A413 Light Weight Drum

[CSX194]

Took apart my a413, history unknown and I found the drums have been drilled for weight reduction. Anyone ever seen this? Obviously less rotational weight is a positive but is there a safety concern?

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[cordes]

That's very interesting if nothing else. In for the responses from experts. How weird.

[wheming]

Any other changes? Gears look stock?

[2.216VTurbo]

I've got a couple of built 413's buuut I built them with a checkbook so I'm with Cordes, gonna wait for someone who knows them to weigh in... Wondering tho, why not twice as many holes? If the builder was drilling for weight reduction it's pretty conservative?

[lightbulb010]

I don't think that poses any safety risk. It may cause the kickdown band to wear a little quicker. Think of it as a drilled brake rotor. You will probably get more bite but at the cost of longevity. I wouldn't make any more holes though for that reason. Chamfering the holes would be a good idea if you don't want the extra bite and just want the weight reduction. In my experience the bands on these transmissions are the strongest part of the system unless you use the "flex band" from an a404. You are way more likely to burn the rear clutch before the bands let go. Even burnt old bands can still do the job in an a413. The clutch packs slip first. With that said the front drum looks a little unhappy. The one in my leaky trans looked worse though and still grabbed 2nd just fine. Was this trans slipping? I think it must have been done as a weight reduction because the sprag drum isn't drilled. It looks like the holes were made with a unibit or something which seems kind of odd. I say run it. If your worried make a scatter shield but I think it will be just fine. The less mass the drums have the more efficient your auto will be. aluminum drums have been used and I would think those aren't as strong. Search "torqueflite low band apply" on google.

[CSX194]

Thanks for the info everyone. The holes appeared to be at least done on a machine. They are very well indexed and the drums have a nice smooth taper. Everything else does appear stock but I'm going to pull my spare parts off the shelf for comparison. I'll get some pics of the other components for a second opinion.

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Scratch that, they are well centered but done with a unibit as mentioned above.

[masterjr33]

I wonder.... maybee FFV car for MPG?? for gas mileage. do the holes look OEM and indexed evenly. or like a machine shop did it?

wonder if someone did this way back when and never documented it. or made some form of cheater transmission for class rules.

[masterjr33]

the more i look at it the more i suspect this was a hornet or circle track or "stock" spec racing trans build...
http://www.onedirt.com/features/edit...-track-racing/

"Transmission gears can also be milled to reduce weight. When the rules require three gears (two forward and one reverse) you can take advantage of eliminating any extra gears. We know of a racer (yep, Racer X) that had the entire first gear milled down to the point where it was simply a spacer. Talk about removing rotating weight. Racer X used second gear to get going and yellow flag laps and third gear was for race speed. Remember, less rotating weight means quicker response. "

[CSX194]

I wonder.... maybee FFV car for MPG?? for gas mileage. do the holes look OEM and indexed evenly. or like a machine shop did it?

wonder if someone did this way back when and never documented it. or made some form of cheater transmission for class rules.

I think they thought it was an advantage for performance. This was pulled from a glhs with stand alone and a stock turbo. Possibly a class racer at some point. It's sat for about 15 years unfortunately. I think someone may have done it by hand but it looks to be a decent job

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[CSX194]

Here is a few pics of the front band that is separated. I'm sure that is why there is some marks on that drum. There is also signs from moisture so it's getting torn down further for a rebuild. Gears also look stock.

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[Reaper1]

This is common to see in old school tranny builds. F'n send it!

[CSX194]

This is common to see in old school tranny builds. F'n send it!

Done. Ship it Lol! Long time no see. Hope your well!

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[zin]

Looks like they took the material from where is was needed least and at least looks like the holes were chamfered, so less likely to crack.

Less rotating weight means faster acceleration, be it a wheel or a trans drum. Some high-horsepower racers are using the 200 4r trans in their racecars for this very reason, even though it wasn't built as tough as the 700 R4. Obviously they're far from stock, but I think you get the point, taking out weight anywhere you can can add up to an win... If you don't go too far and cause a breakage!

Mike

[shackwrrr]

Look like they were done with a step bit

[Force Fed Mopar]

Wonder if it's a heat dissipation thing...

[Reaper1]

Looks like they took the material from where is was needed least and at least looks like the holes were chamfered, so less likely to crack.

Less rotating weight means faster acceleration, be it a wheel or a trans drum. Some high-horsepower racers are using the 200 4r trans in their racecars for this very reason, even though it wasn't built as tough as the 700 R4. Obviously they're far from stock, but I think you get the point, taking out weight anywhere you can can add up to an win... If you don't go too far and cause a breakage!

Mike

I know that the MOPAR guys were using smaller guts in the big cases for less rotating mass.

Done. Ship it Lol! Long time no see. Hope your well!

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Thanks. Doing ok. I can complain a lot, but it does no good.

Wonder if it's a heat dissipation thing...

It also helps evacuate the fluid from in between the plates giving faster shift engagement times.

[bakes]

weight and oil evacuation from between the discs when applying .

[lightbulb010]

The oil evacuation thing is an interesting concept. Does it work well?

Thinking about how oil actually gets to the discs. My memory is a little fuzzy since it's been awhile since I had one of these apart. There are some small holes drilled on the rear clutch drum in the splines for the front clutch discs from the factory. You can see them in the first pic. I think that some oil gets past the seal rings and makes it's way out through those holes. If those holes actually work the way I'm thinking they do, could they be enlarged(in addition to drilling the holes on the outside of the drum) to promote oil flow onto the discs? Is the idea to have less oil in there to begin with and thus enlarging said holes would completely defeat the purpose? I would think that the oil would tend to sling out of the added holes in the outside of the drum and reduce heat dissipation because of less oil contacting the clutches but maybe I'm looking at it the wrong way(I.E. no slip no heat).

[Force Fed Mopar]

Sooo, could this be applied to the A604 also?

[Reaper1]

Sooo, could this be applied to the A604 also?

I would say that it could be applied, but that the computer would muck-up any benefits by trying to compensate for the quicker engagement by slipping the clutch packs even more because it's looking to target a speed differential over a certain time IIRC. We *really* need to be able to get into the tranny controller.