MTFCA Forum

I am working on my Muncie 3 speed and making good progress. I got a brand new idler shaft from Dan Mceachern and a really nice input and output shaft and a bunch of small parts from Karl Von Neumann. The new input and output shafts a fractionally better than my old ones.

The old idler shaft was worn and 22 mm. The new idler shaft is 7/8 so I reamed the case out to fit it (the difference is about 0.010). The bushings in the idler gear are in decent shape so I was planning to ream them to fit the new shaft and run them as well. My question has to do with the interface between the idler and the case. The bushings appear to have had a thrust surface on the end (see picture), which is worn so the end of the gear is running on the case. There is a little back and forth play in the idler gear. They are straight cut gears so there is no real thrust.

So here is the question, did the original bushings extend past the gear to provide a friction surface? If they did I could replace them or machine out a space and press a bronze thrust washer in the end of the gear to build up the thrust surface.

The other question has to do with the pilot bearing between input and output shaft. There is what I consider to be too much play. Anyone know how much clearance there should be in this bushing? The machinists handbook gives a running fit of about 0.001, which I thought I would go with.

Hi Morgan,
I haven't done a Muncie in a long time but I would think excessive end play even with spur gears would be noisy. Also keep in mind wear patterns.
You want to keep old wear patterns in line unless you are trying to get more contact because of wear. The clearance on bushings is 0.002 in all T
bushings & I think that is to tight, I've seen every bushing spun in a T trans because they where to tight. All though the pocket bushing is not
spinning very fast it still needs enough space for oil to enter. I believe someone mentioned a spiral oil groove in that bushing. There is a hole on
the input for oil to pass threw. The first Muncie I did was a worn out mess, I replaced the cluster shaft with one made from a shortened truck
4 spd. Replaced the bushings & bearings. I ran it for 14 years or so I only replaced it because I had a really nice one on the shelf. I changed it
out when I went to a 10 tooth pinion. I highly recommend a 10 tooth pinion it gives you about 3:1 final in over drive.
Craig.

Thanks Craig,
I fit a new thrust bushing to take up some of the fore and aft slack and reamed the old bushings in the idler gear to fit the new (slightly larger dia.) idler shaft. I still need to make a new pilot bushing for between the input and output shaft. Going to work on that tomorrow.