I purchased and installed these Kevlar bands around the year 2000. I estimate that there is less than 5000 miles on this set. Last year when I removed the transmission cover to change the oil, to my surprise, a gulp of oil spilled everywhere. The transmission screen was clogged with lint. I have been unable to determine the cause of the linings disintegrating around the edge. The drum is not cracked and there is nothing protruding from the driven plate. Note that the low speed and reverse band edges seem to show early signs on the same problem, but not nearly as bad as the brake band.
Has anyone seen this before and determined the cause? I've already resigned myself to the idea that I have to replace the bands. But I'm hesitant to put Kevlar bands back in without knowing what caused these to fail in this manner.
Looks like the condition of the drum would have cause this. The edge of the drum looks rough. But that is base on your picture.
Maybe the driven plate has a slightly high edge on it. It could have an edge that's smooth but just a bit higher than the drum.
A little hard to identify, but in the picture it looks like an earlier than 26 brake drum. On the earlier drums the driven plate is flush with the edge of the drum and if either the plate or the drum is larger in circumference or has a rough edge, it might be cutting into the kevlar band.
When I run my finger over the driven plate, there is a very, very slight edge where it meets the drum. I wonder if what I'm seeing is actually on the interior of the band and "squeeze out" versus the actual band edge. Right now it's difficult to tell which it is.
The points raised here are good ones but how perfect the surfaces have to be? The original drums that were in the car were badly scored. But the cotton bands were not shredded. These drums have some imperfections but I can't imagine that they are any worse than most of the used drums that people are running today. I do have spare drums but short of buying new ones, I don't know how they could be any improvement over what I'm already running.
I was hoping that someone would tell me that there have been issues with some of the Kevlar material that has been used over the years.
Dan---if you SEARCH kevlar in the earlier forums, there ARE references to early kevlar band failures. Your photos are the worst kevlar band unravelings I`ve seen! Your bands would be in the "early" catagory (17 years?) and it is quite likely they are not up to the standards of the kevlar bands sold today. I`m a fan of kevlar and suggest you replace them. after checking your drums carefully. Good luck! paul
Turn your drum and check your safety wire twist tie offs. One end might be sticking out and rubbing on the band.
If you don't find anything obvious I would take the time to check everything thoroughly. Kevlar can be very harmful to your drums as they were not designed to have such a tough band wearing on them.
Dan, i suggest you call Steve Coniff, Rocky Mountain Machine Co and talk to him about your issues. He is the major supplier of Kevlar bands and very knowledgeable about transmissions.
Dan, your problems and my posting about rebuilding a clutch driven plate may have some commonality. With a new drum mated to a used driven plate, there will be a step down on the edge of the used driven plate where it has previously worn. I was asking if the driven plate edge could be built up to restore the original diameter but the idea was not met with great enthusiasm.
Do either the low gear and reverse gear bands show the same fraying? If not, it may well be a miss- match between the two components making up the brake drum surface.
Allan from down under.
Thanks for your suggestions. I did some searches of the early forums and there have been reports of fraying on occasion. Everyone's situation is different, but in this case, I can definitely rule out a cracked drum or other things like safety wire ends causing it. The other bands do show early signs of fraying, but not nearly as bad as the brake.
The bands are not the quick change type, so at a minimum, the hogshead is coming off. I should be able to carefully remove the bands so that I can see right where the wear pattern is. I'll post the results when I get there.
Thanks for the contact Kim.
I was finally able to pull the hogshead today. The brake band does not look good. It is not wearing evenly. There is a sharp edge where the driven plate meets the brake drum. This still doesn't seem to match the width of the wear pattern seen on the band. So I can only assume that the drum itself is worn. The low speed drum also has a bit of a lip where it meets the brake drum. But the other bands seem to be ok with uniform wear.
Overall the drums seem to be in a lot worse shape than I remember nearly 20 years ago when I assembled the transmission.
I plan to use the drums off of this spare transmission that I picked up at a sale last year. What are the things I should check to avoid the same kind of problems?
The rest of the day was spent prepping for engine removal.
Well, you know they say that a picture is worth a thousand words. And after taking another look at the picture above I saw what appeared to be a crack in the photo. Sure enough, when you run a finger over the drum in that spot it sure does feel like a crack.
Looks like a dodged a bullet on this one.
I would say that getting 5000 miles out of those bands with the pitting and sharp edges on those drums is doing pretty darn good. Your donor transmission drums look to be very good indeed, with what little we can see of them.
Also, your rivets need to be 90 degrees to the band, not 45. And do your best to get a reverse curl on the tabs and get them swaged deep into the material. It appears as though they have been rubbing on the drum(s).
The dealers sell a tool which will put that curl into the rivets in the absence of a rivet press. All of the Youtube videos you'll see usually show someone beating the tabs flat into the weave, with a ball peen hammer...really not the best way.
Dan, if you intend to use those replacement drums, mark the driven plate and brake drum and re-assemble them in the same place. If you can use both parts they should be the same diameter and there will be no mis-match to cause that uneven wear. It is as near an ideal situation as you can get, provided both parts are serviceable.
Allan from down under.
Dan,I suggest you change to wooden band liners. Every broken drum I have seen (including 4 on my cars) has been with Kevlar liners. Folks say that the brake drum is so thick that you can't break it with Kevlar, your drum disproves that.
Sorry to see this happen to you, but you now have a golden opportunity to discover the joy of wooden band liners!
The wear on the weave was due to drum condition, as this notice is packed with each set of Kevlar linings from Rocky Mtn. Machine.
Your other drum set seems much better in surface finish too. Kevlar is tough, but the weave can be cut by sharp edges of drums, and other defects.
Fitted to good drums, and with pedal notches in good shape to provide proper pedal adj. and travel, Kevlar linings provide excellent results.
Be sure the bands are round and concentric and shaped to strive for band ear distance of 3"-4" after the linings are riveted, and prior to install for best fit around the drum surface too.
Dan, does the crack in your drum co-incide with one of the bolt holes? Quite a few of the narrow drums suffer this occurrence. Usually the crack goes to the centre of the drum, away from the surface, but I have seen others like yours. Cracks at the bolt holes are nowhere as troublesome as those where the drum can flex at the crack. The damage to your linings is more likely to be due to the mis-match between drum and driven plate and the rust pitting om the drum surface.
When you dis-assemble the transmission, check the threaded holes in the drum to see if any of them are also cracked towards the inside. If a brake drum is otherwise sound, a crack or two in this manner need not rule out using the drum again. These cracks have nothing to do with using Kevlar bands. I would not use your drum again, first because of the surface pitting and then due to the crack to the drum surface.
Hope this helps.
Allan from down under.
Thanks a lot for your opinions and input. It certainly looks like after years of reading kevlar discussions on this forum that I've finally been bitten. The bands certainly gave good service up until the point that they started to produce lint.
I consider myself a fairly conservative driver. Failure of the brake drum is particularly interesting since I have a large drum Ruckstell and tend to use the lined brake shoes to slow me down and only the brake to bring me to a stop.
Dan - Thanks for posting a picture of the instructions from Rocky Mountain Machine. This helps to validate the observations that I and others have made in response to the pictures I posted. I bought these bands years ago at Hershey and the linings were already mounted. I do not recall the seller including the instructions above but having this info in hindsight may have prompted me to find nicer drums.
Terry - I was already considering wooden bands but your post may push me in that direction. What's good for Rusty is good for the gander. How many miles have you been averaging per set?
Alan - I will post more pictures after dissection.
Honestly, that crack in the brake drum does not look like it was thermally induced by Kevlar. That simply looks like a fatigue crack in a 100 year old part. Overheated drums typically crack through, and have some small separation. I'd even go so far to say that if the drums look worse/pitted than you remember, that crack may have been there in 2000. Those pits and sharp edges were certainly there in 2000, so the crack could have been, too, and simply overlooked.
Scott, how can you possibly get a crack in a drum with out Kevlar bands?????
Seriously, I have found cracked drums brazed up and still in service, long before Kevlar bands were developed. Then there are the cracked brake drums with the cracks around the driven plate bosses, and the reverse drums with cracks in the webs. We are dealing with 90+ year old mass produced parts subjected to all manner of workloads.
Allan from down under.