Author Topic: 6 bolt Torque Converter  (Read 139 times)

Online JohnnyPopper

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6 bolt Torque Converter
« on: July 12, 2019, 12:58:46 PM »
Hey Guys,

I bought a '88 C-30 and am replacing the th400. Got a used one (warrantied) from a yard I do a lot of business with, the tech pointed out that the T/C has 6 bolts.

Never seen one before, the original has 3.

Does anyone know the significance of why there are 6?

It came out of a '89 step van.

We opened up the pan and it was clean as a whistle.

Thanks for any guidance you can offer!

Offline Stewart G Griffin

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Re: 6 bolt Torque Converter
« Reply #1 on: July 13, 2019, 04:07:05 PM »
i've been seeing a few of these lately, because i have to do research on my own torque converter issues.....

i think 6-lugs are more heavier dutier/diesels.


What engine is in your c-30?

Online zieg85

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Re: 6 bolt Torque Converter
« Reply #2 on: July 13, 2019, 04:17:41 PM »
3 are SAE threads, 3 are Metric.  Choose which set of 3 you need
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 3.21 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
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Online JohnnyPopper

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Re: 6 bolt Torque Converter
« Reply #3 on: July 14, 2019, 09:05:38 PM »
Wow, that's all the difference? You mean my new T/C isn't special after all?  :'(

When wrenching to get this pig out, I ran into bolts Sets, i.e. rear mount bolts,  that were clearly metric, the rest being SAE.

The T/C bolts were/are 15mm.

The only thing I could figure was that the BIG 3 were so $ conscious of cost per vehicle that they went with lower cost hardware where ever they could.

Please feel free to disabuse me if there is another reason!

Online JohnnyPopper

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Re: 6 bolt Torque Converter
« Reply #4 on: Today at 03:04:03 PM »
Carl (Zeig) all the threads are the same. Now what?

Online zieg85

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Re: 6 bolt Torque Converter
« Reply #5 on: Today at 03:33:59 PM »
Choose the 3 that line up with your flex plate
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 3.21 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline Irish_Alley

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Re: 6 bolt Torque Converter
« Reply #6 on: Today at 04:40:25 PM »
i know on my motor swap the flex plate on the motor there was only 3 holes for the th400. someone modified it to fit the 700r4 (made the holes closer to the edge). when i mounted it up to the 4l80e i had to bring the holes back in
If you canít tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Online JohnnyPopper

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Re: 6 bolt Torque Converter
« Reply #7 on: Today at 05:06:11 PM »
There are 6 points on the flexplate. Used all 6.

So there is no indication that this is a heavier duty T/C?

Came out of a delivery van.

Online zieg85

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Re: 6 bolt Torque Converter
« Reply #8 on: Today at 05:17:27 PM »
There are 6 points on the flexplate. Used all 6.

So there is no indication that this is a heavier duty T/C?

Came out of a delivery van.

OK.  I learned something today.  I have 2 TH400's and the flexplate in my 85 has 6 holes.  I will have to check and see if mine is the same way.  I am missing a speedometer drive gear before I put the new transmission back in...
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 3.21 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/