Stripped transmission mount hole. Need advice/ideas on how to fix

While doing a clutch change on my '98 4x4 5spd, I apparently fucked up & completely stripped one of the four holes on the transmission that attach the 'transmission mount' to the trans. The bolt seemed to screw in fine, until it was time to torque it down. Then, it just kept spinning. So, I pulled the bolt out & bunch of the threads came out with it .

What freaked me out the most was seeing that those mounting holes actually go all the way through into the inside of the 'intermediate case' (don't know what it's called). I didn't initially know what was inside that hole, if it went into the 'guts' of the transmission (where the oil & gears are), if it was supposed to go all the way through by design, or if the back of the hole somehow broke.

I do kinda get a whiff of gear oil when I get close to the hole, which is why I thought maybe there was oil behind the hole. Not sure if that's somewhat normal, or if maybe I've got bigger problems, like a broken seal or something.

Anyway, I'm not sure what the best course of action is at this point, so I need some advice.

My first instinct would be that the hole needs to be drilled & tap to the next size up, but that would mean bringing down the tranny *again*, and then trying to separate the 'middle chamber' from the rest of the trans so that I can more easily work on it, right? The idea of messing with any of those old bolts on the trans & risk breaking more shit freaks me out, but I guess I'd have to do it if there's no better option.

Assuming no bolts break, how hard would it be to get this done?

Another option is to say 'fuck it' and leave it as is, which means only running 3 bolts to the transmission mount (not sure how critical this is). Also, I'd have to find a way to plug that hole to avoid getting water & crap in it, correct?

I'm pretty frustrated & bummed out. Whatever feedback & advice you guys could offer would be greatly appreciated.

FYI, in case it matters, this isn't my daily driver; it's more of my project truck at this point.

 

If you’re worried that it penetrates into the case and you might have a leak, stick a q tip up in there and see if it comes back with any transmission fluid on it. It seems unlikely but maybe it gives you some indication into how much of a perforation there may if you’re worried about that. If there is at least you known you’ll have to tackle solving it differently depending on how long you want to drive the truck but worst case scenario, it tells you nothing.

If it were me, even though it’s a giant PITA I’d pull the tranny, again, and tap it with as small of a size up from where you are as to provide bite for a bolt the next size up. Although I can’t tell exactly where those bolts are, they are there for a reason. I am guessing to resist the torsion the transmission is under from the engine so it would bug me that I could be over stressing just one bolt if I ran without the other but that could be just me. You might be able to run fine without it but like I said, it would bother me so I wouldn’t do it personally as I am paranoid about such things. Alternatively if you are confident and have access, you might be able to tap it in place. I am not that good so I’d pull it but you may be more skilled than I am so you could do it.

Good luck with whatever you choose and let us know how it turns out for you.

 

I don't believe they do enter the transmission housing. Think about it, if they did and you pulled the mount, you'd have tranny fluid leaking out. No, I don't believe they go all the way into the housing.

Maybe a cheap bore camera would come in handy here? At least it will give you an idea of what you're dealing with.

$16 USB Snake Inspection Camera, 2.0 MP IP67 Waterproof USB C Borescope, Type-C Scope Camera with 8 Adjustable LED Lights for Android, PC2

https://smile.amazon.com/Inspection-Waterproof-Borescope-Adjustable-Android/dp/B08X1X82DD/

I also wouldn't run it with just 3 mount bolts. Going to have to fashion up some kind of repair and monitor it. Others can advise on that aspect.

Sucks, sorry.

 

The photo makes it look like there is a sleeve in the hole. ??
Since you said the "threads came out with the bolt" after attempting to torque it, I can't believe it is a sleeve.
So, if no sleeve - then tap the hole for a helicoil and install said helicoil. That way you can use the original bolt (and keep them all the same). Piece of cake.

(just don't let the breakoff tang from the helicoil fall inside)

 

The holes do actually go into the housing.
I confirmed it by checking out this rebuild video this guy does:
(jump to the 4:15 mark)

https://www.youtube.com/watch?v=cMJy-au0Eio

and, yeah, I'm also not cool with the idea of only running 3 bolts. Seems pretty sketchy...

There's no sleeve. I think it's just the angle in the picture.

I can still get the bolt to thread all the way in, and it feels pretty good/solid going in. However, once it goes all the way in & bottoms out, it starts to slip & spin. So, I guess it means that there's still some decent amount of threads still intact.

I'm debating either doing a helicoil or maybe that permatex thread repair stuff. The permatex supposedly isn't close to being as strong as a helicoil, but I'd avoid having to deal with drilling.

Based on the video that I posted up above, it looks like I might be able to just remove the transfer case & get inside that middle chamber. That way, I can at least see what's going on inside & clean it out if necessary if I decide to do the helicoil. It would still mean dropping the tranny, cuz there's no way I'm gonna risk trying to drill out that hole from underneath & at a weird angle.

I just hope that I won't have to destroy the brand-new pilot bearing I just put in if I decide to pull the tranny again. uggh...

 

Ahhh ok. Yep into the transfer adaptor housing. Not going to have fluid in it unless that seal is leaky.

I wonder if you could use a longer bolt and then just secure with a plate and lock nut on the inside. Sketchy AF but with 3 good mount bolt it might still be ok. Those mount bolts are 48 ft lbs so not super high torque. You'd just have to secure the trans mount prior to install of the tcase.

Not sure which I would try... bolt/nut or helicoil. I had to bore out one of the transfer case bolt holes where it mates up to the transmission. The housing was damaged during shipping but it also didn't have any threads - it was one where the bolt passes through and threads into the trans.

Sux man. Hopefully you can work up something. Good luck.

EDIT: If the OCD hits you like me and its really bugging you (DIY repair of that bolt hole), just start shopping for a replacement transfer adaptor. Might be able to find one at a local yard for cheap.

https://www.ebay.com/itm/284507160988

That seller also has it up on car-part.com for 50 bucks cheaper. If you go that route, call them direct.

 

@koditten is pretty creative

@gearcruncher is a trans guru

@Empty_Lord does lots of older Taco work

 

Blind hole Helicoil and send it. Get a good kit from mc master carr and not Amazon ebay junk. Just use a caliper to get the depth of the hole, and use masking tape or a collar on the drill bit so you don't go too far.

 

If the boss is big enough go up one bolt size and tap

 

Timesert or Helicoil.

 

If the bolt has a shoulder on it then sometimes you can use washers to shim the bolt out just a bit so the threads are still engaging and it will tighten down that way. Having said that if some of the threads have come out then the rest might follow. A more permanent solution might be in order. You could also find a transmission place that might fix it for you. That would be a little more pricey but should not be too bad and would give you peace of mind that it was done correctly.



Edit: @six5crèéd Any words of wisdom here from your vast experience?

 

Give this a watch.

https://www.youtube.com/watch?v=jknMrFOGMOQ

 

I have subscribed to Project Farm on YouTube. He does great analysis of products, etc.

 

Thanks for the link - Good video. I think we learned more about the average breaking strength of standard grade 5 bolts as far as the thread insert category was concerned. Would have been interesting to go with some grade 8 or 10 bolts to find out which would break first, the insert or new threads, but that's just being nit-picky.

An additional reason I suggest McMaster-Carr for name brand helicoils, is that you can order different length and material inserts, vs whatever you get in the cheap kits. But it is good to know that knock off brands work equally as well in a pinch.

 

I only have ever used the helicoil - stripped some head bolts in my 1915 Ford in 2006. I do like the design of the Timesert though - but boy are they expensive.

 

Yep, no gear oil in that section, and the hole goes all the way through from the factory. It's kind of a void between the trans and tcase, so no worries about tapping it/getting a few metal shavings in there.

I would helicoil.

Worst case scenario you can pull the tcase to gain access. Then you could easily work on it/weld a nut on the inside, etc.

 

this here ^^^

 

How feasible would it be to consider removing the tcase without having to drop the tranny again? is it more/less doable, or am I asking for more trouble?

 

Very feasible.

If you haven't got the electrical connectors or shifter back on already, just pull the 10 or so bolts and it will slide right off the trans. The top bolts are a bit of pain but can be accessed through the shifter tunnel.

 

super feasible. Ive taking the T case off many times without removing the transmission. Transmission jack comes in handy for this but you can do it with any floor jack