1960s 1969 - Rebuilt 472 binding when mating with Transmission

[R Simone]

We just dropped my rebuilt 472 in last week and went to start tightening things up today. We fought it about four hours and accomplished almost nothing except getting the torque converter bolts in then decided to surrender for the day. The car is jacked up pretty high in front to accommodate our "physiques" and despite jacking up the trans, taking weight on and off of the engine, and just letting everything rest, as soon as we got all of the bellhousing bolts close to tight the engine wouldn't turn over - back them out a bit and the engine turns over just fine. We don't know what could be hanging things up..? we're both at a loss and any help or suggestions appreciated. I thought we were on the downhill part of the project and am feeling pretty deflated after today.

The guy that ruined the engine had taken the transmission to a local reputable shop and supposedly had them check it out and reseal where needed, but that relationship ended poorly and I never got the receipt to see what was actually done. I don't think they would have done anything that could have caused this, but I'm second guessing everything right now and wanted to disclose that in case there are other ideas.

Thanks all,

[Dave Shepherd]

Are you sure the converter is fully engaged into the pump, kinda a 2 step process.

[R Simone]

I watched a few videos and will verify - Thanks

[TJ Hopland]

Torque converter was my thought too.  I don't put the bolts in the converter till the bell bolts are tight and as you go you keep checking that the converter is still able to move.  It will have some drag due to that round nub being in the crank but you should still be able to wiggle it around and in and out a bit. 

There are 3 things that need to engage, 4 if you count the initial part going into the seal.  There is the small splines on the input shaft then the fixed splines then last the 2 slots into the pump.  Its usually the pump that slips out. Bad news is if you cranked it down enough to bind up the engine you could have damaged the pump.  I don't remember how tough the 400's pumps were. 

[bcroe]

Here is my method, with dozens of TH400s.  When
the converter is fully engage to the trans, it
should be nearly an inch back from the bellhousing
surface.  I use a bracket to keep it in this
position while bolting the trans to the engine. 

Then remove the bracket, the converter should be
back from the engine, still freely turning.  You
should need to slide the converter forward a
small fraction of an inch to meet the flywheel/
flexplate.  If they are already touching, the
converter was not fully engaged with the trans.
Bruce Roe

[R Simone]

Ugh... I'm getting nervous about pump damage after googling. Assuming engagement was the issue I suppose i need to at least pull the convertor and visually inpsect, but is there any way to tell if the pump was damaged? Am I destined to now pull the trans and have it checked or should I just give it a try?

[R Simone]

We pulled the transmission yesterday and dropped it off at the tranny shop to get checked over. Among all the things I wanted to do it was among the last, but the only thing worse would have been firing it up and either not moving, or moving for a bit and then grenading and having to take it all apart again and even greater expense. Access was easy in it's current state and it actually only took a few hours   

Will advise on what is found for future people in this situation.

[bcroe]

Owners tend to worry about external leaks, but
the seals you need to be concerned about are on
the pistons of the rotating clutch packs.  They
age regardless of miles, and burning up a clutch
pack will ruin a decent trans. 

A few more times with the trans, and you will be
good at it.  A couple special tools (mine are
mostly home made) will really help. 
good luck, Bruce Roe

[TJ Hopland]

I'm curious to hear about the pump.  Looking at photos of the THM400 it looks like its got to be pretty durable but its most likely what was binding the engine so its hard to tell how hard you were pushing on it.

The shop will most likely be happy to demonstrate the installation process to you when you pick it up unless business is real slow and they want to see you back again soon. Seeing how far back it should go and how and what it feels like especially that last step.  The splines don't take too much rotation to engage but its possible to get the pump way off and have to turn 180 to get it back in.     

[R Simone]

We had moved the car around quite a bit and neglected to check that the torque convertor was seated completely.  I hated to do it, but we pulled the trans and had everything checked out "just in case", replaced the pump gear and re-sealed. They said it wasn't visibly cracked, but it had been under some stress and it was a fairly cheap part. They also left a torque convertor "Keeper Inner" bracket on, so that will be helpful when unloading and wrestling it into place. The plan is for take 2 on the install this Friday...

At least I know it's all good now and also got to give her a fresh spray of the correct shade of paint.

[R Simone]

Just closing this one out in case someone runs into this in the future. With the torque convertor in place the trans slid into place like butter... Lesson learned - Thanks everyone