TH400 Torque Converter issue

[arhame]

Ok, now after I have corrected my starter issue, I seem to have run into another problem (go figure).

Over the past few days, I've had an issue with the torque converter - flexplate bolts begin slapping against the plate between the block and transmission. I ended up breaking the flexplate and had to replace it.

Initially I thought it had something to do with the flexplate being fatigued due to the starter issues I was having, so I changed it out. I reassembled everything, and same issue.

Next, I thought it might have had something to do with the new torque converter I installed while troubleshooting the starter issues I was having. I decided that wasn't the problem and simply tried installing shorter torque converter to flexplate bolts. Same problem.

Then it had me thinking that perhaps I didn't get the torque converter pushed in all the way into the pump on the transmission. So, I took it out, and it did seem to hit all three engaugements this time, and put everything together once more. And it worked - for a while.

I drove the jeep around most of the day yesterday with no problems. I began working on resolving other small issues, when all of a sudden last night, I began having the bolts griding against the midplate once more. I had a flashlight with me, and when I checked this time, the torque converter had slid a bit out of the pump and was pushing the flexplate against the midplate.

Ok, so now I've found the problem. The torque converter is coming out of the pump when I get the jeep up to highway speeds. It doesn't seem to be doing this when I am simply riding around town at lower speeds.

Does anyone have any idea on what would possibly cause this?

I'm wondering if it it possible, that the local parts store sold me the wrong torque converter before, and I'm just now finding out about it due to the fact that I'm just now able to drive the thing.

Any ideas, suggestions, or thoughts would be GREATLY appreciated.

Thanks,

Aubrey

[jeepsr4ever]

Aubrey do you have it apart right now? I would look at the two front drive tangs on the fornt of the converter to see if they show signs of scraping.

[kris]

There are several things that cause the flexplate bolts to contact the inspection cover.
What they all have in common is that the thrust bearing/crank journal in your engine has to be destroyed for the crank to move forward enough for this to happen.

Hydromatics are known for balooning converters. This is literally the expanding of the converter from excess pressure. One common cause of this is blocked transmission cooler lines. Google it.
Since you say it is happening at higher speeds, Id start with the cooler lines.

Check your crank endplay. Its easy to do. if its out of spec, do not install a new engine untill you figure out why it happened. Ask me how I know... On second thought, dont.


kris.

[jeepsr4ever]

It could alos be the bolts coming loose becasue they are too small for the hole through the flexplate. His motor was recently rebuilt.

[kris]

I had 1200 miles on my first rebuild when it happened to me.







Do check the bolts, but also check the endplay...


k.

[arhame]

Ok, everything has been pulled back and, and the flexplate was broken yet again (i've now been through 4 of these things with barely 100 miles on the jeep).

The front drive tangs look ok frrom what I can tell.

I've taken the transmission into a local transmission shop here to get a 2nd opinion. He's working on it right now as I type this. He is also thinking this has something to do with line pressure being excessive due to the fact that it only seems to happen when I'm accellerating up to highway speeds. I did install a B&M transpak in this thing and the guy at the shop is thinking that perhaps something has happened with the way I've installed the kit to where it's producing too much pressure.

He's going to put a pressure guage on it to see if this might be the case.

I'll be sure and keep everyone up to date.

Thanks for the replies.

Aubrey

[arhame]

Ok, here we go again.

I installed a new flexplate on Thursday of last week, and got the transmission/transfer case back in on Friday morning. I ran the jeep up to the transmission shop and we installed a pressure guage on it to see if this is what was causing the problem. Well, in reverse at WOT, we hit 265 pounds. In Drive, I believe we hit right at 185. While this is on the high side, I'm not exactly sure if this is high enough to balloon that converter forward enough to break that flexplate. The thing I regret is not checking the pressure BEFORE he took some shim out of the pump to hopefully reduce pressure. So, I'm not exactly sure at what I was at before.

This transmission has one of the B&M Transkit's installed.

Well, this weekend, I payed particular attention to the way I drove the jeep, and took it on a few long cruises just to get some miles on it, paying particular attention to keep it under 2,000 rpms just to see if it would keep it from repeating the issue.

Well, I think the torque converter bolts are about to start slapping again. I noticed it yesterday morning and decided to step away for a bit. This is getting EXTREMELY frustrating. In a bit, I'm going to putter it back up to the transmission shop hopefully BEFORE it breaks, so he can see what the torque converter is doing. It appears as if it's pushing itself off of the input shaft. It appears to be wobbling a bit now when running (yes, I know not good).

If anyone else has any ideas, I'm more than open for suggestions.

I'll keep you informed on what I come up with.

Aubrey

[FuzzFace2]

Do you have the thin spacer in the end of the crank that the converter snout goes into? Both block to trany dowels in place? Might be time to make sure the crank & trany center lines are inline. With the trany bolted in place and the converter in to the trany all the way what is the gap between flex & vert? Thinking you should not have less than 1/8” or more than ¼” if the vert is ballooning more than 1/8” I would get a new vert. If all that is good then time for a solid center flex plate.
Dave ----

[arhame]

Thanks for the response.

Yes, I do have the thin spacer that goes between the flexplate and flexplate bolts.

Both dowel pins are in place and are tight.

I've checked the clearance between the mounting tabs on the converter and the flexplate. right at 3/16"

I'm going to pull this thing out once more, and have the pump completely rebuilt and change out the converter.

As for the solid center flexplate, where could I possibly find one of these?

Thanks again,

Aubrey

[FuzzFace2]

The spacer I am talking about is used just for the TH400 trany setup. That center piece on the convert that fits into the end of the crank. Well the TH400 convert is smaller in dia than a TF one so there is a ring that goes into the end of the crank to take up the difference.
Flex plate would be a SFI rated one or I think you can have a TF one drilled for the TH converter.
Dave ----