400 Flexplate-to-700R4 torque converter- problem?? - Third Generation F-Body Message Boards

Damon · 08-04-2001, 03:06 PM

Just bolted a 1975-vintage 400 in my brother's 87 GTA originally equipped with the L-98 350 and 700R4 auto-box.
Car still has the original torque converter in the trans. My original 1975 400 flexplate bolts right up since it's drilled for both the large and small pattern torque converter (the 700R4 converter usues the small bolt pattern). All is going well UNTIL.......

I go to tighten down the flexplate-to-torque converter bolts. They go in just fine but the torque converter and the flexplate have about 1/4" of space between them. naturally, as I tighten them down the torque converter pops forward that 1/4 inch. YES, I have the flexplate on the right way around.

Is this going to be a problem? How far forward can the converter go before it disengages from the front pump and/or loses it's seal to the rest of the trans?

All other swaps I have done the convter and the flexplate are just about touching eachother even before the bolts go in. The L-98's once piece-style rear seal crank must put the flexplate just a smidge further back than an older style Small Block is my guess.

Problem???

This ad is not displayed to registered members.
Register your free account today and become a member on ThirdGen!

RODS92Z · 08-04-2001, 04:39 PM

Your using the 700 torque convertor on the 400 tranny? If you are that wont work. Straighten me out if I misunderstood.

------------------
1992 Camaro Z-28 5.7L auto t-tops arctic white

1967 Pontiac Catalina 2 door fastback 400 v-8 auto cameo white dark red interior

Damon · 08-04-2001, 05:15 PM

No. I'm bolting a 700R4 to an old 400 ci small bolck (that does NOT have a one piece rear main seal). The problem seems to be that the flexplate on the old style 400 engine sits about 1/4" closer to the engine than the flexplate on the original L-98 350.

This forces the torque converter to pop out about 1/4" from it's fully seated position when I tighten the bolts between the flexplate and torque converter.

The question being- is this going to cause a problem? I am sure a LOT of people have bolted old two-piece rear-main engines in place of original one peice rear main engines and run into this same phenomenon.

SSC · 08-04-2001, 05:26 PM

There is some give with the tq converter and what you discribe is normal for all of them.
As long as you have everthing bolted in correctly "bellhousing to engine" it will be fine.
SSC

CrazyRob75 · 08-04-2001, 05:33 PM

i had the same problem when I hooked my 454 to the 700R4. Did the same thing with the th350 i installed this week. i was worried about it, but bolted it all together and no problems. It is strange though, my buddy has a 355 in his T/A. When we put a new convertor on his th350, the got it tightened to the block, there was NO gap between the convertor and the flexplate. Oh well....don't lose any sleep over it!

------------------
85 Berlinetta Iroc exterior NOW 454 powered, 4.10 gears, 275/60/15 Hoosier Quicktimes freshly installed th350 3200 stall, shift kit, reworked valvebody, Megashifter, Biondo linelock ..........YES, it's street driven!

check it out at http://www.bsronline.net

Damon · 08-04-2001, 07:04 PM

Rob, SSC: Thanks guys- I was starting to freak out. Stuff like that makes the little hairs on the back of my neck stand up. I'm calmed down now.