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'02 2500 HD
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20 Posts
Discussion Starter #1
Recently got an 02 duramax. Did a ton of maintenance on it, changed the trans fluid to Mobil Delvac 1 ATF. Noticed an obvious smoother shift from 1-2. 1500 miles later that was gone, checked the fluid and it was a little dirty.
Decided to drain and fill again along with cleaning inside the pan and change the internal filter. The fluid is more expensive than the filter.

One of the pan bolts was cross threaded and the bolt came out along with the female threads from the transmission
...

Great.

Cussed myself for trying to do a project that probably wasn't entirely necessary...

A short trip to auto zone and I picked up OEMtools generic helicoil kit in size M8x1.25 that came with 3 coils, the necessary tap and a tool to put in the helicoil for about 30 bucks. A tap wrench is needed if you don't have one.

Drilled the hole out to 11/64 as recommended in the kit

Tapped with the provided tap. Only tapped about 3/4 as deep as the original threads because the tap started to require alot of torque at that point and I didn't want to break anything. The deep threads aren't necessary and I was already quite a bit deeper than the length of the helicoil that was in the kit.

Inserted helicoil into newly tapped hole. No need to run helicoil all the way in deep (you can and try to use 2 or buy a longer coil but these bolts only torque to 20 ft lbs and now you have steel threads instead of soft aluminum). Run it until the thread closest to you (the end of the coil) is a half turn inside the hole.

Break the tang - gravity will drop it out


Was able to thread original bolt back in the hole no problem and torque to 20 ft lbs.

Happy I went through all that to get my fluid swapped out and check everything but as usual was a bigger project than I hoped for.

Thought I'd post in case someone else has the same problem.

It really wasn't that hard to repair but drilling into your transmission is nerve racking to say the least.

Cheers
Chris
 

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Ronald Reagan fan
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4,310 Posts
Recently got an 02 duramax. Did a ton of maintenance on it, changed the trans fluid to Mobil Delvac 1 ATF. Noticed an obvious smoother shift from 1-2. 1500 miles later that was gone, checked the fluid and it was a little dirty.
Decided to drain and fill again along with cleaning inside the pan and change the internal filter. The fluid is more expensive than the filter.

One of the pan bolts was cross threaded and the bolt came out along with the female threads from the transmission
...

Great.

Cussed myself for trying to do a project that probably wasn't entirely necessary...

A short trip to auto zone and I picked up OEMtools generic helicoil kit in size M8x1.25 that came with 3 coils, the necessary tap and a tool to put in the helicoil for about 30 bucks. A tap wrench is needed if you don't have one.

Drilled the hole out to 11/64 as recommended in the kit

Tapped with the provided tap. Only tapped about 3/4 as deep as the original threads because the tap started to require alot of torque at that point and I didn't want to break anything. The deep threads aren't necessary and I was already quite a bit deeper than the length of the helicoil that was in the kit.

Inserted helicoil into newly tapped hole. No need to run helicoil all the way in deep (you can and try to use 2 or buy a longer coil but these bolts only torque to 20 ft lbs and now you have steel threads instead of soft aluminum). Run it until the thread closest to you (the end of the coil) is a half turn inside the hole.

Break the tang - gravity will drop it out


Was able to thread original bolt back in the hole no problem and torque to 20 ft lbs.

Happy I went through all that to get my fluid swapped out and check everything but as usual was a bigger project than I hoped for.

Thought I'd post in case someone else has the same problem.

It really wasn't that hard to repair but drilling into your transmission is nerve racking to say the least.

Cheers
Chris
It can be nerve racking no doubt about it.Theres certainly no margin for error when doing repairs like that but glad to hear you got it repaired.Sometimes I see cases where guys will use a smaller diameter bolt with some flat washers and a self locking nut to tighten the pan but also keep enough tension on the gasket so it doesn’t leak but the smaller bolt idea is only good for situations where your able to put a nut on top of the housing.

I once bought a reman 700R4 that way.
 

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'02 2500 HD
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20 Posts
Discussion Starter #3
You could drill all the way through and put a nut on top I think, but that would be harder than the helicoil repair. I read about quite a few other tricks like wrapping the original bolt in aluminum foil or stripping some old wire and using a few little pieces of copper in the hole to help the bolt bite in the old threads, putting some jb weld or epoxy on the end of a piece of threaded rod and running it all the way in and letting it dry overnight creating a stud, then using a nut to secure the pan in that location, you could also just drill and tap to a larger size bolt. Once you start drilling you will realize why the torque spec is so low and why the threads broke in the first place, the metal is very soft.
 

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94 gmc k3500 dually
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39 Posts
In a couple of cases I used jb weld but I sprayed wd-40 on the bolt so it would not stick to the bolt and it has worked. Bolts can be removed and the threads remain intact.
 

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'02 2500 HD
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Discussion Starter #5
In a couple of cases I used jb weld but I sprayed wd-40 on the bolt so it would not stick to the bolt and it has worked. Bolts can be removed and the threads remain intact.
You're saying fill the stripped hole with jb weld, screw the bolt in with a non stick coating and then unscrew it and let the jb weld dry? Or just let the jb weld dry with the bolt in and unscrew it later? I would be afraid I'd jb weld the dang transmission pan on...ha
 

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94 gmc k3500 dually
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39 Posts
Yes I put the bolt in coated with wd and let the jb weld dry then you can remove or torx to specifications. The first time I did this was to take out slop in my forklift steering. In this case a rusted splined shaft where it entered the steering box. This quick fix lasted 10 years before the shafted rusted to the point it needed to be replaced
 
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