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Discussion Starter · #1 ·
I had a buddy call and ask if 700r4's have similar issues to 400's with killing engine thrust. My initial answer was no, but I don't do too much with 700r's or 4L60's so I thought I'd throw this out there. He is swapping an engine in a car for a customer (bigger power) and noticed the fairly fresh GM performance 383 has .045 crank thrust. I told him I doubt it's converter related but I'd dig a little. I didn't build the trans so I can't answer what's done to it, or what converter it is. Thanks.
 

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Check the pilot area of the converter for witness marks from the crank. I've seen bad grounds cause "galling" on the pilot, but it is actually ground path arcing, welding the pilot and crank bore. The converter HAS TO FLOAT in the crank bore.
 

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Discussion Starter · #3 ·
He said the converter slid right back, and had a lot of clearance, but I'll have him check for galling marks, makes sense, thanks!
 

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It is quite possible. These transmissions depending on modifications can make line pressure very fast with high rate boosters and along with that comes modifications to the regulator valves that have trickled down from poor information forwarded about the 700r4 and early lube issues. If high rate boosters and a bigger is better approach to the regulator valve converter regulator land I would expect a ton of push especially during lockup.


Hutch
 

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Discussion Starter · #6 ·
That's good info Hutch, I really couldn't tell you what's done to it but it's good to know because nobody really talks about this. Geoff, I am pretty sure it has a stock one but I will ask, is there something there you are looking for?
 

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I imagine his concern is that a flexplate that doesn't flex is a bad thing.

I've not seen 700/4l60 have thrust problems. But most all I do is not heavily modified.
 

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Does this combo have a thicker, aftermarket flex plate?
Dosen't the stock type plate measure about 1/4 inch from where it mounts to the crank to the raised portion where the torque convertor mounts? If so? You could run a 1/4" thick aftermarket wheel and have the same dimensions.
 
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