[k718cougar]

Many performance C-4 builders have recommended drilling vent holes in the HIGH/REVERSE drum to better evacuate fluid. Would that still hold true with the FORWARD clutch drum? Any advantages?

 

[galaxiex]

Many performance C-4 builders have recommended drilling vent holes in the HIGH/REVERSE drum to better evacuate fluid. Would that still hold true with the FORWARD clutch drum? Any advantages?

Is this a full on race trans?
If so, sure you could drill the drum, beware of weakening it tho.

If it's just a street car, then no, no real advantage.

 

[k718cougar]

Full 1/4 mile drag racing only. This is related to topic "393W not running up to expectations" in another part of this forum.

 

[gregaust]

I've never drilled a forward drum .. Not really any need IMO..

 

[k718cougar]

It seems that it is already drilled. Any problem leaving it in or should I substitute it out for another?

 

[GT350HR]

I agree with Greg , no reason to drill the forward drum. In fact I quit drilling the high gear drums . Makes no difference on longevity or track performance in my testing.
Randy

 

[k718cougar]

Thank you for the input.

Moments ago, I discovered that my "parts" C-4 has a "factory" 1/4" vent hole already drilled in the side of the forward drum. Just FYI...

 

[Tranzman]

Retired trans builder doing research on a c-4 with a brake. In my research I have seen several companies that have stopped drilling the direct drum. They don't say why, just that they have stopped. Possibly from either, A weakening the drum or B shortened band life.

 

[gregaust]

Thank you for the input.

Moments ago, I discovered that my "parts" C-4 has a "factory" 1/4" vent hole already drilled in the side of the forward drum. Just FYI...

That is not a drain hole . That is done during manufacturing , Put something down through it you'll see it lines up with the feed hole to the sealing rings

 

[gregaust]

Retired trans builder doing research on a c-4 with a brake. In my research I have seen several companies that have stopped drilling the direct drum. They don't say why, just that they have stopped. Possibly from either, A weakening the drum or B shortened band life.

Be interesting to find out why :smile2:

 

[gregaust]

It seems that it is already drilled. Any problem leaving it in or should I substitute it out for another?

You could leave it , unless it is drilled excessively that may in some way weaken it .

 

[GT350HR]

Greg ,
The problem "I've" seen with trans brakes is slow release on the high gear clutches and that "kills" them because of the slippage versus "clean release". Nothing to do with drilled holes in the drum or lack of. I bought a trans brake from a very popular east coast company that uses the Winters reverse manual valve body ( like I already ran) and had the high gear clutches go away after 12 runs. I pulled it and went back to the unmodified Winters VB and have over 300 runs with no appreciable wear.
Randy

 

[gregaust]

You know a lot of high clutches can be burnt even before they apply in top gear ... That's why i drill a bleed now for any trans that will see over 6000 in first gear ..
I think that can do damage also

 

[GT350HR]

I completely agree! I forgot about that mod as I do it "automatically" LOL