Need some help with Flex Plate questions...Please. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ChevyDude · 01-26-2005, 05:27 PM

Ok...converting from 3 on the Tree....Not that TREE.....kidding... Let me rephrase....So I'm changing from a 3 speed trans to a 700r4 trans. Engine had a flywheel of course...the question is: How do I determine if I need a 168 tooth flex plate or a 153 tooth flex plate??? Those two seem to be the popular ones for a 350... which I have in this truck. Thanks guys!

neonlarry · 01-26-2005, 06:25 PM

Which starter bolt pattern do you have? The staggered bolt pattern goes with the 168 toothed plate and the 153 toothed unit has the straight bolt pattern.

ChevyDude · 01-26-2005, 06:36 PM

Don't really know the starter bolt pattern....looks like there is 3 bolt holes for the starter forming a squished triangle....Block stamp # 3970010 oil dip stick on the driver's side

3 on the tree · 01-26-2005, 07:19 PM

If you had the motor behind the 3 speed, why not count the teeth on the old flywheel, then get the same tooth count on the flexplate.

neonlarry · 01-26-2005, 07:22 PM

I think all blocks have three holes but the starters have two, straight across or diagonal (staggard). Do you not have the starter? If you have to get a new one take your pick just get the flex plate that matches.

ChevyDude · 01-26-2005, 07:23 PM

Does that work???? and ahhhh had no motor behind the 3 speed...but did have a 350 in FRONT of it. LOL!!!

Starter is long gone...soooo now what?

3 on the tree · 01-26-2005, 07:30 PM

Quote:

Originally Posted by ChevyDude

Does that work???? and ahhhh had no motor behind the 3 speed...but did have a 350 in FRONT of it. LOL!!!

Starter is long gone...soooo now what?

Sorry, I thought it was a front wheel drive(?). If you still have the flywheel you were using, count the teeth on it, then you can get the same on flexplate, and matching starter.

da-burb · 01-26-2005, 07:40 PM

If I am understanding what you have asked you would need a 168 tooth flex plate. The starter that was on your 3spd manual wouldn't be the one to use after the swap. Manual transmission starters have a different nose cone.

ChevyDude · 01-26-2005, 07:41 PM

So what I'm hearing ..is just get a starter and flexplate that match that are for a SBC and I will be good to go. In that case...don't I have to get a smaller starter for the 700r4 anyway?

tommie · 01-26-2005, 09:03 PM

if your going to buy an starter and flywheel, just get the ones that match. i usually go to the auto parts and tell them different years of vehicles that i want my parts off of.

just get the starter and fexplate for the same vehicle. make sure you get the right flexplate, some have a weight on them (externally balanced?) like for newer model 350s (i think the first one i tried was a 91 chevy truck, it had this weight on the flexplate, and wont work with an internally balanced engine) i think i ended up getting a flexplate and starter for a 76' 1/2 ton 2wd thats what i used for my 350, and 700r4 combo. the bolt pattern for a th350 and 700r4 torque converters are the same (correct me if i'm wrong). also be sure to take the old pilot bearing/bushing out of the end of the crankshaft, sometimes the torque converter wants to hit it if its left in there.

time for another beer.

jimfulco · 01-27-2005, 03:12 AM

A 168-tooth flywheel is 14" in diameter. Counting teeth will drive you nuts.

dwaite72lnghrn · 01-27-2005, 06:47 AM

If you need a starter also the only issue's would be what size torque converter and what 350 you are using. Most flexplates are drilled for 2 most common sizes 9.75" and 10.75" torque converter and is the 350 a 2 piece rear seal '85 and earlier or a 1 piece rear seal '86 and later, The crank is a different size. Then buy the flexplate for your application and a starter to match. I think the 153 tooth flexplates are 12.75" and the 168 tooth are 14" in size.

Tx Firefighter · 01-27-2005, 08:36 AM

If it's a pre 86 engine, that is 2 piece rear main seal engine, the most common flexplate is the bigger one. Pioneer part number FRA-100, available at most any parts store.

It's common enough that most parts stores will carry 5 or 10 in stock at all times.

ChevyDude · 01-27-2005, 11:17 AM

Thank you all very much for your help. Engine is pre 86, so it must have a 2 piece rear main seal so 168 tooth it is. Thanks again guys!!

mrein3 · 01-27-2005, 01:57 PM

Don't forget to get shorter flywheel to crank shaft bolts. The ones you got now will be too long with your new flex plate.

dwaite72lnghrn · 01-27-2005, 06:55 PM

Measure your torque converter. The 14" flexplates were drilled for the 10.75" and 11.5" converters from trucks with big TC in th400's. The 1 piece seal engines have a 3" crank mount and the 2 piece seal engine cranks are 3.58". So the TH700r4 might be 9.75 or 10.5 depending what it came out of. Just a note powerglides used the 9.75" holes.

01-26-2005, 05:27 PM	#1
ChevyDude Senior Member Join Date: Jun 2003 Location: Westminster, CO Posts: 3,071	Need some help with Flex Plate questions...Please. Ok...converting from 3 on the Tree....Not that TREE.....kidding... Let me rephrase....So I'm changing from a 3 speed trans to a 700r4 trans. Engine had a flywheel of course...the question is: How do I determine if I need a 168 tooth flex plate or a 153 tooth flex plate??? Those two seem to be the popular ones for a 350... which I have in this truck. Thanks guys! __________________ Alex 1971 Lil' Red 350 SBC 700R4

01-26-2005, 06:25 PM	#2
neonlarry Registered User Join Date: Feb 2002 Location: Vacaville, CA Posts: 2,746	Which starter bolt pattern do you have? The staggered bolt pattern goes with the 168 toothed plate and the 153 toothed unit has the straight bolt pattern. __________________ 70 C/10 Light Red 350/TH350, HEI, Duals w/40 series Flows, 91 seat, LED taillights 99 Pontiac S/C GTP, SLP Ram Air hood, GMPP Konis & springs 95 Neon ACR, MP PCM, AFX UDP, 3.0 CAI

01-26-2005, 06:36 PM	#3
ChevyDude Senior Member Join Date: Jun 2003 Location: Westminster, CO Posts: 3,071	Don't really know the starter bolt pattern....looks like there is 3 bolt holes for the starter forming a squished triangle....Block stamp # 3970010 oil dip stick on the driver's side __________________ Alex 1971 Lil' Red 350 SBC 700R4

01-26-2005, 07:22 PM	#5
neonlarry Registered User Join Date: Feb 2002 Location: Vacaville, CA Posts: 2,746	I think all blocks have three holes but the starters have two, straight across or diagonal (staggard). Do you not have the starter? If you have to get a new one take your pick just get the flex plate that matches. __________________ 70 C/10 Light Red 350/TH350, HEI, Duals w/40 series Flows, 91 seat, LED taillights 99 Pontiac S/C GTP, SLP Ram Air hood, GMPP Konis & springs 95 Neon ACR, MP PCM, AFX UDP, 3.0 CAI

01-26-2005, 07:23 PM	#6
ChevyDude Senior Member Join Date: Jun 2003 Location: Westminster, CO Posts: 3,071	Does that work???? and ahhhh had no motor behind the 3 speed...but did have a 350 in FRONT of it. LOL!!! Starter is long gone...soooo now what? __________________ Alex 1971 Lil' Red 350 SBC 700R4

01-26-2005, 07:19 PM	#4
3 on the tree Registered User Join Date: Oct 2004 Posts: 393	If you had the motor behind the 3 speed, why not count the teeth on the old flywheel, then get the same tooth count on the flexplate.

01-26-2005, 07:40 PM	#8
da-burb "Ochre Ogre" Join Date: Apr 2000 Location: Springfield, MN Posts: 3,558	If I am understanding what you have asked you would need a 168 tooth flex plate. The starter that was on your 3spd manual wouldn't be the one to use after the swap. Manual transmission starters have a different nose cone. __________________ Bowtie Truck Stop Inc. Mid-West GM Truck Restoration Parts Supplier Your Key Parts, Auto Metal Direct, Dynacorn, and Goodmark dealer. like us @ www.facebook.com/BowtieTruckStop 1971 C-10 Suburban (Ochre) 1971 K-10 Suburban (Ochre) 1972 C-10 Suburban (Ochre) 1972 K-20 Suburban (Yellow- that just aint right!) Springfield, Minnesota 56087

01-26-2005, 07:41 PM	#9
ChevyDude Senior Member Join Date: Jun 2003 Location: Westminster, CO Posts: 3,071	So what I'm hearing ..is just get a starter and flexplate that match that are for a SBC and I will be good to go. In that case...don't I have to get a smaller starter for the 700r4 anyway? __________________ Alex 1971 Lil' Red 350 SBC 700R4

01-26-2005, 09:03 PM	#10
tommie 97' Tahoe 2dr/2wd Join Date: Jul 2002 Location: Huffman,TX Posts: 1,168	if your going to buy an starter and flywheel, just get the ones that match. i usually go to the auto parts and tell them different years of vehicles that i want my parts off of. just get the starter and fexplate for the same vehicle. make sure you get the right flexplate, some have a weight on them (externally balanced?) like for newer model 350s (i think the first one i tried was a 91 chevy truck, it had this weight on the flexplate, and wont work with an internally balanced engine) i think i ended up getting a flexplate and starter for a 76' 1/2 ton 2wd thats what i used for my 350, and 700r4 combo. the bolt pattern for a th350 and 700r4 torque converters are the same (correct me if i'm wrong). also be sure to take the old pilot bearing/bushing out of the end of the crankshaft, sometimes the torque converter wants to hit it if its left in there. time for another beer.

01-27-2005, 03:12 AM	#11
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	A 168-tooth flywheel is 14" in diameter. Counting teeth will drive you nuts.

01-27-2005, 06:47 AM	#12
dwaite72lnghrn Registered User Join Date: Jun 2002 Location: central pa Posts: 1,525	If you need a starter also the only issue's would be what size torque converter and what 350 you are using. Most flexplates are drilled for 2 most common sizes 9.75" and 10.75" torque converter and is the 350 a 2 piece rear seal '85 and earlier or a 1 piece rear seal '86 and later, The crank is a different size. Then buy the flexplate for your application and a starter to match. I think the 153 tooth flexplates are 12.75" and the 168 tooth are 14" in size. __________________ 72 longhorn c30 502BB/th400/fact air/4.11rear/ custom camper 72 bug(the better half's) under reconstruction 2009 HHR aqua blue 71 GMC k20 350/sm465 2009 Chevy hd3500 6.6 Victory Red crew cab dually Dave & Jeanne

01-27-2005, 08:36 AM	#13
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	If it's a pre 86 engine, that is 2 piece rear main seal engine, the most common flexplate is the bigger one. Pioneer part number FRA-100, available at most any parts store. It's common enough that most parts stores will carry 5 or 10 in stock at all times. __________________ I'm on the Instagram- @Gearhead_Kevin

01-27-2005, 11:17 AM	#14
ChevyDude Senior Member Join Date: Jun 2003 Location: Westminster, CO Posts: 3,071	Thank you all very much for your help. Engine is pre 86, so it must have a 2 piece rear main seal so 168 tooth it is. Thanks again guys!! __________________ Alex 1971 Lil' Red 350 SBC 700R4

01-27-2005, 01:57 PM	#15
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,253	Don't forget to get shorter flywheel to crank shaft bolts. The ones you got now will be too long with your new flex plate. __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

01-27-2005, 06:55 PM	#16
dwaite72lnghrn Registered User Join Date: Jun 2002 Location: central pa Posts: 1,525	Measure your torque converter. The 14" flexplates were drilled for the 10.75" and 11.5" converters from trucks with big TC in th400's. The 1 piece seal engines have a 3" crank mount and the 2 piece seal engine cranks are 3.58". So the TH700r4 might be 9.75 or 10.5 depending what it came out of. Just a note powerglides used the 9.75" holes. __________________ 72 longhorn c30 502BB/th400/fact air/4.11rear/ custom camper 72 bug(the better half's) under reconstruction 2009 HHR aqua blue 71 GMC k20 350/sm465 2009 Chevy hd3500 6.6 Victory Red crew cab dually Dave & Jeanne



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