Out of 7 reverse drums I have, 4 are cracked in the web, 1 has a crack at the rivet, 1 is loose at the rivets don't see any cracks yet and 1 is in soaking so I can check it. One of the 4, came out of my transmission that I had posted earlier about, has cracks also running into the band surface from two webs. You would think that the least used drum would be less likely to crack, I guess not.
So far out of the same number of low drums and except for some nasty wear on the surface on one and grooves from the rivets a couple of others, only one has a cracked web.
Time to get my feelers out and find some replacements. I have called a guy up in Washington to see what he has and I am gong to send an email to Dave after I hear back from him.
Any ideas why the reverse drums are in the majority of cracked ones?

I see more cracked brake drums. In any case take the good one with the loose rivets and replace the rivets.

You know I checked and rewrote what I had posted 3 times and it still does not read right!

Out of 7 reverse drums I have, 4 are cracked in the web, 1 has a crack at the rivet, 1 is loose at the rivets don't see any cracks yet and 1 is in soaking so I can check it. One of the 4, one came out of my transmission that I had posted earlier about, has cracks also running into the band surface from two webs. You would think that the least used drum would be less likely to crack, I guess not.
So far out of the same number of low drums and except for some nasty wear on the surface of one and grooves from the rivets on a couple of others, only one has a cracked web.
Time to get my feelers out and find some replacements. I have called a guy up in Washington to see what he has and I am gong to send an email to Dave after I hear back from him.
Any ideas why the reverse drums are in the majority of cracked ones?

Hope that reads better!

Sounds like a good plan to re-rivet the one and hope the one soaking is good. Except for the cracks in the bolt holes on a 26-27 wide drum I only have one with a surface crack, mostly they are just chewed up from the clutch disks.

I believe that when backing up people tend to push the reverse pedal just enough to make the car move for fear of going too fast backwards instead of fully stopping the drum. Of course through constant slipping the drum is going to crack. A lot of people also use the reverse to slow down or during panic stops which puts a severe strain on the web and on the rivit area which will cause cracks.

Stephen

My theory is that using the reverse as a brake is the major cause of cracked reverse drums.

I have a pic (that I can't upload) of a reverse drum that had been brazed at cracks in the webb, looked like it had been run a long time that way. KB

Mark, I've noticed the same thing. I build a lot of transmissions and for some reason the reverse drums are usually cracked in the webs. The majority of cracked reverse drums were on original transmissions I've torn down that have never seen anything other than cotton bands.

I always hear of cracked brake drums but I've never seen one and I've seen some abused ones. There is one exception and that is the bolt holes being split out on the 26-27 drums where the driven plate bolts go. The main thing I see on the earlier brake drums is the contact area for the clutch discs being badly worn.

There is a guy that I met at Chickashaw last year that makes the low and reverse drums. I had his business card and can't find it now. His prices were real reasonable and he sold either the drum and you rivet the parts on or you could send him your old drum and he would rivet it.

I concur with Tom with his summation. The old wife's tale about alternating the reverse pedal to slow down going down long grades puts an unusual amount of stress on the reverse drum as it has the lowest gear with the least amount of meat around the webbing - can't be beneficial.

I bought my first T in 1970 from my Great Uncle who was about 80 years old at the time and was still working every day in his garage in Franklin Pa.
He said that back in the day when a Model T with Ohio plates on it pulled up to the garage he knew that they had worn out the brake band. Northeast Ohio is fairly flat and Franklin is in the hills of northwest Pa. about 40 miles from the border. He said that was just enough distance to wear out the brake band if you didn't use reverse some of the time.
I guess using reverse to slow down saves brake lining at the expense of the reverse drum.

I purchased five 26 27 transmissions last year and got 15 broken drums. I wasted eight months of my ever shortening life. I purchased all three brand new and in no time at all had a complete "like new" transmission.

The day of the $15 Model T is over folks ;~)

Mostly agree with you Frank, I bought five for 100. out of that five There was magnets, fly wheels a few good sets of triple gears and probably a few main shafts and four or five drums that look good but might be cracked.
I always go for the "meat and potatos" at a sale. Transmissions are meat and potatos even if they have some rust on the exterior. The more oily grime the better.

The earlier wide brakes drums used slotted screws to mount the driven plate instead of bolts which would make it very difficult to get the fastener tight enough which would allow the plate to pound on the screws. Maybe that is why some are broken around the holes?

Stephen

The cracks in the bolt holes of the 6-7 brake drums come from, in my opinion, for dirt being in the holes. When the bolt is tightened down the pressure from the dirt being compressed has to go somewhere and it usually cracks them to the outside.

Andy, I've not seen evidence of that. I thought it was from being over torqued at some point in their lives. I mocked one up and tightened the bolt way beyond normal and the crack width didn't spread.

I don't mean to hijack this thread, but here is an experiment I'm trying on my "A" crank engine.
1st pic shows the typical crack. 2nd picture I drilled down into the drum and threaded the hole to the bottom. 3rd picture I made studs with blunt ends like set screws, used locktite and installed the studs. dressed the exposed threads on the lathe. I used collars and nuts to fasten the output shaft plate to the drum. I put a couple 1000 miles on it so far and it appears to be holding very well.

Here's the 3rd pic. All 3 wouldn't fit on the 1st post.

Clever, Kenny; just like head studs are better than bolts.

Why didn't I think of that? I have a drum that needs that fix.

rdr

BTW, I'd guess the wide drums crack from the bolts not being tight enough, like Stephen wrote.

Suggest you check the front of the drive plate and the rear of the brake drum for a right angle to the shaft before you bore the drive plate bushing. My last transmission had 17 thou run-out on the drive plate alone.

After reading this post; This is the reason we felt it was best to make the new drums with the gears as most of you have experienced purchasing transmissions covered with dirt only to find out after cleaning that they are junk.
Let's face the fact that most of the parts are at least 100 years old and they weren't babied to say the least.
These cars were meant to be driven most of the time by people who didn't know how to drive a T.

My own Dad tells a story of a hill here in Worcester,Massachusetts that his dad's T couldn't make it up in forward so he would sit on the tailgate and they would back up the hill in reverse.!

Just so people know we are making the drums for the reasons expressed by people in this chat.

http://www.jandm-machine.com/fordModelTtransmissionDrums.html

OK, reverse drums crack in the web. Has anybody seen a complete failure of a reverse drum that started with web cracks? Sometimes, sometimes, cracks are just stress relievers.