Okay, so we all agree a HD case is nice to have, but honestly how many of you guys have broken a TH400 case in a Buick street car that was a failure due to a weak case in one of the areas that is beefed up on the HD case? I do have one core transmission here with a HD case (it's a long shaft from a '67 Oldsmobile). I'll use it to install a Chevrolet Ultra-Bell so it can go behind the highest hp thing I own (supercharged LS engine) but I still think any regular TH400 case would still be fine for me.
BEQUICK That's a HD case. Just behind the upper arch and bolts, you can see 2 steps flowing over the bell. Even if its bolted in the car you can look at the bolts and see the steps. Look forward of the dip stick base and see the casting case number. Should end with 500. Always take pictures of your case before leaving it for rebuild. You may go home with a clean, shiny thinwall.
Our thinwall cases are good for 500 to 600 ft lbs if torque or 700 hp. If your chassis is floppy, you may be adding stress to the case in a different way. I have 1. Boxed frame with poly mounts to the body. 2. Rear axle mounted anti sway bar. 3. Rear trailing arm braces. 4. Left motor mount anchored down. 5. Heavy custom driveshaft and loop. I have heard lots of stories about a--body frame cracks, windshield cracks, rear crossmember disasters. Lower trailing arm ripping loose, causing wrecks, etc. After years of th400 problems, I now have all this in place, and rebuilt heavy case. Unbelievable difference in how solid my 67 GS feels. I trust my car. Peace of mind.
Here is a NOS HD TH400 case for sale (It is not mine, I just thought it was interesting to see a NOS case): https://www.yellowbullet.com/thread...-case-pq-px-pt-bb-ow-steel-vent-tube.2684046/
