question on drilling and tapping C4 pan bolt holes

[ebronco66]

So I finally broke down after trying unsuccesfully to stop leaks in my c4 and took it to a transmission shop to have them assess the situation. They told me what I had figured as much that there were several bolt holes that were stripped and need to be drilled and re-tapped. They also told me they would not do this without dropping the stupid thing. Something about making sure the holes are drilled straight. I just need to know if there is any truth to this or should I call around to find someone who can do this without dropping the whole transmission? Thanks for your thoughts,

Travis

 

[bronko69er]

If It were me, I'd do it myself lying on a creeper under the bronco, assuming you have straight access to the bolt holes. Sounds like they are perfectionists or just want more money for the time it takes to drop the tranny.

 

[SWFLABRONCO]

I'm with Bronko69er, do it yourself. They need to be straight, but not NASA straight. If you are helicoiling, it's a piece of cake. Just dont drill too deep.

 

[iwlbcnu]

The factory holes are your pilot holes, should be straight enough.

 

[Bones]

The factory holes are your pilot holes, should be straight enough.

x2 As long as you're only drilling out to the next tap size, it would be very hard to actually drill a hole that isn't inline with the existing hole. Even as far as drilling too deep, you'll feel how easily the bit will drill through the already threaded region, and then will feel like you hit a wall when you're reached the end of the hole, obvioulsy stop drilling. Or another way to control drill depth is to get out a depth gage, measure how deep the hole is, then measure that same distance on the drill bit. Wrap electrical tap around the drill bit at that point, and when your drilling, stop when the electrical tap reaches the pan mounting surface.

 

[ugly74]

x2 As long as you're only drilling out to the next tap size, it would be very hard to actually drill a hole that isn't inline with the existing hole. Even as far as drilling too deep, you'll feel how easily the bit will drill through the already threaded region, and then will feel like you hit a wall when you're reached the end of the hole, obvioulsy stop drilling. Or another way to control drill depth is to get out a depth gage, measure how deep the hole is, then measure that same distance on the drill bit. Wrap electrical tap around the drill bit at that point, and when your drilling, stop when the electrical tap reaches the pan mounting surface.

do it just like that. the drill will pretty much self align, since the path of least resistance is straight up the middle. going up to 3/8 would be fine, but you could always heli-coil back to the original size. either way...

check your pan for straightness while yer at it. I real recently had mine off, and each bolt hole was pulled up towards the gasket surface, from being overtightened in the past. ball peen hammering them back to flat was pretty simple, and it'll seal better for sure.