Letter 31093

Searching for plating to allow making a Torqueflite tranny from aluminum [Indiana] 

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I'm a 63 year old drag racer who's had the bug since 1958. I've been racing 426 Chrysler hemi's since 1965 and I always do my own work including rebuilding the 727 Torqueflite. In my quest for speed, I want to lighten up the rotating mass inside the transmission which is considerable. This will help generate more acceleration speed. The problem I have is that the aluminum drum I tried to use does not hold up well at all. When I pulled the transmission pan, the bottom of the pan was covered with aluminum paste from the aluminum drum, which by now had a large wide groove in it from the wraparound band used to stop the drum when changing gears. The original drum was cast iron and of course wears like iron with no maintenance other than the usual procedures. I need an aluminum alloy or plating that will give me that kind of service or at least something reasonable that I can live with. I've been told anodizing aluminum will not give me what I need. Is there a plating out there that can give me what I need or do I need to look at hard aluminum alloys.

Richard Lee Troutt
Transmission repair - Converse, IN, United States

Conventional anodizing is typically "soft", usually done for decorative purposes or corrosion resistance. Find a plater that does "hard anodizing", somewhere in the 55-60 RC (Rockwell) range. Nickel plating on aluminum is subject to flaking due to differing expansion rates of the materials. I would confirm the material used in the drum-it should be at least 6061 series, or better yet 7071, both in a T-6 condition for machinability. Leave a good final finish, prior to hard anodizing.

Also some of the newer torque converters (late model Ford E04D's) use a Kevlar type of coating internally, you should talk with a tech assistant at "Sonnax" about this. Have you thought about sleeving the OD of the drum with a steel sleeve? You would still gain some weight reduction, and have a steel surface for the band. Also the temp may be so high at the band face/drum interface that NO plating would survive!

Frank Newberry
- Nederland, CO

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