It was oh so well fitted in the '39 tranny case ... the main clutch gear/thrust bearing race . Had a perfect fit , rolled smoothly , everything was going oh so well . But then I found a 1940 trans that was pretty much complete , and a lot of the parts were in better shape than the '39 trans I had . Two factors influenced my decision to swap to the '40 case , there's a (non-critical) piece broken off the '39 , and the '40 has a spring loaded ball and detent system to lock the shifter drum . So I pressed the race out of the '39 case and into the '40 . And all at once the rollers didn't fit so well . Clutch gear wants to walk into the case when rotated one way , out of it when turned the other . Turns out the hole in the case is egg shaped , .0015" wider than it is tall . So here's the question : I want to set the case up in the milling machine and use my boring head to make it round . This will take about .00075" from the top and bottom , and I'm worried I won't have as tight a press fit as I think is needed . So I'm wondering if using a Loctite sleeve retaining compound will be acceptable to keep things stationary . Having that race spin in the case would be a Very Bad Thing ... My other option , is to repair the '39 case and re-machine the shift cam plunger hole to accept the '40 spring plunger assembly . Shift cams are the same except for the locking area and will swap . I'm finally getting to a point that I have room to work on at least the sub-assemblies to get this bike back on the road . I'm not worried about "ruining" original parts , this bike is a mutt anyway and a modified part that I can use beats a broken part any day .
1939/40 Harley trans questions (2025 Update)
Apr 13, 2019
Last reply: 8 months ago
6 Replies
Well , it's such a small amount ... this race is a really tight press fit now , and I'm hoping that it will still be tight enough after rounding the hole out . A thou and a half split between the sides leaves a mighty fine cut . A couple of things concern me about the build up and re-machine approach . Well , actually 3 things . Finding zero on the hole , this thing has to be dead nuts . Welding on an 80 year old casting in a critical area - it's gotta have some oil soaked in and that means weld grind weld grind repeat until you get a clean repair , welding will also draw whatever temper that casting has , again in a critical area . Whatever I end up doing , pulling the race and miking that hole to make sure I'm right is the first step . If the hole is actually round that means the other one ain't . That's not likely , the race was ground in the lathe while gripped lightly and ran well after installation . Just a very light touch-up to clean up the bearing surface . It ain't likely I'll get to this very soon , just want to have a plan when I do start . Then there's the crankshaft rebuild ... got new bearings and crank pin , by the time I'm done the motor and trans will be completely rebuilt . Now if I could find a set of hi-perf cams for a 45 Flathead ...
I've been conversing about this over at the Harley newsgroup , one of the guys there suggested line lapping it ... that may well be how it was originally fitted in 1939 , I don't know . But that would definitely make sure alignment was spot-on . Several years ago when I discovered this problem I started to make an adjustable lap system , several sizes since other stuff may also need to be lapped in place . I abandoned that project because my skills at that time were not up to the task I set for myself - accuracy wasn't even close to the precision called for . I'm a better machinist now , and have decided on a different approach to making laps for these bearing races . I'll still use the same mandrel and the slugs I was going to use , but I'll machine them smaller then cast a "skin" of maybe lead but more likely wheel weight alloy which will then be machined to the size I need . I've been out in the shop today working on that original lap system , checking it out and cleaning things up . The center drilled in the drive end ain't centered , but dialed in with the 4 jaw chuck and supported with a live center at the other end it has way less than a thou runout . I'll cast a couple of laps and see how that goes , but I'm pretty sure this is the way I'll go with this .
I guess I don't understand what you are trying to do. I thought you had a bore that was out of round and so a bearing race would walk out of it. Are you just going to lap to roundness instead of bore to roundness? Once you do have the bore the way you want it will you still need to Loctite the bearing race in? Or bush and then press the race in? I don't know anything about Harley transmission cases and where the bearings are located. Eric
I'm sorry Eric , I might not have been clear . I have a race that's pressed into the left side of the transmission case , it carries the clutch gear (main input shaft to trans , carries the clutch on the outside) and thrust for the clutch . When this race was pressed into another case I have the bearings rolled perfectly - these are loose rollers with retaining washers on both ends . In the case it is currently pressed into , it ain't workin' so well . The race now measures .0015" larger horizontally than it is tall - it's oval now . What we're talking about lapping is the inside diameter of the race , to make it round IN THIS ORIENTATION in the case . If it's R&R'ed it will have to be indexed to the exact same orientation . Or I can make the hole it's pressed into round . Six of one , half a dozen of the other . I can go either way with what I have on hand except for loctite sleeve retaining stuff .
The external adjust points were one of my favorite features of GM distributors .
On v8 distributors only though.
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