Ongoing 4 spd problems

[hemigtx]

Hey guys, here's a stumper. Something isn't square in my trans and it's wiping out throwout bearings, pilot bushings, and clutches at the cyclic rate. Here's the deal. 72 340 4spd Roadrunner. Very recent rebuild on motor. Checked crankshaft flange run-out (zero). Double-checked straightness of the crank. Dead on. Installed bellhousing on block and aligned it as per the service manual. On the tight side of the tolerance range. I DIDN'T CHECK THE REAR TRANSMISSION MOUNTING SURFACE BECAUSE I WAS TOO LAZY TO BUILD THE NECESSARY BRACKETS. Anyways, rebuilt tranny with new bearings, etc. End result: extremely high wear on all above-mentioned parts and a distinct vibration while driving car. Pulled tranny to install new parts and found a pilot bushing that was worn on one side. It was pretty chewed up and it even somewhat screwed up the input shaft (was able to polish most of it out). Flywheel had a slight groove cut in one side of it from the clutch disc. Now I have a new flywheel (old one had nearly 1/8" ground off the face by a "machine shop" who was trying to "get the cracks out"), new Centerforce dual friction clutch set and I am reluctant to throw all this money away in 4 months by not correcting the problem. Here are some observations/possible problems:
1. Input shaft is VERY loose. Pulled bearing retainer off and I can spin the outer bearing race inside the transmission case. Tried this on another trans, and couldn't do that. The bearing seems to be pressed into the case. The input shaft is noticeably tighter because the bearing isn't rocking in the trans case.

2. The above-mentioned parallelism of the bellhousing. On two occasions I pulled the engine and trans out together. I always figured that an aluminum bellhousing would break rather than warp or bend. Now I wonder if the bellhousing isn't strong enough to hold the weight of the trans. Of course, I had a spare bellhousing laying around for years, and just recently gave it away to a kid (along with a complete 360) who wanted to convert his /6 to v8. The other thing is that when I bought the car, the bellhousing to block bolts were looser than a goose. I'm wondering if there may be too much slop in the dowel pin holes? If I had that other bellhousing, I could have tried that one, but everyone around here wants $50-$60 for theirs! What a rip-off.
3. ??? Any other ideas? This project that should have taken two days (outside) has now taken four. That's actually four WEEKS because I only get Sundays off in the Corps.
Any help would be welcomed. Thanks!
Semper Fi

[hemigtx]

One more thing...My service manual shows those rectangular rear motor mount spacers going on the OUTSIDE of the rear mount, but most people seem to install them BETWEEN the mount and the transmission. Apparently, they are nothing more than big washers to reinforce the rear mount and/or take up the extra length of mounting bolts that are otherwise too long. This should only affect driveline angle and not be the cause of my problems, but is just an observation. Sorry about the LONG post.

[turbododge]

I am not familiar with the procedure for aligning the bell housing in the service manual, but I always indicate the opening of the bellhousing to the crankshaft rotation (adjust with offset dowels) and indicate the face of the bell housing where the transmission mounts to the crank rotation. If the bell has been damaged, the second measurement will be off. Also be sure that your trans bearing retainer is a good fit into the bell housing and not worn or damaged.

[Christopher]

After re-reading your post(which was NOT too long)it reminded me of a very similar problem with my 70 'Bird.The flywheel had been ground at a angle(how I don't know) and ate my brand new Hays clutch setup in about 6 months.Also tore up the pilot bushing so bad there was one side of it completly gone.I ended up replacing the flywheel with a brand new Mopar piece and put in a Ram clutch with 2800# of pressure.This worked great and I had no more problems after that.

[hemigtx]

Christopher and turbododge: Thanks for the input. I trashed my flywheel due to the enthusiastic surfacing job and replaced it with another one I had laying around (which was noticeably heavier). I was wondering if that flywheel may have been the problem. Certainly all the symptoms are the same as Christopher's. What's your take on that sloppy input shaft? I probably have 3/16" side to side slop on that shaft, even with the new bearing. I would like to keep the original tranny in the car (rather than store it), but not at the expense of $700 a year in new clutches.

[mtrv8n]

I may have a problem like yours, and am thinking about a solution. I had horrible vibrations in my 73 cuda, and it went away pretty much when i replaced the 833 tranny with a rebuild. Then, sometime later I had clutch work done, and the vibrations came back. More clutch work, it went away. Recently I had the diff replaced, and guess what? The vibes are back. Whats common to all of this?..i think that the driveshaft may have been re-installed 180 dgrees out of it's original position, and my next step is to have it turned, and balanced if that that only helps a bit.What do you think?

[shannon]

If the problem presist, I would buy a new input shaft bearing. They are about 30 dollars. They are also not that that hard to change. Just pull of the housing that covers the bearing, remove the retainer clip with a couple of flathead screwdrivers, and pop the bearing out with a puller. If you dont have a puller, a tie rod wedge works fine. Just put the fork ends in the retainer clip grove and use it as a LEVER. Tap the tool and go all around the bearing. Dont pry in the same place on the bearing the whole time. It takes some time, but I know that it can be done because I've taken one out this way before. Good luck!!

[hemigtx]

Gents, all great advice. I already installed new bearings. Even then, that input shaft is loose as a goose. It's .085" slop when measured vertically, and "only" .060" slop horizontally. I had the driveline balanced. That was the best $60 I ever spent. Made a huge difference.
I'm going to measure the parallelism of the bellhousing tonight (assuming I can rig up the required apparatus). Hopefully it's way out, and then I will know where my problem is! Thanks again for the input.