E body 4 speed trans.

What's the difference between a small block and a big block e body 4 speed transmission thanks!

the small blocks all used the 23 spline transmissions, the high performance big blocks used the 18 spline hd trans. there are alot of internal differences between the two. but its not a small block/big block difference. you can run a 23 spline behind a big block if your just going to cruise it.

I have a 23 spline behind my 440. 500 hp and 535 ft torque, no issues so far, but I don't drag race it regularly.

So your saying that a small block 4 speed transmission will bolt up to a big block without any modifications

The diameter of the input shaft bearing retainer has to match the hole in your bellhousing so you may need to change the retainer.

The input shaft spline has to match the clutch disc. May need to change the clutch disc.

There are two different throw out bearings for the two different input shafts. Might have to change that also.

There's 3 4spds, smblk, B, RB... 340/23 spline, 383/23 spline, 440/426 18 spline, there's also 2 different input shaft bearing flange diameters, so depending on the bellhousing being used, transmission being used, there's a lot of room for problems to arise when buying/sourcing parts, all the E body transmissions use the tailshaft shifter boss, the transmission external dimensions are all the same regarding bolt patterns/trans mount/ overall length/etc... many combos are possible with aftermarket bells, or machining factory bells..... I have a HEMI 18 spline 4spd behind my 340/6 with a factory bell and an 11 clutch, technically not doable, but with custom machining made possible..

Mike

You could do this, but chances are that you'll need an adapter ring for the input bearing flange to center the tranny, you need to measure the bearing flange outside diameter on the tranny, and you need to measure the bore on the bellhousing you intend to use, if the clutch disc on the BB is 23 spline, your good to go, everything else will bolt up


Mike

What is different between a 340 23 spline and a 383 23 spline?

All 340 23 splines had the 307( small) front bearing in 1970 up. I think 1970 started with 383 23 splines having the 308( big) bearing. It may have been just the rear tail housing bearing. I’ve got all three at the shop so I can look. It’s been awhile since I had a 70 383 trans apart. I’m pretty sure the 69 had the small bearing but the larger od on the bearing retainer. Brewers will know. Tell us what trans you are putting in what applications.

The E body 383/23 spline will have the larger input bearing retainer...

Mike

Yes. Correct. It has the larger 308 bearing just like the hemi 18 box. They both use the same od diameter on the retainer. I just double checked. The 69 383 still has the smaller 307 but it has the larger od bearing retainer size shared with the 68-71 Hemi box. It would still help to know the application of the op.

The SB AAR Cuda and Challenger T/A tranny in 1970 had a different ratio than the regular 23 spline 340 and 383 tranny had, Mopar swap to that close ratio in 1971 and later in both the BB and SB 833NP.
Similar thing on ratio change on the BB 18 spline in 1970 switching too a closer ratio in 1971

1970 E body the 340 Trans has the small bearing retainer, all BB and hemi have the next size larger bearing retainer. Otherwise I can’t think of any external differences to bolt one in.

All 1970 BB and hemi engines use the same bellhousing Aluminum 2982513

Let's not confuse bearing retainer size and bearing size. There are large retainers for 70 SB but with Small input bearing. SO the AAR/TA 340 also had a 307 bearing not the 308 as input?

The 70 SB had the smaller 307 bearing AND the smaller bearing retainer od. The 70 383 had the 308 bearing and the bigger od retainer. However. You could take a 69 383 bearing retainer for a 383 with the small 307 bearing and big Od and install it on a 70 SB trans to fit a 383 bellhousung. You just can’t take a 70 383 trans and install a SB retainer because it has the 308 bearing. You can if you use a 69 383 case. Yes the TA/AAR had the 307 bearing.

Thanks for all the input I should have stated in my original post that the transmission is hopefully going in a 1970 challenger with a 383 magnum.

Ok informative on the SB, I didn't realize they kept the retainer the smaller size for all small block along with bearing.

Yes. If you have a 70 SB E body trans, all you do is get the 69 383 bearing retainer and you are good to go in a 383.