Reverse drums. All cracked.
At what rate do you find them cracked in barn fresh engines? I've only torn down about six transmissions - half of the reverse drums had cracks, none of them all the way to the outer surface. Some of the cracks in the web of reverse drums can likely be lived with (?) - those that can't spread out to the drum surface.
When I rebuilt my 27 engine last year I tore down 12 transmissions. I found one reverse drum that was not cracked but it was heavily pitted. My engine rebuilder had access to a bunch of trans drums. I believe he said he looked thru about 24 reverse drums and found non worth using. I had to buy a new drum and use my old gear. Tom, if the gears are useable on any of the drums shown above, do not scrap the cracked drums. It is a lot cheaper to have your used gear put onto a new drum.
Donnie, the drums have had their gears removed. They won't stack like that otherwise.
Roger, the ratio of cracked drums is about 1:1. Nearly every used reverse drum is cracked. I have seen perhaps a half dozen uncracked ones in my 40 year Model T career. I think the majority of those were from Canadian transmissions.
Interesting you make reference to Canadian transmissions! Do you think there was a manufacturing fault or poor material used? Sending the junk off to the Commonwealth countries? Thirty years ago cracked drums causing rebuilds never seemed to be a problem but in recent years our chapter has had many failures, generally the low speed or brake. Reverse drums have not been a problem? Maybe we don't go backwards very often? I will try to get some pictures of cracked ones.
I think a crack is a crack is a crack. I just can't bring myself to use a drum knowingly.
Having said that I find a cracked drum in every couple of engines out of running cars. Makes you wonder how long they were cracked and if the engine didn't need serviced how long would it had lasted before it really became a problem.
Mike: I agree, knowingly it would be really hard to put it back to use, I was just thinking about all those cracked reverse drums that has been used for so long without problems.. Maybe the production process caused stresses in the webs that resulted in cracks fairly early in the life of most drums that after the initial stress release didn't propagate much?
Here are a couple of examples from earlier posts..
This is the type of crack I was referring to that still might be able to use since it can't go any further:
While these cracks should put the drum in the recycle bin:
Warwick: cracked brake drums? That's a new one for me? Didn't think they were easy to crack?
Anything in common with the failures? Early or late transmissions? Kevlar bands? Mountain driving?
It surprises me this drum cracks, it is reinforced with the flange, where the low drum I would have thought would be most likely to go south first. It looks the weakest. Plus, it's a little harder for us big foots to even get your foot squarely planted on the pedal in the first place.
Most reverse drums that I have seen that actually broke, the owners usually admitted that they had used it as a brake "on occasions!". Quite honestly, the reverse drum is subjected to very little use and certainly not hard use like the low and brake drums. Perhaps the reverse drums have been cracked for years and no one cared! Sometimes I think we might be getting TOO particular. Please don't shoot me!
Does the Montana 500 allow new drums and gears? Eventually there will be no way around it.
I had a hard time finding useable drums, especially brake drums with good drums. I simply took all the overtime I could for six months and bought a complete new trans.
I have an NOS reverse drum assembly 3301 available for sale if anyone is interested. Price is substantially less than the reproductions - refer to the classifieds:
I went through about 10 drums at least trying to find a usable one. The ones I am using look pretty bad, but were the best I could come up with and best I can tell - no cracks.
David, new drums in Montana 500 cars is a bone of contention. Some folks say the new drums are made from a different material (steel) than the original drums and therefore offer an endurance advantage. I say they are the same part doing the same thing in the same manner and therefore should be allowed. I've been running a steel reverse drum in my Montana 500 car since 2010. I've been torn down four times in that car and always passed the tear down.
My rule of thumb is that unless specified in the rules e.g. "no fiberglass fenders allowed", that you can substitute parts that are doing the same thing if they only differ in the material that they are made from.
Polyester capacitors, plastic covered wire, synthetic rubber tires, to list a few examples.
I'd support you there, Tom. As long as the material change doesn't give a substantial weight advantage, new materials shouldn't be banned. If someone made an aluminum copy of a high head, then it wouldn't boost the horsepower - but the car's weight would be like 25 lbs less and that could make it slightly faster up hills, so there's a limit ;)
The new drums we make are of ductile cast iron and they are used in the Montana 500.
All the above mentioned cracks and bad gears are why we started making and continue to make new drums and gears.
There just weren't enough good ones out there.
I imagine people are tired of me endorsing j and m but they do not let you down. Yes a new trans is pricy but its a one shot expense. Thank you John and Mike!