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You could try to go to a 3/8" NPT, but here are the inserts for 1/4" NPT. Can't say I understand how they would work since there is a spiral leakage path around the insert, but I might not know what I don't know in this case.
Thank you both. So RBob says Helicoils won't work, but Scooter provides McMaster links to coils...are you saying that there do exist NPT helicoil style coils and those would work? In theory makes sense.
I didn't know they were a thing until I looked, I just use the filters on McMasters site to find things, those are 1/4-18 NPT thread repair inserts, so they DO EXIST. Whether they work or not is unknown to me and I am only going by the size RBob has specified. I didn't think they were NPT at all, I thought they were metric bubble flare (or something like that). I don't mess with automatics too much so I don't know exactly
Helicoils work, haven't used an NPT one before though... but you're pretty much guaranteed it's coming out with the fitting if you ever remove it, and you'll have to install a new one with the tool.
You could try to go to a 3/8" NPT, but here are the inserts for 1/4" NPT. Can't say I understand how they would work since there is a spiral leakage path around the insert, but I might not know what I don't know in this case.
Well, you learn something new every day. I would guess that if the insert was gooped up with PTFE sealant paste prior to being inserted, then a reasonable amount placed on the fitting, it won't leak. May be worth trying it to save the case.
RBob.
Edit: just checked the price that includes the install tools, ouch. Likely be cheaper to find another case.
Last edited by RBob; Dec 8, 2020 at 09:27 AM.
Reason: ouch
If it helps, here is a shot of the connector. The description says "hoses are -6AN and come with four 5/16 in. inverted flare adapters." I called the manufacturer and they said the thread is a straight thread 1/2"x20 where the 5/16" is the internal diameter. That said, is that Helicoil option from McMaster the only option? I ask because I see many helicoil kits including the install tools in the $25 range. Other thoughts now that you have the size and image? Thx for the help!
The case IIRC is pipe thread; a brass adapter goes into that; then the 5/16" inverted flare on the actual lines hooks up to the adapter. So the fitting in the photo screws into the adapter and won't ever even touch the case.
If the case itself is what's buggered, then either a ¼" NPT Heli-Coil, or perhaps drilling it out and making it 3/8" NPT and adding a bushing if that's even a possibility, are your best bets. I doubt it would be very wise to just try to tap it deeper and let the adapter fitting sink in farther. Although it might work, depending on how deep it would end up having to go.
I've used Heli-Coils extensively with excellent results over the years. I went from a skeptic to a convert on that. But I've never seen or used a pipe thread one. I wouldn't hesitate though, especially not in an application like this where it'll most likely never have to come apart again.
Interesting. My 4L60E case does NOT have any adaptors in those cooler line ports. The 5/16" inverted flare fittings (which are straight threaded) screwed directly into the adaptor. Anyone else have these brass inserts or no? If so, anyone have a part # or is it the part the one 88 RS suggested (https://www.homedepot.com/p/Brass-3-...E&gclsrc=aw.ds)? With the fitting threading into the case, I am not sure how an insert could even fit since the thread & pitch fit now (i.e.: guessing both are 5/16"?). :/ Also, can anyone confirm the case has NPT vs. straight threads? Again, this is concerning if the case is NPT with no fittings and the fitting on the cooler line is straight thread. Sofakingdom, I am glad you are are helicoil convert as I have heard nothing but good things about them. Anyone know if the case's top cooler line hole is the inbound or outbound? Asking because if inbound, less chance of leakage I would guess.
OK, bottom line...is the consensus that the best option would be to tap case to a larger diameter (if so, what size?) and (1) insert a helicoil & brass insert or (2) just a brass insert with thread sealant? Should bore and insert be straight or NPT? Appreciate you!
This gets more and more interesting. To answer one question, the return line is either the upper fitting, or the rear fitting:
The rear fitting is definitely a straight thread, national pipe straight thread (NPS). Note the washer/seal on it.
As for the front fittings, I don't know, the case may be tapped for a tapered thread, but with a straight fitting inserted. Or, tapped for a straight thread with a tapered fitting. Something needs to be done to seal it. On the other hand, these brass front fittings appear to be tightened down to seal directly against the case. Which may be how they seal, and also may be as stated, a straight thread all around:
RBob.
Interesting. Thank you. I should have provided some additional information. This is a LS swap project into a 1991 RS. The engine is a 2002 LS1. The cooler lines are these from Summit: https://www.summitracing.com/parts/add-23-1501. And here is an image of the 4L60E case (which is also an '02). So anyone have a brass fitting part recommendation and tap size recommendation for the upper stripped out case port? And should we use a helicoil or just go with the fitting and thread sealant?
Seems like the first thing to do would be to determine FOR SURE what thread it is. I simply don't know. My experience is with older transmissions, which were pipe (tapered) thread.
IMO though if it turns out that the fitting in the case is inverted flare, such that those lines would screw straight into it, the case is now GARBAGE and should just be melted down. I have no idea how you would go about gracefully repairing that type of a fitting in that situation.
I would see if tapered pipe threads would sufficiently grab what is left of those stripped threads, and if so, then red Loctite an adapter in there permanently.
FYI, the next closest larger thread to tap the case would be M14 x 1.25. Not a perfect match, but close enough to work. But an adapter to go from that to 5/16 NPS probably does not exist. https://www.newmantools.com/tech/pitchconversions.htm
@NoEmission84TA...here you go first shot is the connector separated as requested. Second shows the stripped threads on the upper cooler line port of the case:
For some reason I thought this thread was in regards to the 4L80E. I must need new glasses or such.
Anyway, the pictures & info in my post #12 is for the 4L80E, not the 4L60E.
walkingdead5, that adapter that threads into the case is a straight thread, not tapered. Also, the close up picture of the case threads show a nice machined surface for the adapter to seal on.
I'll bet QwkTrip is correct, that these are non-tapered fittings.
NoAdmission84TA, this link doesn't work any longer: (https://www.exoticspeed.com/products/fitting-1-4-npt-to-6an-flare-male-to-male-straight-adapter). When you say 1/4" NPT, what is the outside diameter? The case port diameter is 1/2" and they are straight thread. So, it seems like the consensus is to tap case to a larger diameter (what size?) and insert a brass insert with thread sealant/Loctite. That said should I also use a Helicoil? What size brass insert? NPS or NPT? Thank you!
Last edited by walkingdead5; Dec 12, 2020 at 01:35 PM.
Reason: added questions
When you say 1/4" NPT, what is the outside diameter? The case port diameter is 1/2" and they are straight thread. So, it seems like the consensus is to tap case to a larger diameter (what size?) and insert a brass insert with thread sealant/Loctite. That said should I also use a Helicoil? What size brass insert? NPS or NPT? Thank you!
I am trying to save your transmission. The repair will not be machine shop perfectly correct, but it will work. The alternative is a new case or new transmission. You don't want to drill and tap a huge hole where those threads are stripped.
Two threads exist that are the smallest oversize up from 1/2" - those are 1/4" NPT (.540" nominal) and M14 x 1.25 (.551"). -6AN adapters are available for both.
Nominal because the threads are tapered, so substitute the word "average". The metric thread is straight.
1/4" NPT has 18 TPI (threads per inch), so only 2 threads different than the stripped 20 TPI.
Your 20 TPI has a pitch of .050". The metric thread pitch works out to a pitch of .049" (1.25 / 25.4).
What all this means is the thread count of either does not match perfectly, but they will screw into each other about 4 full threads before they start to bind. But 4 threads is all you are working with, so this can work. When re-tapped, then you red Loctite the chosen adapter in permanently. Connect your hose. Done.
No Helicoil necessary.
This is great info...thank you. I will pick them up today. In your opinion, which one (1/4"NPT vs M14x1.25) would be recommended over the other in this application? And just to be safe, can you confirm that I will not be torqueing this new fitting into case and simply threading it in 4 threads until it would bind? Thanks for the advice...have not done this before and just want to be safe as I know I've got one shot here!
If you are able to, measure how big that hole became after stripping out. That will be your deciding factor as to what adapter you will choose - either tapered or straight. If shopping locally, buy both adapters and return the one you don't use. Personally, if the initial threads on the tapered fitting grab what is left of the stripped threads almost immediately, then I would choose the tapered. You might need the corresponding tap to ensure good threads in the case to work with. When using taps, be absolutely certain that the tap is (and stays) straight in the hole. And don't let any chips fall into that port! Tapping fluid is your friend here, but a shot of WD-40 will do. You just might get away with not having to use a tap at all. It all depends how the threads want to screw each other. When you are satisfied with the fit, clean both threads and then cover the threads in red Loctite and tighten, but do not overtighten and strip the hole out further. Red Loctite will seal and "glue" those threads together PERMANENTLY. Never try to unscrew that fitting again.
Do you have a school that has shop classes nearby? Machine/tool, Automotive, any shop that can guide you with this.
Try looking for a youtube video showing how to tap a hole.
Last edited by NoEmissions84TA; Dec 13, 2020 at 08:06 PM.
If the threads are stripped then you have to wipe them out completely and start over with a smooth bore. Look up the root diameter of the thread type and that is the minimum drill size you will need to use to clean up the hole. Then figure out what the nearest thread type is that you can use and drill and tap the hole for that.
Loctite makes a liquid thread maker that can hold quite a bit of torque. I can't remember the usable temperature range though. I used it on my cylinder heads when I stripped one of the valve cover screws. I was able to remake the threads and reuse the original bolt.
The tap drill for 1/4-18 NPT is 27/64 or .421". You are already beyond that.
The tap drill for M14 x 1.25 is 12.8mm or .504". This the size you should drill and tap to.
Then install this fitting and connect your hose.
Last edited by NoEmissions84TA; Dec 14, 2020 at 09:21 PM.
Sounds good. I will tap using a 12.8 mm drill bit and M14x1.25 tap. Why is the fitting you recommend an M12? Also, I will use grease on the drill bit & tap to capture metal shavings...any recommendations on removing grease left in the new threads (if I have to) before applying the fitting with red Loctite? Thx!
Sounds good. I will tap using a 12.8 mm drill bit and M14x1.25 tap. Why is the fitting you recommend an M12? Also, I will use grease on the drill bit & tap to capture metal shavings...any recommendations on removing grease left in the new threads (if I have to) before applying the fitting with red Loctite? Thx!
You're right - the link is corrected for the M14 fitting.
Carb cleaner, gasoline, anything that will cut grease will clean the grease out before using Loctite.
Be careful when drilling. There is a bottom there that you absolutely do not want to drill through. Remember it is a port.
Also, when tapping, make sure that the tap does not bottom out. You will strip out your new threads while creating them if the tap bottoms.
You want to buy a bottoming tap.
If you already have a 1/2" (.500) drill bit, then you do not need to buy a 12.8mm drill bit. It's only .004" difference = 1 human hair.
Last edited by NoEmissions84TA; Dec 14, 2020 at 09:49 PM.
Last questions...on post #18 you specify a fitting of "steal or brass but NOT aluminum," yet on post #26, you provide a link for aluminum. Just wanted clarification. Was that to be brass if NPT and aluminum if NPS? Curious as to why just for my own knowledge. And, should I use a washer or o-ring (as shown below) in the fitting or no?
I've never seen one of these transmissions in person, but the photo looks like there is an insert fixed into the transmission housing. if you can get that insert out then you can put a new one back in and problem solved.
@NoEmission84TA...here you go first shot is the connector separated as requested. Second shows the stripped threads on the upper cooler line port of the case:
If you need that sealant on the AN/JIC fitting you need to replace it.
Just looked at the pictures on my big computer screen and those threads aren't totally gone. Seems like a really good candidate for the Loctite thread maker. That way you can just build back up the threads you have and not go through all the other hassles.
If you need that sealant on the AN/JIC fitting you need to replace it.
Usually threads exist only to hold things together and the seal is made somewhere else (chamfer on the nose, o-ring, gasket, etc...). NPT fittings are the odd ball because it literally cannot make a seal on its own, so thread compound must be applied to the threads or the joint will leak. You rarely need thread compound with other types of fittings.
You're right - the link is corrected for the M14 fitting.
Carb cleaner, gasoline, anything that will cut grease will clean the grease out before using Loctite.
Be careful when drilling. There is a bottom there that you absolutely do not want to drill through. Remember it is a port.
Also, when tapping, make sure that the tap does not bottom out. You will strip out your new threads while creating them if the tap bottoms.
You want to buy a bottoming tap.
If you already have a 1/2" (.500) drill bit, then you do not need to buy a 12.8mm drill bit. It's only .004" difference = 1 human hair.
@NoEmissions84TALast questions...on post #18 you specify a fitting of "steal or brass but NOT aluminum," yet on post #26, you provide a link for aluminum. Just wanted clarification. Was that to be brass if NPT and aluminum if NPS? Curious as to why just for my own knowledge. And, should I use a washer or o-ring (as shown in post #29) in the fitting or no?
Also, the Time-Sert thread insert is made for thin walls. I don't know if that means you drill a smaller hole too? You'd have to look at their instructions to find out.
Steel or brass fitting because aluminum on aluminum stands a very good chance of galling (the threads will "weld" themselves together). A steel AN adapter fitting would be best here (and will last much longer), and I couldn't find the fitting you need in steel, only aluminum. Remember, this repair is a one shot deal. The red Loctite will not only seal the threads, but this fitting is never coming out again. You don't need a seal or o-ring.
READ: max torque is in INCH/POUNDS
This will work for a low torque, non-hydraulic application valve cover bolt.
This is not going to hold against ? 200 psi ? hot transmission fluid.
273 in-lbs for the M14 is ~23 ft-lbs. Torque of the cooler line fitting only calls for ~20 ft-lbs anyhow. Either way, I agree where you are going here...I don't trust the form-a-thread to hold against a constant 200 psi pressure of 275 deg. fluid. I will go with the tap w/red loctite and M14 fitting. I could not find an -6AN-M14x1.25 brass or steal fitting either, so I will go with the aluminum. If galling occurs, that's ok since the plan is for this to be permanent anyhow. Thanks all...I'll let ya know how it turns out!
Hey all! Thanks for following up...apologize for the delay...I'm working on this with my son and as a senior, he's been busy with college apps, SATs, and all that...anyhow, it was very ironic that you asked last night as we planned to hit it today...and did! I wanted to thank everyone again for their tips and suggestions. The engine/trans was in place and we didn't want to pull it all out completely again, so we hoisted it up enough to access the bell housing port with tools, etc. Once up, it only took about 40 minutes from start to finish. Here are a few pix of the process from the drill out, metal removal, tapping & sealing in new 6AN adapter fitting. Thanks again
!
When you are satisfied with the fit, clean both threads and then cover the threads in red Loctite and tighten, but do not overtighten and strip the hole out further. Red Loctite will seal and "glue" those threads together PERMANENTLY. Never try to unscrew that fitting again.
