727 rebuild-- Questions

[idahogrumpy]

This is my third transmission rebuild, second time for this transmission. (The rear clutch fried the first time, I either cut a piston seal or it blew out from pressure)

(The failed transmission had blued parts in it and I did not trust it.)
This build will start with a new core and will be built with Alto clutches and Kolene steels.
New HP bands. It has the 3.8 band lever. The case has the bolt in over running clutch and oil passage hole drilled for better flow to the over running clutch. Pump vent plugged and new vent installed in the tail shaft. Orifice installed in front clutch feed. 15 springs installed in front clutch retainer. All new bushings and seals. The rear servo is a super servo. The accumulator has the spring removed and will have a blocker rod. The oil pump has been checked and is well with in spec. The clutches will be set up according to Munroes book on 727 transmissions. I understand about the correct end plays and such. I have a new Turbo Action forward pattern manual valve body and a Turbo Action 3400 stall torque converter.

The car is a street driven (on occasion), 1/4 mile raced 1973 Dodge Charger. The car has a mild built 440 and a Dana 60, 4:56 rear end.

My question is this. I have read when installing a trans brake that a 1/16 hole can be drilled in the rear clutch piston to keep from blowing the piston seals from high line pressure associated with the trans brake installation. I know I am not installing a trans brake, however the manual valve body does increase line pressure and I did have a rear clutch failure on my last build. (Again I might have cut seals during installation)
Can I or should I drill this hole or would it have an adverse affect on the street ability of this transmission? Should a 1/16 hole be drilled in the front clutch drum as well?
Are there any other things that can be done while this is apart to make it a bit more reliable?
Thanks Kyle

[John_Kunkel]

The line pressure associated with some transbrake valve bodies is over 200 psi, the usual manual VB pressure doesn't warrant drilling either the front or rear piston.

Blocking the accumulator is one of the best ways to blow the seals and/or damage the Belleville in the rear clutch.

[idahogrumpy]

 John, Thanks for the response.
I have one more question. What is the thickness of the wavy snap that holds the return spring and spacer on the rear clutch? I have a thick wavy snap ring  and a thin wavy snap ring and I can not remember which one goes to the rear clutch. I have searched high and low for the thickness of this part and can not find a spec on it. Both will fit, although the thick wavy ring is pretty snug. The thin one was a better fit in that location and that was what I used. The transmission has not been installed and if I am wrong I can still fix it relatively easy at this point. I used a regular snap ring of proper size to replace the wavy snap ring on the front clutch. 

This has been bugging the hell out of me, lost sleep and everything.                                   
Thanks Kyle 

[John_Kunkel]

The wavy snap ring (Mopar calls it a spring) that retains the rear clutch Belleville is a little less than .050" thick, I don't have any for the front clutch because I always toss them.

[idahogrumpy]

I have extras of both, (different transmissions) I will measure both and post the sizes here, maybe someone can use the information.
Thanks again John.                   Kyle