question

[brigond]

As I have posted in the past , I'm looking to buy a 71 or 72 charger. I'm considering picking up a clean, plain charger at a lower cost and installing a big block later.I'm going to look at a manual trany , 318 charger. My question is ..... Would a big block (440) bolt up to the manual transmission that the original 318  is currently bolted to ? How about an automatic, would a big block bolt up to the same automatic tranny  a 318 engine is bolted to? Will I need to change the transmission in both cases? Thanks

[RallyeMike]

The bolt pattern on the back of small and big blocks are different. There are big block automatics trans, and small block automatic trans. For a 4-speed, the trans will work behind either, but the bell housing is different between big and small block engines.

[bakerhillpins]

IIRC the drive shaft is a different length as well. 

Can't find that thread right now though.

[brigond]

Thanks again. let me get this clear. So I will need a new trany along with a big block in the case of an automatic  car.

If the car has a manual trany I will be able to bolt up a big block ?

[The70RT]

Thanks again. let me get this clear. So I will need a new trany along with a big block in the case of an automatic  car.

If the car has a manual trany I will be able to bolt up a big block ?

The manual trans is the same but the bell housings are specific to big and sm blks. You will need a K-member or modify it.

[brigond]

Forgive my lack of knowledge on this. So the big block will bolt up to a small block manual trany even though the bell housings are different but I'm assuming the difference will cause fitting issues so the k member will need to be changed or modified. If I got it right , what kind of modification. How much is a k member for a b block?

[RCKSTR]

Forgive my lack of knowledge on this. So the big block will bolt up to a small block manual trany even though the bell housings are different but I'm assuming the difference will cause fitting issues so the k member will need to be changed or modified. If I got it right , what kind of modification. How much is a k member for a b block?

If you take the small block bellhousing off the transmission and install a big block bellhousing, yes, you can use the transmssion. A big block will not bolt up to your current small block bellhousing. I belive its an engine mount/oil pan issue that makes it neccissary to modify the K member. Someone else will chime in here with specifics.

[JB400]

I don't know if a smallblock trans will bolt up to a bigblock or not, but if it does, you'll be picking tranny parts out of your leg.  /6 and smallblocks both got the same trans unless it was in a high hp configuration.  Pick your parts carefully.  Big blocks had bigger parts for a reason.

[RCKSTR]

I thought there was only 2 versions, the 23 spline, and the 18 spline (hemi only). From what I understand the 23 spline will hold up fine unless your seriously abusing it (hard launches and slicks)

[JB400]

I think where you are getting confused is the big block had 2 different trans.

[Cooter]

The difference between the 18 spline and 23 spline transes as far as streength goes for the average "Street" car are nill. I've personally NEVER seen a 23 spline break but once. (Owner/racer knew it had a bad front bearing and beat the hell outta it until it skint the input shaft.)

IMO< the 18 spline is worthless to anybody but resto folks that just have to have it. I've seen 23 splines hold up behind BB Ford's, Chevies, Mopars, etc...Think about it, why would Chrysler offer a LOWER spline count as a STRONGER trans when EVERY single Axle manufacturer offers 40 spline axles as an upgrade? As far as I'm concerned there was only a couple A833's that weren't considered "Close ratio" trans's. OD and 1964 A-body come to mind.

As far as paying $1500 for one trans and $600 for the other? Gimme the 23 spline all day long. I've seen 'em live with Liberty conversions behind BBC's making in excess of 700 HP on slicks.

FYI- - The SMALL BLOCK had twoo offeringsa in the form of Automatic trans'...
The light duty 904, and the HEAVY DUTY 727..

BB only had ONE OFFERING in Auotmatic form....the 727...

[kab69440]

The lower spline count is due to the splines being physically larger. It is the stronger of the two inputs because there is less chance of stripping the splines in the clutch disc.

Also another correction: The 18 spline was not Hemi only. It was installed behind B/RB engines.

[Cooter]

The lower spline count is due to the splines being physically larger. It is the stronger of the two inputs because there is less chance of stripping the splines in the clutch disc.

Also another correction: The 18 spline was not Hemi only. It was installed behind B/RB engines.

Ofcourse, but Bigger spline count/ Stronger aside, I don't buy it. Maybe others will, but I don't buy it, as those VIPER T56 trans with those engines making WAY more power and torque than ANY 426 Hemi out the factory woulda had something like 6 Splines on the Input shaft, instead of the 26 Spline or whatever it has.

[kab69440]

A 6 spline count would be weaker, as the depth of cut necessary to create them would compromise the  structural integrity and thereby the torsional resistance at the center of  the shaft.  If you look at the input of the 18 and 23 inputs side by side, there is a marked difference in depth and breadth of cut. Of course, everything has its limit, and eventually the size if the spline will weaken the shaft itself.  The splined circumference is a way for the clutch disc to spin the shaft. The uncut center is what transmits that loading force into gearbox.


As I understand it, the problems with drag racing the 23 spline tranny were seldom with the input and more with the later models aluminum case. Those are what usually fail under high torque stress.

[Daytona R/T SE]

All "B" body V-8 K members in 71 and 72 will accept any V-8 from 273 to the 440 with the exception of the 426 Hemi.

Starting in 1973 the K members were different between the LA and B/RB engines

[bull]

Just buy one with a big block and save yourself the grief.

[RallyeMike]

All "B" body V-8 K members in 71 and 72 will accept any V-8 from 273 to the 440 with the exception of the 426 Hemi.

Yup.

For clarity,

1. If you have a 71-72 small block/automatic and and want to change to big block/automatic, you will need a big block automatic transmission. The drive shaft will have to be shortened. The K member does not need to be changed.

2. If you have a 71-72 small block/manual and want to change to big block/manual, the manual transmission will work, the drive shaft will work, but you will need to place a big block bell housing between the big block and trans to connect it.

3. If you have a small block/automatic and want to change to big block/manual, then you need everything from the motor to the drive shaft.

There are a host other changes that come with going from small to big block like, radiator, exhaust, and wiring.

Last comment: Small block 4-speed 71-72's are reasonably rare, so it may not be the best starting point.

[brigond]

Thanks . You  all answered my questions. I'll probably save myself the" grief". I just liked the idea of finding a manual trany in a nice condition charger. I figured it would be a good starting point. It is a good start if your lookin for a project.

[areibel]

I thought there was only 2 versions, the 23 spline, and the 18 spline (hemi only). From what I understand the 23 spline will hold up fine unless your seriously abusing it (hard launches and slicks)

There are basically two versions period, the 23 spline and the 18 spline.  If you're looking at a 23 spline, they're pretty much interchangable.  There are a few minor differences, the gear ratios are slightly different depending on what it came out of, and there may be differences in the shifter or trans mount locations are, but if you find a cast iron 833 you can bolt it in behind any /6, B or RB and be safe- if you'd blow one up, you'd blow any of them up.  The only ones I had any problems with were the later aluminum cased ones.  I put three into my mild 318 Aspen R/T before I gave up and swapped in an iron one.   For some reason I couldn't keep synchros in the aluminum ones, I tried two junkyard ones after I broke the original, and had one rebuilt by a pro- it broke too!  Always the same thing, big boom then stuck in gear.  The iron one outlasted the car.