Reinstalling engine-TC too tight?

After MANY hours of wrestling the 6.5 back into the 1994 2500 Suburban, I began bolting the bellhousing up. When I went to bolt the flexplate to the TC, it was already pinched together too tight to move. I talked with an experienced mechanic at my boat dealership (not diesel experience) who told me the TC may have moved forward, and I should be careful about making sure it was properly seated on two pins that come out of the front pump. He said he had seen this happen and when you tighten the bellhousing, if they aren't lined up you can break them off. So I guess my question is, on this 94 2500 w/ 6.5 would this two pronged sytem he's talking about be the right one? I was thinking for a heavier duty setup like this, the connection would be more like a splined shaft.
I loosened the bellhousing back up and the TC spins fine, but I cannot feel any place as I spin it around that will let it go back farther. It will come forward rather easy, but it only goes back to where I found it upon engine reinstall. I'm afraid to bolt back together without knowing more, and I REALLY don't want to pull the engine a 3rd time to get a better shot at the TC. Does anyone know how I can be sure the TC is properly seated prior to bolting it all up again? Thanks very much.

Your mechanic was most likely correct.
You do need to make sure it is fully seated. It can be hard to tell that it is. The best I can tell you is the TC when seated will be very close to the trans housing. Maybe 3/16"-1/4" gap between housing and TC at the outer dia of the TC.
Good luck

Correct. The TC outer shaft needs to engage the tabs on the pump. If they don't, you will experience what you did. The connection needs to be loosened (move either the engine or tranny), and the TC rotated until the tabs engage. If you don't, tranny pump and/or flex plate damage can occur. The shaft bushing/seal could be hung, but it's very unlikely, and the most common reason for your issue is the pump tabs.

Thanks guys. I played with it a little more and unfortunately I just can't tell. I tried to move it forward, then slowly spin it around while pushing backwards, to see if I could feel it seat onto something. It only goes back as deep as where I found it. I never touched the TC while the engine was out, but I did jack the tranny up and down a lot trying to get everything together, so I guess it could have moved forward a little, but it should not have spun. I can look up behind the converter to see where it goes in, and I can see approximately 3/8" of the hub between the back of the large face of the converter and the front of the tranny. When I pull it out, the hub looks shiny compared to what was already showing, leading me to believe it is in the same position as always, however it did sit this way for many months. If it moved out right after I pulled the motor, that previously shiny surface could have tarnished over the months, giving me a false indication. This is driving me nuts. How far does it sit on the pins? Maybe it is on, and I can't even move the TC forward enough to pull it off?
Dave

Be Careful!!!!!!

The TC has to slip onto the splined shaft and then also the two ears into the pump. You'll feel it hit twice. You need to keep spinning the TC while pushing in on it at the same time. Sometimes it doesn't want to slip in without giving a fight. You MUST do this step or you will ruin the pump in the transmission...trust me, I know! I did the same thing one time. I ended up tightening the tranny to engine bolts before checking the TC, and I ended up crushing the front pump. When the TC is properly seated, you will have at least an inch or more between the flexplate the TC after the tranny and engine are bolted together. Then you slide the TC forward to meet up with the flexplate.

Take your time, make sure it's right, or else you'll have to pull the tranny to get the front pump repaired.

If you have already tightened the bellhousing bolts all the way down, chances are pretty good that you've already ruined the pump in the transmission, and that's why you can't get the TC to seat all the way in.

Casey

If you bolt it up as is, one (or both) of two things is very likely to happen. The flex plate will break, and/or the pump thrust bushing will disintegrate, trashing the pump, and possibly more of the tranny.

The tabs engage a little more than 1/4". If you have 3/8" clearance between the TC and pump housing, it may be too much (I'm not absolutely certain on the acceptable tolerance). Another possibility (if it is possible), is the flex plate installation. Could it be backwards, or off-keyed? I've never tried to install one backwards, so I don't know if it's possible. If it is, I may have done it myself at some time. The engine is externally balanced, so correct clocking of the flexplate is critical. Does the flexplate and TC appear to be aligned and true (other than the closeness)?

Dmax,
Thanks again for your help. The plate is correct and indexed. I think there is a good possibility the TC was out too far and off the tabs, and I may have broken the tabs when I tightened the engine to the bellhousing. I see no other reason for the tightness. As it sits now, the tranny support mount bolts are all the way back in the slots, I have 1/4" at the top of the housing to the block, and 3/8" at the bottom, and the TC just rubs the plate at the raised points where it attaches. I think I should have more clearance than that and the TC should sit back farther. I also have a support bracket from the motor mount to the bell housing cover installed incorrectly as well, so I'm just going to pull it again to fix that and pull the TC to look at the pump and gear tabs. There is so much to put together, I really don't want to take a chance and find out when I get it running that the tranny has a problem, then have to undo it all again. Is there anything I can/ should do when I have the TC out and the front pump and gear are exposed? Thanks again,
Dave

Casey,
Thanks for the reply. I also posted this in the 6.5 engine section, and everyone is thinking about the same now. Your info about a full inch of clearance is helpful, but also a little confusing. Most people are telling me the TC only seats onto (or into) the pump about 1/4", so if the block and housing are tight and I pull the TC a full inch forward, I could possibly be pulling it off, right? Yippie! I get to pull the engine a third time!!!! Fun fun fun!!!
Dave

The clearance is with the TC pushed completely rearward. When it is bolted up to the flexplate, the clearance is significantly more. Why pull the engine? In my experience, it has been many times easier to pull the tranny. If the engine is in, I'd leave it, and back off the tranny. It's easier to align everything from the rear.

I don't think we need 2 threads about this. I'll merge the other thread in the 6.5 forum into this one.

Quote:

---

Originally Posted by fastboat

Casey,
Your info about a full inch of clearance is helpful, but also a little confusing. Most people are telling me the TC only seats onto (or into) the pump about 1/4", so if the block and housing are tight and I pull the TC a full inch forward, I could possibly be pulling it off, right?
Dave

---

My memory is a little fuzzy, so I might be wrong about the inch of clearance. I do know that when everything is proper, you have some space between the TC and flexplate, and that you have to pull the TC forward to meet up with the flexplate.

Casey

Well last night I spent a bunch of time playing with this. After getting the engine out of the way again and fixing the mount issue, I started moving the TC in and out and spinning it. I didn't see any cut in slots or tabs, but two flat spots cut into the otherwise perfectly round TC shaft. Are the tabs inside the front pump, or is this a different design? Anyhow, I could pull it forward almost enough to get it off, but not quite. Then I spun it a little and tried to push it back in, which it would not do, so I figured I was now out of the detents everyone was trying to help me make sure I was in. I continued to move it and found the detent again and it slid back in. It looked to be in the same amount as before. So while I had the chance, I did it a bunch of times. I was trying to see if in fact there were a couple of different detents, and whether or not I was hitting them all. As far as I could get it out, I could see the very beginnings of some splines on the shaft coming out of the tranny. The TC would set back on there, then catch, then I would move it around and push some more and it would set back onto what I have to assume are those two flat spots I see on the TC shaft. I then tried to get it to go even farther than this questionable depth I've been at for a while. I turned it slowly and in small increments while pushing backward and wiggling, feeling for even the slightest more movement with no results. So here I am- convinced it can't go back any more. I may be right, or I may be in denial- having already crushed stuff in there, I really don't know yet. As I put the engine back I sat under there for several minutes going over all this different info in my mind and comparing the distance between the bellhousing and block to the TC and flexplate. The distances looked almost identical again, which most people say is wrong, there should be more room. So being the rational, patient person I am, I said "screw it, I'm sick of this already" and decided to just press on. I started the bolts into the TC while I could move everything easily, but didn't tighten them. Then I started bolting the block tight. If I messed up the tranny the first time it is too late now anyway, and I really want to know if I did the engine build right. I'm putting everything together just to the point the engine will fire, then if it does I'll shift the tranny and hope for the best. I also broke off an oil cooler fitting in the block last night- that should be a lot of fun to get out:mad:! I'm so upset about all this- I was really hoping to have a good experience with the build and teach myself a few things. Wrenching on stuff and challenging myself with new territory is usually like therapy for me, but I'm way past that point now and it is now nothing but aggravation. Sorry to vent- thanks again for all the info. I'll update with the results, hopefully soon.
Dave

Damaging the pump while the TC is misaligned is one thing. Start it and you risk trashing the entire housing, among other more expensive stuff (read: new tranny, not just a minor repair).

I pretty much figured that it could be worse by doing that, but I just don't see how it can be in the wrong place after moving it around the other night. I'll try to spin it around tonight and see how it feels. If it won't move with a wrench on the flywheel to TC bolts, I'll reconsider. Thanks again.

Finally got to fire it off and then cross my fingers and grab the shift. Everything is fine!!:cool: Thanks for the help. Lots more details in the 6.5 diesel forum.........
Dave