:1 ratio (a "2-series" diff, if it IS a corporate 8.5") or a 3.08 ratio, which is the "3-series" carrier. The 3-series is preferred because it allows a wider choice in ratios of aftermarket ring and pinions to be used.

You have a TH400- there's no problem w/the strength there, although yours will likely have the less-desirable 71-up intermediate roller clutch instead of the smooth inner race direct drum sprag-type. But rebuilt w/quality components, it will work fine for your deal, IMHO.
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Old 07-10-2010, 02:55 PM
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I was planning on either having it rebuilt or rebuilding it myself. Might as well since the motor will be out anyhow.
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Old 07-10-2010, 08:21 PM
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TH400s came behind many many many 454s. They have no problems with them at all. I am using a 78 TH400 behind a 454 in my 79 C10 and it has never been rebuilt. It sat outside of the old 78 for a few years under a tarp out in the elements without the cooler lines being capped. I didnt realize that until I went to use it. Anyways its still working fine and its been behind two 454s now. Tough trans.
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Old 07-12-2010, 01:12 PM
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Did you put it on the 454 with the adapter plates, or no?
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Old 07-12-2010, 01:18 PM
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Speaking for myself, I've used the TCI adapter both to use a Chevy engine and a BOP transmission (both TH350 and TH400) as well as the other way around- a 455 Pontiac w/a Chevy short tailshaft TH400 in a Camaro. Worked fine.
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Old 07-12-2010, 01:32 PM
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Sounds good to me, man.
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