Educate me - Crankshaft / 4-speed questions

[BuickGS65]

Forgive my ignorance -

(1) What is the "crankshaft adapter & bearing" used only on '65 GS 4-speeds?
Group 0.649 # 1365976

(2) Why does the '65 GS 401 ("400") have a different crankshaft vs. the ordinary 401 & 425?
Group 0.646 # 1372918 vs. 1361799

Thanks.

[Loren At 65GS]

Dan,

  That is the pilot bushing that supports and centers the transmission input shaft.  On an automatic car, the crankshaft end has a large hole machined into it. The torque convertor has a round part that fits up to the crank shaft end.
It is impossible to mate up an auto torque convertor if the crankshaft has a pilot bushing in place.  The pilot bearing must be removed, Been there and done that.

  So, in actuality, the cranks are the same.  The pilot bushing is an added in piece for the manual transmission application.

  Loren

[Loren At 65GS]

Regarding your second question. I would need to check the application of the part in regards to year.

In '63, the 401 and 425 were available, but the transmission options were manual or a Dynaflow automatic.  The rear of the crankshaft is machined for the Dynaflow and has a protruding lip which will not allow the use of a '64-'66 automatic flex plate.

  Loren

[gssizzler]

Adapter and bearing where also used on the 64-66 Wildcats and the 65-66 GS's! I want to say all 64-66 cranks where machined for this! Not sure about the earlier one's! Tom or Russ Martin would know this? As far as cranks don't know of and differences? The part number you have may be specific to the year used when the model first came out! Then some part numbers are grouped or superseded!

[WkillGS]

(1) What is the "crankshaft adapter & bearing" used only on '65 GS 4-speeds?
Group 0.649 # 1365976

That number is also listed for 64-66 Skylark GS & Wildcat in the 1940-72 master parts book.

Dorman products makes a bushing that will work.  # 690-035   Original app is for use as a chev powerglide adapter.
Prices are all over the place, from $45 on eBay to $10 on Amazon to $25 for a 5 pack from Rockauto.

[BuickGS65]

Thanks guys! I did not know this!

So my guess is that the 65 4 Speed crank already included the adapter - hence the different part number?

As far as everyone knows, the cranks are all the same for 64-66 400/401/425????

[WkillGS]

As far as I know, 64-66 cranks were the same.
It was written, perhaps in the 1980's, that the 425 crank was cast iron. That was incorrect, they are forged.
I believe it was '63 and earlier blocks that used a thrust bearing with a narrower flange. 64-66 main bearing sets have a different part number than 61-63.