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which auto trans for 56 chev?

3K views 27 replies 7 participants last post by  db flyer 
#1 ·
Hi all, I am new at this. and want to change my manual trans. to auto.
I will probably get a variety of opinions but so be it. I have a 56 chev with a 283 and would like some decent gas mileage. I am not going to hot rod or race, just need a basic auto so my wife can drive the car too. I have seen some folks talk about a 2004R and 700R4. I am mechanical inclined so could probably overhaul myself with help from member experience. Thanks for any help
 
#2 ·
I think you've answered your own question. BUT, if you use the 200R4 you won't have to change out or shorten your driveline. You may have to change out the slip yoke, depends on what trans you have now. It would be best if you sidemounted the engine, and you'll need a trans cross member; if you already have a trans cross member, it will need to be moved back to line up with the 200R4. You could also keep your front mounts (if that's what you have now), use a trans cross member, but also mid mount the trans at the bellhousing. All these are available from any of the tri-five vendors. The throttle valve linkage on the 200R4 or the 700R4 is a critical adjustment item.
 
#3 ·
56 chev auto trans?

Thanks for your reply junior stocker. I have a couple more questions.
Do you or any other member know where to buy a rebuilt 2004r or700r4
at a decent price? And do you think these are my best trans. options or
is there another trans. you would recomend? Also, I need a torque converter and was wondering if the $110 ones seen on Summit site are
really ok for just my type of cruising to the store and around town and not racing etc. ? Also, you mention installing the cross member under the bell housing allowing the use of current motor mounts, is that right. Thanks
 
#4 ·
The cross member would be installed at the transmission mount on the extension housing. IF you have stock type front mounts in your car, then with the engine mounted at the front and the trans at the rear, it makes for a lot of stress to those components, over that distance; so you would want to also support the "middle" somehow, ie. with what are called mid-mounts. Most guys will convert to side engine mounts and a transmission mount/crossmember (a 3 point style mount) like a more modern car/truck. I said go with a 200R4 because you have a 283 and were'nt interested in a "hot rod". If you ever plan to go to a larger CID engine (like a 350), it would be best to use a 700R4. BUT, a 200R4 will allow you to keep your stock drive shaft, and a 700R4 will need a new or modified shaft as that trans is longer. I don't think you can get a lock-up torque converter for $100.00, at least not a very good one. IF it were me, building the direction you seem to be going (a cruiser, not a bruiser) I'd go with a TH350, and it'll be the right length also as long as it has the 6 inch extension housing (TH350 trans come in 3 different lengths). NOW, don't forget that these overdrive automatics require some added electrical wiring to make them function correctly, while a TH350 won't. I'd watch CraigsList.Org in your area for a good deal on a rebuilt TH350 from a private party. You could also go with the TH350 lockup model; it'd be somewhere between a regular TH350 and an overdrive trans. ALL the tri-five/55-57 Chevrolet vendors have whatever you'll need to do any of these conversions.
 
#5 ·
56 chev trans?

Thanks again for the info J. Stocker. When you say a TH350 lockup is between a th350 and an overdrive trans. such as a 2004r what would that be? Sad to say I am not sure what lockup does. I have heard that a th350 is a 2 speed and the others are 3 speed. Does the th350 get very low mileage compared to the overdrive trans? I would like to make this conversion as simple and inexpensive as I can but not wind up with a
10 mpg car. Again thanks for the replies
 
#6 ·
TH350-C, or lock up TH350's, were GM's sort of first attempt at getting better milage with an auto trans. The converter has a clutch in it internally that "locks up" so there is essentially no slippage with the converter in lock up mode. That's what I meant by somewhere between a TH350 and an actual overdrive auto trans. IF your 56 has a stock rear end, and it was always an auto trans car, then the rear end ratio is 3.55:1. With only a 283, if you stick an overdrive in the car, the gears you have, it won't make for the "best" combo. You said originally, "cruising and around town"; you probably don't really need an overdrive trans. TH350 would be a lot cheaper than an overdrive, easier to install, and more than you need; a TH350-C would be one step above that, but before an overdrive. My 56 Sedan Delivery is a Borg Warner Super T-10 car, my 57 Sedan Delivery (former O/SA Junior Stock Class Drag Car) currently has a cast iron Powerglide in it (had been raced originally with an old 4-speed Hydro). It will probably get one of my own built aluminum Powerglides, or a TH350. It is a 220 HP 283 powered car. I personally don't have any experience with overdrive automatic transmissions, other than my 90 Mustang LX 5.0, which I just sold last week. I think I'll keep things that way. Powerglides, are 2-speeds, TH350's are 3-speeds, 200R4 is a "4-speed" with 4th being the overdrive, 700R4 is also a "4-speed" with 4th the overdrive.
 
#8 ·
56 chev. trans.?

Thanks J. Stocker for the info. My 56 has the standard 3 speed on the column and the stock rear end as far as I know. Dont think it was ever an automatic, so as I understand your info, when I change to a th350 I do not need to change rear end gears? Also, is there an electrical kit I need to install for the th350c lockup trans. and, the mild driving I intend to do around town would I benifit by the th350c ? I like the idea of better fuel mileage, but wonder what the cost difference between the two trans.
Thanks
 
#9 · (Edited)
If you have ever replaced a turbo 350 with a 200R4 or 700R4 you will probably never want a Turbo 350 again for several reasons the overdrive transmissions have a lower first gear ratio that will get you off the line quicker and on the freeway 2-4 more MPG, been there done that! now that I am back in the "Blue Oval" fold I am running an AOD.As far as the crossmember swap it is EZ since you are in AZ you can get the Trans-Dapt universal crossmember at Lopers,you check for level drill 4 holes in frame and bolt it in with grade 8 bolts about 30 minutes work.Get the Lokar TV cable for the new trans as they are EZ to work with.With either overdrive you will want a 1987-92 core as they have all the reliability upgrades.ABC Transmissions on McDowell in Phoenix is good on prices.
 
#10 ·
Your stick shift 56 will have a 3.70:1 rear end gear ratio. I still say, for your intended use, a TH350 would be the way to go. An overdrive will work fine, but do you really need it? If you do a lot of open road/freeway driving then an overdrive is just the ticket. But for just in town cruising and errands and such, you won 't be using overdrive. True, the overdrives have a lower first gear, that and your rear end gears will make it a bit more responsive. IF it were me, with how your car is currently set up, I would stick a 3-ring Saginaw 4-speed (3.11 first gear) in it.
 
#11 ·
56 chev. trans. ?

Thanks for the replys. I was leaning towards a lockup th350 I believe you call it. Hey J. stocker you through me a curve ball. What do you mean by a
Saginaw 4 speed 3.11 ? Is that the rear end and if so, 4 speed?
Also did you see my post about electric hookup for th350c ? Thanks.
Sorry about being so dumb on these issues.
 
#12 ·
Saginaw 4-speed; there are several difference ones, each with different gear ratios, and they're fairly cheap (I just gave one away, along with the Saginaw 3-speed overdrive trans I sold to the guy). The "3-ring" only refers to some circumferential markings on the input shaft splines. They come with NO rings, a single ring, 2 rings and 3 rings. The 3-ring came in Monzas and Vegas, and most consider it a light duty trans. BUT, it would be fine for a stock 283 powered, lower geared rear (such as 3.70:1), car that is just driven for enjoyment, and not beatin' on. You're cars already a stick, a Saginaw will both right in, and only need a yoke change and shifter. Besides, when people look in your car, and see the floor shift and 4-speed knob........... they;ll know it's not just another automatic transmissioned, yawn-yawn, nother' one.

You might want to go over to ChevyTalk.Org, the 55-57 forums, or Tri-Five.com. I go by 56sedandelivery on those two sites; a wealth of info is available on either one, although I prefer CT.Org.
 
#13 ·
56 chev. trans.?

I guess I must have creeped on the thread it seems to have gone off a little. My reason for changing out my chev. from the current stick shift on the column to an automatic on the floor is because my wife wants to drive the car, but will not because she is a little shiftless. Ha! So I am going to go auto. I believe from the members response a th350 or th350c will be an eaiser change. I dont want to change rear end gears if the stock one will work and not be detrimental to the auto trans. I believe you folks said I would need an elec. kit for a lockup 350c ? And would that be a little better than a non lockup for my mild driving around town? So, what do you think about the 2 trans. for my car and will my rear end gears which I think are 3:70 based on being told the car originaly came that way be alright. Once again thanks for all your help
 
#14 ·
db flyer said:
I guess I must have creeped on the thread it seems to have gone off a little. My reason for changing out my chev. from the current stick shift on the column to an automatic on the floor is because my wife wants to drive the car, but will not because she is a little shiftless. Ha! So I am going to go auto. I believe from the members response a th350 or th350c will be an eaiser change. I dont want to change rear end gears if the stock one will work and not be detrimental to the auto trans. I believe you folks said I would need an elec. kit for a lockup 350c ? And would that be a little better than a non lockup for my mild driving around town? So, what do you think about the 2 trans. for my car and will my rear end gears which I think are 3:70 based on being told the car originaly came that way be alright. Once again thanks for all your help

Just go with a TH350 NON LOCK UP.
 
#15 ·
I agree^^^
TH350C can be annoying around town, you'de have the Lockup switched off anyway because of engine lugging.

Factory setup 80-86 used a Vacuum switch :boxing: to control lockup, and you know those years the engine looked like it had a Spider Web of Vac hoses. 1 leak and the Lockup wouldn't work right. Lockup too early and wouldn't unlock when needed. :smash:
 
#16 ·
56 chev. trans. ?

thanks for the info guys. I have a th350 coming tomorrow, and was wondering after putting on the new cross member at the rear of trans. should I order mid mounts I believe J. Stocker called them? Do the mid mounts attach to the trans. bell housing? Thanks.
 
#17 ·
IF you have the stock front mounts on the engine, and are going to use a rear cross member trans mount, then the mid mounts are really something you should install. They bolt to the trans bell housing using the bolts that bolt the trans to the engine; the ones on either side of the engine-trans locating dowels. Then another part bolts to the stock frame ears where the stock bell housing mounts also mount; a biscuit type isolator goes between the two parts. I've known one person who only used the mid mounts, and let the trans hang off the engine like the stock transmissions do; I wound'nt trust that however with an aluminum bodied auto trans. IF your engine/car has already been converted to engine side mounts, then only the rear cross member trans mount is needed. E-bay has all the parts you'll need, and cheaper than the major tri five vendors normally sell stuff for. IF you go with side engine mounts, be sure the 283 is not a 57, as it will not have side mount bosses cast in the block.
 
#18 ·
56 chev auto?

Thanks for the info J. Stocker. I hate to bother you again, however I cannot find the mid mounts on ebay or summit ect. I must not be hitting the right website. Also cannot not find a crossmember so may have to go to junkyard and adapt something. Thanks
 
#19 ·
db flyer said:
Thanks for the info J. Stocker. I hate to bother you again, however I cannot find the mid mounts on ebay or summit ect. I must not be hitting the right website. Also cannot not find a crossmember so may have to go to junkyard and adapt something. Thanks

if you re-read junior post number 4, he tells you to find the side mounts at the tri-5 parts vendors

If you google tri 5 engine side mounts, many links appear
 
#22 ·
a 350 engine and turbo 350 transmission are really the standard hotrod setup. With your 3.70:1 rear gear ratio you will be turning about 3000 rpm at 60 mph with 26" tires. Thats how my pickup is setup and its fine for around town driving. You can even take it on short trips up the highway without issue.

The turbo 350 transmission is simple to setup, reliable as heck and all it needs is some downshift linkage hooked to your throttle and a vacuum line from the carb. You can find them rebuilt for cheap or buy a used one and have it rebuilt by a shop. also very cheap.
 
#23 ·
56 chev. trans?

Hi and thanks for all the info, especially Junior Stocker. I put the trans. in the car yesterday and started fabricating my motor mounts using the stock mount that mounted to the old bell housing. Next I will fabricate a crossmember. The next problem I have is my starter mounted to the bell housing, so I guess I have to buy another one that mounts to the block with the 3 bolts coming vertical from bottom of block. I guess the current starter was used for 3 or 4 years? My block looks to have the 3 staggerd bolt pattern. When I bought this car 3 years ago the owner said it was a 265 engine but when I checked the numbers on block it seems to come back as a 283. Anyway guess I`ll get this thing running someday. I bought a shifter from a mustang at wrecking yard and had to turn the trans. lever up instead of down. Think it will work alright. I may have to bend the rod so to get the shift sequence right without binding. Also, it seems as though I have to mount the shifter towards the driver on a little angle? Either that or fabricate a rod with a 90 degree at either end and see what I come up with for smooth shifting. Thanks again for listening and the info I`ve gotten.
 
#24 ·
The starter you need will depend on what size Flexplate you have.
153-tooth / 12-3/4" Flexplate uses a starter with a 2-Bolt straight across bolt pattern.
168-tooth / 14-1/4" Flexplate uses a starter with a 2-bolt staggered bolt pattern.
Make sure you get the correct knurled/shouldered starter bolts, some starters come with new bolts.
 
#25 ·
56 chev. trans.?

Well, another problem with the trans. conversion. Tried to put in drive line and wrong teeth match. The trans has 26 teeth and driveline has 16. I had seen a statement that the yoke could be changed, but dont know if Autozone or Checker, Napa would have one so wondering where to start. Also, when I put the drive line it look as though I would have about three quaters of an inch between yoke and tail end. Not sure if the yoke will even slip in that far. Thanks for your replies. This has been quite a project.
 
#26 ·
db flyer said:
Well, another problem with the trans. conversion. Tried to put in drive line and wrong teeth match. The trans has 26 teeth and driveline has 16. I had seen a statement that the yoke could be changed, but dont know if Autozone or Checker, Napa would have one so wondering where to start. Also, when I put the drive line it look as though I would have about three quaters of an inch between yoke and tail end. Not sure if the yoke will even slip in that far. Thanks for your replies. This has been quite a project.

the spline count on the t-350 is 27 on the out put shaft
 
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