Somebody help me understand a little bit about the options available for using an automatic transmission on a project truck. I have a '56 Chevy 1500 that is going to be on the receiving end of a beefed up 454 ci big block chevy (425 HP or so), and have no idea what kind of auto tranny I should be looking for. I definitely want something with overdrive, for whatever that's worth. Can someone please explain to me the differences betweem at TH350, 700R4, etc?

Up until now, I thought we were going to be using a Muncie 4 speed. Dad, however, seems to have changed his mind...

A 455BB with a Turbo 400 AT might be easier to find. That combination was used for years by GM, particularly Buick.

TH400's are pretty easy to find and will take the abuse of a 454 real well. 700R4's are gaining in popularity now because they finally got their act together - they used to have a reputation for being kinda weak.

The 400 is a bit beefier than the 350 (and heavier)... which is why it became the auto of choice for a long time among the hot rod crowd. I hear some folks are getting good and beefing up a 350 now to where it can be used reliably and save some pounds... but those are mostly drag racers. Their definition of "reliable" is a bit shorter term than mine.

I'm also seeing 4L80E's getting used but I know zilch about those.


I was looking for a good comparison site for you and I found an interesting one on the 700R4 (to me anyway)

http://www.smokemup.com/tech/700r4.php

Either one of the 700R4 or the TH400 will have a real good support base in terms of aftermarket parts or shops that deal with them.


Edit: Forgot one thing... there is a difference between bell housings, so make sure whoever you buy from knows you need it for a Chevy. I'm not an auto trans guru, but I've had it beaten into my head there's three bell's out there... Chevy, "Corporate", and "BOP" (Buick/Olds/Pontiac). The Chevy or the Corporate will get the job done for ya (Corporate fits both Chevy and BOP).


One more edit: While plentiful, neither the TH400 or TH350 have overdrives. If having an OD is a necessity, I'd send you looking for the 700R4. Might try asking the same question on www.chevytalk.com to make sure I'm not steering you wrong. I'm mostly a T-10 or Muncie guy myself.

[This message has been edited by Boozoo (edited 9/21/2006 6:27p).]

Awesome - thanks!

WE already have the 454, so at least we're half way there!

How about a Powerglide?

TH400 w/gearbenders overdrive....or spend some cash to get a 700R4 built right.

CATAG: what the heck is gearbender's overdrive?

I would stick with a 400. If you are just making a cruiser, put a 3.42 rear end or maybe even a 3.73. I would not worry about an overdrive with a 454, as fuel economy is obviously not an issue.

Gearvendors:

www.gearvendors.com

It ain't cheap though.


That's a good point about economy not being much of an issue with a 454. I don't know what your budget is, but that might drive it more than anything when you start looking at how much all of this costs. One thing going for the TH400 is you don't really have to do much of anything to use it unless you just want to or you plan on doing some drivetrain abusing at the track.

That's just it. Fuel economy is an issue for me (i'm not building this thing to sit around), but I dont think my dad cares a bit (he'd be happy with it being a toy).

All good advice. I'm definitely leaning towards a TH400 with 3.73's out back...

Or getting a fuelie small block. Hmm.

Schall02 .... The subject of fuel economy has arisen ... and from that evolves the subject of emissions controls. Those expose the next question you might soon be considering: What carb should I choose to feed this machine?

The carbs selected by GM for the 350/455/454 Big Blocks in the years 60s thru 80s was the Quadrajet.

Now in the early days of emissions controls GM autos were having a devil of a time meeting standards with their Big Block lines. Not eager to have to totally redesign the big engines they were so proud of, GM decided to try to squeak under each standard wire by fiddling with the original Quadrajet carb. That was a joke. The outcome was plastic spaghetti vacuum lines that looked like a bird nest surrounding the carb that connected a variety of little vacuum valves, heat sender valves, and gosh knows what else. In the 70s they added electrical components to the Quadrajet to control things like idle mixture and and something else (I forget.) The result was about a dozen different models of the Quadrajet, each one developed to fit into some crackpot emissions control scheme of vacuum lines and miscellaneous valves. It was a worthless approach ... because by the second year in the life of the car most of the plastic lines were broken or misrouted or unplugged.

The moral of this story is, if you plan to go back with the Quadrajet you need to select a model that is basically devoid of the tinkerings of the GM intellectuals as they tried to beat the emissions system ... because I do not think you could duplicate the vacuum control systems of later model years.

I have rebuilt many Quadrajets and spent a lot of time correcting the routing of those vacuum lines on various models ... but I am not knowledgeable enough to advise you on which way to go.

I am sure several people can give you more and better advice so I defer to their judgement on which way to go. It is a subject to be considered even at this early date.

Schall,
Gotta agree with the 700R4 tranny. But I think you'll get better service out of a Holley or Edlebrock carb.
post pics of your project when you can.
Dennis

Our lifelong tranny guy in Dallas recommends the 7004R as well, though he highly recommended that it be from a 1986 model year. The guy knows his stuff.

If I buy one new, I'll probably buy a Holley carb (maybe 850 cfm). I really dont have much of a preference though if I can find a good used after-market one.

Somebody tell me how to post pictures and I will. I have to find someplace to host them before I can link to them, right?

Yes you do have to find a host. Mine went belly up last week and I lost my whole library!
I also would like a recommendation on free photo hosting that can be linked to. Also, it helps if the servive lets you browse your "My Pictures" folders to upload from.

Someone help us.
Thanks

Listen to your tranny guy... they know what breaks most often and why.

For a free host, Photobucket seems to be working pretty well for me. There are quite a few others, too. I also have paid web space at Lunar Pages that's been pretty much trouble free for the last 3 or 4 years.

Gracias!

A turbo 400 trans will work well, maybe an upgraded or modified would be good. I have one behind my overbored 455 right now, and it is a solid trans.

Quadra-junk!

700R4

Quadrajets are OK if you get the right one. Most people don't understand how to tune one.... if you do end up with one, grab a decent book on one and maybe hang out on www.v8buick.com. Even though you're dealing with a BBC, those guys LOVE Q-jets and will set you straight on them.

Your best chance if you buy a new carb no matter what brand you buy is to call their factory tech line before you go to someone else like Summit to buy it. Tell them exactly what you have (you'll need to know the engine specs, stall speed, rear gears, etc) and they'll get you in the right carb. Do that and the majority of the time, all you end up doing is just tweaking the idle mix.

I had twin Quadrajets on a 455 in a 1964 Electra 225. What a joke trying to tune two at once ... with most of the adjustments being in linkage. I doubt I ever got more than 5 mpg. Passing gear left a huge cloud of black smoke! (I saw one a couple of years ago in town ... same setup. I did NOT make an offer on it.)

wow! triple post ....

[This message has been edited by fossil_ag (edited 9/28/2006 10:20p).]

[This message has been edited by fossil_ag (edited 9/28/2006 10:22p).]

Right...gearvenders, I was close!

As promised...

Latest shot of the '56:


The aforementioned 454:

That looks like a real good start!

Saw this on Craigslist. What do you guys think I should think of it?

http://sanantonio.craigslist.org/pts/214041779.html

quote:

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700R4 CHEVY TRANSMISSION HEAVY DUTY - $500

I bought this tranny off ebay several months back for a project and never used it. I cannot remember all the specs on it but I shopped around for a while looking for the best, heavy duty trans I could find and this was it. It is completly rebuilt with all new soft and hard parts and all the best, performance, name brands. It is built to take over 600hp. I paid over $800 for it. This tranny is ready to be bolted in your hot rod.

---

While I know that it makes driving a lot easier, if you are dumping in an automatic with that beast of an engine .. erm you are going to lose something like 20-30% efficiency with an automatic due to the way an automatic works.

Torque converters are crappy and if you are going to spend for that kind of nice engine, why saddle it with an automatic? That is just sad to me.

You could get the same performance out of a nice 350 with a manual transmission that you are going to get out of that 454 with an automatic.

I agree with that, and would prefer a standard. My dad, however, whom this truck is partly being built for, wants an auto. So there ya go.

Not too shabby. Need to find out what it came out of so you don't get stuck with the weaker early versions. Play it safe and ask your tranny guy, too.

If you're concerned with fuel economy, Q-jet is the way to go. It's basically the next best thing to fuel injection in that regard.

I'd get one of the Q-jet replacements from Edelbrock though. IIRC, the throttle shafts waller out their bores in the q-jet as the miles go by and no amount of rebuilding or tuning will solve the idle/off-idle/vacuum leak issues.

I have a TH400 with a 3.73 rear and a 350 small block. Works fine for me and I have a 1948 chevy pickup

Remember the ABC's of good carburetion: Always Buy Carter.

Contact Carbking at the address below to give you the best information on carbs for that engine. It is VERY important to get a carb with the correct port sizes for the year and model of the engine. This is to ensure that you get the proper CFM to that engine. His prices can be high, but pick his brain to find out the correct match.

http://www.thecarburetorshop.com/