700R4 Torque Converter Mounting Lugs

[Mr. D]

Hi,

I have searched the forums and the web but did not find any info. Any experts out there?

An auto parts store is has a round lug TC, but mine is square lug.

Are they interchangeable? They look a little different, and not just the lugs. I suspect that they are all interchangeable.

The engine in my truck is just a 4.1L 250 six.

thanks in advance

Mr. D

[Mr. D]

I think I found my answer, thanks for looking.
I do not see any complaints about the round lugs here or on the internet, so they must be ok.

The three square lug design replaced 6 round lugs on the diesel TCs, so the square are stronger, but the round are ok for all but diesel.

Mr. D

[oldenginebuilder]

Originally Posted by Mr. D

I think I found my answer, thanks for looking.
I do not see any complaints about the round lugs here or on the internet, so they must be ok.

The three square lug design replaced 6 round lugs on the diesel TCs, so the square are stronger, but the round are ok for all but diesel.

Mr. D

Bunch of hoikey right there. The 6.2 diesel was the only diesel ever bolted to a 700R-4 by GM, and the 6.2 never offered more than 257 ft-lbs when bolted to a 700R-4. Why it had 6-lug? Only 3 people on earth know, and they never told.
Look at the 700R-4's history: The torquiest engine it ever held was the GMC Typhoon, with 360-365 ft-lbs. Used a 3-lug setup. As did the 345-TQ TPI 350 in 'vettes and Z28s.
I have a good-running 6.2 diesel, bolted to a 3-lug torque converter ( and the whole rest of the matching 700R-4 ) from a '91 Camaro RS LO3. Been driving it this way for a few years now, no issues. In fact, it drives really well.
Round or square also doesn't matter, 365 ft-lbs isn't enough to rip them loose or break them.

[Mr. D]

You are correct sir..

I did not read quite close enough, and thought that diesels had been 6 lug only.

I should have said that the early design round lug TCs had 3 or 6, but the late design square had only 3, so "assuming" the same engines both early and late, the square lug must be stronger. As you point out, the engines in front of the trannys might be different from year to year though, so the assumption might be wrong too.

My source is here: http://www.phoenixtrans.com/lockuplowdown.pdf
page 11: look for "Fourth Digit" I can't copy and paste from pdf files or I would.

Mr. D