Transmission Gurus, how bad did I foul it up?

[derf]

I'm working on getting the transmission adapter onto my 700R4 for the swap. The kit came with some studs to put in the transmission and the adapter slides over the studs and you put the nuts and lock washers on.

Well, I put the studs in and they weren't going in past the first couple of threads without some resistance. So I double nutted them and turned them in to the recommended install depth. On the top, they went through the bosses with no problem. On the bottom, I ran into a problem.

The bottom two holes are blind holes and I ran the studs in too far and broke through the casting. They didn't get noticeably harder to turn so I blew right through the end on both sides.

Before I go to the transmission shop and ask the people who have a vested interest in selling me a new transmission case and the labor to swap the guts over, I wanted to ask people here what they think.

Here's a picture of the passenger side break through. It's open to the outside so I'm not necessarily as worried about it.



The drivers side is what I'm more concerned about. It opens up into a fluid passage.



That's the inside of the governor housing and it's a space where fluid will be in constant contact with the hole.


The biggest question I have is whether the damage is structural enough to need a new case. Do I need to swap all of the guts from this transmission to a new case or can I get by with just sealing the hole on the drivers side with some thread sealer or RTV?

[Romanov]

Sorry, but you are going to need a new case. Or, you are going to have to plug, weld, and tap a new tread hole.

[derf]

Originally Posted by Romanov

Sorry, but you are going to need a new case. Or, you are going to have to plug, weld, and tap a new tread hole.

The thread showing is coming from the bottom up. It's for a mount but I won't be using that mount. The adapter has a foot on it that I'll be using.

The hole was blown out by the stud coming in from the side in those pictures.

[fsjparts]

have had great luck with jb weld....I'd run that....just seal it up real good

[turtlejoe]

I'm going to add to this as if you were going to seal it up somehow and trudge forward. I can't really see, but you'll want to make sure and get rid of sharp edges and corners - especially the corners. These are stress concentrators and have a chance of starting and propagating cracks. Smooth and round is what you're going for, and yes, it means removing more material so be gentle. Depending on the sharp corner (and access) you can stop-drill at the apex so the cracks won't start and grow.

Even though you're not going to use that boss or load it directly, the housing will still be distributing some kind of load throughout the circumference. Heat cycles, vibration, asymmetric loading and unloading ... you'd be surprise how much damage can be done (over time) when it's all focused on a weakened area. We deal with this a lot on fielded aircraft that have developed structural cracks, and also damage created by over zealous maintenance folks. J-B Weld may seal it up, but it's not the structural repair welding would provide - but maybe that's not necessary here.

It's all speculation since I don't have a really good feel the damaged area and have absolutely no clue about the kind of loading the part really sees. Just things to consider.

Clean it up, assess the situation and JB it up if it looks OK, and see where it goes. Good luck!

[The Colonel]

I'd have it TIG welded.

[derf]

Originally Posted by turtlejoe

I'm going to add to this as if you were going to seal it up somehow and trudge forward. I can't really see, but you'll want to make sure and get rid of sharp edges and corners - especially the corners. These are stress concentrators and have a chance of starting and propagating cracks. Smooth and round is what you're going for, and yes, it means removing more material so be gentle. Depending on the sharp corner (and access) you can stop-drill at the apex so the cracks won't start and grow.

Even though you're not going to use that boss or load it directly, the housing will still be distributing some kind of load throughout the circumference. Heat cycles, vibration, asymmetric loading and unloading ... you'd be surprise how much damage can be done (over time) when it's all focused on a weakened area. We deal with this a lot on fielded aircraft that have developed structural cracks, and also damage created by over zealous maintenance folks. J-B Weld may seal it up, but it's not the structural repair welding would provide - but maybe that's not necessary here.

It's all speculation since I don't have a really good feel the damaged area and have absolutely no clue about the kind of loading the part really sees. Just things to consider.

Clean it up, assess the situation and JB it up if it looks OK, and see where it goes. Good luck!

Yeah, that's what concerns me. The studs in the bottom holes are going through a lot more "meat" in the housing. But with a broken off chunk, what else could go wrong?

I don't want to do it but I may just load up the transmission into the truck and have it rebuilt with a new case. Again. It's going to cost me plenty to have it done but not knowing what might go wrong makes me want to be better safe than sorry.

[turtlejoe]

Originally Posted by derf

Yeah, that's what concerns me. The studs in the bottom holes are going through a lot more "meat" in the housing. But with a broken off chunk, what else could go wrong?

I don't want to do it but I may just load up the transmission into the truck and have it rebuilt with a new case. Again. It's going to cost me plenty to have it done but not knowing what might go wrong makes me want to be better safe than sorry.

Worry will wear you out in a hurry. I noticed the last time I took the Cherokee to Ouray that 800 miles of worry each way pretty much wore me out. Imagine how much it would cost you though if you did the cross-your-fingers repair and got yourself stranded because of it 800 miles away? It will be spendy to have it swapped, but you'll rest much easier. Keep the old piece too - you can give the weld repair a shot once your skill increases. New class project maybe?

[710 Burner]

Originally Posted by The Colonel

I'd have it TIG welded.

at a minimum. That is the governor housing so JB is not going to stand up to the hydraulic pressure pushing on that chunk.