T-20 drums and shift pins

[brushcutter]

While inspecting a couple of used t-20's I found some pitting on the drums of one and grooves on the drums of another. I spoke to our welder at work and asked him about getting them welded up so I could turn them back to spec. He welds up worn spindles for some of the axles that our company builds, using a tig unit and rotator and being a certified nuclear welder, of course he said yes. I also spoke to Richard C who told me that the drums could be spray welded but tigged would be even better, cool. Is there anyone here that does this? I've never read anything about it but I haven't done a search either. This could save me a lot of cash down the road. 8 drums salvaged = big bucks $$$$$$

Also does anyone know off hand what the hardness is on the shift pins? Some of mine are slightly to badly worn. I think RC gets $8.00 for them, don't know if that is each or by the set, but that IS high for two 3/4" pieces of steel. There is an excellent metal shop near where I live that is very good about keeping, or getting whatever I need and there are several on-line sources for things such as this. We have a Rockwell tester at work and I carried one to test, but didn't have time, it seems that I have become a one-man department, so I am usually busier than a one armed flagman during rush hour, and yesterday was worse than usual. I can't see good sense in paying that kind of money for these little pins; when I could very well buy feet of metal and have a lifetime supply ya' know.

[mepa]

shift pins

the 1/4in pin on diamond shifter is a hardened dowell pin pressed into main body--hard to get out,but i have ground them off and drilled new holes on opposite side then instal on opposite side of tranny,p.s. use a reamer that is.002thousnth under size.hope this saves you $$&grief

[brushcutter]

Thanks Mepa, I can get the old pins out, I was just wondering about this for future reference. If I know the hardness I can probably come up with something more durable and buy it in length that I can cut, even doubling my saving...cha-ching $

BTW if you can get your hands on a set of Knippex adjustable pliers (similar to channellocks)you can get about anything loose, they are awesome! I have 4 pair- 6", 10", 12", and 22". Everybody at work likes the 22" pair, they are engraved with "Gregg's Big Ass Pliers". I just call them T-Rex.

[jerseybigfoot]

The problem you have with welding is distortion from the heat. The drum gear tolerance may change if there is allot welding across the surface. You may review with your welder his procedure for maintaining the gear integrity. He may also want to preheat the drum and maintain it a an elevated temp during the weld process. If you can weld up the grooving and pits with a minimal amount of weld probably the better. Mark M may have some additional advise.Spray welding is a mechanical bond and does not localize the heat as much.

[brushcutter]

Yes, that is a concern, I kinda look at it like this: I have a housing that is dead, bands that are dead, and drums that are dead. I would use all this with better (but not new) bands and see what happens. One thing is for sure, I can't kill what is there now any deader than it already is. I am also concerned about the finish, the new ones appear to have been ground to spec, they are really shiny. I think it would be best to start by checking the hardness, which is what they do with the spindles, and then do the dye test for cracks before and after welding.

[jerseybigfoot]

Sounds like you have it figured out. I'd also recommend taking diametrical measurements of the ring gear root and crest. If it works I'm sure there are allot of drums laying around that we need welded. Maybe not enough to let your retire, but probably a good beer allowance.

[brushcutter]

Not hardly!!! LOL! Now if we get TOO technical I'll have to get our QA guys involved, the head of that department was in the aerospace industry some time back and gears were his thing.

But you are right, there would be a lot of precise measurements to take, and I don't even have a list of tolerances to work from. What do you think check everything, weld, check again then turn and check again?

[Roger S]

Back in the '80's I worked at a tool and cutter shop. They did simple sharpening and also designed complicated metal cutting tooling. Anyway, they would out source "flame spraying" to build up worn surfaces. We would precision grind the surface to true and prep it, and have it sprayed a few thousandths thick of a choice of metals, and then finish grind the surface. I don't know the details about heat, and it wouldn't be cheap. It was a good, high quality fix, though.

[brushcutter]

While talking to Richard, another fix he mentioned was a speedy sleeve. These I am familiar with, and they might be worth looking into, probably the least expensive fix available. If you are not familiar with them, they are used on shafts, to prevent and repair wear caused by seals. They would probably work at the seal areas on Argo axles also. They are held in place using adhesives.

[mark m.]

Those drums are made out of ductile cast iron with a high carbon content. Tig welding on them would be my last resort. Spray weld would be my choice if it absolutely had to be saved.

Depending on how bad the pitting and grooving is I would suggest just turning them down till they clean up on a lathe. You can safely take of 10 to 15 thousands. Usually this is all thats needed.

You would have turn them down initially to remove the rusted pitted areas prior to spray welding so what have you got to lose?

Let us know how you make out as this could be good information for any who does a search on rebuilding there T20.

Mark

[jerseybigfoot]

Thanks Mark wasn't sure of the material. I bet if someone has the dimensions of a new drum we could probably establish limits of how much can be turned off. The drums seem beefy enough that quite a bit could be machined off. The problem I see is the band length. I would think relined bands would easily take up .040 on a machined drum.

[brushcutter]

Dang tha' bad luck!... We had a welding supplier come and demo a spray rig but I didn't get to see it in action. I would have to agree with you Mark, the drums definitely appear to be made of cast iron, the sand marks are a dead giveaway. But check this out, Lester (our chief welder in charge) said that if we can figure out all the techy stuff, and there were enough of these things to pay off, he is not against buying a rig and doing them as a sideline. We haven't talked pricing and I don't want to risk infringing on our forums commercial interest rule, but if this process could done for $80 to $100 per drum this would be a huge savings for members in need of such a service. I think R.C. gets quite a bit more for his drums, not sure what R.I. gets. If nothing else we might find a cheap process whereby we could go to a well tooled machine shop and get them done at a cheaper price. I think I am gonna take one of the really chewed up ones(p.o. ran gear oil in it bands started eating drums) and have the CWIC look it over and see what he thinks.

Also RC said that the drums could be turned down....NONE ... do I smell something?

[Roger S]

Also RC said that the drums could be turned down....NONE

Never been in a t20, but thinking about automatic transmissions.. if there's enough meat to machine the drums smaller, what's left is where the band anchors end up in their workable travel. .040" off the OD means .120 circumference times 2? band wraps = a 1/4" difference in band adustment. If that's the issue, bands with thicker lining, or shorter bands, or longer anchors..

[jerseybigfoot]

A more practical approach would be to Machine the drums for a shrink fit steel ring. There is not allot of heat generated in a T-20 that would cause the rings to get loose ..010 shrink would be allot of force holding the ring in place. I understand there were racing t-20 drums machined from steel so I don't think the material would be a factor. I already install steel rings on outboard drums where they fit the bronze bushings with good results

[whipper-ag]

Mark M is right. The drums are ductile cast iron. Finish O.D. is 6.210. Write it down somewhere so you don't have to hunt for it if you ever need to know.

I talked with Matt @ R.I. about the specs on the T-20 drums. He said that you can safely turn the drums .030 undersize. That's only .015 per side. In a lot of cases that isn't enough to clean up any grooves or pitting. Anthing smaller than .030 may still work, but your bands would have to have a lot of material on them & in good shape. The more you turn the bands down, the farther the plungers will come out of the T-20. What you have to watch for is that the plungers don't come out so far as to expose the O-ring.

In my opinion, welding is not a good option. The heat will distort the ring gear & you'll lose the burnell hardness of the drum. Joe M. just sent me 4 drums, (2) that had been welded to see if any of them could be saved. The ones that were welded were all ready .050 undersize & still probably needed another .050 just to clean up the terrible weld job. Maybe Joe can post a pic of one of his welded drums. The (2) that I was able to clean up, he posted in his gallery. In my opinion the metal spray is a quick fix. It may look good, but in the end, you won't have the right burnell hardness & possibly ruin a good set of bands. Just something to think about since pulling a T-20 out is not much fun, especially if you have to do it again down the road, because you tried to cut corners. It's the brain of the machine. It's too important not to fix it the right way. Sometimes that means spending a few bucks. Fix it right, the first time, while you've got it apart.

Whipper