Muddz

I'm not certain what happen but one of my 42RE bolt holes stripped out, kept turning while torquing down. The bolt doesn't appear to have suffered much damage, but am going to order a new OEM bolt. The majority of the damage must have been with the bolt hole.

Instead of trying to install another bolt, torquing it down, I think I should first heli-coil the damaged bolt hole.

It appears a helicoil can be installed without removing the oil pan (that has a drain plug). Taking measurements, the hole is around ~1 inch deep and the bolt ~.6 inch in length.

I believe the threads are 5/16-18. So I need a 5/16-18 helicoil kit with either a .5 or 1 inch helicoils?

4.3L XJ

Yes, you can helicoil it. As long as the hole is outside the pan and the area where the oil is, you can do it without removing the pan, although it would be easier to do it without the pan in the way. You will need to reach inside the hole and break off the cross piece on the bottom of the coil when done. That will take some really small needle nose pliers.

Muddz

I've come across different lengths 5/16-18 helicoil inserts such as from ~.4xx in to .75 in

The hole is approx 1 inch deep I'm thinking of getting some inserts that are 3/4" or 1 inch long.

I suppose I could try and retapp the bolt hole with a 5/16-18 tap, install a new bolt and see if it torques down ok to 150 in. lbs (12.5 foot lbs)

I'm using an OEM re-usable gasket that doesn't require any silicon or sealant so I suppose I can just loosen the bolts to adjust the pan so the hole is better exposed. Otherwise I would need to drain and save the oil, remove the pan and install the helicoil with the pan removed.

4.3L XJ

If you have any threads left, I wouldn't try to strip them out any further. The tap you get will follow the old threads, which helps a lot when you insert the new threads

Muddz

What I observed with a flashlight the bolt hole had debri shavings caused by the bolt having stronger steel than the transmission. After cleaning the hole out there appears to be some threads that potentially could be tapped out. The bolt doesn't appear to have suffered much damage. Perhaps not quite a sharp as a brand new one.

I tapped out the bolt hole with a 5/16-18 NC tap however somethings wrong as another pulled pan bolt doesn't feel right seems to fit too loose.

So I'm going to drill out the hole with a 21/64 drill bit and insert a 5/16-18 x 5/8 helicoil which hopefully will repair the bolt hole.

I verified the bolt size is 5/16-18 x 5/8 inch and ordered a new oem bolt based on a part number from a Jeep Parts manual . p/n 4723548 which is superseded by p/n 6036330A

SCREW AND WASHER. Hex Head. .312-18x.625.
This Fits Your 1995 Jeep Grand Cherokee 4.0L I6 Power Tech, 4-Spd. Automatic 42RE
Part Number: 04723548 (MD952155; 06023355; J8121145) 5/16"-18 x 5/8

Some helico8ils the length is specified as the diameter of a helicoil as 1D, 1.5D, 2D, etc.

D = diameter

1D = 1 x 5/16 = .3125 in.
1.5D = 1.5 x 5/16 = 0.46875 in.
2D = 2 x 5/16 (.3125) = .625 inch = 5/8 in. (I think I should use at least a 2D length)

The longest 5/16-18 helicoil I was able to find so far on eBay is specified as 3/4 in. (.75) long.

Most of the helicoil kits come with shorter helicoils. Kits found with longer heli-coils are ~2+ times the cost.

dave1123

Personally I would use a 1/2 inch long Helicoil insert set flush with the outer edge, then using a steel rod small enough to fit inside the coil, break off the drive tang by a tap with a hammer on it. Then the bolt will pass into the area beyond the coil freely. I've only been using Helicoils for most of my life for various things. Helicoils require a special tap to thread the hole before the insert goes in.

Muddz

I guess I could have saved some money just buying some 2D inserts, a 21/64th drill bit and using a 5/16-18 tap I have in my tool box. Then use some sort of rod the correct size to install the inserts. However I wasn't certain if doing it that way would work or not as the inserts are designed to work with an insertion tool that requires additional pressure to install the inserts once the hole is drilled and tapped.

After looking around at various 5/16-18 kits I found some kits with an insertion tool, a 5/15-18 tap and short or medium inserts.

None of the kits for around $20.00 included a 21/64 in. drill bit, some didn't include insertion tools.

MY bolt is 5/8 inch and the bolt hole is ~1 inch deep. So I was looking for a kit with 2D, 2.5D or 3D inserts.

All of the kits found on ebay that included longer inserts 2D or longer run $50.00 or more, usually include an assortment of inserts, short, medium, and long.

The less expensive kits (~$20.00 to ~$25.00) you need to purchased additional longer inserts. A 1.5D insert is ~0.468 inch would also work but I wanted a kit that included at least 2D which is .625 or 5/8 inch. same as the bolt.

Eventually found an E-Z LOK SK20920 that includes 10 x .625 (2D) 304 stainless inserts, insertion tools, 5/16-18 tap and 21/64 drill bit for approx. ~$35.00 with shipping


If you need a kit with 3 different size inserts small, med. and large there is a kit on eBay for $50.00 Heli-Coil #5401-5, other stores on the net are selling for $70.00+

https://www.ebay.com/itm/Heli-Coil-N...qnuL:rk:8:pf:0

https://catalog.stanleyengineeredfas.../5401-5?reg=R1

Short Insert = .321, Medium Insert = .469 Long Insert = .625

The insertion tool may prove to be neccsary as when you insert the helicoil into tapped hole they normally don't install easily. Additional torque is normally required to install inserts.

If a kit doesn't include a tang breaker, you should be able to break the tang with a small screw driver or thin needle nose pliers.

97grand4.0

Having dropped my pan numerous times I notice it seems to leak a bit even with new gasket etc. So I thought, just today in fact, it's probably the pan itself has lost its little bit of bend where the bolts go in, to press it into the gasket. This was after torquing to the spec. So ..maybe a new pan would help too.

dave1123

The pan where the bolts go in should be FLAT! not dimpled. If they've got dimples, put a block of steel under the bolt area and flatten them with a hammer.

Muddz, I guess I should have been more specific. The kit should have a special tap, inserts, an installation tool, and a tang breakoff tool in it to be complete. You need to drill the hole to the specified size, tap it using the special tap, install the insert by screwing it in with the installation tool until it's flush or just below the surface, then put the breakoff tool in the insert and tap it with a hammer. Then use gravity or air pressure to remove the broken tang from the hole. The length of the insert is not that important as long as it's shorter than the drilled hole because once the tang is removed, the bolt will pass beyond the insert in depth. The breakoff tool is nothing more than a piece of round stock that is flat on the end and is just small enough to pass thru the installed insert. If it's too small, it won't break off the tang cleanly.

Helicoil inserts are not rocket science. They are just a piece of diamond-shaped stainless steel wire wound like a spring and sized so that when installed in a threaded hole of the proper size, restore the hole threads to the original size for the bolt. In addition the tap is not a 5/16-18 tap. It's a 5/16 -18 HELICOIL tap which is over 3/8 inch in diameter. The drill size you need for the tap is a "Q" drill, which is .332" in diameter. Notice that's bigger than your bolt! The closest fractional size drill is 21/64 which is also larger than your bolt. That's .328" and your bolt is .312". Your 5/16 tap will fall into it.

You're talking to a toolmaker with over 50 years experience doing this stuff!

Muddz

"In addition the tap is not a 5/16-18 tap. It's a 5/16 -18 HELICOIL tap which is over 3/8 inch in diameter. The drill size you need for the tap is a "Q" drill, which is .332" in diameter. Notice that's bigger than your bolt! The closest fractional size drill is 21/64 which is also larger than your bolt. That's .328" and your bolt is .312". Your 5/16 tap will fall into it. "

This is news to me and probably another reason why I ordered a kit. I do have a couple of 5/16-18 taps but your saying a helicoil requires a 5/15-18 "helicoil" tap?

Also Is It important to have a letter size drill such as "Q"? Information I found is Q bit diameter = 0.3320" (8.433 mm). Closest fraction size drill bit is 21/64 = 0.3281" (8.334 mm). So a Q bit 0.3320" (8.433 mm), is slightly larger than a 21/64th in drill bit?

It's been a few years since I've helicoiled using a Napa metric kit. I've only worked with helicoils a few times and it's always been from a kit.

A video I recently viewed about E-Z LOK helicoils shows their inserts have loctite installed on each insert. The pics of the E-Z LOK kit shows plain inserts without any loctite.

This is a transmission pan bolt. Do you think I should use a little loctite before installing the insert?

dave1123

The helicoil insert is designed to be tight in the hole because the installation tool compresses it when it goes in, like winding up a spring. It won't come out easily and loc-tite is not necessary. The 21/64 drill is only .004" smaller than a Q drill, so the size difference is insignificant. It appears that in the trade now, the letter drill series is being eliminated because so many metric sizes are available now. The best part about using a helicoil is the resulting threaded hole is far stronger than the original, especially in aluminum, AND a steel bolt won't corrode in place. As a matter if fact, stainless steel and aluminum tend to not get along anyhow, so once it's exposed to water and salt, you won't get the insert out possibly ever!