Looks like I'll be thread tapping trans filter bolt mounting hole


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Old 12-10-18, 08:05 PM
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Looks like I'll be thread tapping trans filter bolt mounting hole

92' Ranger Supercab with 2.9 V6 and automatic transmission. I've been jury rigging the stripped transmission filter mounting bolt hole for the last few years. I was fixing it again this weekend, and I could tell that I'm running out of salvageable threads.

I've already started reading about drilling, tapping, and use of thread inserts such as Helicoil or E-Z Lock.

1. When the time comes, what kind of drill bit should I use on the aluminum transmission valve body. That's where the filter mounting hole is. Do I use carbide....titanium....cobalt?

2. I believe this is solid aluminum. How long would it take to drill into the existing mounting bolt hole? Would a 7 Amp power drill be enough? I

This will be a new one for me later in 2019. Never done drill and tap. Might as well learn about it now.
 
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Old 12-11-18, 03:57 AM
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With aluminum almost any drill will work. Drill bit wait till you get the helicoil it will tell you what drill size you will need. your problem will be not drilling to far into case. Be sure not to go past the old threads.
 
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Old 12-11-18, 05:43 AM
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Ok. Copy that on not drilling too far. On this valve body, only the upper part of the hole is threaded. The lower part is smooth bore. I assume aluminum is a soft metal. Am I am looking at minutes.......30 minutes..........an hour to drill? Naturally I will proceed with caution since this will be my first time.

I'm kind of leaning towards E-Z Lock Solid Wall inserts because you don't need to buy special STI taps
 
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Old 12-11-18, 05:46 AM
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More like 3 seconds to drill. Aluminum is very soft. I imagine drilling a nice clean hole with a hand drill could be tricky. Make sure you use the right bit. I think I would personally try reaming the hole out then tapping it using the next size up, and getting a new drain plug. I haven't done this first hand, but it seems plausible.
 
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Old 12-11-18, 05:49 AM
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In my experience, I would say "seconds" !

And while it's important to not drill too deep, you want to drill deep enough.

I've had HeliCoils which didn't seat all the way to the bottom, and there is no provision for removing them once inserted so you can start over.

I've chosen to use a "bottoming" tap whenever possible, so that the HeliCoil can be positioned as deep as possible, and all of the new stainless steel threads can be put to use.
 
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Old 12-11-18, 06:36 AM
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Ok. This is all good to know. By the way, this isn't a drain plug. It's a mounting bolt hole for a transmission fluid filter which I change every 1.5 years or so.
 
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Old 12-26-18, 06:19 PM
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This discussion can be closed to avoid wasting anyone's time. I'll do the thread tapping late in 2019 for the next transmission fluid/filter change. I'll save this inquiry too. Thanks.
 
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Old 12-27-18, 05:07 AM
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If the mounting bolt has a coarse thread, I would first try tapping hole with a fine thread tap, same bolt diameter. As stated earlier, get a bottoming tap. If the filter mounting bolt can't be replaced with a standard fine thread bolt, you need to get a fine thread die (or thread chaser) for the bolt size involved and recut the threads on the original bolt. There is no drilling required with this approach.
 
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Old 12-27-18, 05:51 AM
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Thanks Bob. Interesting variation you propose on the drill-free approach. I'll print out this discussion. There is no question that I will need to tap and thread next time time I change the fluid. Right now mounting bolt is held in with 'Mr Grip' insert strips, Threadlocker blue and lock nuts

Thanks all,

Happy Holidays.
 
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Old 12-27-18, 08:52 AM
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It's a mounting bolt hole for a transmission fluid filter which I change every 1.5 years or so.

Why do you change the fluid and filter so often?
 
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Old 12-27-18, 12:28 PM
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Because of the extreme summer temperatures in Arizona. Also, it gives me an opportunity to see how that stripped bolt hole is doing. My previous transmission lasted a very long time before I had to replace it because of the fluid and filter changes.
 
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Old 02-12-19, 06:46 AM
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I ordered three E-Z LOK thin wall thread inserts. No special tools needed. I can use my own thread tap and drill bit. When I change my trans fluid and filter in 2020, I'll tap a new mounting hole in the valve body.
 
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Old 04-27-20, 08:59 AM
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Following up from 2019. I completed latest transmission fluid and filter change this weekend. I was able to tap the filter mounting bolt hole to M8-1.25mm. This is the bolt hole in the valve body.

But the bolt hole on the filter was not wide enough for an M8 bolt. So I had to bore out the filter bolt hole with my Dremel. Then I was able to mount the filter with an M8 allen stud, nut, and lock washer.

The new threads I tapped work perfectly. But I don't like tampering with the bolt hole in the filter. I don't know if the mounting area of the filter is open to the fluid channels inside the filter. I hope there is no leakage from the bolt hole. The transmission works fine

Now for the fluid/filter change in 2021, I have to see if I can find a thread insert with M8 external threads and M6 or 1/4-20 internal threads. I shouldn't be altering the bolt hole diameter in the filter.
 
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Old 04-27-20, 03:20 PM
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If the filter mounting bolts are coarse thread, I would consider tapping the hole with a fine pitch tap and get fine thread bolts.
 
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Old 04-27-20, 09:04 PM
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I can't tap it any wider without risking any damage to the valve body, So I'm stuck with 8mm. But I did find M8-1.25 outer diameter threaded inserts with M5-.08 inner diameter. An M5 mounting bolt would fit through the filter bolt hole.

Either that, or I could bore out the filter mount hole every 1.5 years when I change the filter and fluid. And I could run into problems with that.
 
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Old 04-28-20, 05:37 AM
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Why do you have to tap or drill for clearance if you are using a nut and lock washer on the stud. Just get the largest diameter stud that goes through everything.
 
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Old 04-28-20, 07:50 AM
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I already got the largest diameter stud or bolt to go through everything. That's what I was trying to say. But it's too wide for the mounting hole on the filter.
 
 

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