Auto conversion from 3 speed saginaw - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dgaskins21 · 03-10-2010, 08:45 PM

If I took an th350 off a 70's to early 80's truck what all would I need to do to get the bell housing tranny and drive shaft to fit my 68 C10 250cui?
Any help would be appreciated.

Thanks Dan

davepl · 03-10-2010, 08:58 PM

The Chevy bellhousing bolt pattern has been standard since at -least- 1955, maybe before that.

You'd need a flexplate that matches your starter (same number of teeth as your current flywheel, unless your starter is modern enough to handle both).

You'd need the converter for the TH350.

You'll need some kind of shifter, either a column and linkage from an auto truck or you could use a cable-driven floor mount shifter.

Sorry, don't know the difference in lengths.

culp7 · 03-10-2010, 09:00 PM

just my $.02 but i'd keep the 3-speed, they are getting harder and harder to find everyday and i personally love the uniqueness

dgaskins21 · 03-10-2010, 09:53 PM

Are you stating that a th350 will bolt to my current bell housing?
And all I need is to match up the starter teeth to the flex plate? Also a torque converter a cross member and a drive shaft?

capev86 · 03-10-2010, 10:05 PM

my 72 burb has the saginaw and i'm keeping it. gonna put a 406sbc in front of it and hopefully add the OD unit that was available. personally, if i was going to the trouble of changing over, i'd get a 200-4r or 700-r4 for the overdrive. the 350 is a good trans, but it sounds like you are losing the "fun factor" and not gaining any advantages, unless you do a lot of towing....which i plan to do with my truck with the saginaw.

Tx Firefighter · 03-10-2010, 10:55 PM

The TH350 has a built in bellhousing. You will need to remove your existing trans and it's bellhousing.

You will need to swap starter nosecones or buy a different starter too. Your current starter bolts to the bellhousing with 3 bolts. The automatic trans does not have this provision and the starter is therefore bolted to the block with two bolts. The nosecones interchange if you like to keep your current starter and avoid buying another whole starter instead.

You will need the auto trans flexplate (flywheel).

You will need to remove the existing trans crossmember (it's riveted into place) and install an auto trans type of crossmember beneath the tail of the auto trans.

Need shifter and cooler for trans.

dgaskins21 · 03-10-2010, 11:25 PM

If I could find a 700-R4 I would use it. My next question is about the drive shaft. Is there a difference in length or can I just bolt on the drive shaft I get with the new auto?

dgaskins21 · 03-17-2010, 03:41 AM

I went ahead and did a floor shifter conversion for my 3 speed works great I need to find a better frame though mine is rotted out in the rear cab is in great shape for a northern truck all repairable and so is the dog house thanks for all the help guys

03-10-2010, 08:45 PM	#1
dgaskins21 Registered User Join Date: Feb 2010 Location: Indianapolis Posts: 21	Auto conversion from 3 speed saginaw If I took an th350 off a 70's to early 80's truck what all would I need to do to get the bell housing tranny and drive shaft to fit my 68 C10 250cui? Any help would be appreciated. Thanks Dan

03-10-2010, 08:58 PM	#2
davepl Registered User Join Date: Aug 2006 Location: Redmond, WA Posts: 6,332	Re: Auto conversion from 3 speed saginaw The Chevy bellhousing bolt pattern has been standard since at -least- 1955, maybe before that. You'd need a flexplate that matches your starter (same number of teeth as your current flywheel, unless your starter is modern enough to handle both). You'd need the converter for the TH350. You'll need some kind of shifter, either a column and linkage from an auto truck or you could use a cable-driven floor mount shifter. Sorry, don't know the difference in lengths. __________________ 1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible

03-10-2010, 09:00 PM	#3
culp7 HickTown Join Date: Apr 2009 Location: ANDOVER, Kansas Posts: 355	Re: Auto conversion from 3 speed saginaw just my $.02 but i'd keep the 3-speed, they are getting harder and harder to find everyday and i personally love the uniqueness __________________ 1993 Ford Mustang Vert w/ 2.3 1969 Chevy C/10 w/350 1968 Chevy C-20 w/250 1976 Dodge Aspen W/ 225 2000 Toyota Tundra w/4.7 1987 Dodge Ram D-100 w/360 255/70-15 ___________ (oo)══╬══(oo) ‾‾‾‾‾‾‾‾‾‾‾

03-10-2010, 09:53 PM	#4
dgaskins21 Registered User Join Date: Feb 2010 Location: Indianapolis Posts: 21	Re: Auto conversion from 3 speed saginaw Are you stating that a th350 will bolt to my current bell housing? And all I need is to match up the starter teeth to the flex plate? Also a torque converter a cross member and a drive shaft?

03-10-2010, 10:05 PM	#5
capev86 Registered User Join Date: May 2009 Location: Eliot, Maine Posts: 1,314	Re: Auto conversion from 3 speed saginaw my 72 burb has the saginaw and i'm keeping it. gonna put a 406sbc in front of it and hopefully add the OD unit that was available. personally, if i was going to the trouble of changing over, i'd get a 200-4r or 700-r4 for the overdrive. the 350 is a good trans, but it sounds like you are losing the "fun factor" and not gaining any advantages, unless you do a lot of towing....which i plan to do with my truck with the saginaw.

03-10-2010, 10:55 PM	#6
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: Auto conversion from 3 speed saginaw The TH350 has a built in bellhousing. You will need to remove your existing trans and it's bellhousing. You will need to swap starter nosecones or buy a different starter too. Your current starter bolts to the bellhousing with 3 bolts. The automatic trans does not have this provision and the starter is therefore bolted to the block with two bolts. The nosecones interchange if you like to keep your current starter and avoid buying another whole starter instead. You will need the auto trans flexplate (flywheel). You will need to remove the existing trans crossmember (it's riveted into place) and install an auto trans type of crossmember beneath the tail of the auto trans. Need shifter and cooler for trans. __________________ I'm on the Instagram- @Gearhead_Kevin

03-10-2010, 11:25 PM	#7
dgaskins21 Registered User Join Date: Feb 2010 Location: Indianapolis Posts: 21	Re: Auto conversion from 3 speed saginaw If I could find a 700-R4 I would use it. My next question is about the drive shaft. Is there a difference in length or can I just bolt on the drive shaft I get with the new auto?

03-17-2010, 03:41 AM	#8
dgaskins21 Registered User Join Date: Feb 2010 Location: Indianapolis Posts: 21	Re: Auto conversion from 3 speed saginaw I went ahead and did a floor shifter conversion for my 3 speed works great I need to find a better frame though mine is rotted out in the rear cab is in great shape for a northern truck all repairable and so is the dog house thanks for all the help guys



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