I was thinking of ways to prolong the lives of early ford transmissions and would like to know if anybody has any thoughts on the idea, one thought was if using a steel flywheel over an aluminum or visa versa would it distribute power in any different fashion while letting out the clutch, also has anybody ever first hand drag raced one by gearing the car to launch it in second and just shift to third gear. I spoke to BIG JOHN 37 on the Hamb about trying to do the Cryogenic process to the internals of a 39 box as well. I have a couple cars that use the early box and I do not want to change them. My best luck for keeping them together so far is making the end tolerance as tight as possible by milling the correct sized spacer/washer to tighten them up while putting them together. Let's hear some different thoughts.
One thing to make damned sure of is to run rear tires that spin and don't stick! About the time you really hook it up, the axle keys will shear if you're lucky, and the transmission will crunch if you're not. This wasn't such a big deal in the days when a replacement gearbox would run you somwhere under $10.00, and every junkyard had them.
lol as much as I wanted to put a pair of slicks on for the drags I opted against it for that reason, instead bfg 820-15's with about 45 lbs of pressure to try and keep them spinning, I'm planning on running it first week in oct.
Best way to keep a '39 box from not exploding upon a hard launch at the drags behind anything other than a flathead is two fold: 1) Rolling starts -not possible at Island or 2) keep it in the parking lot. I couldn't resist the wise *** comments, Joe. Sorry. See you at Hershey.
Both circle track and drag sources have told me that the endplay is the critical factor. One dragster builder said that he had converted from '39 to T85 because of breakage and then gone back to '39 after finding out about endplay. I have found the same info in old mags applied to the '55-7 Chevy trans, a box that was blown by the hundreds at the strip in the sixties... There are things to watch...endplay in cluster is obvious. Up top is a different story... you can eliminate endplay at both end bearings completely and be destroyed by the gap in the middle, the one that can't be felt once upper end is tight at both extremes. This is addressed by measuring distance between snaprings with upper ***embly between centers and then blueprinting down to that. Issues here are both actual sloppiness at center pilot bearing and the radical reduction of actual engagement of the synchro when there's a gap. I have an excellent article by Ch***is Research (a dragster factory!) from about 1950 on this. Will pos*** when I attain scanning technology, but can get you Joisey guys copies. Just tell me what exit... Ch***is research built to zero clearance. They were working on extreme uses, of course. The article promises that they will send you a race ready trans for $76.80, so no need to get your hands dirty! Generally, rail dragster weight cars ran only upper two gears. I don't think the '39 transmissions were ever viable for dragging over 3,000 pound or so cars. The endplay makes lots of sense...on engagement, movement of spiral cut gears with play would be iinstant and violent. The synchro problem with a loose fit between input and output gears at center pilot was also alarming...engagement of only .100 is all there is, and every bit of slop is subtracted right here! I've never blueprinted one for endplay, and look forward to tinkering with this. This stuff wasn't in the factory and aftermarket overhaul books I worked from, and I actually never thought about the axial forces generated on spiral cut gears. The '55 Chevy info I found clinched it...those trans were grenades even on low cl*** stockers at the dragstrips. Exact same problems as the '39. Ford transmissions seem to have survived into the 10's on '32 Ford sized cars and deep into the 9's or 8's on dragsters...while some people blow them backing out of the garage. Clearly, there were secrets a**** the thinkers!
More... Radial precision is pretty obvious; worn out bearings will allow gear teeth to climb, greatly weakening gears' resistance to stress AND adding forces tending to blow case apart. The article gives numbers for high precision end bearings...that needs to be researched to see if any such are currently available. I know many bearings are available in a tighter grade. They consider Ford parts OK for cluster bearings, but prefer a "precision Torrington" replacement. Need to find us a bearing consultant. I do know some unusably bad repro cluster bearings are readily available from resto catalogs, so at leasy use best Ford ones you can locate. For dragsters, gears are annealed and re-heat treated to softer than stock. Before heat treat, gears are plated to prevent carbon-inclusion case hardening by accident. This process is probably not at all desireable for a street car. This is closely similar to current offerings of extra-soft gears for 9" Ford rears to allow them to survive hard dragstrip use...but not for the street.
this is interesting as I had heard about this way back, and never knew if it was actually true. This guy I knew was the local paperboy, and he had a sideline building 'bullet proof' transmissions. As a kid his brother used to let him work on his cars by rebuilding the transmissions. He got a 'rep' for building strong ford boxes for many years. Much later I asked him what he did to make them strong and he said he "shimmed them tight". GGGG well anyway thats all I recalled about that conversation long ago, and I think this is what he meant .
Why wait for the inevitable?---Shearing all the teeth off the cluster main! Just replace the '39 box with a later model 4 spd. (T-10). Been there & done that!!-----------Don
Along with endplay tightening everywhere (and knowing that fixing the ends doesn't cover all the parts with play on the upper shaft), for drag use they did the same things that draggers do now to make those 9" Fords with 5.13 gear survive: re-heat treat the gears to softer. I have the formulasused by Ch***is research on that. Results in softer gears for shock resistance, but less resistance to long term wear on the street. Keys in rear should be nearly irrelevant if hubs properly tightened (nearly 200!) and lapped for tight fit.
gads!yes haha I remember cussing them keys, I didnt realize how tight you had to go on them axles, we did shine up the tapers but didnt lap them, bakwen we were youngndum. gggg Later in life I learned about taper fits, first it was the amount of torq that was needed to tighten volkswagon hubs, and then when i worked in diesel locomotive motor shop and how the drive gears were removed and installed on tapered motor shafts, they were stictly taper fit with no keyways.
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