No_snivelling

Agreed. Loctite retaining compound #648 has a shear strength of 3,900 PSI and #638 has an even greater strength of 4,500 PSI.
The bond area of this ring gear has to be far greater than 1 square inch, so we are talking about tons of shear load capability here.

Loctite is now owned by Henkel and their website offers a very interesting design manual for retaining compounds that suggests their compounds can be superior to press and shrink fits.
They encourage users to call in and they can calculate total shear given your specific application. I have spoken with their application engineers in the past and can attest that they are easy to reach and to deal with, even if you are an individual and not a corporation.

HBP

Thanks for the suggestions! Be great if this could be fixed in place.

Contacted Henkel and spoke to a gent who sounded new but did try to be helpful. He recommended #603 as it has lower viscosity than #648 and thought it may penetrate the gap between the ring gear and torque converter better given they don't have a specific wicking compound that would work in this application. If the ring gear looks to be centered with no lateral play I may try rotating it as the retaining compound is applied to try and facilitate better penetration into the gap. The #603 has a 10 minute working time at room temp and the #648 is 5 minutes.

I asked about the operating temperature of the converter affecting the bond and he said the #603 is rated up to 300F and the #648 to 350F. Does anyone have an idea what max temp the converter assembly might reach?

He also advised using a cleaning agent or their 7649 primer/activator before applying the retaining compound but wasn't sure if the cleaner would remain liquid and not evaporate in the tight gap between the ring gear and the torque converter, hampering the bond as usually the parts are able to be separated before cleaning and bonding. I am inclined to not use a cleaner given it may not evaporate but am open to suggestions.

No_snivelling

Hmmm, sounds like you got a newbie application engineer. Have you tried downloading the Loctite retaining compound design manual? It is chock full of great info and IIRC it mentions that some of these products don't need any primer or activator.

I assumed you would be able to remove the ring gear for cleaning and application of the the chosen retaining compound. This would eliminate the need for wicking. Is this not the case?

HBP

Thanks for the reply. I'll take a look and see if I can find the design manual. The #603 and the #648 don't require the use of the primer/activator but he said it has a cleaning capacity too and I think that's why he suggested it. Though the issue of it remaining in the tight gap is still a possibility.

Unfortunately when rotated by hand it looks like the ring gear is sandwiched in between the front and back of the coverter during assembly and not simply press or shrink fit on top, so it doesn't look like it can be removed.

No_snivelling

Right. I just re-read the thread and it does talk about turning the weld off in order to remove the ring gear. I had forgotten about that. Well that sucks. Can you actually see and have access to the the edge between the gear and converter in order to apply a cleaner or the retaining compound? If you cannot get it clean, I don't know how much confidence I would have in just using the retaining compound, but I guess the cost is low to give it a try. Were you planning on doing this through the starter hole?

HBP

It's tight but I do think there's enough access through the starter hole to apply both the cleaner and the retaining compound. My thinking was to have a friend hand turn the engine in small increments as I both applied the retaining compound and turned the ring gear to encourage migration into the gap. I figure the 10 minute set time of the #603 should be enough to get one full revolution of the engine/torque converter done.

The 7649 primer/activator will speed up the cure time of any retaining compound so I'm hesitant to use that as a cleaning agent. He did suggest isopropyl as an alternative thinking it may evaporate from the gap more completely but I have my doubts given the tightness. The ring gear is fairly easy to turn so maybe the gap is larger than I think it is and residual cleaning liquid won't be a factor.

FWIW he thinks the chance of success is good esp if the retaining compound can be applied on both sides of the ring gear. But he also seems new so I don't know if that's based in experience or just a hunch.

Your last post got me thinking of another idea. Since the ring gear is sandwiched I wondered about drilling a hole through the ridge on the converter and into the ring gear and inserting a pin (with the loctite on it) to hold the gear in place as an alternative to the previous plan. If you look at Mark's first photo above of the converter it would be at the 5 o'clock position on the converter in the area between the weld and the ring gear.

No_snivelling

Why not douse it liberally with a spray can of brake cleaner and leave it overnight to dry? That stuff is supposed to evaporate quickly and not leave residue behind. You could always use a heat gun to encourage evaporation and drying.
Good idea to spin the ring gear by hand to encourage migration, but be carefully your buddy does not rotate the engine while your fingers are in there.

I agree with your hesitation to use the activator. You need time to get the retaining compound application done and 10 minutes is not a lot of time. You will have to work fast.

"...if the retaining compound can be applied on both sides of the ring gear" Not sure I understand. Are we not talking about filling the radial gap between the inside diameter of the ring gear and the outside diameter of the converter?

Personally I would not drill any holes into the ring gear and the metal of the converter must be pretty thin, is it not? In any case, I doubt one pin would be enough.

HBP

Yes, but the catch is that because the ring gear is sandwiched in the converter on both the front and back sides, the radial gap at the bottom isn't directly accessible or visible. So the front and back lower half of the ring gear sides are up against the converter, and to reach the radial gap at the bottom of the ring gear the retaining compound has to migrate down through the "side gap". I believe he was thinking if I can apply the compound to both the front and back sides of the ring gear where it meets the converter, chances of successful migration to the bottom radial gap will be higher. I don't know if there's any benefit or bond achieved by having the retaining compound in the space between the sides of the ring gear and the converter as well as the radial gap at the bottom of the ring gear?

No_snivelling

Sorry. I had no idea that access to that critical ID/OD interface was so poor.

In a perfect world the ring gear would be removed, cleaned, Loctite applied and then reassembled. I have a high degree of confidence that that would work but it seems without cutting welds, that will be impossible.
By your description, I doubt much (if any) Loctite will make it to the critical gap especially since they are non-wicking compounds. Perhaps welding is the best option after all.

HBP

Yes it's a bit of an odd set up and not really favorable to much other than welding it seems.

No_snivelling

How big is the gap between the sides of the gear and the converter?

It seems like mark_in_maine had his welded when the engine/trans were out of the car.
I was wondering if a good welder could do it through the starter hole.

HBP

I don't think the gap is large at all and that was part of my concern with using a liquid cleaner, having it remain in the tight space and hamper the Loctite. I was thinking of trying to get a feeler gauge in there but there's not a lot of room. I'm curious if the Loctite would be helpful in bonding the sides of the gear to the converter as well as the bottom (if it's able to migrate that far)? If that's the case it may be worth a try. I don't know if the shear forces are different for the sides of the gear vs the bottom. In the demo videos where they're bonding a bearing onto a shaft, they claim that if you want to disassemble it, you just pull (or press if it doesn't give) the shaft from the bearing.

I wondered the same thing about welding through the hole. I don't know how much of a concern balancing is, having the welds be the same size and 180 degrees apart.

No_snivelling

Most Loctite products don't work well if the gap is too large. Any luck finding the Loctite manual I spoke of?
My gut feel is anything more than maybe 0.005" - 0.010" gap will not have great bond strength and application on the side of the gear just seems like a bad idea to me. Also consider what happens if some of the Loctite runs onto the gear teeth and hardens there?

I would assume that Mark had his stitch-welded; Short welds, evenly spaced in probably a lot more than just two places, but that's just my guess.

HBP

Yes I think this is the Loctite Manual you're thinking of? Loctite Manual

I suspect the excess compound outside the seam would eventually harden but isn't it anerobic?

Yes I would think at least 4 opposing welds would be required, maybe more. Would hate to have to go back in due to weld failure.

No_snivelling

Yes, that is the correct manual. Note on page 10 where it says:

"The best performance for slip fits is achieved using clearances between 0.025 mm and 0.075 mm (0.001 in. and 0.003 in.), or with interference fits. Performance is reduced as the clearance is increased."

Also worth noting is that all of their applications are for ID and OD use. I don't see any examples of side bonding.

For equally spaced welds, can you count the teeth and use them as your guide? I am not a mechanical engineer by any stretch, but my gut says 4 good welds of about an inch long should do the trick. I am thinking of the resistance when I turn over the engine with a wrench; it is a fairly low torque that is needed.