Difference in T-400 BW and BA transmissions?

As I have mentioned before on the Forum I am changing over the 67 Sportwagon to a GS400 clone. I will be installing a rebuilt GS400 engine with a mild cam which originally came with a T-400 auto trans model BA. The Sportwagon now has a T-400 Model BW trans in it. Could the difference be in the shifting points or would one guess the BA is more stout for the 400 engine? I am going to rebuild one or the other to put in the car behind the 400 engine and looking for opinions or information on the two different models.

In listing the different models for the T-400 the Buick Chassis Service Manual discusses the operation of the different models when it breaks down the Servo and Accumulator functions which is all Greek to me. The BA and BW are listed differently in this section as the differences are pointed out in the Operation of Controls section for each gear or park. It would seem to make sense to use the BA model T-400 since it came with the 400 engine but thought I would get opinions or comments from knowledgeable folks on the forum.

Any Buick engineers out there that can furnish information? Any comments and opinions are welcome.

 

If the later Stage 1 transmissions can be used as an example, the BA probably has an extra clutch disc and higher line pressure through the use of a spacer washer on the regulator spring...but your wagon transmission may have some heavy duty elements of it's own. I'd use the BA, it probably has higher shift points and crisper shifts, all things being equal.

 

I am not a Buick Powertrain engineer, but I have rebuilt more 67 VP TH 400's than I can recall. The transmissions are identical, save for valve body calibrations. Your BW trans will work fine, assuming it's in serviceable condition.

The BB trans is one of the very few TH400 models that contained the different hard parts (direct drum piston, and 1 extra clutch/steel). The vast majority of all TH 400's from 65-69 are identical inside. The differences are in valve body calibrations, and they all respond to aftermarket shift kit installation.

 

Thank you much Jim and Rhett. Based on your comments and other discussions with a couple of folks I have decided to go with the GS400 BA transmission and then offer the Sportwagon 340 engine and trans for sale as a unit . The 340 is running well and there don't appear to be any issues with the transmission.

 

Not sure, but if one trans is a (67) switch pitch, and the other is not a switch pitch,
keeping a switch pitch in the car allows a notable improvement in smoothness
and performance when used with a manual switch or an electronic switch pitch
controller. Bruce Roe

 

To my knowledge, all 65-67 400's are Variable Pitch. But make sure you check.. in that vintage, the dual spade electrical plug on the side is the best way to ID it, with it still mounted to the engine. That dual spade plug was used later on, but not until the 69 models with the TCS system.

 

I think the pre-'70 units all have the more desirable smooth race direct drum and allows the use of a 34 element sprag (one way clutch). Can anyone confirm this?

Thanks, Matt