I bought the wrong transmission for my 66.

jpl572103 said
So this is from Brewers. Same casting number on my tailshaft.

Extension housing casting number C-99539 (with dual shifter pads, BOTH GOOD) for 1970-up B/E-body (also used on Dodge truck A833 overdrive 1976-1987) 18/23 spline input transmissions with 30 spline output/308 bearing. Baked and shot blasted. Uses SR229 bearing snap ring, NOT INCLUDED. (See EH539RO for extension housing, for use on E-body rear shifter location ONLY, $179.95)

I'm pretty sure my transmission is from a dodge truck 76-87 23 spline input, 30 out. And because the rear shift mount bosses have not been drilled, I bet this is not a B/E trans, but is out of a truck. 10-4. But!!!! I wonder if the B/E 4 speed will bolt right in due to the tailshaft housing casting numbers being the same.
As long as the trans mount location is the same? maybe. Great info on this site btw. Off to bed, have to wake at 3:15.

Here’s a great article with a bunch of info on the 833, and specifically the 833 OD.

4 Speed Transmissions transmission

If your transmission is an OD then it’s a truck transmission with that tailshaft housing. The B/E 833’s are the same length and use the same tail housing, but they never had OD transmissions as the OD’s didn’t start until ‘75.

The trucks used the forward shift pad mount (as did the B bodies), and E bodies used the rear pad. Since the rear pad isn’t drilled it means it was made after the E-body run ended, so, truck transmission. The F bodies also got overdrives but they used the A-body tail housing. The shift pad on the A/F body transmission is not in the same spot as the forward B body/truck shift pad location.

If your transmission is an OD it also has the 5.125” input bearing retainer.

So, if you want to keep your car as is, you can use a ‘70-74 B/E body 833. Driveshaft length will be the same, use the forward shift pad. You’ll need a spacer ring to keep your current bellhousing, or you’ll have to swap out the input bearing retainer on the B/E 833. I can’t remember if all the B/E transmissions had the 308 bearing but if it does you can just swap on the larger outer diameter bearing retainer because it has the same bolt pattern. There was also an “adapter” input bearing available for while that had a 307 bearing bolt pattern but the larger 5.125” outer diameter.

This article covers putting a B/E body 833 in an A-body, so it has some information on what was probably changed in your car

B/E body four-speed in an A-body