Drilling Torque Converter for Drain Plug

[4xWriter]

My intention is to drill and tap a drain plug into a Ford 4R75E torque converter. Until just recently, they were drilled from the factory but they have since stopped. I intend to drill it in the same relative position of the OE converter through the very convenient bellhousing hole, which they have not as yet eliminated. The plugs were installed in the outer circumference of the converter housing, not at the forward edge as were many others.

My question is this: How much effect on balance would this have? We're talking an approximately 1/8-inch hole and a corresponding plug. I tend to think the effect would be negligible... but you tell me.

Anecdotally, I have done this before on three GM transmissions with no apparent balance issues, but those plugs were installed on the mounting face of the converter (towards the engine) and not on the outer circumference. If that matters.

Jim Allen
Keeping the Good Old Days of Four-Wheeling Alive

 

[evelrod]

Worse case scenario---You will need to have the TC removed and re balanced...Not a small job. On the other hand, why not put in TWO drain plugs?

Nothing ventured, etc. I have >200,000 miles on the Dodge/Cummins trans with no problems, but I sure would have liked the ability to drain the TC on occasion.

Rod

 

[Bribyk]

A better question might be... what tolerance grade are torque-converter or flywheels balanced to in the automotive world? Try this link for a calculator:

http://www.corvib.com/vibration/balance_tolerance_calculator.cfm

Putting two opposed plugs, as Rod said, is probably the best solution as my rough estimate puts you in the "general" balancing category, Grade 6.3.

 

[GMIracing]

On a sealed Torque Converter, the risk of contaminating the Converter with debris from the drilling process greatly outweighs any benefit that the drain plug will ever have.

 

[4xWriter]

GMIRacing: IMO, the risk is fairly minimal if you, A- drill at a slow speed with depth control on the bit, B-drill with the converter full of oil so whatever does go in will be flushed out and C- tap with a well greased tap. I will admit, I had to calm my nerves the first time!

As I said, I've done this three previous times with no ill effects. The balance issue is what got me wondering.



Jim Allen
Keeping the Good Old Days of Four-Wheeling Alive

 

[MintJulep]

If you can actually collect all the chips, just weight them. Weigh the plug.

Otherwise, you are removing approximately a cylinder of material with a known? density.

In either case the amount of weight to compensate is pretty easy to figure.

 

[MikeHalloran]

Or, punch a hole and use an express tap.



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

I was never game to drill a hole in a converter even though I knew it to be full of burnt oil. Fear of chips remaining inside was my de motivation.

If I did I would do two holes, for balance AND for a breather for quick drain.

Regards

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[strokersix]

Seems to me to be less risky to just drop the pan, add a drain plug in the pan if not equipped, then drain, run, and refill as many times as needed until you think it's flushed enough.

 

[4xWriter]

Well, it's done. No discernible problems with balance revved to 5250. Used a single hardened 1/8 in plug with a copper gasket. Took 10 minutes. The worst part was the oil running down my arm while I tapped, though that washed all the chips out as well. Thanks, all, for the exercise of thought on my behalf.

Jim Allen
Keeping the Good Old Days of Four-Wheeling Alive

 

[Bribyk]

I would imagine a torque converter is fairly tolerant to imbalance anyway, since they are filled with a fluid. Would it not self-balance anyway, like putting BB's in an offroad tire? I don't understand how this works but I'm sure Jim is familiar with this practice.

 

[Newmanite]

I have done this also and have had no ill effects.I only assume that when you say plug you mean "pop rivet"?

 

[4xWriter]

Nope, I drilled and tapped a hardened steel plug almost identical to the factory type. The converter housing is 1/8 to 3/16 inch thick, so there was plenty of mean for threads

Jim Allen
Keeping the Good Old Days of Four-Wheeling Alive

 

[franzh]

On a torque converter with a lock up clutch one may run into the risk of drilling into the lockup hub area. I also had one former technician run the tapered tap too far into the converter and turned the 1/8 NPT tap fully into the converter. Both of them required a removal and replacement.

Franz

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[evelrod]

"...one former technician..." Yeah, I can see the 'former' part, but I'm a bit skeptical about the 'technician' part.

Rod

 

[berkshire]

franzh (Automotive)
Did you give him time to collect his tools?
B.E.

 

[dicer]

I have a factory publication someplace that mentions drilling the torque converter to drain it. With fluid in it, that will pretty much force the chips down and out, your biggest concern is getting a face full of oil.
I don't think there will be a huge balance problem, if you use an internal hex plug, since material is being removed and the plug is partially adding that back you should be okay. If there is a problem accurately position another plug 180 degrees from that one.