547975 3 Versions

General Motors Casting Number 54975 Bellhousing

The "975" is an aluminum bellhousing for B.O.P.

(Buick, Olds and Pontiac) engines.

Warning : I have found at least 3 different versions

of casting #547975 clutch housing.

I have one version that is identical

(except for the casting number)

to the 9785581 and 977822 clutch housings.

Another version has the "peanut" ball stud boss

with the upper area tapped (standard B.O.P.).

And yet another version has the "peanut stud boss

tapped in the lower area (78-87 A & G Body)

Transmission View
In this picture you can see the two starter housing (ears),
which allows it to fit Buick, Pontiac and Oldsmobile

engines. And the extra holes for Ford transmissions.
.

Part # 1
Some versions have the casting number that is cast

into the drivers side starter "ear".

Part # 2

Some versions have the casting number that is cast

into the drivers side, under the z bar mounting

bracket holes.

Top
The "V" at the top of the casting is another B.O.P.
identifier.

Fork side

The fork hole is the standard (Approximatly 3" x 2 1/4")

size.

Bottom
This bell takes the same type of,
one piece sheet metal clutch inspection cover as
the "581" and "882" clutch covers,
that is held in place by three 5/16"-18 bolts.

Passenger Side View

Clutch Side Version 1
Here you can see the two starter "ears" and the
engine mounting flange, with six clearance holes
for bolts and two dowel holes.

Inside View Version 1
This picture reveals the fork mounting stud location
and beefy reinforcements around all mounting holes.

Notice: The single stud mounting boss.

Clutch Side Version 2

All mounting holes are the same for all three

versions.

Inside View Version 2
This version has the double stud boss with the

tapped hole in the upper area. This makes it a

replacement for casting #9785581.

Quick Reference

Size: 166 tooth flywheel

Engine Bolt Pattern: Buick, Olds, Pontiac

Transmission Bolt Pattern: GM and Ford

Transmission to Bellhousing Threads: 1/2"-13

Center Hole Size: 4 5/8"

Ballstud Threads: 13/16"-16

Inspection Plate Bolt Threads: 5/16"-18

Face to Face Measurement: 6 5/16"

Starter Mounted: No

Starter Nose: Dual

Note: all measurements are approximate.

Disclaimer:

Factory correct applications are your responsibility. GM made part and part # changes with no rhyme but a reason (no production interruptions at any cost).

Application charts are for replacement parts that were available at the time of parts book printing, and when possible model specific assembly manuals.

My observations come from the parts I have in my collection or other reliable sources your parts may differ.

If Factory correctness is your goal, do more research, join car clubs,

forums and buy an assembly manual if one is available for your Project Car (you wont be sorry).

This is a fun and interesting part of the hobby!