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#66052 09/19/2006 9:39 PM | Joined: Apr 2001 Posts: 268 Shop Shark | | Shop Shark Joined: Apr 2001 Posts: 268 | Can anyone out there tell me when or what year GMC changed from a 4 bolt flywheel to a 6 bolt flywheel and when did Chevy change from a 4 bolt to 6 bolt? And the difference between a 153 tooth flywheel and a 168 tooth flywheel.
Dance like no one is watching,
Sing like no one is listening,
Love like you've never been hurt.
1948 GMC FC101 1/2t Pickup w/270 and SM420
1948 GMC FC253 1t Factory 80"x9' Flatbed Dually
1948 Chevy COE 2 Ton 8'x15' Flatbed
1950 GMC 354-24 2 Ton 8'X12' Flatbed w/Dump Hoist
1953 GMC 454-30 3 Ton 8'x14' Flatbed w/Dump Hoist
1953 GMC 454-30 3 Ton Cab and Chassis
1942 Clarkator 6 MILL-44 Heavy Aircraft Tug
1942 Ford (9N) Moto Tug with 1/2 yard Loader
1947 Oliver OC3 HG-42 Tract-Crawler Bull Dozier w/6' Blade
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#66053 09/19/2006 11:30 PM | Joined: Sep 2003 Posts: 1,820 Shop Shark | | Shop Shark Joined: Sep 2003 Posts: 1,820 | I've got three different Chevrolet flywheels on hand and one on my truck and all of them are 6 bolt flywheels. At least one of them is a 139 tooth flywheel which is for use with a 6 volt starter. The others are 168 tooth flywheels and they are for use with 12 volt starters. The crank on my old 52 model 216 was also set up for a 6 bolt flywheel. 6 volt and 12 volt starters are kind of hard to tell apart when looking at the teeth, but they are definitely different. GMC may be, and probably is, a different situation, especially the earlier years, 30's and 40's. Joe 
"Truckin' Around .......... Since 1937!" My name is Joe and I am addicted to Classic Country Music. I just can't hep myself.Operators are standing by to take your calls! Now cruising in the Passing Lane | | |
#66054 09/20/2006 3:13 AM | Joined: May 2001 Posts: 7,438 Extreme Gabster | | Extreme Gabster Joined: May 2001 Posts: 7,438 | GMC went to 6 bolt beginning with the '54 248. They and '55 1st series flywheels are 139 tooth and use a 6V starter. If you put a later 248, 270 or 302 in a 6V truck you'll need to find one of these flywheels or convert to 12V because they have 168 tooth flywheels.
Never heard of a 153 tooth flywheel. Are you sure it's GM? | | |
#66055 09/21/2006 12:14 AM | Joined: Oct 2001 Posts: 3,458 Extreme Gabster | | Extreme Gabster Joined: Oct 2001 Posts: 3,458 | The 139 tooth ring gear will fit on a 168 tooth flywheel if you have a machine shop turn the flywheel down to fit the gear. However, the converse is not true.
Paint & Body Shop moderator
A lone amateur built the Ark. A large group of professionals built the Titanic. | | | | | Joined: Apr 2001 Posts: 268 Shop Shark | | Shop Shark Joined: Apr 2001 Posts: 268 | Hi All,
This came up because my 270 uses a 4 bolt fly wheel and I was trying to find a larger clutch and fly wheel setup. My 270 has the 9 1/8 inch clutch.
I wanted an 11 inch clutch for towing. Then someone came up with a 4 bolt, 13 inch clutch and flywheel out of a school bus...weeeeeee, I bought it.
Then I found a 4 bolt, 11 inch clutch and fly wheel, which I also bought.
Then I found a 11 clutch and flywheel for my 248 which has a 6 bolt crank.
Dance like no one is watching,
Sing like no one is listening,
Love like you've never been hurt.
1948 GMC FC101 1/2t Pickup w/270 and SM420
1948 GMC FC253 1t Factory 80"x9' Flatbed Dually
1948 Chevy COE 2 Ton 8'x15' Flatbed
1950 GMC 354-24 2 Ton 8'X12' Flatbed w/Dump Hoist
1953 GMC 454-30 3 Ton 8'x14' Flatbed w/Dump Hoist
1953 GMC 454-30 3 Ton Cab and Chassis
1942 Clarkator 6 MILL-44 Heavy Aircraft Tug
1942 Ford (9N) Moto Tug with 1/2 yard Loader
1947 Oliver OC3 HG-42 Tract-Crawler Bull Dozier w/6' Blade
| | | | | Joined: Feb 2006 Posts: 1,867 Shop Shark | | Shop Shark Joined: Feb 2006 Posts: 1,867 | I only have one chevrolet 4 bolt flywheel. It came off a 1937 216 in a 1941 chevy 1/2 ton truck. Other than that all the Chevrolet flywheels I have are 6 bolt ranging from 1946-1954.
I'm a little lax on GMC info.
Jeff | | |
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