1967 GMC - 305 V6 - TH400 Flexplate - The 1947 - Present Chevrolet & GMC Truck Message Board Network

StinkyDogCB · 01-16-2010, 12:50 PM

I have a 1967 3/4 ton GMC with a 305 V6 and a TH400. The truck is completely stock and was handed down to me by my grandfather who was the original owner. The truck has one problem... it has a cracked flexplate and I need to get it replaced or fixed (it's cracked on one of the tabs where it's bolted to the torque converter). The problem is that I can't find a replacement flexplate anywhere! It's not your regular run of the mill 350 v8 style flexplate... it looks more like a 235 I-6 flywheel with a small triangular shaped flexplate attached to the back.

Does anyone know where I can find a replacement flexplate (used or new) for my truck? Has anyone else run into this problem with the GMC 305 V6s and automatic transmissions? Has anyone had any luck taking parts like this to a machine shop to get fixed? Can it be fixed? Any suggestions and ideas you have would be greatly appreciated. Thank you very much!

factorystock · 01-16-2010, 01:15 PM

Go to the "6066gmcguy" website for a link to a company who makes auto trans parts for this engine. Once on site, click on Transmission Data, in the middle of home page. Automatics is near bottom of this page. Bendtsens Trans Adapters make have what your looking for.1966 GMC's also used the 305 with the TH400.

StinkyDogCB · 01-16-2010, 03:08 PM

Thank you for the information, I really appreciate it. I'll look into it and post what I find out. Has anyone done business with this company? If anyone has an original flexplate to sell, please let me know. Thanks!

*sharpie1972* · 01-16-2010, 03:25 PM

PM sent. Sharpie

StinkyDogCB · 01-16-2010, 08:25 PM

Sharpie: Thanks for the PM... lets keep in touch.

As a side note, does anyone know if a Powerglide flexplate will work with the TH400 transmission with the 305 v6?

CCCC · 01-16-2010, 10:14 PM

To see a cracked flex plate is not uncommon - especially to guys in trans repair shops - it happened a lot with some models.

Careful - if it cracks very much and enables play or vibration of the shaft and you drive too many miles that way it can begin to throw shavings and pieces inside the box - stuff gets pumped throughout and you will need a rebuild. Talk to a good trans shop - they know where to get them used and new - and they know which ones are stronger. Sooner is better.

StinkyDogCB · 01-16-2010, 10:44 PM

Thanks for the advice! Are there typical reasons for cracks to develop on a flexplate?

01-16-2010, 12:50 PM	#1
StinkyDogCB Registered User Join Date: Jan 2010 Location: Tempe, AZ Posts: 9	1967 GMC - 305 V6 - TH400 Flexplate I have a 1967 3/4 ton GMC with a 305 V6 and a TH400. The truck is completely stock and was handed down to me by my grandfather who was the original owner. The truck has one problem... it has a cracked flexplate and I need to get it replaced or fixed (it's cracked on one of the tabs where it's bolted to the torque converter). The problem is that I can't find a replacement flexplate anywhere! It's not your regular run of the mill 350 v8 style flexplate... it looks more like a 235 I-6 flywheel with a small triangular shaped flexplate attached to the back. Does anyone know where I can find a replacement flexplate (used or new) for my truck? Has anyone else run into this problem with the GMC 305 V6s and automatic transmissions? Has anyone had any luck taking parts like this to a machine shop to get fixed? Can it be fixed? Any suggestions and ideas you have would be greatly appreciated. Thank you very much!

01-16-2010, 01:15 PM	#2
factorystock Registered User Join Date: Feb 2007 Location: west coast Posts: 3,396	Re: 1967 GMC - 305 V6 - TH400 Flexplate Go to the "6066gmcguy" website for a link to a company who makes auto trans parts for this engine. Once on site, click on Transmission Data, in the middle of home page. Automatics is near bottom of this page. Bendtsens Trans Adapters make have what your looking for.1966 GMC's also used the 305 with the TH400.

01-16-2010, 03:08 PM	#3
StinkyDogCB Registered User Join Date: Jan 2010 Location: Tempe, AZ Posts: 9	Re: 1967 GMC - 305 V6 - TH400 Flexplate Thank you for the information, I really appreciate it. I'll look into it and post what I find out. Has anyone done business with this company? If anyone has an original flexplate to sell, please let me know. Thanks!

01-16-2010, 03:25 PM	#4
sharpie1972 Account Suspended Join Date: Apr 2007 Location: Powell, Wyoming Posts: 4,973	Re: 1967 GMC - 305 V6 - TH400 Flexplate PM sent. Sharpie

01-16-2010, 08:25 PM	#5
StinkyDogCB Registered User Join Date: Jan 2010 Location: Tempe, AZ Posts: 9	Re: 1967 GMC - 305 V6 - TH400 Flexplate Sharpie: Thanks for the PM... lets keep in touch. As a side note, does anyone know if a Powerglide flexplate will work with the TH400 transmission with the 305 v6?

01-16-2010, 10:14 PM	#6
CCCC Registered User Join Date: Mar 2007 Location: San Pedro River, SE Arizona Posts: 734	Re: 1967 GMC - 305 V6 - TH400 Flexplate To see a cracked flex plate is not uncommon - especially to guys in trans repair shops - it happened a lot with some models. Careful - if it cracks very much and enables play or vibration of the shaft and you drive too many miles that way it can begin to throw shavings and pieces inside the box - stuff gets pumped throughout and you will need a rebuild. Talk to a good trans shop - they know where to get them used and new - and they know which ones are stronger. Sooner is better. __________________ CCCC 67 Sting Ray Coupe 327 4sp; 68 K10 Suburban 327 4sp; 69 K20 Lifted 383 4sp; 69 C80 Fire Truck 478 V6 5sp/2sp; 69 C20 Longhorn 327 4sp; 70 C30 Wrecker 350 4sp; 70 C30 Flat Bed 350 4sp; 71 C20 LWB 350 4sp; 72 K5 Blazer 350 4sp; 72 C30 Flat Bed Gooseneck Hauler with sleeper 350/TH400; 72 C20 Longhorn 402 4sp; 52 Mack LTL Supercharged Cummins 5sp x 3sp; 01 Dodge 5.9 HO Cummins 6spd; 02 Safari Trek 2430 8.1 Vortec on Workhorse Chassis; 03 Silverado 2500 HD 4wd Duramax/Allison Moved but still in the family 70 C20 Custom Camper 350/TH350; 72 K5 Blazer CST Highlander 350/TH350 Recently sent to new homes 72 C30 MoHome 402 4sp; 72 K5 Blazer Conv 350 4sp; 75 GMC 6000 Aerial 350 w Allison; 72 GMC 3500 Utility 350 4sp; 70 GMC 3500, 350 4sp Last edited by CCCC; 01-16-2010 at 10:14 PM.

01-16-2010, 10:44 PM	#7
StinkyDogCB Registered User Join Date: Jan 2010 Location: Tempe, AZ Posts: 9	Re: 1967 GMC - 305 V6 - TH400 Flexplate Thanks for the advice! Are there typical reasons for cracks to develop on a flexplate?

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