Has anyone tried putting a modern day automatic trans in there c body? Or is it better to go with overdrive?
modern trannys
- Thread starter Kelly Coleman
- Start date
bronze turbine
Active Member
My thoughts: modern trannies are completely computer controlled. You'd have to install some kind of computer controls in your c-body. Seems to me it would be a lot of effort and expense. I've heard there are overdrive kits that can be fitted to a c-body, but I've never seen or used one. I think that would be the better choice for cost and effort. If you were to go with the overdrive, you'd probably need to change the rear axle ratio, since most c-bodies already came with a very tall 2.76 gear.
Within the past two weeks, there was a thread on a poster who put a modern ZF 8-spd in a '66 Newport, plus the Gen III Hemi. The neat thing about this car is that the OP and some associates adapted electronics from other cars to make it work.
In prior threads on putting the ZF 8-spd in C-bodies, the electronics were replaced with a "tree" of brass fittings and manual pressure switches.
Way prior to that, a few car magazines had articles on replacing the OEM TFs with the 1980s TF+OD automatics (which might require a bit of transmission tunnel modifications). On those earlier TFs, OD was toggle-switched.
A MAIN thing when considering any OD automatic, other than cost of doing the job and getting the driveshaft length changed . . . is the resulting final drive ratio in OD. Which means in a carbureted car, best if the OD final drive ratio is above 2.4, depending upon rear tire size. That way, OD can be fully used on the Interstate below about 80mph. The OTHER thing is that if the car already has a 2.7 or 2.4 rear axle ratio, no gain in anything other than off-line acceleration as most of the 8-spd automatics have a low gear of about 4.50 or lower AND after changing the rear axle to about 3.55 or lower, similar OD final drive ratios will happen.
An engine with port fuel injection (especially) or throttle body fuel injection (as the early OEM systems were AND the bulk of the later "self-learning" carburetor replacement EFIs are) and can tolerate lower-number OD final drive ratios as they are not relying upon air flow through the carburetor to meter and atomize the fuel into the engine.
So, "possibilities exist" to do that modern TF conversion, just depends upon many factors of making it happen. Just do NOT figure to pay for it with fuel savings alone, in your lifetime.
One other side issue . . . you'll probably need a bigger alternator to power the computer system for the transmission and any EFI system. THEN you'll also need to perform the "Ammeter Bypass" procedure, of which there are a few threads in here on how to do and why.
Enjoy!
CBODY67
In prior threads on putting the ZF 8-spd in C-bodies, the electronics were replaced with a "tree" of brass fittings and manual pressure switches.
Way prior to that, a few car magazines had articles on replacing the OEM TFs with the 1980s TF+OD automatics (which might require a bit of transmission tunnel modifications). On those earlier TFs, OD was toggle-switched.
A MAIN thing when considering any OD automatic, other than cost of doing the job and getting the driveshaft length changed . . . is the resulting final drive ratio in OD. Which means in a carbureted car, best if the OD final drive ratio is above 2.4, depending upon rear tire size. That way, OD can be fully used on the Interstate below about 80mph. The OTHER thing is that if the car already has a 2.7 or 2.4 rear axle ratio, no gain in anything other than off-line acceleration as most of the 8-spd automatics have a low gear of about 4.50 or lower AND after changing the rear axle to about 3.55 or lower, similar OD final drive ratios will happen.
An engine with port fuel injection (especially) or throttle body fuel injection (as the early OEM systems were AND the bulk of the later "self-learning" carburetor replacement EFIs are) and can tolerate lower-number OD final drive ratios as they are not relying upon air flow through the carburetor to meter and atomize the fuel into the engine.
So, "possibilities exist" to do that modern TF conversion, just depends upon many factors of making it happen. Just do NOT figure to pay for it with fuel savings alone, in your lifetime.
One other side issue . . . you'll probably need a bigger alternator to power the computer system for the transmission and any EFI system. THEN you'll also need to perform the "Ammeter Bypass" procedure, of which there are a few threads in here on how to do and why.
Enjoy!
CBODY67
1970FuryConv
Old Man with a Hat
A518 seems most popular.
A518 conversion on a pushbutton 727
A518 conversion on a pushbutton 727
A500/a518 are straight forward hydraulic controlled. I have had a500 in mine for almost 15yrs.
Nag1 or TF8 can be done by writing a $1000-1500 check for the electronics. Plus buy the trans. Plus custom tunnel work. They are a superior product to be sure but order of magnitude more involved.
Flipping 8 switches all the time would be way worse than a manual VB trans on the street imo. Cool to prove it can be done but a pita to live with.
Nag1 or TF8 can be done by writing a $1000-1500 check for the electronics. Plus buy the trans. Plus custom tunnel work. They are a superior product to be sure but order of magnitude more involved.
Flipping 8 switches all the time would be way worse than a manual VB trans on the street imo. Cool to prove it can be done but a pita to live with.
As mentioned there are option, what do you mean by "Modern" what is the goal? Just OD? if so the 518/RH46 is a good candidate. It's essentially an old school 727 with OD on the back. The early 2 pin units are non lockup, later 3 pin has lockup and will need a switch for the lockup to engage. Challenge is that they only made them for Small Blocks. You can do it with a big block but need to do a bit of surgery by cutting off the bell and bolting on an Ultra Bell housing. makes it pretty easy for Starter mounting and end play etc. If you use an adapter plate there will be some pain and anguish to get things just right, but it can be done.
518/46rh is as modern as you would need to go due to the tremendous torque our big blocks put out . 6/7/8… speed tranies are used to keep a lower torque engine in a narrow powerband continuously.
Or for towing purposes….
Or for towing purposes….
I was a little curious about this thread, wasn't really thinking of a trans swap for my '67 Monaco (with small-block 318 and 727) but I did some goog'ling of the trans P/N's mentioned in this thread, and came across someone very near me selling this:
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Mopar 46 RH A518 over drive transmission. 2 wire pin control. Perfect for any mopar hot rod. Tranny worked good when pulled but should be resealed before using at a minimum.
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Asking $600 (CAN). I've reached out, no response yet. I like the idea of a lock-up convertor (which I guess this doesn't have) but at least the OD would give better highway MPG yes?
I am planning on taking the engine/trans out to do a sub-frame swap, so would this trans be an improvement? No electronics required?
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Mopar 46 RH A518 over drive transmission. 2 wire pin control. Perfect for any mopar hot rod. Tranny worked good when pulled but should be resealed before using at a minimum.
----
Asking $600 (CAN). I've reached out, no response yet. I like the idea of a lock-up convertor (which I guess this doesn't have) but at least the OD would give better highway MPG yes?
I am planning on taking the engine/trans out to do a sub-frame swap, so would this trans be an improvement? No electronics required?
He says drive shaft would def have to be shortened. Says I could re-use my t-convertor (not sure why?). Just need to apply 12 V to engage OD.
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It's probably not worth it from what I read. Parasitic losses are higher with the OD units so city driving will give worse MPG.
The whole purpose of this question was/is to try and get "BETTER" MPG. car had 2.92 or 2.76 gears OE[ have to look for sure] Has 3.23 now. Was thinking if I put a gear vender in and changed gears to 3.92 range, I could have "fun" when I wanted and better MPG crusing???
yes, I've been running 3.91's and moving down the road at 80mph in comfort for years. No way to do that without OD. Strong off the line and keep up with the Kia's on the freeway.
70bigblockdodge
Old Man with a Hat
OD is the only way to go nowadays. I know some of the old farts other than myself don't want the hassle, fine whatever.
My car has 3.23 gear and a .72 od ratio in a manual trans I'm in the mid 2k at 80 mph and I get 14-16 mpg from a 440 in a 68 Charger. Carburetor works fine, many mid seventies cars of all makes with super tall rear gear and 235/75r15 tires cruised many of thousands of miles in the 2 something range, and if it's too slow or gears to tall at 50 mph I put it back in 3rd and it's 1:1 again.
Nothing sucks worse than spinning at 3k plus at 75-80 mph for 4 hours and then a old lady in a KIA passed you at 80. No thanks. I'm cutting bending, hanging clutch pedals or whatever to put a od in any car I'm using to run any distances on the highway.
I had to drive my B.I.Ls. car back from this year's Nats in Columbus Ohio. 3.55 / 727 ,15" wheels with tall rubber and im running 3-3500 rpm 70-80 mph. Miserable and the A/C kept cycling off and on as pressure would climb to quickly because of probably 4k compressor rpm.
I put OD in the same category as headers they are a absolute must on all of my cars.
I don't need a od In my race car, but it will get something as I move towards a eventual drag and drive participation.
My car has 3.23 gear and a .72 od ratio in a manual trans I'm in the mid 2k at 80 mph and I get 14-16 mpg from a 440 in a 68 Charger. Carburetor works fine, many mid seventies cars of all makes with super tall rear gear and 235/75r15 tires cruised many of thousands of miles in the 2 something range, and if it's too slow or gears to tall at 50 mph I put it back in 3rd and it's 1:1 again.
Nothing sucks worse than spinning at 3k plus at 75-80 mph for 4 hours and then a old lady in a KIA passed you at 80. No thanks. I'm cutting bending, hanging clutch pedals or whatever to put a od in any car I'm using to run any distances on the highway.
I had to drive my B.I.Ls. car back from this year's Nats in Columbus Ohio. 3.55 / 727 ,15" wheels with tall rubber and im running 3-3500 rpm 70-80 mph. Miserable and the A/C kept cycling off and on as pressure would climb to quickly because of probably 4k compressor rpm.
I put OD in the same category as headers they are a absolute must on all of my cars.
I don't need a od In my race car, but it will get something as I move towards a eventual drag and drive participation.
330dTA
Senior Member
Gear Vendors is a good choice, but you’d be better off with a 3.55 rear end.
There never was a 2.92 option on a 300. Imperials had that. Standard gears for your ’70 300 would have been 2.76. (That is what I have in my ’70 NYer, and I hate it. Makes the car a dog.) 3.23 gears were an option 1970.
On FB you will find a site dedicated to mating a ZF8-speed with a RB big block. It can be done, and it improves the drivability phenomenously, but it it is a pretty laborious route. Not a drag-and-drop kind of thing. If you are mechanically inclined, go for it.
marty koirtyohann
Well-Known Member
if u put in a over drive u havr to modify the trany tunnel for clearance thats wha clay kussuth told me rhen u will only get 90k out of the 4 speed od mopar trany before its shot
marty koirtyohann
Well-Known Member
THERE R SOME SHOPS THAT SELL A ADAPTOR SO U CAN PUT A 700R4 BEHINND A MOPAR 440 THEY CLAIM IT WILL HANDLE 800+ Have BUT THE GUYS A&A TRANSMISSION TOLD ME DONT DO IT IF U TOW AANYTHING . THE TRANS HAS ALL IT CAN DO IN HANDLING THE CAR LE ALONE A TRAILER / NOW I KNOW U DIDNT SAYIF U EWAS GOING TO TOW WH IT OR NOT BUT IF IWAS U I WOULD STSY AWAY FROM THE NEW ELECTRONIC OVERDRIB=VE STUFF . ITS LIKE THE GUYS THAT TRY TO OPUT A 5 OR 6 SPEED SICK MANUAL YTRANY IN . TALK TO 1 OF THEM OF ALL THE HEADAKES THEY HAD TO GO THROUGH IT GE IT RIGHT (i HAD A FREIND THAY PUT A MODERAN STICK SHIFR IN HIS CHALLENGER AFTER 10 TRYS HE GOT 1 T]RIGHT . NOW HE DRIVES IT ALL OVER BU ONCE ESTARTED HE HAD RTO GO THROUGH IT xause they had chopped up the trany tunnel so much it ewould had costed him tripple to put it back stock
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